Research Article Improving the Performance of a...
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Research ArticleImproving the Performance of a Semitransparent BIPV byUsing High-Reflectivity Heat Insulation Film
Huei-Mei Liu1 Chin-Huai Young2 Der-Juinn Horng1
Yih-Chearng Shiue1 and Shin-Ku Lee3
1Department of Business Administration National Central University Taoyuan 320 Taiwan2Department of Construction Engineering National Taiwan University of Science and Technology Taipei 106 Taiwan3Research Center for Energy Technology and Strategy National Cheng Kung University Tainan 701 Taiwan
Correspondence should be addressed to Shin-Ku Lee sklee1015gmailcom
Received 24 February 2016 Revised 8 May 2016 Accepted 22 May 2016
Academic Editor Prakash Basnyat
Copyright copy 2016 Huei-Mei Liu et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited
Currently standard semitransparent photovoltaic (PV) modules can largely replace architectural glass installed in the windowsskylights and facade of a building Their main features are power generation and transparency as well as possessing a heatinsulating effect Through heat insulation solar glass (HISG) encapsulation technology this study improved the structure of atypical semitransparent PV module and explored the use of three types of high-reflectivity heat insulation films to form the HISGbuilding-integrated photovoltaics (BIPV) systems Subsequently the authors analyzed the influence of HISG structures on theoptical thermal and power generation performance of the original semitransparent PVmodule and the degree to which enhancedperformance is possible The experimental results indicated that the heat insulation performance and power generation of HISGswere both improved Selecting an appropriate heat insulation film so that a larger amount of reflective solar radiation is absorbed bythe back side of the HISG can yield greater enhancement of power generation The numerical results conducted in this study alsoindicated that HISG BIPV system not only provides the passive energy needed for power loading in a building but also decreasesthe energy consumption of the HVAC system in subtropical and temperate regions
1 Introduction
Both soaring energy costs and the effects of climate changemean that greater attention is now being paid to reducingenergy consumption According to a report by the Interna-tional Energy Agency (IEA) [1] to prevent a further rise inthe global temperature of 2∘C by 2050 it is necessary to setannual reduction goals for greenhouse gas emissions withreductions in energy use being an important part of this Theenergy consumption of the construction sector accounts foraround 30 to 40 of a countryrsquos total energy consumptionand has the greatest potential for energy saving among allsectors For example it is estimated that emissions of carbondioxide will be reduced by approximately 15 billion tons peryear with the application of the design concepts of net zeroenergy or zero carbon buildings As such in recent yearsmany countries have been approving the planning design
and construction of net zero energy buildings (or zero carbonbuildings) and putting such buildings into their nationalpolicy objectives thus further raising interest in this field [2ndash4]
Among all the available renewable energy sources solarenergy is the most abundant being an inexhaustible sourceof clean energy Moreover photovoltaic (PV) module tech-nology has been widely used in modern industry to directlyconvert solar energy into electricity Traditionally a PVmodule is installed in open areas that are exposed to directsunlight in order to generate electricity However in an urbanenvironment there is limited space on a buildingrsquos roof andthus the walls or building curtains can be utilized effectivelyfor this purpose For instance a PVmodule can be combinedwith construction components such as glass curtains wallswindows or roof structures to form an integrated designThis design is known as building-integrated photovoltaics
Hindawi Publishing CorporationInternational Journal of PhotoenergyVolume 2016 Article ID 4174216 15 pageshttpdxdoiorg10115520164174216
2 International Journal of Photoenergy
(BIPV) and this technology shows great potential for thedevelopment of more effective solar modules Theoreticallyas a BIPV module is combined with building materials itcan effectively reduce overall construction costs and is thusexpected to shorten the energy payback time (EPBT)
Researchers in many countries have been assessing thebenefits of this technology For example in the United King-dom Hammond et al [5] assessed a 21 kWp monocrystallinesilicon BIPV module applied to a roof and found thatits EPBT was 45 years The results also showed that theimplementation of a government program the ldquoLow CarbonBuilding Programmerdquo (or LCBP) would facilitate the eco-nomic benefits of this BIPV module and further shorten theEPBT In the United States Keoleian and Lewis [6] assesseda 2 kWp thin-film-type (120572-Si) BIPV module integrated witha roof They installed it in different regions from PortlandOregon to Phoenix Arizona to examine the EPBT with theresults showing that this lay between 339 and 552 years Luand Yang assessed a 22 kWp monocrystalline silicon BIPVmodule used on a roof and wall in Hong Kong When themodule was installed in different orientations on the wallits EPBT ranged from 71 years (the best scenario) to 200years (when themodule was installed on a vertical wall facingwest) [7] In Malaysia Seng et al [8] assessed 1 kWp BIPVmodules using different crystalline Si technologies namelymonocrystalline polycrystalline and thin-film-type 120572-Si inwhich the EPBTs were respectively 32ndash44 22ndash30 and 19ndash26 years In Europe Oliver and Jackson [9] integrated apolycrystalline silicon BIPV module into building walls andfound that its EPBT was 55 years All these works showthat BIPV modules have been widely studied and that manycountries are making efforts to reduce the overall cost ofinstallation in order to effectively reduce the EPBT as wellas achieve mass production and universalization
Compared to the nontransparent BIPVmodule the semi-transparent BIPV module with improved visible light trans-mission performance has attracted greater attention in recentyears When a semitransparent PV module is integratedinto building curtains efficient visible light transmission canreduce the energy consumption of indoor lighting With anappropriate design solar radiation can even be reflected in anindoor environment reducing building cooling energy usagedirectly and so effectively enhance the thermal and visualcomfort of a building To achieve visible light transmissionthis type of PV module mostly uses thin-film solar paneltechnology
Copper indium gallium selenide (CIGS) amorphoussilicon (a-Si) CdTe and organic solar cells are widely usedon the market Moreover CIGS solar cells have been used inbuilding-attached photovoltaics (BAPV) [10] However themanufacturing costs of CIGS solar cells are still relativelyhigher resulting in a greater EPBT Therefore recent studiestend to focus on a-Si thin-film-type solar panelsThemoduleefficiency of a-Si solar cell is currently around 10 [11] Dueto the single-junction structure of such cells they are unableto absorb the solar energy spectrum effectively and so have arelatively low photoelectric conversion efficiency Thereforemodern solar cell research has introduced dual-junction solarcells working in tandem (a-Si120583c-Si) which can widen the
range of the solar light absorption spectrum by modulatingthe energy gap through the structure of tandem-junctionmodule improving the sunlight-to-electrical-energy conver-sion efficiency The efficiency has now reached around 123of the energy of standard sunlight (1000Wm2) for thetandem-junction modules now available on the market[11] Although tandem-junction (a-Si120583c-Si) technology canincrease the power generation efficiency of a module itsefficiency is still lower than that of crystalline silicon-typeand CIGS solar cells Nevertheless the literature [6ndash9] showsthat the EPBTs of amorphous BIPV modules were shorterthan those of crystalline silicon BIPV modules because theconstruction costs of the latter are still too high
Therefore some a-Si120583c-Si manufacturers have movedtowards manufacturing BIPV modules in order to developa semitransparent PV module that can replace architecturalglass so that the building possesses good views and aes-thetics In the United Kingdom Yun et al [12] theoreticallyanalyzed vertical solar panel walls and then analyzed theeffects that different proportions of transparent windows andsolar panels had on the indoor comfort and visible lightutilizationThey reported that transparent windows coveringaround 50 to 60 of the entire wall would achieve thebest energy-saving effects in a building The literature thussuggests that using light transmission is essential to zerocarbon building design
In Japan Wong et al [13] applied a semitransparent PVmodule to the skylight of a building Under optimal con-ditions the semitransparent solar skylight allowed 50radiation transmission and could contribute a maximum of53 of indoor heating and cooling energy consumptionas compared to a roof design using only an opaque BIPVIn China Li et al [14] made a theoretical analysis of theapplication of semitransparent PV modules in offices Theirresults also showed that their application not only couldreduce energy usage for indoor lighting and air-conditioningequipment but also had a surplus electricity output whichwill be conducive to the development of net zero energybuildings In Saudi Arabia Radhi [15] conducted an analysisof semitransparent PVmodules applied to the south and westwalls of a buildingThe EPBTs lay between 12 and 13 years soin order to effectively develop PV modules it is necessary toconsider and design them as a whole
In Brazil Didone and Wagner [16] simulated the energy-saving performance of semitransparent thin-film PV mod-ules located in two different climates in Brazil and theGerman city of Frankfurt Their results showed that withproper control a semitransparent thin-film window can notonly save energy for indoor lighting and air conditioning butalso generate surplus electricity In 2014 Ng and Mithraratnereviewed the development of semitransparent PV modulesand studied six types of commercially obtainable thin-filmPV modules applied to office buildings in Singapore Theirstudy used a life cycle assessment (LCA) method to explorethe EPBTs carbon emissions and cost reductions The LCAmethod can be used to facilitate the design of a building [17]and the results showed that the application of a semitrans-parent PV module is more in line with the concept of zero
International Journal of Photoenergy 3
carbon building compared to the use of an opaque BIPVmodule Many studies have analyzed the energy efficiencyof semitransparent PV modules and attempted to reduce theEPBT with increasing the power generation ability being themain factor in this
In a previous study [18] our team combined a thin-film-type semitransparent PVmodule with a high-reflectivity heatinsulation film to develop a type of heat insulation solar glass(HISG) that simultaneously possesses power generation heatinsulation and energy-saving functions After sunlight passesthrough the semitransparent PVmodule the remaining lightsourcewill be reflected by the high-reflectivity heat insulationfilm to the back side of the semitransparent PV module sothat the module can once again absorb the reflected lightand have a higher power output Moreover because of themultilayered structure of the HISG the solar heat passingthrough the HISG can gradually be isolated in each layerof the material After the sunlight passes through the firstlayer (the semitransparent PV module) part of the energyis converted to electrical energy For the remaining radiantheat the high-reflectivity heat insulation film will effectivelyisolate the residual radiant heat and block the ultraviolet lightby 100
The structure of the dual air gaps can reduce the thermaltransmittance (119880-value) effectively isolating the conductedheat of the glass so that the heat cannot be conducted fromthe glass to the indoor environment and hence it has verygood insulation properties In terms of saving energy duringsummer since the shading coefficient of HISG is very low theheat of solar radiation cannot easily enter the building signif-icantly reducing the startup frequency of the air-conditioningcompressor and thus achieving reduced energy consumptionfor cooling During winter since the thermal transmittanceof the HISG is very low the glass has good isolation andinsulation performance so warm air can be kept inside theroom and cannot easily be dissipated achieving reducedenergy consumption for heatingThe functional principles ofthe HISG are described in Figure 1
In this research we adopt three different types of semi-transparent PV module technologies and combine threedifferent types of energy-saving films with high reflectanceto encapsulate HISG BIPV systems Subsequently we explorethe optical and thermal properties and overall power genera-tion effects and use simulation software to calculate the powergeneration and energy-saving effects of each HISG as appliedto actual buildings in Taiwan with a subtropical climate andin London England with a temperate climate
2 Methodology
21 Preparation of Heat Insulation Solar Glass The proposedHISGs are mainly composed of a thin-film-type semitrans-parent PV module high-reflectivity heat insulation film andrear glass HISG constructed in this study is a three-layerglazing systemThe first layer is a transparent PVmodule onthe back of which is a 04mm thick layer of high-reflectivityheat insulation film between two layers of spacers Rear glass
is placed behind the second spacer layer which forms anair gap on both sides of the high-reflectivity heat insulationfilm Three types of semitransparent PV module a tandemlaser module tandem transparent conducting oxide (TCO)module and a-Si TCO module were selected as the frontlayer of the HISG in this study The cell structure of thesemodules is illustrated in Figures 2(a) 2(b) and 2(c) In orderto study the effects of heat insulation films with differentreflectance values on the gains in power generation heatinsulation and energy-saving performance of the HISG thisstudy adopts three different types of Heat Mirror films withdifferent reflectance values
22 Tests of Optical and Thermal Properties Based on ISO9050 and ISO 10292 [19 20] a UVVisNIR spectrophotome-ter (Hitachi U4100) FTIR spectrometer (Thermo iS50) andthermal conductivity analyzer (TCi) are used to measurethe optical properties and thermal performance of the ninetypes of HISGs The optical properties include solar directtransmittance (300sim2500 nm) solar direct reflectance (300sim2500 nm) visible light transmittance (380sim780 nm) visiblelight reflectance (380sim780 nm) and ultraviolet light trans-mittance (300sim380 nm)The thermal performance propertiesinclude the solar heat gain coefficient (SHGC) shading coef-ficient (SC) and thermal transmittance (119880-value) Since theHISGs used in this study aremultilayer ones composed of twoor more sheets of flat glass individual measurements must bemade of every component during the optical measurementsThe related formulae in ISO 9050 were used to calculatethe overall optical and thermal performances The relevantformulae are as follows
221 Visible Light Transmittance 120591119881 and Reflectance 120588
119881 of
Triple Glazing The light transmittance 120591119881 and reflectance
120588119881 of each component are calculated using the following
formulae
120591119881=
sum780
380
119863120582times 119881 (120582) times 120591 (120582) times Δ120582
sum780
380
119863120582times 119881 (120582) times Δ120582
120588119881=
sum780
380
119863120582times 119881 (120582) times 120588 (120582) times Δ120582
sum780
380
119863120582times 119881 (120582) times Δ120582
(1)
where 119863120582is the relative spectral distribution of illuminant
D65 (see ISOCIE 10526) 120591(120582) is the spectral transmittance ofglazing 120588(120582) is the spectral reflectance of glazing119881(120582) is thespectral luminous efficiency for photopic vision defining thestandard observer for photometry and Δ120582 is the wavelengthinterval
In the case of multiple glazing the spectral transmittance120591(120582) and reflectance 120588(120582)will be obtained by calculation fromthe spectral characteristics of the individual componentsFor the spectral transmittance 120591(120582) and reflectance 120588(120582) asa function of the spectral characteristics of the individualcomponents of the unit the following formulae are obtained
4 International Journal of Photoenergy
SemitransparentPV module
High-reflectivityheat insulation film
Rear glass
Sunlight
Heat insulation
1st-timepower generation
2nd-timepower generation
(i) Enhance power generation(ii) Reduce heat penetration
(iii) Reduce Tsol SHGC SC value and U-value
(a)
High-reflectivityheat insulation film
Rear glass
2nd air gap
1st air gap
2nd steel spacer
1st steel spacer
Junction box
SemitransparentPV module
9mm 6mm 6mm 6mm
27mm
Structure of HISG
(b)
Figure 1 Functional principles and cross-sectional structure of heat insulation solar glass
Glass
TCO
a-Si
120583c-Si
Al
EVA
Glass
(a) Tandem laser module
Glass
TCO
EVA
Glass
TCO
a-Si
120583c-Si
(b) Tandem TCO module
Glass
TCO
a-Si
EVA
Glass
TCO
(c) a-Si TCO module
Figure 2 Cell structure of the tandem laser tandem TCO and a-Si TCO module
120591 (120582) =
1205911(120582) times 120591
2(120582) times 120591
3(120582)
[1 minus 1205882(120582) times 120588
1015840
1
(120582)] [1 minus 1205883(120582) times 120588
1015840
2
(120582)] minus 1205912
2
1205883(120582) times 120588
1015840
1
(120582)
120588 (120582) = 1205881(120582) +
1205912
1
(120582) times 1205882(120582) [1 minus 120588
1015840
2
(120582) times 1205883(120582)] + 120591
2
1
(120582) times 1205912
2
(120582) times 1205883(120582)
[1 minus 1205881015840
1
(120582) times 1205882(120582)] [1 minus 120588
1015840
2
(120582) times 1205883(120582)] minus 120591
2
2
times 1205881015840
1
(120582) times 1205881015840
3
(120582)
(2)
where 1205911(120582) is the spectral transmittance of the outer (first)
pane 1205912(120582) is the spectral transmittance of the second pane
1205913(120582) is the spectral transmittance of the third (inner) pane1205881(120582) is the spectral reflectance of the outer (first) pane
measured in the direction of incident radiation 12058810158401
(120582) is thespectral reflectance of the outer (first) pane measured in the
opposite direction of incident radiation 1205882(120582) is the spectral
reflectance of the second pane measured in the directionof incident radiation 1205881015840
2
(120582) is the spectral reflectance of thesecond pane measured in the opposite direction of incidentradiation 120588
3(120582) is the spectral reflectance of the third (inner)
pane measured in the direction of incident radiation 12058810158403
(120582) is
International Journal of Photoenergy 5
the spectral reflectance of the third (inner) pane measured inthe opposite direction of incident radiation
222 Solar Direct Transmittance 120591119890 and Reflectance 120588
119890 of
Triple Glazing Thesolar direct transmittance and reflectanceare obtained as follows
120591119890=
sum2500
780
119878120582times 120591 (120582) times Δ120582
sum2500
780
119878120582times Δ120582
120588119890=
sum2500
780
119878120582times 120588 (120582) times Δ120582
sum2500
780
119878120582times Δ120582
(3)
where 119878120582is the relative spectral distribution of the solar radi-
ation
223 UV Transmittance UV transmittance is obtained asfollows
120591119890=
sum380
300
119878120582times 120591 (120582) times Δ120582
sum380
300
119878120582times Δ120582
(4)
224 119880-Value Calculation The thermal transmittance ofglazing also known as the119880-value is the rate of heat transferthrough one squaremeter of glazing divided by the differencebetween the ambient temperatures on each side The methodspecified by ISO 10292 is based on a calculation from thefollowing equation
1
119880
=
1
ℎ119905
+
1
ℎ119890
+
1
ℎ119894
(5)
where ℎ119894is the interior heat transfer coefficient ℎ
119890is the
exterior heat transfer coefficient ℎ119905is the conductance of the
multiple glazing unit
225 Total Solar Energy Transmittance The total solarenergy transmittance (also known as solar heat gain coeffi-cient) is the sum of the solar direct transmittance 120591
119890and the
secondary heat transfer factor 119902119894towards the inside
119892 = 120591119890+ 119902119894 (6)
The secondary heat transfer factor results from heat transferby convection and longwave IR-radiation of that part of theincident solar radiation which has been absorbed by theglazingThe secondary heat transfer factor towards the insideof triple glazing is calculated using the following formula
119902119894
=
((1205721198901+ 1205721198902+ 1205721198903) ℎ119890+ (1205721198902+ 1205721198903) Λ12+ 1205721198903Λ23)
1ℎ119894+ 1ℎ119890+ 1Λ
12+ 1Λ
23
(7)
where 1205721198901is the solar direct absorptance of the outer (first)
pane within the triple glazing 1205721198902is the solar direct absorp-
tance of the second pane within the triple glazing 1205721198903is the
solar direct absorptance of the third pane of the triple glazingΛ12is the thermal conductance between the outer surface of
the outer (first) pane and the center of the second pane Λ23
is the thermal conductance between the center of the secondpane and the center of the third pane
226 Shading Coefficient (SC) The shading coefficient ofglass is a measure of the total amount of heat passing throughthe glazing compared with that through single clear glass Itis approximately equal to the SHGC divided by 087
23 Test of Gains in Power Generation Performance Tests ofthe gain in power generation were made based on the stan-dard test conditions (STC) in the test standard given by theInternational Electrotechnical Commission IEC 61646 [21]for a thin-film PV module in order to explore the powergeneration characteristics of the nine types ofHISGdescribedabove The effects of each combination of materials on thegain in power generation capacity of the semitransparent PVmodule were then analyzed and compared
24 Assessment of Energy-Saving Performance In this studyAutodesk Ecotect Analysis was adopted to conduct simula-tions of building power generation and energy by adoptingthe results of the power generation test optical test andthermal test as the material parameters and choosing Tainanin Taiwan and London in the United Kingdom as the simu-lated locations The simulation was used to obtain the powergeneration capacity and energy consumption performanceof the HISGs in real-world applications on buildings insubtropical and temperate regions
241 BuildingModel Ecotect was used in this study tomodela single building The building body consists of a roof andfour walls to form an enclosed space in order to facilitatethe simulation of air-conditioning energy consumption Themain body of the building is facing south The roof has amonopitched roof structure with an incline angle of 235∘ andis composed of 10 piecestimes 10 pieces giving a total of 100 piecesof PV modules with a size of approximately 14m times 11m Theoverall dimensions of the building body are approximately14m times 10m times 83m as illustrated in Figure 3
242 Setting Parameters for the Simulation In terms of thematerial parameters the four surrounding walls are definedas being constructed of composite materials (110mm brickoutside plus 75mm timber frame with 10mm plasterboardinside) with a 119880-value of 177WmK whereas values forthe material parameters of each PV module come from theresults of the power generation and optical and thermal testsin this paper For the air-conditioning energy consumptionthis study uses a mixed-mode air-conditioning system forcooling and heating The usage time is 24 hours the comforttemperature range is 20∘Cndash26∘C the startup temperaturesetting for a cold room is 26∘C and the startup temperaturesetting for a warm room is 18∘C The simulation of the air-conditioning energy consumption was conducted for a wholeyear
3 Results and Discussion
31 Optical Properties The transmittance and reflectancecoefficient versus wavelength of each component are shownin Figures 4 and 5 respectively Table 1 shows the optical
6 International Journal of Photoenergy
Table 1 Optical properties of each component and HISGs
ModuleItem
Solar directtransmittance
Solar directreflectance
Visible lighttransmittance
Visible lightreflectance
UVtransmittance
Tandem laser module 709 1007 84 527 001Tandem TCOmodule 1833 679 220 515 001a-Si TCO module 2349 730 435 512 001Heat insulation film A 6814 1688 9532 483 175Heat insulation film B 4063 3089 8412 601 136Heat insulation film C 3315 4071 6104 2233 100Rear glass 8115 504 8885 566 6239Tandem laser-A HISG 407 1017 723 535 0Tandem laser-B HISG 25 1024 639 535 0Tandem laser-C HISG 208 1030 478 545 0Tandem TCO-A HISG 1034 744 188 515 0Tandem TCO-B HISG 626 788 166 515 0Tandem TCO-C HISG 516 821 123 515 0a-Si TCO-A HISG 1326 837 372 514 0a-Si TCO-B HISG 803 909 329 514 0a-Si TCO-C HISG 662 964 243 517 0
1400m
833
m
1009m
1100m110m
395
m
140m
Figure 3 The 3D model of the building body
properties of each component based on ISO 9050The valuesof lighting transmittance for the three PV modules were inthe 709ndash2349 range and those for the three heat insulationfilms were in the range of 3315ndash6814 The measurementresults show that the tandem lasermodule and heat insulationfilm C had better heat insulation effects They could thusbe used in hot climates where there is a need to reducesolar heat transmission especially in buildings where largetransparent surfaces are fitted Furthermore the tandem lasermodule and heat insulation filmA had better visibilities eventhoughwith the former the back-contact electrodematerial isopaque Part of the power-generating layers and back-contactelectrode layer in the tandem laser module were removed
using a transverse laser cutting method to enable the moduleto be light-transmissible It is also worth noting that the lowervisible light transmittance in other modules is mainly due toabsorption of the TCO layers The UV transmittances of thePVmodule and heat insulation film are less than 2meaningthat the performances of the HISGs with regard to isolatingUV light were very good
In the cell structure of the tandem TCO module thematerials of the power-generating layers are the same as thoseof the tandem laser module but in terms of the back-contactelectrode a TCO material with good light transmission andconduction properties was adopted Though TCO has highoptical transparency it does decrease light transmission fromUV to IR Therefore the tandem TCO module has a light-transmissible property and its insulation of solar thermalenergy is poorer than that of the tandem laser module Inaddition as the color of transmitted light tends to be winered part of its visible light transmittance was poorer Thematerial of the rear electrode in the cell structure of the a-Si TCO module was the same as that of the tandem TCOmoduleAs such it also has a light-transmissible property andthe transmitted light color tends to be orange red Howeverin the power-generating layer the a-Si TCO module had asingle-layer structure without a layer of 120583c-Si so its visiblelight transmittance was slightly better than that of the tandemTCOmodule Furthermore as it has no 120583c-Si layer to absorbthe solar light its solar radiation transmittance was slightlypoorer than that of the tandem TCOmodule
As shown in Figure 6 the measurement results for thesolar direct transmittance indicated that the addition ofa reflective layer reduces the transmittance of HISGs Forthe tandem laser tandem TCO and a-Si TCO modulethe solar direct transmittance was originally 709 1833
International Journal of Photoenergy 7
0
10
20
30
40
50Tr
ansm
ittan
ce (
)
Wavelength (nm)
Tandem laser moduleTandem TCO modulea-Si TCO module
300 600 900 1200 1500 1800 2100 2400
(a)
0
10
20
30
40
50
60
70
80
90
100
Tran
smitt
ance
()
Wavelength (nm)300 600 900 1200 1500 1800 2100 2400
Heat insulation film AHeat insulation film BHeat insulation film C
(b)
0
20
40
60
80
100
Tran
smitt
ance
()
Wavelength (nm)500 1000 1500 2000 2500
Glass
(c)
Figure 4 Transmittance spectra of each component (a) semitransparent PV module (b) heat insulation film and (c) rear glass
and 2349 but after being encapsulated into the HISGit dropped to 208ndash407 516ndash1034 and 662ndash1326respectively The visible light transmittance was originally84 22 and 435 but after being encapsulated into theHISG it dropped to 478ndash723 123ndash188 and 243ndash372respectively
After the various semitransparent PVmodules were inte-grated into the HISG with the various heat insulation filmsall their solar direct reflectance values increased slightly sothe encapsulationwas slightly beneficial to the heat insulatingeffect of the HISGs Moreover after being encapsulated intothe HISGs the effects on the visible light reflectance were allless severe falling to around 5 Therefore the HISGs willnot necessarily cause environmental light pollution
With regard to the UV transmittance since most of theUV light is absorbed by the semitransparent PV moduleand the heat insulation film the UV transmittance valuesof all the HISGs are 0 This means that the UV isolationperformances are very good and able to protect interiorfurnishings from aging and the skin from damage caused byUV radiation
32 Thermal Properties The surface emissivity of an objectrefers to its ability to release heat via thermal radiation afterabsorbing solar radiation The surface emissivity of eachcomponent is thus an important parameter affecting the heatinsulation performance of a HISG In this paper the spectralreflectance of each component on the exterior and interior
8 International Journal of Photoenergy
02468
101214161820222426
Refle
ctan
ce (
)
Wavelength (nm)
Tandem laser moduleTandem TCO modulea-Si TCO module
300 600 900 1200 1500 1800 2100 2400
(a)
0
10
20
30
40
50
60
70
Refle
ctan
ce (
)
Wavelength (nm)300 600 900 1200 1500 1800 2100 2400
Heat insulation film AHeat insulation film BHeat insulation film C
(b)
0
10
20
30
40
50
60
70
80
90
100
Refle
ctan
ce (
)
Wavelength (nm)
Glass
300 600 900 1200 1500 1800 2100 2400
(c)
Figure 5 Reflectance spectra of each component (a) semitransparent PV modules (b) heat insulation films and (c) rear glass
sides was measured using FTIR and then the emissivityvalue of each component was obtained by ISO 10292 asshown in Table 2 It can be seen that as the surfaces ofthe semitransparent PV modules and rear glass were not allcoated by a film the emissivity values for the exterior andinterior sides were 084 While the heat insulation filmswere mainly composed of PET material there was no filmcoating the interior surface of the film so the emissivityvalues were all 076 Meanwhile the exterior surfaces of theheat insulation films all had a multilayer metal coating sothe surface emissivity values were lower than the surfaceemissivity values on the indoor side The surface emissivity
of heat insulation film C is 0033 which is thus categorized asa Low-E film
Table 3 shows the thermal performances of the three typesof PVmodules and the nine types of HISGs with the SHGCsshading coefficients and overall heat transfer coefficients (119880-values) The results indicate that the multilayer structureof the HISG reduced the solar direct transmittance andsince the heat insulation films were coated with transparentmetal films this reflected the solar radiation heat promptingthe SHGCs to be reduced to half the levels seen with thesemitransparent PVmodulesThismeans that the quantity ofsolar radiation heat passing through the HISG was half that
International Journal of Photoenergy 9
0
2
4
6
8
10
12
545
478
103
208
535
639
1024
25
535
723
1017
407
00 0001
527
84
1007
709
UV
tran
smitt
ance
Visib
le li
ght
refle
ctan
ce
Visib
le li
ght
tran
smitt
ance
Sola
r rad
iatio
nre
flect
ance
Sola
r rad
iatio
ntr
ansm
ittan
ce
Tran
smitt
ance
and
refle
ctan
ce (
)
Tandem laser moduleTandem laser-A HISG
Tandem laser-B HISGTandem laser-C HISG
(a)
0
2
4
6
8
10
12
14
16
18
20
0 00001
515515515515
123166
18822
821788744
679516
626
1034
1833
UV
tran
smitt
ance
Visib
le li
ght
refle
ctan
ce
Visib
le li
ght
tran
smitt
ance
Sola
r rad
iatio
nre
flect
ance
Sola
r rad
iatio
ntr
ansm
ittan
ce
Tran
smitt
ance
and
refle
ctan
ce (
)Tandem TCO moduleTandem TCO-A HISG
Tandem TCO-B HISGTandem TCO-C HISG
(b)
02468
101214161820222426
000001
517514
514512
243329
372435
964909
83773
662803
1326
2349
UV
tran
smitt
ance
Visib
le li
ght
refle
ctan
ce
Visib
le li
ght
tran
smitt
ance
Sola
r rad
iatio
nre
flect
ance
Sola
r rad
iatio
ntr
ansm
ittan
ce
Tran
smitt
ance
and
refle
ctan
ce (
)
a-Si TCO modulea-Si TCO-A HISG
a-Si TCO-B HISGa-Si TCO-C HISG
(c)
Figure 6 Optical properties of the HISGs (a) tandem laser module (b) tandem TCOmodule and (c) a-Si TCO module
passing through the semitransparent PV modules In termsof the 119880-value since all the semitransparent PV moduleswere assembled with 4mm times 4mm laminated glass the 119880-values based on ISO 10292 for all modules were 563Wm2-K The addition of heat insulation films and dual air gaps toform a multilayer structure greatly reduced the 119880-values oftheHISGs (1755Wm2-Kndash1824Wm2-K)Moreover havingheat insulation films with different emissivity values is one
of the main causes of the decline in the 119880-value Since heatinsulation film C had the lowest surface emissivity theHISGs assembled using film C also possessed lower119880-values(1755Wm2-K)
33 Power Generation Gain Performance The power genera-tion test results for the front and back sides of each semitrans-parent PV module are shown in Table 4 The measurement
10 International Journal of Photoenergy
Table 2 Emissivity of each component
Item Emissivity ofindoor side
Emissivity ofoutdoor side
Tandem laser module 084 084Tandem TCOmodule 084 084a-Si TCO module 084 084Heat insulation film A 076 0135Heat insulation film B 076 0045Heat insulation film C 076 0033Rear glass 084 084
Table 3Thermal properties of the semitransparent PVmodules andHISGs
ModuleItem
SHGC Shadingcoefficient 119880-value
Tandem lasermodule 03 0345 563
Tandem laser-AHISG 0151 0174 1824
Tandem laser-BHISG 0135 0155 1757
Tandem laser-CHISG 0129 0148 1755
Tandem TCOmodule 038 0437 563
Tandem TCO-AHISG 0218 025 1824
Tandem TCO-BHISG 0184 0211 1757
Tandem TCO-CHISG 0171 0196 1755
a-Si TCOmodule 041 0471 563
a-Si TCO-AHISG 0249 0286 1824
a-Si TCO-BHISG 0207 0238 1757
a-Si TCO-CHISG 019 0218 1755
results show that the power output for the front side of thetandem laser module was 126029W with an efficiency of8184 while that of the back side was only 1019W Thereason for this is the cell structure of the tandem lasermoduleas the bottom back-contact conductive layer is Al whichdoes not possess power generation characteristicsThereforeafter being illuminated by direct light there should not be apower generation effect However because the tandem lasermodule was subjected to transverse laser cutting during themanufacturing process light can pass through from the backsideThe light could then undergo refraction or transmissionat the rear glass so some of the light is able to enter the power-generating layer from the laser cut slits and so the back side
Table 4 Results of tests of electrical characteristics in STC for initialstates of the original transparent PV module (a) front side and (b)back side
(a)
Test itemTandemlaser
module
TandemTCO
module
a-SiTCO
moduleModule efficiency () 8184 811 778Maximum power output(W) 126029 124843 119796
Open circuit voltage (V) 167382 171629 111606Short circuit current (A) 1133 1038 1595Maximum voltage (V) 131026 140561 86939Maximum electric current(A) 0962 0888 1378
Fill factor 06644 07008 06731
(b)
Test itemTandemlaser
module
TandemTCO
module
a-SiTCO
moduleModule efficiency () 0066 0723 5361Maximum power output(W) 1019 11134 82566
Open circuit voltage (V) 109965 156555 108648Short circuit current (A) 0026 0108 1213Maximum voltage (V) 40348 132561 83918Maximum electric current(A) 0025 0084 0984
Fill factor 03506 06576 06264
of the tandem laser module also possesses a slight powergeneration effect
The power output of the front side of the tandem TCOmodule was 124843W with an efficiency of 811 whereasthat of the back side was only 11134W The reason why theefficiency from back-side illumination is low is due to lightabsorption in the lower bandgap 120583c-Si cell which allowslimited light into the a-Si cell The current output would belimited by the smaller current value from the a-Si and so alower efficiency is generated
The front-side power output of the a-Si TCOmodule was119796W with an efficiency of 778 whereas the back-sidepower output of the a-Si TCO module reached 82566WThe power-generating layer of the a-Si TCO module is thea-Si layer which is also classified as a cell structure withdual-surface power generation characteristics so the back-side power output was higher compared to that of the formertwo modules However the reason for the difference in thefront-side and back-side power outputs of the a-Si TCOmodule is that the materials of the front and rear glasswere different The front glass was ultraclear glass with morethan 90 visible light transmittance Meanwhile in orderto increase the loading strength of the BIPV the rear glasswas mostly tempered glass or heat-strengthened glass with
International Journal of Photoenergy 11
lower transmissivity In addition before entering the power-generating layer from the back side the light still needs to passthrough a layer of EVA plastic film which will also reduce thesolar irradianceThe back-side power output of the a-Si TCOmodule was thus only 69 of the front-side power output
The results of the electrical tests of each semitransparentPV module and each combination of HISGs are shown inTable 5 The results for power generation gain are shownin Table 6 The experimental results indicated that boththe power generation and efficiency of tandem laser HISGexhibited slightly increasing trends the power generationincreased by around 001ndash013 and the efficiency increasedby around 0001ndash001 However the power generationand efficiency of tandem TCO HISG and a-Si TCO HISGdisplayed increasing trends For the tandem TCO HISGthe power generation improved by around 327ndash1006 andthe efficiency increased by around 027ndash082 For the a-SiTCOHISG the power generation increased by around 094ndash307 and the efficiency increased by around 007ndash024The power-generating layer of the tandem TCOmodule is a-Si120583c-Si but that of the a-Si TCO module is a single layer ofa-Si The absorption spectrum of the tandem TCO module(300 nmndash1100 nm) is wider than that of the a-Si TCOmodule(300 nmndash750 nm) The back side of the tandem TCO HISGcan thus absorb higher effective irradiance than the a-Si TCOHISG This means that the efficiency enhanced rate of thetandemTCOHISG is higher than that of the a-Si TCOHISGIt is also worth noting that selecting an appropriate heatinsulation film in order to absorb a larger amount of reflectivesolar radiation by the back side of theHISG can lead to greaterenhancement of power generation
34 Simulation of Energy-Saving Performance The simula-tion results for the power generation of each HISG installedin the buildings and the energy consumption of the heatingventilation and air-conditioning (HVAC) system are shownin Table 7 As Tainan is located in a subtropical region inTaiwan where there is sufficient sunlight the annual powergeneration of each module was higher than that of themodules in London and the power outputs ranged between16328 kW and 18727 kW London is located in a temperatezone with mostly cloudy weather and thus the annual powergeneration only ranged between 8493 kWand 9741 kWTheseresults show that different climate zones andweather patternsare the main factors affecting the power generation of BIPVmodules
The simulation results in Table 7 also show that the poweroutputs of each HISG were larger than those of the originalsemitransparent PV modules That is the power enhance-ments of the tandem laser HISG were around 001ndash012those of the tandem TCO HISG were around 327ndash1006and those of the a-Si TCO HISG were around 094ndash307The simulated results also reveal that the percentage gainsin power generation for each HISG installed on the roofs ofbuildings as BIPV roofs are consistent with the experimentalresults under STC from IEC 61646 Therefore adding heatinsulation films onto semitransparent PV modules to forma HISG in order to enhance the power output of the modulesis beneficial in reducing the EPBT of the entire BIPV system
The simulation results for the energy consumption of theHVAC systems of buildings in Tainan Taiwan and LondonUK are shown in Tables 8 and 9 respectively As Tainan islocated in a subtropical region the use of a heater is lesscommon and the HVAC system is mostly used for coolingso the energy consumption for the latter is much higher thanthat for heating On the other hand London is located in atemperate region and the HVAC system is mainly used forheating so the energy consumption for this is much higherthan that for cooling
Furthermore the main factors affecting the energy con-sumption of theHVAC system are the shading coefficient andthe 119880-value of the envelope The shading coefficient and 119880-value of each HISG are lower than those of the semitrans-parent PV modules During summer solar radiation cannotenter the room easily through the HISG so cooling energycan be saved During winter the 119880-value of the HISG isvery low owing to the multilayer structure and althoughsolar radiation cannot enter the room easily the heat will beretained inside the room and will not dissipate easily andhence the amount of energy used for heating can also bereduced Therefore the simulation results for the HISGs allindicate greater energy-saving performance in the annualenergy consumption of the HVAC system The results showthat the HISG can save 2911ndash3219 of cooling energy 4734ndash4815 of heating energy and 3268ndash3575 of the totalenergy consumption of the HVAC system in subtropicalregions and 3727ndash4412 of cooling energy 3905ndash3986 ofheating energy and 3905ndash3986 of total energy consump-tion of the HVAC system in temperate regions Among all theHISGs the HISG encapsulated version using heat insulationfilm C had the best energy-saving performance
As seen in the simulation results given above the HISGcan not only enhance the power generation but also becauseof the better heat insulation performance shorten the EPBTof the entire HISG BIPV application on a building
4 Conclusion
The concepts of net zero energy zero energy and passiveenergy are becoming more important as part of the energyconservation policies adopted by the construction industryBIPV technology currently has great potential for effectivedevelopment of solar module techniques Theoretically if aBIPV module is combined with building materials it caneffectively reduce overall construction costs save energymodulate the indoor temperature and shorten the energypayback time (EPBT)
In this work the authors adopted three different types ofsemitransparent PV modules and combined three differenttypes of high-reflectivity films to encapsulate HISG BIPVsystems The optical and thermal properties and the overallpower generation effects of each HISG were investigated Inaddition Autodesk software was used to calculate the powergeneration and energy-saving effects of each HISG as appliedto actual buildings in Taiwan with a subtropical climate andEngland with a temperate climate As a result due to thethree-layer structure of the HISGwith a high-reflectivity heatinsulation film the heat insulation performance (SHGC and
12 International Journal of Photoenergy
Table5Testresults
forthe
vario
usBIPV
mod
ules
andHISGsu
nder
STC
Testitem
Tand
emlaser
mod
ule
Tand
emlaser-A
HISG
Tand
emlaser-BHISG
Tand
emlaser-CHISG
Tand
emTC
Omod
ule
Tand
emTC
O-A
HISG
Tand
emTC
O-B
HISG
Tand
emTC
O-C
HISG
a-SiTC
Omod
ule
a-Si
TCO-A
HISG
a-SiTC
O-B
HISG
a-Si
TCO-C
HISG
Efficiency
()
8184
8185
8189
8194
811
837
874
892
778
785
787
802
Maxim
umpo
wer
output
(W)
126029
12604
2126105
126187
124843
128926
134658
137399
119796
120921
121125
123475
Opencircuit
voltage
(V)
1673
821672
531672
81167313
1716
291716
441718
86172036
1116
061115
971116
131117
10
Shortcirc
uit
current(A)
1133
1134
1133
1134
1038
1074
1125
1150
1595
1612
1615
1650
Maxim
umvoltage
(V)
1310
261294
33130098
1292
07140561
1391
73138796
138027
86939
8733
787341
84561
Maxim
umele
ctric
current(A)
0962
0974
0969
0977
0888
0926
0970
0995
1378
1385
1387
1460
Fillfactor
066
44066
4606654
06651
07008
06996
06964
06944
06731
06721
06719
06698
International Journal of Photoenergy 13
Table 6 Results of power generation gain tests of the semitransparent PV modules and each combination of HISG under STC
ModuleItem
Power generation (W) Power generationenhancement () Module efficiency () Module efficiency
enhancement ()Tandem laser module 126029 mdash 8184 mdashTandem laser-A HISG 126042 001 8185 0001Tandem laser-B HISG 126105 006 8189 0005Tandem laser-C HISG 126187 013 8194 0010Tandem TCOmodule 124843 mdash 811 mdashTandem TCO-A HISG 128926 327 837 027Tandem TCO-B HISG 134658 786 874 064Tandem TCO-C HISG 137399 1006 892 082a-Si TCO module 119796 mdash 778 mdasha-Si TCO-A HISG 120921 094 785 007a-Si TCO-B HISG 121125 111 787 009a-Si TCO-C HISG 123475 307 802 024
Table 7 Power generation results for building body simulations
Module LocationTainan Taiwan (kW) Power enhancement () London UK (kW) Power enhancement ()
Tandem laser module 17178 mdash 8935 mdashTandem laser-A HISG 17179 001 8936 001Tandem laser-B HISG 17188 006 8940 006Tandem laser-C HISG 17199 012 8946 012Tandem TCOmodule 17016 mdash 8851 mdashTandem TCO-A HISG 17573 327 9141 327Tandem TCO-B HISG 18354 786 9547 786Tandem TCO-C HISG 18727 1006 9741 1006a-Si TCO module 16328 mdash 8493 mdasha-Si TCO-A HISG 16481 094 8573 094a-Si TCO-B HISG 16509 111 8587 111a-Si TCO-C HISG 16830 307 8754 307
Table 8 Simulation results for energy consumption of HVAC systems for the building body in the Tainan region of Taiwan
Module Cooling energyconsumption (kW)
Cooling energysaving ()
Heating energyconsumption
(kW)
Heating energysaving ()
Total HVAC systemenergy consumption
(kW)
Total HVACenergy saving
()Tandem laser module 28632 mdash 6924 mdash 35556 mdashTandem laser-A HISG 20296 2911 3639 4744 23935 3268Tandem laser-B HISG 20053 2996 3590 4815 23643 3350Tandem laser-C HISG 19958 3029 3591 4814 23549 3377Tandem TCOmodule 29495 mdash 6894 mdash 36390 mdashTandem TCO-A HISG 20793 2950 3623 4745 24415 3291Tandem TCO-B HISG 20412 3080 3576 4813 23988 3408Tandem TCO-C HISG 20201 3151 3583 4803 23784 3464a-Si TCO module 30368 mdash 6869 mdash 37236 mdasha-Si TCO-A HISG 20952 3101 3617 4734 24569 3402a-Si TCO-B HISG 20593 3219 3568 4806 24161 3511a-Si TCO-C HISG 20347 3300 3577 4793 23924 3575
14 International Journal of Photoenergy
Table 9 Simulation results for energy consumption of HVAC systems for the building body in London UK
ModuleCooling energyconsumption
(kW)
Cooling energysaving ()
Heating energyconsumption
(kW)
Heating energysaving ()
Total HVAC system energyconsumption (kW)
Total HVACenergy saving
()Tandem laser module 306 mdash 116818 mdash 117123 mdashTandem laser-A HISG 181 4085 71203 3905 71384 3905Tandem laser-B HISG 171 4412 70570 3959 70741 3960Tandem laser-C HISG 173 4346 70491 3966 70664 3967Tandem TCOmodule 271 mdash 117612 mdash 117883 mdashTandem TCO-A HISG 170 3727 71497 3921 71667 3920Tandem TCO-B HISG 164 3948 70753 3984 70917 3984Tandem TCO-C HISG 165 3911 70734 3986 70899 3986a-Si TCO module 287 mdash 117214 mdash 117501 mdasha-Si TCO-A HISG 175 3902 71273 3919 71448 3919a-Si TCO-B HISG 172 4007 70640 3973 70812 3973a-Si TCO-C HISG 171 4042 70566 3980 70737 3980
119880-value) showed an improvement Although the multilayerstructure of HISG would affect the visible light transmit-tance in practice it does not have a significant impact onthe view through the glass Moreover although the solardirect reflectance values all showed improving trends thevisible light reflectance was only around 5 which will notnecessarily cause environmental light pollution Comparedto the original modules the power generation and moduleefficiency of all HISGs were found to have increased Of allthe combinations of HISGs the gain in power generation ofthe tandem TCO-C HISG was the highest as the power gen-eration was improved by 1006 and the module efficiencywas improved by 082The results of the simulation showeda very similar trendwith regard to the level of electrical powergeneration based on experimental data that was obtainedusing the standard test conditions (STC) for measurementcontained in IEC 61646The simulation results also indicatedthat theHISG has a significant effect on the amount of energythat can be saved when using the HVAC system in bothsubtropical and temperate regions
This paper thus provides valuable information for renew-able energy planners and architectural designers who areinterested in using HISG BIPV systems
Competing Interests
The authors declare that there are no competing interestsregarding the publication of this paper
Acknowledgments
This study was supported by the Ministry of Science andTechnology of Taiwan under Projects MOST 105-3113-F-011-001 and MOST 105-3113-E-006-006-CC2
References
[1] M van der Hoeven Energy and Climate ChangemdashWorld EnergyOutlook Special Report International Energy Agency 2015
[2] P Jones S S Hou and X Li ldquoTowards zero carbon designin offices integrating smart facades ventilation and surfaceheating and coolingrdquoRenewable Energy vol 73 pp 69ndash76 2015
[3] W Pan ldquoSystem boundaries of zero carbon buildingsrdquo Renew-able and Sustainable Energy Reviews vol 37 pp 424ndash434 2014
[4] S Berry K Davidson and W Saman ldquoDefining zero carbonand zero energy homes from a performance-based regulatoryperspectiverdquo Energy Efficiency vol 7 no 2 pp 303ndash322 2014
[5] G P Hammond H A Harajli C I Jones and A B WinnettldquoWhole systems appraisal of a UK Building Integrated Photo-voltaic (BIPV) system energy environmental and economicevaluationsrdquo Energy Policy vol 40 no 1 pp 219ndash230 2012
[6] G A Keoleian and GM Lewis ldquoModeling the life cycle energyand environmental performance of amorphous silicon BIPVroofing in the USrdquo Renewable Energy vol 28 no 2 pp 271ndash2932003
[7] L Lu andHX Yang ldquoEnvironmental payback time analysis of aroof-mounted building-integrated photovoltaic (BIPV) systemin Hong Kongrdquo Applied Energy vol 87 no 12 pp 3625ndash36312010
[8] L Y Seng G Lalchand and G M Sow Lin ldquoEconomicalenvironmental and technical analysis of building integratedphotovoltaic systems in Malaysiardquo Energy Policy vol 36 no 6pp 2130ndash2142 2008
[9] M Oliver and T Jackson ldquoEnergy and economic evaluation ofbuilding-integrated photovoltaicsrdquo Energy vol 26 no 4 pp431ndash439 2001
[10] L Sabnani A Skumanich E Ryabova and R Noufi Devel-oping Market Opportunities for Flexible Rooftop Applicationsof PV Using Flexible CIGS Technology Market ConsiderationsNational Renewable Energy Laboratory (NREL) Golden ColoUSA 2011
[11] M A Green K Emery Y Hishikawa W Warta and E DDunlop ldquoSolar cell efficiency tables (version 47)rdquo Progress inPhotovoltaics Research and Applications vol 24 no 1 pp 3ndash112016
[12] G Y Yun M McEvoy and K Steemers ldquoDesign and overallenergy performance of a ventilated photovoltaic facaderdquo SolarEnergy vol 81 no 3 pp 383ndash394 2007
International Journal of Photoenergy 15
[13] PWWong Y ShimodaM NonakaM Inoue andMMizunoldquoSemi-transparent PV thermal performance power generationdaylight modelling and energy saving potential in a residentialapplicationrdquo Renewable Energy vol 33 no 5 pp 1024ndash10362008
[14] D H W Li T N T Lam W W H Chan and A H L MakldquoEnergy and cost analysis of semi-transparent photovoltaic inoffice buildingsrdquo Applied Energy vol 86 no 5 pp 722ndash7292009
[15] H Radhi ldquoEnergy analysis of facade-integrated photovoltaicsystems applied to UAE commercial buildingsrdquo Solar Energyvol 84 no 12 pp 2009ndash2021 2010
[16] E L Didone and A Wagner ldquoSemi-transparent PV windowsa study for office buildings in Brazilrdquo Energy and Buildings vol67 pp 136ndash142 2013
[17] P K Ng and N Mithraratne ldquoLifetime performance of semi-transparent building-integrated photovoltaic (BIPV) glazingsystems in the tropicsrdquo Renewable and Sustainable EnergyReviews vol 31 pp 736ndash745 2014
[18] C H Young Y L Chen and P C Chen ldquoHeat insulation solarglass and application on energy efficiency buildingsrdquo Energyand Buildings vol 78 pp 66ndash78 2014
[19] International Organization for Standardization ISO 9050 Glassin BuildingmdashDetermination of Light Transmittance Solar DirectTransmittance Total Solar Energy Transmittance UltravioletTransmittance and Related Glazing Factors International Orga-nization for Standardization Basel Switzerland 2003
[20] International Organization for Standardization ldquoISO10292glass in buildingmdashcalculation of steady-state U values (thermaltransmittance) of multiple glazingrdquo Tech Rep InternationalOrganization for Standardization Geneva Switzerland 1994
[21] International Standard ldquoThin-film terrestrial photovoltaic (pv)modulesmdashdesign qualification and type approvalrdquo IEC 616462008
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Inorganic ChemistryInternational Journal of
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International Journal ofPhotoenergy
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Carbohydrate Chemistry
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Journal of
Chemistry
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Advances in
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Analytical Methods in Chemistry
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Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
SpectroscopyInternational Journal of
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The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Medicinal ChemistryInternational Journal of
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Chromatography Research International
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Applied ChemistryJournal of
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Quantum Chemistry
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CatalystsJournal of
2 International Journal of Photoenergy
(BIPV) and this technology shows great potential for thedevelopment of more effective solar modules Theoreticallyas a BIPV module is combined with building materials itcan effectively reduce overall construction costs and is thusexpected to shorten the energy payback time (EPBT)
Researchers in many countries have been assessing thebenefits of this technology For example in the United King-dom Hammond et al [5] assessed a 21 kWp monocrystallinesilicon BIPV module applied to a roof and found thatits EPBT was 45 years The results also showed that theimplementation of a government program the ldquoLow CarbonBuilding Programmerdquo (or LCBP) would facilitate the eco-nomic benefits of this BIPV module and further shorten theEPBT In the United States Keoleian and Lewis [6] assesseda 2 kWp thin-film-type (120572-Si) BIPV module integrated witha roof They installed it in different regions from PortlandOregon to Phoenix Arizona to examine the EPBT with theresults showing that this lay between 339 and 552 years Luand Yang assessed a 22 kWp monocrystalline silicon BIPVmodule used on a roof and wall in Hong Kong When themodule was installed in different orientations on the wallits EPBT ranged from 71 years (the best scenario) to 200years (when themodule was installed on a vertical wall facingwest) [7] In Malaysia Seng et al [8] assessed 1 kWp BIPVmodules using different crystalline Si technologies namelymonocrystalline polycrystalline and thin-film-type 120572-Si inwhich the EPBTs were respectively 32ndash44 22ndash30 and 19ndash26 years In Europe Oliver and Jackson [9] integrated apolycrystalline silicon BIPV module into building walls andfound that its EPBT was 55 years All these works showthat BIPV modules have been widely studied and that manycountries are making efforts to reduce the overall cost ofinstallation in order to effectively reduce the EPBT as wellas achieve mass production and universalization
Compared to the nontransparent BIPVmodule the semi-transparent BIPV module with improved visible light trans-mission performance has attracted greater attention in recentyears When a semitransparent PV module is integratedinto building curtains efficient visible light transmission canreduce the energy consumption of indoor lighting With anappropriate design solar radiation can even be reflected in anindoor environment reducing building cooling energy usagedirectly and so effectively enhance the thermal and visualcomfort of a building To achieve visible light transmissionthis type of PV module mostly uses thin-film solar paneltechnology
Copper indium gallium selenide (CIGS) amorphoussilicon (a-Si) CdTe and organic solar cells are widely usedon the market Moreover CIGS solar cells have been used inbuilding-attached photovoltaics (BAPV) [10] However themanufacturing costs of CIGS solar cells are still relativelyhigher resulting in a greater EPBT Therefore recent studiestend to focus on a-Si thin-film-type solar panelsThemoduleefficiency of a-Si solar cell is currently around 10 [11] Dueto the single-junction structure of such cells they are unableto absorb the solar energy spectrum effectively and so have arelatively low photoelectric conversion efficiency Thereforemodern solar cell research has introduced dual-junction solarcells working in tandem (a-Si120583c-Si) which can widen the
range of the solar light absorption spectrum by modulatingthe energy gap through the structure of tandem-junctionmodule improving the sunlight-to-electrical-energy conver-sion efficiency The efficiency has now reached around 123of the energy of standard sunlight (1000Wm2) for thetandem-junction modules now available on the market[11] Although tandem-junction (a-Si120583c-Si) technology canincrease the power generation efficiency of a module itsefficiency is still lower than that of crystalline silicon-typeand CIGS solar cells Nevertheless the literature [6ndash9] showsthat the EPBTs of amorphous BIPV modules were shorterthan those of crystalline silicon BIPV modules because theconstruction costs of the latter are still too high
Therefore some a-Si120583c-Si manufacturers have movedtowards manufacturing BIPV modules in order to developa semitransparent PV module that can replace architecturalglass so that the building possesses good views and aes-thetics In the United Kingdom Yun et al [12] theoreticallyanalyzed vertical solar panel walls and then analyzed theeffects that different proportions of transparent windows andsolar panels had on the indoor comfort and visible lightutilizationThey reported that transparent windows coveringaround 50 to 60 of the entire wall would achieve thebest energy-saving effects in a building The literature thussuggests that using light transmission is essential to zerocarbon building design
In Japan Wong et al [13] applied a semitransparent PVmodule to the skylight of a building Under optimal con-ditions the semitransparent solar skylight allowed 50radiation transmission and could contribute a maximum of53 of indoor heating and cooling energy consumptionas compared to a roof design using only an opaque BIPVIn China Li et al [14] made a theoretical analysis of theapplication of semitransparent PV modules in offices Theirresults also showed that their application not only couldreduce energy usage for indoor lighting and air-conditioningequipment but also had a surplus electricity output whichwill be conducive to the development of net zero energybuildings In Saudi Arabia Radhi [15] conducted an analysisof semitransparent PVmodules applied to the south and westwalls of a buildingThe EPBTs lay between 12 and 13 years soin order to effectively develop PV modules it is necessary toconsider and design them as a whole
In Brazil Didone and Wagner [16] simulated the energy-saving performance of semitransparent thin-film PV mod-ules located in two different climates in Brazil and theGerman city of Frankfurt Their results showed that withproper control a semitransparent thin-film window can notonly save energy for indoor lighting and air conditioning butalso generate surplus electricity In 2014 Ng and Mithraratnereviewed the development of semitransparent PV modulesand studied six types of commercially obtainable thin-filmPV modules applied to office buildings in Singapore Theirstudy used a life cycle assessment (LCA) method to explorethe EPBTs carbon emissions and cost reductions The LCAmethod can be used to facilitate the design of a building [17]and the results showed that the application of a semitrans-parent PV module is more in line with the concept of zero
International Journal of Photoenergy 3
carbon building compared to the use of an opaque BIPVmodule Many studies have analyzed the energy efficiencyof semitransparent PV modules and attempted to reduce theEPBT with increasing the power generation ability being themain factor in this
In a previous study [18] our team combined a thin-film-type semitransparent PVmodule with a high-reflectivity heatinsulation film to develop a type of heat insulation solar glass(HISG) that simultaneously possesses power generation heatinsulation and energy-saving functions After sunlight passesthrough the semitransparent PVmodule the remaining lightsourcewill be reflected by the high-reflectivity heat insulationfilm to the back side of the semitransparent PV module sothat the module can once again absorb the reflected lightand have a higher power output Moreover because of themultilayered structure of the HISG the solar heat passingthrough the HISG can gradually be isolated in each layerof the material After the sunlight passes through the firstlayer (the semitransparent PV module) part of the energyis converted to electrical energy For the remaining radiantheat the high-reflectivity heat insulation film will effectivelyisolate the residual radiant heat and block the ultraviolet lightby 100
The structure of the dual air gaps can reduce the thermaltransmittance (119880-value) effectively isolating the conductedheat of the glass so that the heat cannot be conducted fromthe glass to the indoor environment and hence it has verygood insulation properties In terms of saving energy duringsummer since the shading coefficient of HISG is very low theheat of solar radiation cannot easily enter the building signif-icantly reducing the startup frequency of the air-conditioningcompressor and thus achieving reduced energy consumptionfor cooling During winter since the thermal transmittanceof the HISG is very low the glass has good isolation andinsulation performance so warm air can be kept inside theroom and cannot easily be dissipated achieving reducedenergy consumption for heatingThe functional principles ofthe HISG are described in Figure 1
In this research we adopt three different types of semi-transparent PV module technologies and combine threedifferent types of energy-saving films with high reflectanceto encapsulate HISG BIPV systems Subsequently we explorethe optical and thermal properties and overall power genera-tion effects and use simulation software to calculate the powergeneration and energy-saving effects of each HISG as appliedto actual buildings in Taiwan with a subtropical climate andin London England with a temperate climate
2 Methodology
21 Preparation of Heat Insulation Solar Glass The proposedHISGs are mainly composed of a thin-film-type semitrans-parent PV module high-reflectivity heat insulation film andrear glass HISG constructed in this study is a three-layerglazing systemThe first layer is a transparent PVmodule onthe back of which is a 04mm thick layer of high-reflectivityheat insulation film between two layers of spacers Rear glass
is placed behind the second spacer layer which forms anair gap on both sides of the high-reflectivity heat insulationfilm Three types of semitransparent PV module a tandemlaser module tandem transparent conducting oxide (TCO)module and a-Si TCO module were selected as the frontlayer of the HISG in this study The cell structure of thesemodules is illustrated in Figures 2(a) 2(b) and 2(c) In orderto study the effects of heat insulation films with differentreflectance values on the gains in power generation heatinsulation and energy-saving performance of the HISG thisstudy adopts three different types of Heat Mirror films withdifferent reflectance values
22 Tests of Optical and Thermal Properties Based on ISO9050 and ISO 10292 [19 20] a UVVisNIR spectrophotome-ter (Hitachi U4100) FTIR spectrometer (Thermo iS50) andthermal conductivity analyzer (TCi) are used to measurethe optical properties and thermal performance of the ninetypes of HISGs The optical properties include solar directtransmittance (300sim2500 nm) solar direct reflectance (300sim2500 nm) visible light transmittance (380sim780 nm) visiblelight reflectance (380sim780 nm) and ultraviolet light trans-mittance (300sim380 nm)The thermal performance propertiesinclude the solar heat gain coefficient (SHGC) shading coef-ficient (SC) and thermal transmittance (119880-value) Since theHISGs used in this study aremultilayer ones composed of twoor more sheets of flat glass individual measurements must bemade of every component during the optical measurementsThe related formulae in ISO 9050 were used to calculatethe overall optical and thermal performances The relevantformulae are as follows
221 Visible Light Transmittance 120591119881 and Reflectance 120588
119881 of
Triple Glazing The light transmittance 120591119881 and reflectance
120588119881 of each component are calculated using the following
formulae
120591119881=
sum780
380
119863120582times 119881 (120582) times 120591 (120582) times Δ120582
sum780
380
119863120582times 119881 (120582) times Δ120582
120588119881=
sum780
380
119863120582times 119881 (120582) times 120588 (120582) times Δ120582
sum780
380
119863120582times 119881 (120582) times Δ120582
(1)
where 119863120582is the relative spectral distribution of illuminant
D65 (see ISOCIE 10526) 120591(120582) is the spectral transmittance ofglazing 120588(120582) is the spectral reflectance of glazing119881(120582) is thespectral luminous efficiency for photopic vision defining thestandard observer for photometry and Δ120582 is the wavelengthinterval
In the case of multiple glazing the spectral transmittance120591(120582) and reflectance 120588(120582)will be obtained by calculation fromthe spectral characteristics of the individual componentsFor the spectral transmittance 120591(120582) and reflectance 120588(120582) asa function of the spectral characteristics of the individualcomponents of the unit the following formulae are obtained
4 International Journal of Photoenergy
SemitransparentPV module
High-reflectivityheat insulation film
Rear glass
Sunlight
Heat insulation
1st-timepower generation
2nd-timepower generation
(i) Enhance power generation(ii) Reduce heat penetration
(iii) Reduce Tsol SHGC SC value and U-value
(a)
High-reflectivityheat insulation film
Rear glass
2nd air gap
1st air gap
2nd steel spacer
1st steel spacer
Junction box
SemitransparentPV module
9mm 6mm 6mm 6mm
27mm
Structure of HISG
(b)
Figure 1 Functional principles and cross-sectional structure of heat insulation solar glass
Glass
TCO
a-Si
120583c-Si
Al
EVA
Glass
(a) Tandem laser module
Glass
TCO
EVA
Glass
TCO
a-Si
120583c-Si
(b) Tandem TCO module
Glass
TCO
a-Si
EVA
Glass
TCO
(c) a-Si TCO module
Figure 2 Cell structure of the tandem laser tandem TCO and a-Si TCO module
120591 (120582) =
1205911(120582) times 120591
2(120582) times 120591
3(120582)
[1 minus 1205882(120582) times 120588
1015840
1
(120582)] [1 minus 1205883(120582) times 120588
1015840
2
(120582)] minus 1205912
2
1205883(120582) times 120588
1015840
1
(120582)
120588 (120582) = 1205881(120582) +
1205912
1
(120582) times 1205882(120582) [1 minus 120588
1015840
2
(120582) times 1205883(120582)] + 120591
2
1
(120582) times 1205912
2
(120582) times 1205883(120582)
[1 minus 1205881015840
1
(120582) times 1205882(120582)] [1 minus 120588
1015840
2
(120582) times 1205883(120582)] minus 120591
2
2
times 1205881015840
1
(120582) times 1205881015840
3
(120582)
(2)
where 1205911(120582) is the spectral transmittance of the outer (first)
pane 1205912(120582) is the spectral transmittance of the second pane
1205913(120582) is the spectral transmittance of the third (inner) pane1205881(120582) is the spectral reflectance of the outer (first) pane
measured in the direction of incident radiation 12058810158401
(120582) is thespectral reflectance of the outer (first) pane measured in the
opposite direction of incident radiation 1205882(120582) is the spectral
reflectance of the second pane measured in the directionof incident radiation 1205881015840
2
(120582) is the spectral reflectance of thesecond pane measured in the opposite direction of incidentradiation 120588
3(120582) is the spectral reflectance of the third (inner)
pane measured in the direction of incident radiation 12058810158403
(120582) is
International Journal of Photoenergy 5
the spectral reflectance of the third (inner) pane measured inthe opposite direction of incident radiation
222 Solar Direct Transmittance 120591119890 and Reflectance 120588
119890 of
Triple Glazing Thesolar direct transmittance and reflectanceare obtained as follows
120591119890=
sum2500
780
119878120582times 120591 (120582) times Δ120582
sum2500
780
119878120582times Δ120582
120588119890=
sum2500
780
119878120582times 120588 (120582) times Δ120582
sum2500
780
119878120582times Δ120582
(3)
where 119878120582is the relative spectral distribution of the solar radi-
ation
223 UV Transmittance UV transmittance is obtained asfollows
120591119890=
sum380
300
119878120582times 120591 (120582) times Δ120582
sum380
300
119878120582times Δ120582
(4)
224 119880-Value Calculation The thermal transmittance ofglazing also known as the119880-value is the rate of heat transferthrough one squaremeter of glazing divided by the differencebetween the ambient temperatures on each side The methodspecified by ISO 10292 is based on a calculation from thefollowing equation
1
119880
=
1
ℎ119905
+
1
ℎ119890
+
1
ℎ119894
(5)
where ℎ119894is the interior heat transfer coefficient ℎ
119890is the
exterior heat transfer coefficient ℎ119905is the conductance of the
multiple glazing unit
225 Total Solar Energy Transmittance The total solarenergy transmittance (also known as solar heat gain coeffi-cient) is the sum of the solar direct transmittance 120591
119890and the
secondary heat transfer factor 119902119894towards the inside
119892 = 120591119890+ 119902119894 (6)
The secondary heat transfer factor results from heat transferby convection and longwave IR-radiation of that part of theincident solar radiation which has been absorbed by theglazingThe secondary heat transfer factor towards the insideof triple glazing is calculated using the following formula
119902119894
=
((1205721198901+ 1205721198902+ 1205721198903) ℎ119890+ (1205721198902+ 1205721198903) Λ12+ 1205721198903Λ23)
1ℎ119894+ 1ℎ119890+ 1Λ
12+ 1Λ
23
(7)
where 1205721198901is the solar direct absorptance of the outer (first)
pane within the triple glazing 1205721198902is the solar direct absorp-
tance of the second pane within the triple glazing 1205721198903is the
solar direct absorptance of the third pane of the triple glazingΛ12is the thermal conductance between the outer surface of
the outer (first) pane and the center of the second pane Λ23
is the thermal conductance between the center of the secondpane and the center of the third pane
226 Shading Coefficient (SC) The shading coefficient ofglass is a measure of the total amount of heat passing throughthe glazing compared with that through single clear glass Itis approximately equal to the SHGC divided by 087
23 Test of Gains in Power Generation Performance Tests ofthe gain in power generation were made based on the stan-dard test conditions (STC) in the test standard given by theInternational Electrotechnical Commission IEC 61646 [21]for a thin-film PV module in order to explore the powergeneration characteristics of the nine types ofHISGdescribedabove The effects of each combination of materials on thegain in power generation capacity of the semitransparent PVmodule were then analyzed and compared
24 Assessment of Energy-Saving Performance In this studyAutodesk Ecotect Analysis was adopted to conduct simula-tions of building power generation and energy by adoptingthe results of the power generation test optical test andthermal test as the material parameters and choosing Tainanin Taiwan and London in the United Kingdom as the simu-lated locations The simulation was used to obtain the powergeneration capacity and energy consumption performanceof the HISGs in real-world applications on buildings insubtropical and temperate regions
241 BuildingModel Ecotect was used in this study tomodela single building The building body consists of a roof andfour walls to form an enclosed space in order to facilitatethe simulation of air-conditioning energy consumption Themain body of the building is facing south The roof has amonopitched roof structure with an incline angle of 235∘ andis composed of 10 piecestimes 10 pieces giving a total of 100 piecesof PV modules with a size of approximately 14m times 11m Theoverall dimensions of the building body are approximately14m times 10m times 83m as illustrated in Figure 3
242 Setting Parameters for the Simulation In terms of thematerial parameters the four surrounding walls are definedas being constructed of composite materials (110mm brickoutside plus 75mm timber frame with 10mm plasterboardinside) with a 119880-value of 177WmK whereas values forthe material parameters of each PV module come from theresults of the power generation and optical and thermal testsin this paper For the air-conditioning energy consumptionthis study uses a mixed-mode air-conditioning system forcooling and heating The usage time is 24 hours the comforttemperature range is 20∘Cndash26∘C the startup temperaturesetting for a cold room is 26∘C and the startup temperaturesetting for a warm room is 18∘C The simulation of the air-conditioning energy consumption was conducted for a wholeyear
3 Results and Discussion
31 Optical Properties The transmittance and reflectancecoefficient versus wavelength of each component are shownin Figures 4 and 5 respectively Table 1 shows the optical
6 International Journal of Photoenergy
Table 1 Optical properties of each component and HISGs
ModuleItem
Solar directtransmittance
Solar directreflectance
Visible lighttransmittance
Visible lightreflectance
UVtransmittance
Tandem laser module 709 1007 84 527 001Tandem TCOmodule 1833 679 220 515 001a-Si TCO module 2349 730 435 512 001Heat insulation film A 6814 1688 9532 483 175Heat insulation film B 4063 3089 8412 601 136Heat insulation film C 3315 4071 6104 2233 100Rear glass 8115 504 8885 566 6239Tandem laser-A HISG 407 1017 723 535 0Tandem laser-B HISG 25 1024 639 535 0Tandem laser-C HISG 208 1030 478 545 0Tandem TCO-A HISG 1034 744 188 515 0Tandem TCO-B HISG 626 788 166 515 0Tandem TCO-C HISG 516 821 123 515 0a-Si TCO-A HISG 1326 837 372 514 0a-Si TCO-B HISG 803 909 329 514 0a-Si TCO-C HISG 662 964 243 517 0
1400m
833
m
1009m
1100m110m
395
m
140m
Figure 3 The 3D model of the building body
properties of each component based on ISO 9050The valuesof lighting transmittance for the three PV modules were inthe 709ndash2349 range and those for the three heat insulationfilms were in the range of 3315ndash6814 The measurementresults show that the tandem lasermodule and heat insulationfilm C had better heat insulation effects They could thusbe used in hot climates where there is a need to reducesolar heat transmission especially in buildings where largetransparent surfaces are fitted Furthermore the tandem lasermodule and heat insulation filmA had better visibilities eventhoughwith the former the back-contact electrodematerial isopaque Part of the power-generating layers and back-contactelectrode layer in the tandem laser module were removed
using a transverse laser cutting method to enable the moduleto be light-transmissible It is also worth noting that the lowervisible light transmittance in other modules is mainly due toabsorption of the TCO layers The UV transmittances of thePVmodule and heat insulation film are less than 2meaningthat the performances of the HISGs with regard to isolatingUV light were very good
In the cell structure of the tandem TCO module thematerials of the power-generating layers are the same as thoseof the tandem laser module but in terms of the back-contactelectrode a TCO material with good light transmission andconduction properties was adopted Though TCO has highoptical transparency it does decrease light transmission fromUV to IR Therefore the tandem TCO module has a light-transmissible property and its insulation of solar thermalenergy is poorer than that of the tandem laser module Inaddition as the color of transmitted light tends to be winered part of its visible light transmittance was poorer Thematerial of the rear electrode in the cell structure of the a-Si TCO module was the same as that of the tandem TCOmoduleAs such it also has a light-transmissible property andthe transmitted light color tends to be orange red Howeverin the power-generating layer the a-Si TCO module had asingle-layer structure without a layer of 120583c-Si so its visiblelight transmittance was slightly better than that of the tandemTCOmodule Furthermore as it has no 120583c-Si layer to absorbthe solar light its solar radiation transmittance was slightlypoorer than that of the tandem TCOmodule
As shown in Figure 6 the measurement results for thesolar direct transmittance indicated that the addition ofa reflective layer reduces the transmittance of HISGs Forthe tandem laser tandem TCO and a-Si TCO modulethe solar direct transmittance was originally 709 1833
International Journal of Photoenergy 7
0
10
20
30
40
50Tr
ansm
ittan
ce (
)
Wavelength (nm)
Tandem laser moduleTandem TCO modulea-Si TCO module
300 600 900 1200 1500 1800 2100 2400
(a)
0
10
20
30
40
50
60
70
80
90
100
Tran
smitt
ance
()
Wavelength (nm)300 600 900 1200 1500 1800 2100 2400
Heat insulation film AHeat insulation film BHeat insulation film C
(b)
0
20
40
60
80
100
Tran
smitt
ance
()
Wavelength (nm)500 1000 1500 2000 2500
Glass
(c)
Figure 4 Transmittance spectra of each component (a) semitransparent PV module (b) heat insulation film and (c) rear glass
and 2349 but after being encapsulated into the HISGit dropped to 208ndash407 516ndash1034 and 662ndash1326respectively The visible light transmittance was originally84 22 and 435 but after being encapsulated into theHISG it dropped to 478ndash723 123ndash188 and 243ndash372respectively
After the various semitransparent PVmodules were inte-grated into the HISG with the various heat insulation filmsall their solar direct reflectance values increased slightly sothe encapsulationwas slightly beneficial to the heat insulatingeffect of the HISGs Moreover after being encapsulated intothe HISGs the effects on the visible light reflectance were allless severe falling to around 5 Therefore the HISGs willnot necessarily cause environmental light pollution
With regard to the UV transmittance since most of theUV light is absorbed by the semitransparent PV moduleand the heat insulation film the UV transmittance valuesof all the HISGs are 0 This means that the UV isolationperformances are very good and able to protect interiorfurnishings from aging and the skin from damage caused byUV radiation
32 Thermal Properties The surface emissivity of an objectrefers to its ability to release heat via thermal radiation afterabsorbing solar radiation The surface emissivity of eachcomponent is thus an important parameter affecting the heatinsulation performance of a HISG In this paper the spectralreflectance of each component on the exterior and interior
8 International Journal of Photoenergy
02468
101214161820222426
Refle
ctan
ce (
)
Wavelength (nm)
Tandem laser moduleTandem TCO modulea-Si TCO module
300 600 900 1200 1500 1800 2100 2400
(a)
0
10
20
30
40
50
60
70
Refle
ctan
ce (
)
Wavelength (nm)300 600 900 1200 1500 1800 2100 2400
Heat insulation film AHeat insulation film BHeat insulation film C
(b)
0
10
20
30
40
50
60
70
80
90
100
Refle
ctan
ce (
)
Wavelength (nm)
Glass
300 600 900 1200 1500 1800 2100 2400
(c)
Figure 5 Reflectance spectra of each component (a) semitransparent PV modules (b) heat insulation films and (c) rear glass
sides was measured using FTIR and then the emissivityvalue of each component was obtained by ISO 10292 asshown in Table 2 It can be seen that as the surfaces ofthe semitransparent PV modules and rear glass were not allcoated by a film the emissivity values for the exterior andinterior sides were 084 While the heat insulation filmswere mainly composed of PET material there was no filmcoating the interior surface of the film so the emissivityvalues were all 076 Meanwhile the exterior surfaces of theheat insulation films all had a multilayer metal coating sothe surface emissivity values were lower than the surfaceemissivity values on the indoor side The surface emissivity
of heat insulation film C is 0033 which is thus categorized asa Low-E film
Table 3 shows the thermal performances of the three typesof PVmodules and the nine types of HISGs with the SHGCsshading coefficients and overall heat transfer coefficients (119880-values) The results indicate that the multilayer structureof the HISG reduced the solar direct transmittance andsince the heat insulation films were coated with transparentmetal films this reflected the solar radiation heat promptingthe SHGCs to be reduced to half the levels seen with thesemitransparent PVmodulesThismeans that the quantity ofsolar radiation heat passing through the HISG was half that
International Journal of Photoenergy 9
0
2
4
6
8
10
12
545
478
103
208
535
639
1024
25
535
723
1017
407
00 0001
527
84
1007
709
UV
tran
smitt
ance
Visib
le li
ght
refle
ctan
ce
Visib
le li
ght
tran
smitt
ance
Sola
r rad
iatio
nre
flect
ance
Sola
r rad
iatio
ntr
ansm
ittan
ce
Tran
smitt
ance
and
refle
ctan
ce (
)
Tandem laser moduleTandem laser-A HISG
Tandem laser-B HISGTandem laser-C HISG
(a)
0
2
4
6
8
10
12
14
16
18
20
0 00001
515515515515
123166
18822
821788744
679516
626
1034
1833
UV
tran
smitt
ance
Visib
le li
ght
refle
ctan
ce
Visib
le li
ght
tran
smitt
ance
Sola
r rad
iatio
nre
flect
ance
Sola
r rad
iatio
ntr
ansm
ittan
ce
Tran
smitt
ance
and
refle
ctan
ce (
)Tandem TCO moduleTandem TCO-A HISG
Tandem TCO-B HISGTandem TCO-C HISG
(b)
02468
101214161820222426
000001
517514
514512
243329
372435
964909
83773
662803
1326
2349
UV
tran
smitt
ance
Visib
le li
ght
refle
ctan
ce
Visib
le li
ght
tran
smitt
ance
Sola
r rad
iatio
nre
flect
ance
Sola
r rad
iatio
ntr
ansm
ittan
ce
Tran
smitt
ance
and
refle
ctan
ce (
)
a-Si TCO modulea-Si TCO-A HISG
a-Si TCO-B HISGa-Si TCO-C HISG
(c)
Figure 6 Optical properties of the HISGs (a) tandem laser module (b) tandem TCOmodule and (c) a-Si TCO module
passing through the semitransparent PV modules In termsof the 119880-value since all the semitransparent PV moduleswere assembled with 4mm times 4mm laminated glass the 119880-values based on ISO 10292 for all modules were 563Wm2-K The addition of heat insulation films and dual air gaps toform a multilayer structure greatly reduced the 119880-values oftheHISGs (1755Wm2-Kndash1824Wm2-K)Moreover havingheat insulation films with different emissivity values is one
of the main causes of the decline in the 119880-value Since heatinsulation film C had the lowest surface emissivity theHISGs assembled using film C also possessed lower119880-values(1755Wm2-K)
33 Power Generation Gain Performance The power genera-tion test results for the front and back sides of each semitrans-parent PV module are shown in Table 4 The measurement
10 International Journal of Photoenergy
Table 2 Emissivity of each component
Item Emissivity ofindoor side
Emissivity ofoutdoor side
Tandem laser module 084 084Tandem TCOmodule 084 084a-Si TCO module 084 084Heat insulation film A 076 0135Heat insulation film B 076 0045Heat insulation film C 076 0033Rear glass 084 084
Table 3Thermal properties of the semitransparent PVmodules andHISGs
ModuleItem
SHGC Shadingcoefficient 119880-value
Tandem lasermodule 03 0345 563
Tandem laser-AHISG 0151 0174 1824
Tandem laser-BHISG 0135 0155 1757
Tandem laser-CHISG 0129 0148 1755
Tandem TCOmodule 038 0437 563
Tandem TCO-AHISG 0218 025 1824
Tandem TCO-BHISG 0184 0211 1757
Tandem TCO-CHISG 0171 0196 1755
a-Si TCOmodule 041 0471 563
a-Si TCO-AHISG 0249 0286 1824
a-Si TCO-BHISG 0207 0238 1757
a-Si TCO-CHISG 019 0218 1755
results show that the power output for the front side of thetandem laser module was 126029W with an efficiency of8184 while that of the back side was only 1019W Thereason for this is the cell structure of the tandem lasermoduleas the bottom back-contact conductive layer is Al whichdoes not possess power generation characteristicsThereforeafter being illuminated by direct light there should not be apower generation effect However because the tandem lasermodule was subjected to transverse laser cutting during themanufacturing process light can pass through from the backsideThe light could then undergo refraction or transmissionat the rear glass so some of the light is able to enter the power-generating layer from the laser cut slits and so the back side
Table 4 Results of tests of electrical characteristics in STC for initialstates of the original transparent PV module (a) front side and (b)back side
(a)
Test itemTandemlaser
module
TandemTCO
module
a-SiTCO
moduleModule efficiency () 8184 811 778Maximum power output(W) 126029 124843 119796
Open circuit voltage (V) 167382 171629 111606Short circuit current (A) 1133 1038 1595Maximum voltage (V) 131026 140561 86939Maximum electric current(A) 0962 0888 1378
Fill factor 06644 07008 06731
(b)
Test itemTandemlaser
module
TandemTCO
module
a-SiTCO
moduleModule efficiency () 0066 0723 5361Maximum power output(W) 1019 11134 82566
Open circuit voltage (V) 109965 156555 108648Short circuit current (A) 0026 0108 1213Maximum voltage (V) 40348 132561 83918Maximum electric current(A) 0025 0084 0984
Fill factor 03506 06576 06264
of the tandem laser module also possesses a slight powergeneration effect
The power output of the front side of the tandem TCOmodule was 124843W with an efficiency of 811 whereasthat of the back side was only 11134W The reason why theefficiency from back-side illumination is low is due to lightabsorption in the lower bandgap 120583c-Si cell which allowslimited light into the a-Si cell The current output would belimited by the smaller current value from the a-Si and so alower efficiency is generated
The front-side power output of the a-Si TCOmodule was119796W with an efficiency of 778 whereas the back-sidepower output of the a-Si TCO module reached 82566WThe power-generating layer of the a-Si TCO module is thea-Si layer which is also classified as a cell structure withdual-surface power generation characteristics so the back-side power output was higher compared to that of the formertwo modules However the reason for the difference in thefront-side and back-side power outputs of the a-Si TCOmodule is that the materials of the front and rear glasswere different The front glass was ultraclear glass with morethan 90 visible light transmittance Meanwhile in orderto increase the loading strength of the BIPV the rear glasswas mostly tempered glass or heat-strengthened glass with
International Journal of Photoenergy 11
lower transmissivity In addition before entering the power-generating layer from the back side the light still needs to passthrough a layer of EVA plastic film which will also reduce thesolar irradianceThe back-side power output of the a-Si TCOmodule was thus only 69 of the front-side power output
The results of the electrical tests of each semitransparentPV module and each combination of HISGs are shown inTable 5 The results for power generation gain are shownin Table 6 The experimental results indicated that boththe power generation and efficiency of tandem laser HISGexhibited slightly increasing trends the power generationincreased by around 001ndash013 and the efficiency increasedby around 0001ndash001 However the power generationand efficiency of tandem TCO HISG and a-Si TCO HISGdisplayed increasing trends For the tandem TCO HISGthe power generation improved by around 327ndash1006 andthe efficiency increased by around 027ndash082 For the a-SiTCOHISG the power generation increased by around 094ndash307 and the efficiency increased by around 007ndash024The power-generating layer of the tandem TCOmodule is a-Si120583c-Si but that of the a-Si TCO module is a single layer ofa-Si The absorption spectrum of the tandem TCO module(300 nmndash1100 nm) is wider than that of the a-Si TCOmodule(300 nmndash750 nm) The back side of the tandem TCO HISGcan thus absorb higher effective irradiance than the a-Si TCOHISG This means that the efficiency enhanced rate of thetandemTCOHISG is higher than that of the a-Si TCOHISGIt is also worth noting that selecting an appropriate heatinsulation film in order to absorb a larger amount of reflectivesolar radiation by the back side of theHISG can lead to greaterenhancement of power generation
34 Simulation of Energy-Saving Performance The simula-tion results for the power generation of each HISG installedin the buildings and the energy consumption of the heatingventilation and air-conditioning (HVAC) system are shownin Table 7 As Tainan is located in a subtropical region inTaiwan where there is sufficient sunlight the annual powergeneration of each module was higher than that of themodules in London and the power outputs ranged between16328 kW and 18727 kW London is located in a temperatezone with mostly cloudy weather and thus the annual powergeneration only ranged between 8493 kWand 9741 kWTheseresults show that different climate zones andweather patternsare the main factors affecting the power generation of BIPVmodules
The simulation results in Table 7 also show that the poweroutputs of each HISG were larger than those of the originalsemitransparent PV modules That is the power enhance-ments of the tandem laser HISG were around 001ndash012those of the tandem TCO HISG were around 327ndash1006and those of the a-Si TCO HISG were around 094ndash307The simulated results also reveal that the percentage gainsin power generation for each HISG installed on the roofs ofbuildings as BIPV roofs are consistent with the experimentalresults under STC from IEC 61646 Therefore adding heatinsulation films onto semitransparent PV modules to forma HISG in order to enhance the power output of the modulesis beneficial in reducing the EPBT of the entire BIPV system
The simulation results for the energy consumption of theHVAC systems of buildings in Tainan Taiwan and LondonUK are shown in Tables 8 and 9 respectively As Tainan islocated in a subtropical region the use of a heater is lesscommon and the HVAC system is mostly used for coolingso the energy consumption for the latter is much higher thanthat for heating On the other hand London is located in atemperate region and the HVAC system is mainly used forheating so the energy consumption for this is much higherthan that for cooling
Furthermore the main factors affecting the energy con-sumption of theHVAC system are the shading coefficient andthe 119880-value of the envelope The shading coefficient and 119880-value of each HISG are lower than those of the semitrans-parent PV modules During summer solar radiation cannotenter the room easily through the HISG so cooling energycan be saved During winter the 119880-value of the HISG isvery low owing to the multilayer structure and althoughsolar radiation cannot enter the room easily the heat will beretained inside the room and will not dissipate easily andhence the amount of energy used for heating can also bereduced Therefore the simulation results for the HISGs allindicate greater energy-saving performance in the annualenergy consumption of the HVAC system The results showthat the HISG can save 2911ndash3219 of cooling energy 4734ndash4815 of heating energy and 3268ndash3575 of the totalenergy consumption of the HVAC system in subtropicalregions and 3727ndash4412 of cooling energy 3905ndash3986 ofheating energy and 3905ndash3986 of total energy consump-tion of the HVAC system in temperate regions Among all theHISGs the HISG encapsulated version using heat insulationfilm C had the best energy-saving performance
As seen in the simulation results given above the HISGcan not only enhance the power generation but also becauseof the better heat insulation performance shorten the EPBTof the entire HISG BIPV application on a building
4 Conclusion
The concepts of net zero energy zero energy and passiveenergy are becoming more important as part of the energyconservation policies adopted by the construction industryBIPV technology currently has great potential for effectivedevelopment of solar module techniques Theoretically if aBIPV module is combined with building materials it caneffectively reduce overall construction costs save energymodulate the indoor temperature and shorten the energypayback time (EPBT)
In this work the authors adopted three different types ofsemitransparent PV modules and combined three differenttypes of high-reflectivity films to encapsulate HISG BIPVsystems The optical and thermal properties and the overallpower generation effects of each HISG were investigated Inaddition Autodesk software was used to calculate the powergeneration and energy-saving effects of each HISG as appliedto actual buildings in Taiwan with a subtropical climate andEngland with a temperate climate As a result due to thethree-layer structure of the HISGwith a high-reflectivity heatinsulation film the heat insulation performance (SHGC and
12 International Journal of Photoenergy
Table5Testresults
forthe
vario
usBIPV
mod
ules
andHISGsu
nder
STC
Testitem
Tand
emlaser
mod
ule
Tand
emlaser-A
HISG
Tand
emlaser-BHISG
Tand
emlaser-CHISG
Tand
emTC
Omod
ule
Tand
emTC
O-A
HISG
Tand
emTC
O-B
HISG
Tand
emTC
O-C
HISG
a-SiTC
Omod
ule
a-Si
TCO-A
HISG
a-SiTC
O-B
HISG
a-Si
TCO-C
HISG
Efficiency
()
8184
8185
8189
8194
811
837
874
892
778
785
787
802
Maxim
umpo
wer
output
(W)
126029
12604
2126105
126187
124843
128926
134658
137399
119796
120921
121125
123475
Opencircuit
voltage
(V)
1673
821672
531672
81167313
1716
291716
441718
86172036
1116
061115
971116
131117
10
Shortcirc
uit
current(A)
1133
1134
1133
1134
1038
1074
1125
1150
1595
1612
1615
1650
Maxim
umvoltage
(V)
1310
261294
33130098
1292
07140561
1391
73138796
138027
86939
8733
787341
84561
Maxim
umele
ctric
current(A)
0962
0974
0969
0977
0888
0926
0970
0995
1378
1385
1387
1460
Fillfactor
066
44066
4606654
06651
07008
06996
06964
06944
06731
06721
06719
06698
International Journal of Photoenergy 13
Table 6 Results of power generation gain tests of the semitransparent PV modules and each combination of HISG under STC
ModuleItem
Power generation (W) Power generationenhancement () Module efficiency () Module efficiency
enhancement ()Tandem laser module 126029 mdash 8184 mdashTandem laser-A HISG 126042 001 8185 0001Tandem laser-B HISG 126105 006 8189 0005Tandem laser-C HISG 126187 013 8194 0010Tandem TCOmodule 124843 mdash 811 mdashTandem TCO-A HISG 128926 327 837 027Tandem TCO-B HISG 134658 786 874 064Tandem TCO-C HISG 137399 1006 892 082a-Si TCO module 119796 mdash 778 mdasha-Si TCO-A HISG 120921 094 785 007a-Si TCO-B HISG 121125 111 787 009a-Si TCO-C HISG 123475 307 802 024
Table 7 Power generation results for building body simulations
Module LocationTainan Taiwan (kW) Power enhancement () London UK (kW) Power enhancement ()
Tandem laser module 17178 mdash 8935 mdashTandem laser-A HISG 17179 001 8936 001Tandem laser-B HISG 17188 006 8940 006Tandem laser-C HISG 17199 012 8946 012Tandem TCOmodule 17016 mdash 8851 mdashTandem TCO-A HISG 17573 327 9141 327Tandem TCO-B HISG 18354 786 9547 786Tandem TCO-C HISG 18727 1006 9741 1006a-Si TCO module 16328 mdash 8493 mdasha-Si TCO-A HISG 16481 094 8573 094a-Si TCO-B HISG 16509 111 8587 111a-Si TCO-C HISG 16830 307 8754 307
Table 8 Simulation results for energy consumption of HVAC systems for the building body in the Tainan region of Taiwan
Module Cooling energyconsumption (kW)
Cooling energysaving ()
Heating energyconsumption
(kW)
Heating energysaving ()
Total HVAC systemenergy consumption
(kW)
Total HVACenergy saving
()Tandem laser module 28632 mdash 6924 mdash 35556 mdashTandem laser-A HISG 20296 2911 3639 4744 23935 3268Tandem laser-B HISG 20053 2996 3590 4815 23643 3350Tandem laser-C HISG 19958 3029 3591 4814 23549 3377Tandem TCOmodule 29495 mdash 6894 mdash 36390 mdashTandem TCO-A HISG 20793 2950 3623 4745 24415 3291Tandem TCO-B HISG 20412 3080 3576 4813 23988 3408Tandem TCO-C HISG 20201 3151 3583 4803 23784 3464a-Si TCO module 30368 mdash 6869 mdash 37236 mdasha-Si TCO-A HISG 20952 3101 3617 4734 24569 3402a-Si TCO-B HISG 20593 3219 3568 4806 24161 3511a-Si TCO-C HISG 20347 3300 3577 4793 23924 3575
14 International Journal of Photoenergy
Table 9 Simulation results for energy consumption of HVAC systems for the building body in London UK
ModuleCooling energyconsumption
(kW)
Cooling energysaving ()
Heating energyconsumption
(kW)
Heating energysaving ()
Total HVAC system energyconsumption (kW)
Total HVACenergy saving
()Tandem laser module 306 mdash 116818 mdash 117123 mdashTandem laser-A HISG 181 4085 71203 3905 71384 3905Tandem laser-B HISG 171 4412 70570 3959 70741 3960Tandem laser-C HISG 173 4346 70491 3966 70664 3967Tandem TCOmodule 271 mdash 117612 mdash 117883 mdashTandem TCO-A HISG 170 3727 71497 3921 71667 3920Tandem TCO-B HISG 164 3948 70753 3984 70917 3984Tandem TCO-C HISG 165 3911 70734 3986 70899 3986a-Si TCO module 287 mdash 117214 mdash 117501 mdasha-Si TCO-A HISG 175 3902 71273 3919 71448 3919a-Si TCO-B HISG 172 4007 70640 3973 70812 3973a-Si TCO-C HISG 171 4042 70566 3980 70737 3980
119880-value) showed an improvement Although the multilayerstructure of HISG would affect the visible light transmit-tance in practice it does not have a significant impact onthe view through the glass Moreover although the solardirect reflectance values all showed improving trends thevisible light reflectance was only around 5 which will notnecessarily cause environmental light pollution Comparedto the original modules the power generation and moduleefficiency of all HISGs were found to have increased Of allthe combinations of HISGs the gain in power generation ofthe tandem TCO-C HISG was the highest as the power gen-eration was improved by 1006 and the module efficiencywas improved by 082The results of the simulation showeda very similar trendwith regard to the level of electrical powergeneration based on experimental data that was obtainedusing the standard test conditions (STC) for measurementcontained in IEC 61646The simulation results also indicatedthat theHISG has a significant effect on the amount of energythat can be saved when using the HVAC system in bothsubtropical and temperate regions
This paper thus provides valuable information for renew-able energy planners and architectural designers who areinterested in using HISG BIPV systems
Competing Interests
The authors declare that there are no competing interestsregarding the publication of this paper
Acknowledgments
This study was supported by the Ministry of Science andTechnology of Taiwan under Projects MOST 105-3113-F-011-001 and MOST 105-3113-E-006-006-CC2
References
[1] M van der Hoeven Energy and Climate ChangemdashWorld EnergyOutlook Special Report International Energy Agency 2015
[2] P Jones S S Hou and X Li ldquoTowards zero carbon designin offices integrating smart facades ventilation and surfaceheating and coolingrdquoRenewable Energy vol 73 pp 69ndash76 2015
[3] W Pan ldquoSystem boundaries of zero carbon buildingsrdquo Renew-able and Sustainable Energy Reviews vol 37 pp 424ndash434 2014
[4] S Berry K Davidson and W Saman ldquoDefining zero carbonand zero energy homes from a performance-based regulatoryperspectiverdquo Energy Efficiency vol 7 no 2 pp 303ndash322 2014
[5] G P Hammond H A Harajli C I Jones and A B WinnettldquoWhole systems appraisal of a UK Building Integrated Photo-voltaic (BIPV) system energy environmental and economicevaluationsrdquo Energy Policy vol 40 no 1 pp 219ndash230 2012
[6] G A Keoleian and GM Lewis ldquoModeling the life cycle energyand environmental performance of amorphous silicon BIPVroofing in the USrdquo Renewable Energy vol 28 no 2 pp 271ndash2932003
[7] L Lu andHX Yang ldquoEnvironmental payback time analysis of aroof-mounted building-integrated photovoltaic (BIPV) systemin Hong Kongrdquo Applied Energy vol 87 no 12 pp 3625ndash36312010
[8] L Y Seng G Lalchand and G M Sow Lin ldquoEconomicalenvironmental and technical analysis of building integratedphotovoltaic systems in Malaysiardquo Energy Policy vol 36 no 6pp 2130ndash2142 2008
[9] M Oliver and T Jackson ldquoEnergy and economic evaluation ofbuilding-integrated photovoltaicsrdquo Energy vol 26 no 4 pp431ndash439 2001
[10] L Sabnani A Skumanich E Ryabova and R Noufi Devel-oping Market Opportunities for Flexible Rooftop Applicationsof PV Using Flexible CIGS Technology Market ConsiderationsNational Renewable Energy Laboratory (NREL) Golden ColoUSA 2011
[11] M A Green K Emery Y Hishikawa W Warta and E DDunlop ldquoSolar cell efficiency tables (version 47)rdquo Progress inPhotovoltaics Research and Applications vol 24 no 1 pp 3ndash112016
[12] G Y Yun M McEvoy and K Steemers ldquoDesign and overallenergy performance of a ventilated photovoltaic facaderdquo SolarEnergy vol 81 no 3 pp 383ndash394 2007
International Journal of Photoenergy 15
[13] PWWong Y ShimodaM NonakaM Inoue andMMizunoldquoSemi-transparent PV thermal performance power generationdaylight modelling and energy saving potential in a residentialapplicationrdquo Renewable Energy vol 33 no 5 pp 1024ndash10362008
[14] D H W Li T N T Lam W W H Chan and A H L MakldquoEnergy and cost analysis of semi-transparent photovoltaic inoffice buildingsrdquo Applied Energy vol 86 no 5 pp 722ndash7292009
[15] H Radhi ldquoEnergy analysis of facade-integrated photovoltaicsystems applied to UAE commercial buildingsrdquo Solar Energyvol 84 no 12 pp 2009ndash2021 2010
[16] E L Didone and A Wagner ldquoSemi-transparent PV windowsa study for office buildings in Brazilrdquo Energy and Buildings vol67 pp 136ndash142 2013
[17] P K Ng and N Mithraratne ldquoLifetime performance of semi-transparent building-integrated photovoltaic (BIPV) glazingsystems in the tropicsrdquo Renewable and Sustainable EnergyReviews vol 31 pp 736ndash745 2014
[18] C H Young Y L Chen and P C Chen ldquoHeat insulation solarglass and application on energy efficiency buildingsrdquo Energyand Buildings vol 78 pp 66ndash78 2014
[19] International Organization for Standardization ISO 9050 Glassin BuildingmdashDetermination of Light Transmittance Solar DirectTransmittance Total Solar Energy Transmittance UltravioletTransmittance and Related Glazing Factors International Orga-nization for Standardization Basel Switzerland 2003
[20] International Organization for Standardization ldquoISO10292glass in buildingmdashcalculation of steady-state U values (thermaltransmittance) of multiple glazingrdquo Tech Rep InternationalOrganization for Standardization Geneva Switzerland 1994
[21] International Standard ldquoThin-film terrestrial photovoltaic (pv)modulesmdashdesign qualification and type approvalrdquo IEC 616462008
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Inorganic ChemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Carbohydrate Chemistry
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
Physical Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom
Analytical Methods in Chemistry
Journal of
Volume 2014
Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
SpectroscopyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Medicinal ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chromatography Research International
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Applied ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Theoretical ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Spectroscopy
Analytical ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Quantum Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Organic Chemistry International
ElectrochemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CatalystsJournal of
International Journal of Photoenergy 3
carbon building compared to the use of an opaque BIPVmodule Many studies have analyzed the energy efficiencyof semitransparent PV modules and attempted to reduce theEPBT with increasing the power generation ability being themain factor in this
In a previous study [18] our team combined a thin-film-type semitransparent PVmodule with a high-reflectivity heatinsulation film to develop a type of heat insulation solar glass(HISG) that simultaneously possesses power generation heatinsulation and energy-saving functions After sunlight passesthrough the semitransparent PVmodule the remaining lightsourcewill be reflected by the high-reflectivity heat insulationfilm to the back side of the semitransparent PV module sothat the module can once again absorb the reflected lightand have a higher power output Moreover because of themultilayered structure of the HISG the solar heat passingthrough the HISG can gradually be isolated in each layerof the material After the sunlight passes through the firstlayer (the semitransparent PV module) part of the energyis converted to electrical energy For the remaining radiantheat the high-reflectivity heat insulation film will effectivelyisolate the residual radiant heat and block the ultraviolet lightby 100
The structure of the dual air gaps can reduce the thermaltransmittance (119880-value) effectively isolating the conductedheat of the glass so that the heat cannot be conducted fromthe glass to the indoor environment and hence it has verygood insulation properties In terms of saving energy duringsummer since the shading coefficient of HISG is very low theheat of solar radiation cannot easily enter the building signif-icantly reducing the startup frequency of the air-conditioningcompressor and thus achieving reduced energy consumptionfor cooling During winter since the thermal transmittanceof the HISG is very low the glass has good isolation andinsulation performance so warm air can be kept inside theroom and cannot easily be dissipated achieving reducedenergy consumption for heatingThe functional principles ofthe HISG are described in Figure 1
In this research we adopt three different types of semi-transparent PV module technologies and combine threedifferent types of energy-saving films with high reflectanceto encapsulate HISG BIPV systems Subsequently we explorethe optical and thermal properties and overall power genera-tion effects and use simulation software to calculate the powergeneration and energy-saving effects of each HISG as appliedto actual buildings in Taiwan with a subtropical climate andin London England with a temperate climate
2 Methodology
21 Preparation of Heat Insulation Solar Glass The proposedHISGs are mainly composed of a thin-film-type semitrans-parent PV module high-reflectivity heat insulation film andrear glass HISG constructed in this study is a three-layerglazing systemThe first layer is a transparent PVmodule onthe back of which is a 04mm thick layer of high-reflectivityheat insulation film between two layers of spacers Rear glass
is placed behind the second spacer layer which forms anair gap on both sides of the high-reflectivity heat insulationfilm Three types of semitransparent PV module a tandemlaser module tandem transparent conducting oxide (TCO)module and a-Si TCO module were selected as the frontlayer of the HISG in this study The cell structure of thesemodules is illustrated in Figures 2(a) 2(b) and 2(c) In orderto study the effects of heat insulation films with differentreflectance values on the gains in power generation heatinsulation and energy-saving performance of the HISG thisstudy adopts three different types of Heat Mirror films withdifferent reflectance values
22 Tests of Optical and Thermal Properties Based on ISO9050 and ISO 10292 [19 20] a UVVisNIR spectrophotome-ter (Hitachi U4100) FTIR spectrometer (Thermo iS50) andthermal conductivity analyzer (TCi) are used to measurethe optical properties and thermal performance of the ninetypes of HISGs The optical properties include solar directtransmittance (300sim2500 nm) solar direct reflectance (300sim2500 nm) visible light transmittance (380sim780 nm) visiblelight reflectance (380sim780 nm) and ultraviolet light trans-mittance (300sim380 nm)The thermal performance propertiesinclude the solar heat gain coefficient (SHGC) shading coef-ficient (SC) and thermal transmittance (119880-value) Since theHISGs used in this study aremultilayer ones composed of twoor more sheets of flat glass individual measurements must bemade of every component during the optical measurementsThe related formulae in ISO 9050 were used to calculatethe overall optical and thermal performances The relevantformulae are as follows
221 Visible Light Transmittance 120591119881 and Reflectance 120588
119881 of
Triple Glazing The light transmittance 120591119881 and reflectance
120588119881 of each component are calculated using the following
formulae
120591119881=
sum780
380
119863120582times 119881 (120582) times 120591 (120582) times Δ120582
sum780
380
119863120582times 119881 (120582) times Δ120582
120588119881=
sum780
380
119863120582times 119881 (120582) times 120588 (120582) times Δ120582
sum780
380
119863120582times 119881 (120582) times Δ120582
(1)
where 119863120582is the relative spectral distribution of illuminant
D65 (see ISOCIE 10526) 120591(120582) is the spectral transmittance ofglazing 120588(120582) is the spectral reflectance of glazing119881(120582) is thespectral luminous efficiency for photopic vision defining thestandard observer for photometry and Δ120582 is the wavelengthinterval
In the case of multiple glazing the spectral transmittance120591(120582) and reflectance 120588(120582)will be obtained by calculation fromthe spectral characteristics of the individual componentsFor the spectral transmittance 120591(120582) and reflectance 120588(120582) asa function of the spectral characteristics of the individualcomponents of the unit the following formulae are obtained
4 International Journal of Photoenergy
SemitransparentPV module
High-reflectivityheat insulation film
Rear glass
Sunlight
Heat insulation
1st-timepower generation
2nd-timepower generation
(i) Enhance power generation(ii) Reduce heat penetration
(iii) Reduce Tsol SHGC SC value and U-value
(a)
High-reflectivityheat insulation film
Rear glass
2nd air gap
1st air gap
2nd steel spacer
1st steel spacer
Junction box
SemitransparentPV module
9mm 6mm 6mm 6mm
27mm
Structure of HISG
(b)
Figure 1 Functional principles and cross-sectional structure of heat insulation solar glass
Glass
TCO
a-Si
120583c-Si
Al
EVA
Glass
(a) Tandem laser module
Glass
TCO
EVA
Glass
TCO
a-Si
120583c-Si
(b) Tandem TCO module
Glass
TCO
a-Si
EVA
Glass
TCO
(c) a-Si TCO module
Figure 2 Cell structure of the tandem laser tandem TCO and a-Si TCO module
120591 (120582) =
1205911(120582) times 120591
2(120582) times 120591
3(120582)
[1 minus 1205882(120582) times 120588
1015840
1
(120582)] [1 minus 1205883(120582) times 120588
1015840
2
(120582)] minus 1205912
2
1205883(120582) times 120588
1015840
1
(120582)
120588 (120582) = 1205881(120582) +
1205912
1
(120582) times 1205882(120582) [1 minus 120588
1015840
2
(120582) times 1205883(120582)] + 120591
2
1
(120582) times 1205912
2
(120582) times 1205883(120582)
[1 minus 1205881015840
1
(120582) times 1205882(120582)] [1 minus 120588
1015840
2
(120582) times 1205883(120582)] minus 120591
2
2
times 1205881015840
1
(120582) times 1205881015840
3
(120582)
(2)
where 1205911(120582) is the spectral transmittance of the outer (first)
pane 1205912(120582) is the spectral transmittance of the second pane
1205913(120582) is the spectral transmittance of the third (inner) pane1205881(120582) is the spectral reflectance of the outer (first) pane
measured in the direction of incident radiation 12058810158401
(120582) is thespectral reflectance of the outer (first) pane measured in the
opposite direction of incident radiation 1205882(120582) is the spectral
reflectance of the second pane measured in the directionof incident radiation 1205881015840
2
(120582) is the spectral reflectance of thesecond pane measured in the opposite direction of incidentradiation 120588
3(120582) is the spectral reflectance of the third (inner)
pane measured in the direction of incident radiation 12058810158403
(120582) is
International Journal of Photoenergy 5
the spectral reflectance of the third (inner) pane measured inthe opposite direction of incident radiation
222 Solar Direct Transmittance 120591119890 and Reflectance 120588
119890 of
Triple Glazing Thesolar direct transmittance and reflectanceare obtained as follows
120591119890=
sum2500
780
119878120582times 120591 (120582) times Δ120582
sum2500
780
119878120582times Δ120582
120588119890=
sum2500
780
119878120582times 120588 (120582) times Δ120582
sum2500
780
119878120582times Δ120582
(3)
where 119878120582is the relative spectral distribution of the solar radi-
ation
223 UV Transmittance UV transmittance is obtained asfollows
120591119890=
sum380
300
119878120582times 120591 (120582) times Δ120582
sum380
300
119878120582times Δ120582
(4)
224 119880-Value Calculation The thermal transmittance ofglazing also known as the119880-value is the rate of heat transferthrough one squaremeter of glazing divided by the differencebetween the ambient temperatures on each side The methodspecified by ISO 10292 is based on a calculation from thefollowing equation
1
119880
=
1
ℎ119905
+
1
ℎ119890
+
1
ℎ119894
(5)
where ℎ119894is the interior heat transfer coefficient ℎ
119890is the
exterior heat transfer coefficient ℎ119905is the conductance of the
multiple glazing unit
225 Total Solar Energy Transmittance The total solarenergy transmittance (also known as solar heat gain coeffi-cient) is the sum of the solar direct transmittance 120591
119890and the
secondary heat transfer factor 119902119894towards the inside
119892 = 120591119890+ 119902119894 (6)
The secondary heat transfer factor results from heat transferby convection and longwave IR-radiation of that part of theincident solar radiation which has been absorbed by theglazingThe secondary heat transfer factor towards the insideof triple glazing is calculated using the following formula
119902119894
=
((1205721198901+ 1205721198902+ 1205721198903) ℎ119890+ (1205721198902+ 1205721198903) Λ12+ 1205721198903Λ23)
1ℎ119894+ 1ℎ119890+ 1Λ
12+ 1Λ
23
(7)
where 1205721198901is the solar direct absorptance of the outer (first)
pane within the triple glazing 1205721198902is the solar direct absorp-
tance of the second pane within the triple glazing 1205721198903is the
solar direct absorptance of the third pane of the triple glazingΛ12is the thermal conductance between the outer surface of
the outer (first) pane and the center of the second pane Λ23
is the thermal conductance between the center of the secondpane and the center of the third pane
226 Shading Coefficient (SC) The shading coefficient ofglass is a measure of the total amount of heat passing throughthe glazing compared with that through single clear glass Itis approximately equal to the SHGC divided by 087
23 Test of Gains in Power Generation Performance Tests ofthe gain in power generation were made based on the stan-dard test conditions (STC) in the test standard given by theInternational Electrotechnical Commission IEC 61646 [21]for a thin-film PV module in order to explore the powergeneration characteristics of the nine types ofHISGdescribedabove The effects of each combination of materials on thegain in power generation capacity of the semitransparent PVmodule were then analyzed and compared
24 Assessment of Energy-Saving Performance In this studyAutodesk Ecotect Analysis was adopted to conduct simula-tions of building power generation and energy by adoptingthe results of the power generation test optical test andthermal test as the material parameters and choosing Tainanin Taiwan and London in the United Kingdom as the simu-lated locations The simulation was used to obtain the powergeneration capacity and energy consumption performanceof the HISGs in real-world applications on buildings insubtropical and temperate regions
241 BuildingModel Ecotect was used in this study tomodela single building The building body consists of a roof andfour walls to form an enclosed space in order to facilitatethe simulation of air-conditioning energy consumption Themain body of the building is facing south The roof has amonopitched roof structure with an incline angle of 235∘ andis composed of 10 piecestimes 10 pieces giving a total of 100 piecesof PV modules with a size of approximately 14m times 11m Theoverall dimensions of the building body are approximately14m times 10m times 83m as illustrated in Figure 3
242 Setting Parameters for the Simulation In terms of thematerial parameters the four surrounding walls are definedas being constructed of composite materials (110mm brickoutside plus 75mm timber frame with 10mm plasterboardinside) with a 119880-value of 177WmK whereas values forthe material parameters of each PV module come from theresults of the power generation and optical and thermal testsin this paper For the air-conditioning energy consumptionthis study uses a mixed-mode air-conditioning system forcooling and heating The usage time is 24 hours the comforttemperature range is 20∘Cndash26∘C the startup temperaturesetting for a cold room is 26∘C and the startup temperaturesetting for a warm room is 18∘C The simulation of the air-conditioning energy consumption was conducted for a wholeyear
3 Results and Discussion
31 Optical Properties The transmittance and reflectancecoefficient versus wavelength of each component are shownin Figures 4 and 5 respectively Table 1 shows the optical
6 International Journal of Photoenergy
Table 1 Optical properties of each component and HISGs
ModuleItem
Solar directtransmittance
Solar directreflectance
Visible lighttransmittance
Visible lightreflectance
UVtransmittance
Tandem laser module 709 1007 84 527 001Tandem TCOmodule 1833 679 220 515 001a-Si TCO module 2349 730 435 512 001Heat insulation film A 6814 1688 9532 483 175Heat insulation film B 4063 3089 8412 601 136Heat insulation film C 3315 4071 6104 2233 100Rear glass 8115 504 8885 566 6239Tandem laser-A HISG 407 1017 723 535 0Tandem laser-B HISG 25 1024 639 535 0Tandem laser-C HISG 208 1030 478 545 0Tandem TCO-A HISG 1034 744 188 515 0Tandem TCO-B HISG 626 788 166 515 0Tandem TCO-C HISG 516 821 123 515 0a-Si TCO-A HISG 1326 837 372 514 0a-Si TCO-B HISG 803 909 329 514 0a-Si TCO-C HISG 662 964 243 517 0
1400m
833
m
1009m
1100m110m
395
m
140m
Figure 3 The 3D model of the building body
properties of each component based on ISO 9050The valuesof lighting transmittance for the three PV modules were inthe 709ndash2349 range and those for the three heat insulationfilms were in the range of 3315ndash6814 The measurementresults show that the tandem lasermodule and heat insulationfilm C had better heat insulation effects They could thusbe used in hot climates where there is a need to reducesolar heat transmission especially in buildings where largetransparent surfaces are fitted Furthermore the tandem lasermodule and heat insulation filmA had better visibilities eventhoughwith the former the back-contact electrodematerial isopaque Part of the power-generating layers and back-contactelectrode layer in the tandem laser module were removed
using a transverse laser cutting method to enable the moduleto be light-transmissible It is also worth noting that the lowervisible light transmittance in other modules is mainly due toabsorption of the TCO layers The UV transmittances of thePVmodule and heat insulation film are less than 2meaningthat the performances of the HISGs with regard to isolatingUV light were very good
In the cell structure of the tandem TCO module thematerials of the power-generating layers are the same as thoseof the tandem laser module but in terms of the back-contactelectrode a TCO material with good light transmission andconduction properties was adopted Though TCO has highoptical transparency it does decrease light transmission fromUV to IR Therefore the tandem TCO module has a light-transmissible property and its insulation of solar thermalenergy is poorer than that of the tandem laser module Inaddition as the color of transmitted light tends to be winered part of its visible light transmittance was poorer Thematerial of the rear electrode in the cell structure of the a-Si TCO module was the same as that of the tandem TCOmoduleAs such it also has a light-transmissible property andthe transmitted light color tends to be orange red Howeverin the power-generating layer the a-Si TCO module had asingle-layer structure without a layer of 120583c-Si so its visiblelight transmittance was slightly better than that of the tandemTCOmodule Furthermore as it has no 120583c-Si layer to absorbthe solar light its solar radiation transmittance was slightlypoorer than that of the tandem TCOmodule
As shown in Figure 6 the measurement results for thesolar direct transmittance indicated that the addition ofa reflective layer reduces the transmittance of HISGs Forthe tandem laser tandem TCO and a-Si TCO modulethe solar direct transmittance was originally 709 1833
International Journal of Photoenergy 7
0
10
20
30
40
50Tr
ansm
ittan
ce (
)
Wavelength (nm)
Tandem laser moduleTandem TCO modulea-Si TCO module
300 600 900 1200 1500 1800 2100 2400
(a)
0
10
20
30
40
50
60
70
80
90
100
Tran
smitt
ance
()
Wavelength (nm)300 600 900 1200 1500 1800 2100 2400
Heat insulation film AHeat insulation film BHeat insulation film C
(b)
0
20
40
60
80
100
Tran
smitt
ance
()
Wavelength (nm)500 1000 1500 2000 2500
Glass
(c)
Figure 4 Transmittance spectra of each component (a) semitransparent PV module (b) heat insulation film and (c) rear glass
and 2349 but after being encapsulated into the HISGit dropped to 208ndash407 516ndash1034 and 662ndash1326respectively The visible light transmittance was originally84 22 and 435 but after being encapsulated into theHISG it dropped to 478ndash723 123ndash188 and 243ndash372respectively
After the various semitransparent PVmodules were inte-grated into the HISG with the various heat insulation filmsall their solar direct reflectance values increased slightly sothe encapsulationwas slightly beneficial to the heat insulatingeffect of the HISGs Moreover after being encapsulated intothe HISGs the effects on the visible light reflectance were allless severe falling to around 5 Therefore the HISGs willnot necessarily cause environmental light pollution
With regard to the UV transmittance since most of theUV light is absorbed by the semitransparent PV moduleand the heat insulation film the UV transmittance valuesof all the HISGs are 0 This means that the UV isolationperformances are very good and able to protect interiorfurnishings from aging and the skin from damage caused byUV radiation
32 Thermal Properties The surface emissivity of an objectrefers to its ability to release heat via thermal radiation afterabsorbing solar radiation The surface emissivity of eachcomponent is thus an important parameter affecting the heatinsulation performance of a HISG In this paper the spectralreflectance of each component on the exterior and interior
8 International Journal of Photoenergy
02468
101214161820222426
Refle
ctan
ce (
)
Wavelength (nm)
Tandem laser moduleTandem TCO modulea-Si TCO module
300 600 900 1200 1500 1800 2100 2400
(a)
0
10
20
30
40
50
60
70
Refle
ctan
ce (
)
Wavelength (nm)300 600 900 1200 1500 1800 2100 2400
Heat insulation film AHeat insulation film BHeat insulation film C
(b)
0
10
20
30
40
50
60
70
80
90
100
Refle
ctan
ce (
)
Wavelength (nm)
Glass
300 600 900 1200 1500 1800 2100 2400
(c)
Figure 5 Reflectance spectra of each component (a) semitransparent PV modules (b) heat insulation films and (c) rear glass
sides was measured using FTIR and then the emissivityvalue of each component was obtained by ISO 10292 asshown in Table 2 It can be seen that as the surfaces ofthe semitransparent PV modules and rear glass were not allcoated by a film the emissivity values for the exterior andinterior sides were 084 While the heat insulation filmswere mainly composed of PET material there was no filmcoating the interior surface of the film so the emissivityvalues were all 076 Meanwhile the exterior surfaces of theheat insulation films all had a multilayer metal coating sothe surface emissivity values were lower than the surfaceemissivity values on the indoor side The surface emissivity
of heat insulation film C is 0033 which is thus categorized asa Low-E film
Table 3 shows the thermal performances of the three typesof PVmodules and the nine types of HISGs with the SHGCsshading coefficients and overall heat transfer coefficients (119880-values) The results indicate that the multilayer structureof the HISG reduced the solar direct transmittance andsince the heat insulation films were coated with transparentmetal films this reflected the solar radiation heat promptingthe SHGCs to be reduced to half the levels seen with thesemitransparent PVmodulesThismeans that the quantity ofsolar radiation heat passing through the HISG was half that
International Journal of Photoenergy 9
0
2
4
6
8
10
12
545
478
103
208
535
639
1024
25
535
723
1017
407
00 0001
527
84
1007
709
UV
tran
smitt
ance
Visib
le li
ght
refle
ctan
ce
Visib
le li
ght
tran
smitt
ance
Sola
r rad
iatio
nre
flect
ance
Sola
r rad
iatio
ntr
ansm
ittan
ce
Tran
smitt
ance
and
refle
ctan
ce (
)
Tandem laser moduleTandem laser-A HISG
Tandem laser-B HISGTandem laser-C HISG
(a)
0
2
4
6
8
10
12
14
16
18
20
0 00001
515515515515
123166
18822
821788744
679516
626
1034
1833
UV
tran
smitt
ance
Visib
le li
ght
refle
ctan
ce
Visib
le li
ght
tran
smitt
ance
Sola
r rad
iatio
nre
flect
ance
Sola
r rad
iatio
ntr
ansm
ittan
ce
Tran
smitt
ance
and
refle
ctan
ce (
)Tandem TCO moduleTandem TCO-A HISG
Tandem TCO-B HISGTandem TCO-C HISG
(b)
02468
101214161820222426
000001
517514
514512
243329
372435
964909
83773
662803
1326
2349
UV
tran
smitt
ance
Visib
le li
ght
refle
ctan
ce
Visib
le li
ght
tran
smitt
ance
Sola
r rad
iatio
nre
flect
ance
Sola
r rad
iatio
ntr
ansm
ittan
ce
Tran
smitt
ance
and
refle
ctan
ce (
)
a-Si TCO modulea-Si TCO-A HISG
a-Si TCO-B HISGa-Si TCO-C HISG
(c)
Figure 6 Optical properties of the HISGs (a) tandem laser module (b) tandem TCOmodule and (c) a-Si TCO module
passing through the semitransparent PV modules In termsof the 119880-value since all the semitransparent PV moduleswere assembled with 4mm times 4mm laminated glass the 119880-values based on ISO 10292 for all modules were 563Wm2-K The addition of heat insulation films and dual air gaps toform a multilayer structure greatly reduced the 119880-values oftheHISGs (1755Wm2-Kndash1824Wm2-K)Moreover havingheat insulation films with different emissivity values is one
of the main causes of the decline in the 119880-value Since heatinsulation film C had the lowest surface emissivity theHISGs assembled using film C also possessed lower119880-values(1755Wm2-K)
33 Power Generation Gain Performance The power genera-tion test results for the front and back sides of each semitrans-parent PV module are shown in Table 4 The measurement
10 International Journal of Photoenergy
Table 2 Emissivity of each component
Item Emissivity ofindoor side
Emissivity ofoutdoor side
Tandem laser module 084 084Tandem TCOmodule 084 084a-Si TCO module 084 084Heat insulation film A 076 0135Heat insulation film B 076 0045Heat insulation film C 076 0033Rear glass 084 084
Table 3Thermal properties of the semitransparent PVmodules andHISGs
ModuleItem
SHGC Shadingcoefficient 119880-value
Tandem lasermodule 03 0345 563
Tandem laser-AHISG 0151 0174 1824
Tandem laser-BHISG 0135 0155 1757
Tandem laser-CHISG 0129 0148 1755
Tandem TCOmodule 038 0437 563
Tandem TCO-AHISG 0218 025 1824
Tandem TCO-BHISG 0184 0211 1757
Tandem TCO-CHISG 0171 0196 1755
a-Si TCOmodule 041 0471 563
a-Si TCO-AHISG 0249 0286 1824
a-Si TCO-BHISG 0207 0238 1757
a-Si TCO-CHISG 019 0218 1755
results show that the power output for the front side of thetandem laser module was 126029W with an efficiency of8184 while that of the back side was only 1019W Thereason for this is the cell structure of the tandem lasermoduleas the bottom back-contact conductive layer is Al whichdoes not possess power generation characteristicsThereforeafter being illuminated by direct light there should not be apower generation effect However because the tandem lasermodule was subjected to transverse laser cutting during themanufacturing process light can pass through from the backsideThe light could then undergo refraction or transmissionat the rear glass so some of the light is able to enter the power-generating layer from the laser cut slits and so the back side
Table 4 Results of tests of electrical characteristics in STC for initialstates of the original transparent PV module (a) front side and (b)back side
(a)
Test itemTandemlaser
module
TandemTCO
module
a-SiTCO
moduleModule efficiency () 8184 811 778Maximum power output(W) 126029 124843 119796
Open circuit voltage (V) 167382 171629 111606Short circuit current (A) 1133 1038 1595Maximum voltage (V) 131026 140561 86939Maximum electric current(A) 0962 0888 1378
Fill factor 06644 07008 06731
(b)
Test itemTandemlaser
module
TandemTCO
module
a-SiTCO
moduleModule efficiency () 0066 0723 5361Maximum power output(W) 1019 11134 82566
Open circuit voltage (V) 109965 156555 108648Short circuit current (A) 0026 0108 1213Maximum voltage (V) 40348 132561 83918Maximum electric current(A) 0025 0084 0984
Fill factor 03506 06576 06264
of the tandem laser module also possesses a slight powergeneration effect
The power output of the front side of the tandem TCOmodule was 124843W with an efficiency of 811 whereasthat of the back side was only 11134W The reason why theefficiency from back-side illumination is low is due to lightabsorption in the lower bandgap 120583c-Si cell which allowslimited light into the a-Si cell The current output would belimited by the smaller current value from the a-Si and so alower efficiency is generated
The front-side power output of the a-Si TCOmodule was119796W with an efficiency of 778 whereas the back-sidepower output of the a-Si TCO module reached 82566WThe power-generating layer of the a-Si TCO module is thea-Si layer which is also classified as a cell structure withdual-surface power generation characteristics so the back-side power output was higher compared to that of the formertwo modules However the reason for the difference in thefront-side and back-side power outputs of the a-Si TCOmodule is that the materials of the front and rear glasswere different The front glass was ultraclear glass with morethan 90 visible light transmittance Meanwhile in orderto increase the loading strength of the BIPV the rear glasswas mostly tempered glass or heat-strengthened glass with
International Journal of Photoenergy 11
lower transmissivity In addition before entering the power-generating layer from the back side the light still needs to passthrough a layer of EVA plastic film which will also reduce thesolar irradianceThe back-side power output of the a-Si TCOmodule was thus only 69 of the front-side power output
The results of the electrical tests of each semitransparentPV module and each combination of HISGs are shown inTable 5 The results for power generation gain are shownin Table 6 The experimental results indicated that boththe power generation and efficiency of tandem laser HISGexhibited slightly increasing trends the power generationincreased by around 001ndash013 and the efficiency increasedby around 0001ndash001 However the power generationand efficiency of tandem TCO HISG and a-Si TCO HISGdisplayed increasing trends For the tandem TCO HISGthe power generation improved by around 327ndash1006 andthe efficiency increased by around 027ndash082 For the a-SiTCOHISG the power generation increased by around 094ndash307 and the efficiency increased by around 007ndash024The power-generating layer of the tandem TCOmodule is a-Si120583c-Si but that of the a-Si TCO module is a single layer ofa-Si The absorption spectrum of the tandem TCO module(300 nmndash1100 nm) is wider than that of the a-Si TCOmodule(300 nmndash750 nm) The back side of the tandem TCO HISGcan thus absorb higher effective irradiance than the a-Si TCOHISG This means that the efficiency enhanced rate of thetandemTCOHISG is higher than that of the a-Si TCOHISGIt is also worth noting that selecting an appropriate heatinsulation film in order to absorb a larger amount of reflectivesolar radiation by the back side of theHISG can lead to greaterenhancement of power generation
34 Simulation of Energy-Saving Performance The simula-tion results for the power generation of each HISG installedin the buildings and the energy consumption of the heatingventilation and air-conditioning (HVAC) system are shownin Table 7 As Tainan is located in a subtropical region inTaiwan where there is sufficient sunlight the annual powergeneration of each module was higher than that of themodules in London and the power outputs ranged between16328 kW and 18727 kW London is located in a temperatezone with mostly cloudy weather and thus the annual powergeneration only ranged between 8493 kWand 9741 kWTheseresults show that different climate zones andweather patternsare the main factors affecting the power generation of BIPVmodules
The simulation results in Table 7 also show that the poweroutputs of each HISG were larger than those of the originalsemitransparent PV modules That is the power enhance-ments of the tandem laser HISG were around 001ndash012those of the tandem TCO HISG were around 327ndash1006and those of the a-Si TCO HISG were around 094ndash307The simulated results also reveal that the percentage gainsin power generation for each HISG installed on the roofs ofbuildings as BIPV roofs are consistent with the experimentalresults under STC from IEC 61646 Therefore adding heatinsulation films onto semitransparent PV modules to forma HISG in order to enhance the power output of the modulesis beneficial in reducing the EPBT of the entire BIPV system
The simulation results for the energy consumption of theHVAC systems of buildings in Tainan Taiwan and LondonUK are shown in Tables 8 and 9 respectively As Tainan islocated in a subtropical region the use of a heater is lesscommon and the HVAC system is mostly used for coolingso the energy consumption for the latter is much higher thanthat for heating On the other hand London is located in atemperate region and the HVAC system is mainly used forheating so the energy consumption for this is much higherthan that for cooling
Furthermore the main factors affecting the energy con-sumption of theHVAC system are the shading coefficient andthe 119880-value of the envelope The shading coefficient and 119880-value of each HISG are lower than those of the semitrans-parent PV modules During summer solar radiation cannotenter the room easily through the HISG so cooling energycan be saved During winter the 119880-value of the HISG isvery low owing to the multilayer structure and althoughsolar radiation cannot enter the room easily the heat will beretained inside the room and will not dissipate easily andhence the amount of energy used for heating can also bereduced Therefore the simulation results for the HISGs allindicate greater energy-saving performance in the annualenergy consumption of the HVAC system The results showthat the HISG can save 2911ndash3219 of cooling energy 4734ndash4815 of heating energy and 3268ndash3575 of the totalenergy consumption of the HVAC system in subtropicalregions and 3727ndash4412 of cooling energy 3905ndash3986 ofheating energy and 3905ndash3986 of total energy consump-tion of the HVAC system in temperate regions Among all theHISGs the HISG encapsulated version using heat insulationfilm C had the best energy-saving performance
As seen in the simulation results given above the HISGcan not only enhance the power generation but also becauseof the better heat insulation performance shorten the EPBTof the entire HISG BIPV application on a building
4 Conclusion
The concepts of net zero energy zero energy and passiveenergy are becoming more important as part of the energyconservation policies adopted by the construction industryBIPV technology currently has great potential for effectivedevelopment of solar module techniques Theoretically if aBIPV module is combined with building materials it caneffectively reduce overall construction costs save energymodulate the indoor temperature and shorten the energypayback time (EPBT)
In this work the authors adopted three different types ofsemitransparent PV modules and combined three differenttypes of high-reflectivity films to encapsulate HISG BIPVsystems The optical and thermal properties and the overallpower generation effects of each HISG were investigated Inaddition Autodesk software was used to calculate the powergeneration and energy-saving effects of each HISG as appliedto actual buildings in Taiwan with a subtropical climate andEngland with a temperate climate As a result due to thethree-layer structure of the HISGwith a high-reflectivity heatinsulation film the heat insulation performance (SHGC and
12 International Journal of Photoenergy
Table5Testresults
forthe
vario
usBIPV
mod
ules
andHISGsu
nder
STC
Testitem
Tand
emlaser
mod
ule
Tand
emlaser-A
HISG
Tand
emlaser-BHISG
Tand
emlaser-CHISG
Tand
emTC
Omod
ule
Tand
emTC
O-A
HISG
Tand
emTC
O-B
HISG
Tand
emTC
O-C
HISG
a-SiTC
Omod
ule
a-Si
TCO-A
HISG
a-SiTC
O-B
HISG
a-Si
TCO-C
HISG
Efficiency
()
8184
8185
8189
8194
811
837
874
892
778
785
787
802
Maxim
umpo
wer
output
(W)
126029
12604
2126105
126187
124843
128926
134658
137399
119796
120921
121125
123475
Opencircuit
voltage
(V)
1673
821672
531672
81167313
1716
291716
441718
86172036
1116
061115
971116
131117
10
Shortcirc
uit
current(A)
1133
1134
1133
1134
1038
1074
1125
1150
1595
1612
1615
1650
Maxim
umvoltage
(V)
1310
261294
33130098
1292
07140561
1391
73138796
138027
86939
8733
787341
84561
Maxim
umele
ctric
current(A)
0962
0974
0969
0977
0888
0926
0970
0995
1378
1385
1387
1460
Fillfactor
066
44066
4606654
06651
07008
06996
06964
06944
06731
06721
06719
06698
International Journal of Photoenergy 13
Table 6 Results of power generation gain tests of the semitransparent PV modules and each combination of HISG under STC
ModuleItem
Power generation (W) Power generationenhancement () Module efficiency () Module efficiency
enhancement ()Tandem laser module 126029 mdash 8184 mdashTandem laser-A HISG 126042 001 8185 0001Tandem laser-B HISG 126105 006 8189 0005Tandem laser-C HISG 126187 013 8194 0010Tandem TCOmodule 124843 mdash 811 mdashTandem TCO-A HISG 128926 327 837 027Tandem TCO-B HISG 134658 786 874 064Tandem TCO-C HISG 137399 1006 892 082a-Si TCO module 119796 mdash 778 mdasha-Si TCO-A HISG 120921 094 785 007a-Si TCO-B HISG 121125 111 787 009a-Si TCO-C HISG 123475 307 802 024
Table 7 Power generation results for building body simulations
Module LocationTainan Taiwan (kW) Power enhancement () London UK (kW) Power enhancement ()
Tandem laser module 17178 mdash 8935 mdashTandem laser-A HISG 17179 001 8936 001Tandem laser-B HISG 17188 006 8940 006Tandem laser-C HISG 17199 012 8946 012Tandem TCOmodule 17016 mdash 8851 mdashTandem TCO-A HISG 17573 327 9141 327Tandem TCO-B HISG 18354 786 9547 786Tandem TCO-C HISG 18727 1006 9741 1006a-Si TCO module 16328 mdash 8493 mdasha-Si TCO-A HISG 16481 094 8573 094a-Si TCO-B HISG 16509 111 8587 111a-Si TCO-C HISG 16830 307 8754 307
Table 8 Simulation results for energy consumption of HVAC systems for the building body in the Tainan region of Taiwan
Module Cooling energyconsumption (kW)
Cooling energysaving ()
Heating energyconsumption
(kW)
Heating energysaving ()
Total HVAC systemenergy consumption
(kW)
Total HVACenergy saving
()Tandem laser module 28632 mdash 6924 mdash 35556 mdashTandem laser-A HISG 20296 2911 3639 4744 23935 3268Tandem laser-B HISG 20053 2996 3590 4815 23643 3350Tandem laser-C HISG 19958 3029 3591 4814 23549 3377Tandem TCOmodule 29495 mdash 6894 mdash 36390 mdashTandem TCO-A HISG 20793 2950 3623 4745 24415 3291Tandem TCO-B HISG 20412 3080 3576 4813 23988 3408Tandem TCO-C HISG 20201 3151 3583 4803 23784 3464a-Si TCO module 30368 mdash 6869 mdash 37236 mdasha-Si TCO-A HISG 20952 3101 3617 4734 24569 3402a-Si TCO-B HISG 20593 3219 3568 4806 24161 3511a-Si TCO-C HISG 20347 3300 3577 4793 23924 3575
14 International Journal of Photoenergy
Table 9 Simulation results for energy consumption of HVAC systems for the building body in London UK
ModuleCooling energyconsumption
(kW)
Cooling energysaving ()
Heating energyconsumption
(kW)
Heating energysaving ()
Total HVAC system energyconsumption (kW)
Total HVACenergy saving
()Tandem laser module 306 mdash 116818 mdash 117123 mdashTandem laser-A HISG 181 4085 71203 3905 71384 3905Tandem laser-B HISG 171 4412 70570 3959 70741 3960Tandem laser-C HISG 173 4346 70491 3966 70664 3967Tandem TCOmodule 271 mdash 117612 mdash 117883 mdashTandem TCO-A HISG 170 3727 71497 3921 71667 3920Tandem TCO-B HISG 164 3948 70753 3984 70917 3984Tandem TCO-C HISG 165 3911 70734 3986 70899 3986a-Si TCO module 287 mdash 117214 mdash 117501 mdasha-Si TCO-A HISG 175 3902 71273 3919 71448 3919a-Si TCO-B HISG 172 4007 70640 3973 70812 3973a-Si TCO-C HISG 171 4042 70566 3980 70737 3980
119880-value) showed an improvement Although the multilayerstructure of HISG would affect the visible light transmit-tance in practice it does not have a significant impact onthe view through the glass Moreover although the solardirect reflectance values all showed improving trends thevisible light reflectance was only around 5 which will notnecessarily cause environmental light pollution Comparedto the original modules the power generation and moduleefficiency of all HISGs were found to have increased Of allthe combinations of HISGs the gain in power generation ofthe tandem TCO-C HISG was the highest as the power gen-eration was improved by 1006 and the module efficiencywas improved by 082The results of the simulation showeda very similar trendwith regard to the level of electrical powergeneration based on experimental data that was obtainedusing the standard test conditions (STC) for measurementcontained in IEC 61646The simulation results also indicatedthat theHISG has a significant effect on the amount of energythat can be saved when using the HVAC system in bothsubtropical and temperate regions
This paper thus provides valuable information for renew-able energy planners and architectural designers who areinterested in using HISG BIPV systems
Competing Interests
The authors declare that there are no competing interestsregarding the publication of this paper
Acknowledgments
This study was supported by the Ministry of Science andTechnology of Taiwan under Projects MOST 105-3113-F-011-001 and MOST 105-3113-E-006-006-CC2
References
[1] M van der Hoeven Energy and Climate ChangemdashWorld EnergyOutlook Special Report International Energy Agency 2015
[2] P Jones S S Hou and X Li ldquoTowards zero carbon designin offices integrating smart facades ventilation and surfaceheating and coolingrdquoRenewable Energy vol 73 pp 69ndash76 2015
[3] W Pan ldquoSystem boundaries of zero carbon buildingsrdquo Renew-able and Sustainable Energy Reviews vol 37 pp 424ndash434 2014
[4] S Berry K Davidson and W Saman ldquoDefining zero carbonand zero energy homes from a performance-based regulatoryperspectiverdquo Energy Efficiency vol 7 no 2 pp 303ndash322 2014
[5] G P Hammond H A Harajli C I Jones and A B WinnettldquoWhole systems appraisal of a UK Building Integrated Photo-voltaic (BIPV) system energy environmental and economicevaluationsrdquo Energy Policy vol 40 no 1 pp 219ndash230 2012
[6] G A Keoleian and GM Lewis ldquoModeling the life cycle energyand environmental performance of amorphous silicon BIPVroofing in the USrdquo Renewable Energy vol 28 no 2 pp 271ndash2932003
[7] L Lu andHX Yang ldquoEnvironmental payback time analysis of aroof-mounted building-integrated photovoltaic (BIPV) systemin Hong Kongrdquo Applied Energy vol 87 no 12 pp 3625ndash36312010
[8] L Y Seng G Lalchand and G M Sow Lin ldquoEconomicalenvironmental and technical analysis of building integratedphotovoltaic systems in Malaysiardquo Energy Policy vol 36 no 6pp 2130ndash2142 2008
[9] M Oliver and T Jackson ldquoEnergy and economic evaluation ofbuilding-integrated photovoltaicsrdquo Energy vol 26 no 4 pp431ndash439 2001
[10] L Sabnani A Skumanich E Ryabova and R Noufi Devel-oping Market Opportunities for Flexible Rooftop Applicationsof PV Using Flexible CIGS Technology Market ConsiderationsNational Renewable Energy Laboratory (NREL) Golden ColoUSA 2011
[11] M A Green K Emery Y Hishikawa W Warta and E DDunlop ldquoSolar cell efficiency tables (version 47)rdquo Progress inPhotovoltaics Research and Applications vol 24 no 1 pp 3ndash112016
[12] G Y Yun M McEvoy and K Steemers ldquoDesign and overallenergy performance of a ventilated photovoltaic facaderdquo SolarEnergy vol 81 no 3 pp 383ndash394 2007
International Journal of Photoenergy 15
[13] PWWong Y ShimodaM NonakaM Inoue andMMizunoldquoSemi-transparent PV thermal performance power generationdaylight modelling and energy saving potential in a residentialapplicationrdquo Renewable Energy vol 33 no 5 pp 1024ndash10362008
[14] D H W Li T N T Lam W W H Chan and A H L MakldquoEnergy and cost analysis of semi-transparent photovoltaic inoffice buildingsrdquo Applied Energy vol 86 no 5 pp 722ndash7292009
[15] H Radhi ldquoEnergy analysis of facade-integrated photovoltaicsystems applied to UAE commercial buildingsrdquo Solar Energyvol 84 no 12 pp 2009ndash2021 2010
[16] E L Didone and A Wagner ldquoSemi-transparent PV windowsa study for office buildings in Brazilrdquo Energy and Buildings vol67 pp 136ndash142 2013
[17] P K Ng and N Mithraratne ldquoLifetime performance of semi-transparent building-integrated photovoltaic (BIPV) glazingsystems in the tropicsrdquo Renewable and Sustainable EnergyReviews vol 31 pp 736ndash745 2014
[18] C H Young Y L Chen and P C Chen ldquoHeat insulation solarglass and application on energy efficiency buildingsrdquo Energyand Buildings vol 78 pp 66ndash78 2014
[19] International Organization for Standardization ISO 9050 Glassin BuildingmdashDetermination of Light Transmittance Solar DirectTransmittance Total Solar Energy Transmittance UltravioletTransmittance and Related Glazing Factors International Orga-nization for Standardization Basel Switzerland 2003
[20] International Organization for Standardization ldquoISO10292glass in buildingmdashcalculation of steady-state U values (thermaltransmittance) of multiple glazingrdquo Tech Rep InternationalOrganization for Standardization Geneva Switzerland 1994
[21] International Standard ldquoThin-film terrestrial photovoltaic (pv)modulesmdashdesign qualification and type approvalrdquo IEC 616462008
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Inorganic ChemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Carbohydrate Chemistry
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
Physical Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom
Analytical Methods in Chemistry
Journal of
Volume 2014
Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
SpectroscopyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Medicinal ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chromatography Research International
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Applied ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Theoretical ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Spectroscopy
Analytical ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Quantum Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Organic Chemistry International
ElectrochemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CatalystsJournal of
4 International Journal of Photoenergy
SemitransparentPV module
High-reflectivityheat insulation film
Rear glass
Sunlight
Heat insulation
1st-timepower generation
2nd-timepower generation
(i) Enhance power generation(ii) Reduce heat penetration
(iii) Reduce Tsol SHGC SC value and U-value
(a)
High-reflectivityheat insulation film
Rear glass
2nd air gap
1st air gap
2nd steel spacer
1st steel spacer
Junction box
SemitransparentPV module
9mm 6mm 6mm 6mm
27mm
Structure of HISG
(b)
Figure 1 Functional principles and cross-sectional structure of heat insulation solar glass
Glass
TCO
a-Si
120583c-Si
Al
EVA
Glass
(a) Tandem laser module
Glass
TCO
EVA
Glass
TCO
a-Si
120583c-Si
(b) Tandem TCO module
Glass
TCO
a-Si
EVA
Glass
TCO
(c) a-Si TCO module
Figure 2 Cell structure of the tandem laser tandem TCO and a-Si TCO module
120591 (120582) =
1205911(120582) times 120591
2(120582) times 120591
3(120582)
[1 minus 1205882(120582) times 120588
1015840
1
(120582)] [1 minus 1205883(120582) times 120588
1015840
2
(120582)] minus 1205912
2
1205883(120582) times 120588
1015840
1
(120582)
120588 (120582) = 1205881(120582) +
1205912
1
(120582) times 1205882(120582) [1 minus 120588
1015840
2
(120582) times 1205883(120582)] + 120591
2
1
(120582) times 1205912
2
(120582) times 1205883(120582)
[1 minus 1205881015840
1
(120582) times 1205882(120582)] [1 minus 120588
1015840
2
(120582) times 1205883(120582)] minus 120591
2
2
times 1205881015840
1
(120582) times 1205881015840
3
(120582)
(2)
where 1205911(120582) is the spectral transmittance of the outer (first)
pane 1205912(120582) is the spectral transmittance of the second pane
1205913(120582) is the spectral transmittance of the third (inner) pane1205881(120582) is the spectral reflectance of the outer (first) pane
measured in the direction of incident radiation 12058810158401
(120582) is thespectral reflectance of the outer (first) pane measured in the
opposite direction of incident radiation 1205882(120582) is the spectral
reflectance of the second pane measured in the directionof incident radiation 1205881015840
2
(120582) is the spectral reflectance of thesecond pane measured in the opposite direction of incidentradiation 120588
3(120582) is the spectral reflectance of the third (inner)
pane measured in the direction of incident radiation 12058810158403
(120582) is
International Journal of Photoenergy 5
the spectral reflectance of the third (inner) pane measured inthe opposite direction of incident radiation
222 Solar Direct Transmittance 120591119890 and Reflectance 120588
119890 of
Triple Glazing Thesolar direct transmittance and reflectanceare obtained as follows
120591119890=
sum2500
780
119878120582times 120591 (120582) times Δ120582
sum2500
780
119878120582times Δ120582
120588119890=
sum2500
780
119878120582times 120588 (120582) times Δ120582
sum2500
780
119878120582times Δ120582
(3)
where 119878120582is the relative spectral distribution of the solar radi-
ation
223 UV Transmittance UV transmittance is obtained asfollows
120591119890=
sum380
300
119878120582times 120591 (120582) times Δ120582
sum380
300
119878120582times Δ120582
(4)
224 119880-Value Calculation The thermal transmittance ofglazing also known as the119880-value is the rate of heat transferthrough one squaremeter of glazing divided by the differencebetween the ambient temperatures on each side The methodspecified by ISO 10292 is based on a calculation from thefollowing equation
1
119880
=
1
ℎ119905
+
1
ℎ119890
+
1
ℎ119894
(5)
where ℎ119894is the interior heat transfer coefficient ℎ
119890is the
exterior heat transfer coefficient ℎ119905is the conductance of the
multiple glazing unit
225 Total Solar Energy Transmittance The total solarenergy transmittance (also known as solar heat gain coeffi-cient) is the sum of the solar direct transmittance 120591
119890and the
secondary heat transfer factor 119902119894towards the inside
119892 = 120591119890+ 119902119894 (6)
The secondary heat transfer factor results from heat transferby convection and longwave IR-radiation of that part of theincident solar radiation which has been absorbed by theglazingThe secondary heat transfer factor towards the insideof triple glazing is calculated using the following formula
119902119894
=
((1205721198901+ 1205721198902+ 1205721198903) ℎ119890+ (1205721198902+ 1205721198903) Λ12+ 1205721198903Λ23)
1ℎ119894+ 1ℎ119890+ 1Λ
12+ 1Λ
23
(7)
where 1205721198901is the solar direct absorptance of the outer (first)
pane within the triple glazing 1205721198902is the solar direct absorp-
tance of the second pane within the triple glazing 1205721198903is the
solar direct absorptance of the third pane of the triple glazingΛ12is the thermal conductance between the outer surface of
the outer (first) pane and the center of the second pane Λ23
is the thermal conductance between the center of the secondpane and the center of the third pane
226 Shading Coefficient (SC) The shading coefficient ofglass is a measure of the total amount of heat passing throughthe glazing compared with that through single clear glass Itis approximately equal to the SHGC divided by 087
23 Test of Gains in Power Generation Performance Tests ofthe gain in power generation were made based on the stan-dard test conditions (STC) in the test standard given by theInternational Electrotechnical Commission IEC 61646 [21]for a thin-film PV module in order to explore the powergeneration characteristics of the nine types ofHISGdescribedabove The effects of each combination of materials on thegain in power generation capacity of the semitransparent PVmodule were then analyzed and compared
24 Assessment of Energy-Saving Performance In this studyAutodesk Ecotect Analysis was adopted to conduct simula-tions of building power generation and energy by adoptingthe results of the power generation test optical test andthermal test as the material parameters and choosing Tainanin Taiwan and London in the United Kingdom as the simu-lated locations The simulation was used to obtain the powergeneration capacity and energy consumption performanceof the HISGs in real-world applications on buildings insubtropical and temperate regions
241 BuildingModel Ecotect was used in this study tomodela single building The building body consists of a roof andfour walls to form an enclosed space in order to facilitatethe simulation of air-conditioning energy consumption Themain body of the building is facing south The roof has amonopitched roof structure with an incline angle of 235∘ andis composed of 10 piecestimes 10 pieces giving a total of 100 piecesof PV modules with a size of approximately 14m times 11m Theoverall dimensions of the building body are approximately14m times 10m times 83m as illustrated in Figure 3
242 Setting Parameters for the Simulation In terms of thematerial parameters the four surrounding walls are definedas being constructed of composite materials (110mm brickoutside plus 75mm timber frame with 10mm plasterboardinside) with a 119880-value of 177WmK whereas values forthe material parameters of each PV module come from theresults of the power generation and optical and thermal testsin this paper For the air-conditioning energy consumptionthis study uses a mixed-mode air-conditioning system forcooling and heating The usage time is 24 hours the comforttemperature range is 20∘Cndash26∘C the startup temperaturesetting for a cold room is 26∘C and the startup temperaturesetting for a warm room is 18∘C The simulation of the air-conditioning energy consumption was conducted for a wholeyear
3 Results and Discussion
31 Optical Properties The transmittance and reflectancecoefficient versus wavelength of each component are shownin Figures 4 and 5 respectively Table 1 shows the optical
6 International Journal of Photoenergy
Table 1 Optical properties of each component and HISGs
ModuleItem
Solar directtransmittance
Solar directreflectance
Visible lighttransmittance
Visible lightreflectance
UVtransmittance
Tandem laser module 709 1007 84 527 001Tandem TCOmodule 1833 679 220 515 001a-Si TCO module 2349 730 435 512 001Heat insulation film A 6814 1688 9532 483 175Heat insulation film B 4063 3089 8412 601 136Heat insulation film C 3315 4071 6104 2233 100Rear glass 8115 504 8885 566 6239Tandem laser-A HISG 407 1017 723 535 0Tandem laser-B HISG 25 1024 639 535 0Tandem laser-C HISG 208 1030 478 545 0Tandem TCO-A HISG 1034 744 188 515 0Tandem TCO-B HISG 626 788 166 515 0Tandem TCO-C HISG 516 821 123 515 0a-Si TCO-A HISG 1326 837 372 514 0a-Si TCO-B HISG 803 909 329 514 0a-Si TCO-C HISG 662 964 243 517 0
1400m
833
m
1009m
1100m110m
395
m
140m
Figure 3 The 3D model of the building body
properties of each component based on ISO 9050The valuesof lighting transmittance for the three PV modules were inthe 709ndash2349 range and those for the three heat insulationfilms were in the range of 3315ndash6814 The measurementresults show that the tandem lasermodule and heat insulationfilm C had better heat insulation effects They could thusbe used in hot climates where there is a need to reducesolar heat transmission especially in buildings where largetransparent surfaces are fitted Furthermore the tandem lasermodule and heat insulation filmA had better visibilities eventhoughwith the former the back-contact electrodematerial isopaque Part of the power-generating layers and back-contactelectrode layer in the tandem laser module were removed
using a transverse laser cutting method to enable the moduleto be light-transmissible It is also worth noting that the lowervisible light transmittance in other modules is mainly due toabsorption of the TCO layers The UV transmittances of thePVmodule and heat insulation film are less than 2meaningthat the performances of the HISGs with regard to isolatingUV light were very good
In the cell structure of the tandem TCO module thematerials of the power-generating layers are the same as thoseof the tandem laser module but in terms of the back-contactelectrode a TCO material with good light transmission andconduction properties was adopted Though TCO has highoptical transparency it does decrease light transmission fromUV to IR Therefore the tandem TCO module has a light-transmissible property and its insulation of solar thermalenergy is poorer than that of the tandem laser module Inaddition as the color of transmitted light tends to be winered part of its visible light transmittance was poorer Thematerial of the rear electrode in the cell structure of the a-Si TCO module was the same as that of the tandem TCOmoduleAs such it also has a light-transmissible property andthe transmitted light color tends to be orange red Howeverin the power-generating layer the a-Si TCO module had asingle-layer structure without a layer of 120583c-Si so its visiblelight transmittance was slightly better than that of the tandemTCOmodule Furthermore as it has no 120583c-Si layer to absorbthe solar light its solar radiation transmittance was slightlypoorer than that of the tandem TCOmodule
As shown in Figure 6 the measurement results for thesolar direct transmittance indicated that the addition ofa reflective layer reduces the transmittance of HISGs Forthe tandem laser tandem TCO and a-Si TCO modulethe solar direct transmittance was originally 709 1833
International Journal of Photoenergy 7
0
10
20
30
40
50Tr
ansm
ittan
ce (
)
Wavelength (nm)
Tandem laser moduleTandem TCO modulea-Si TCO module
300 600 900 1200 1500 1800 2100 2400
(a)
0
10
20
30
40
50
60
70
80
90
100
Tran
smitt
ance
()
Wavelength (nm)300 600 900 1200 1500 1800 2100 2400
Heat insulation film AHeat insulation film BHeat insulation film C
(b)
0
20
40
60
80
100
Tran
smitt
ance
()
Wavelength (nm)500 1000 1500 2000 2500
Glass
(c)
Figure 4 Transmittance spectra of each component (a) semitransparent PV module (b) heat insulation film and (c) rear glass
and 2349 but after being encapsulated into the HISGit dropped to 208ndash407 516ndash1034 and 662ndash1326respectively The visible light transmittance was originally84 22 and 435 but after being encapsulated into theHISG it dropped to 478ndash723 123ndash188 and 243ndash372respectively
After the various semitransparent PVmodules were inte-grated into the HISG with the various heat insulation filmsall their solar direct reflectance values increased slightly sothe encapsulationwas slightly beneficial to the heat insulatingeffect of the HISGs Moreover after being encapsulated intothe HISGs the effects on the visible light reflectance were allless severe falling to around 5 Therefore the HISGs willnot necessarily cause environmental light pollution
With regard to the UV transmittance since most of theUV light is absorbed by the semitransparent PV moduleand the heat insulation film the UV transmittance valuesof all the HISGs are 0 This means that the UV isolationperformances are very good and able to protect interiorfurnishings from aging and the skin from damage caused byUV radiation
32 Thermal Properties The surface emissivity of an objectrefers to its ability to release heat via thermal radiation afterabsorbing solar radiation The surface emissivity of eachcomponent is thus an important parameter affecting the heatinsulation performance of a HISG In this paper the spectralreflectance of each component on the exterior and interior
8 International Journal of Photoenergy
02468
101214161820222426
Refle
ctan
ce (
)
Wavelength (nm)
Tandem laser moduleTandem TCO modulea-Si TCO module
300 600 900 1200 1500 1800 2100 2400
(a)
0
10
20
30
40
50
60
70
Refle
ctan
ce (
)
Wavelength (nm)300 600 900 1200 1500 1800 2100 2400
Heat insulation film AHeat insulation film BHeat insulation film C
(b)
0
10
20
30
40
50
60
70
80
90
100
Refle
ctan
ce (
)
Wavelength (nm)
Glass
300 600 900 1200 1500 1800 2100 2400
(c)
Figure 5 Reflectance spectra of each component (a) semitransparent PV modules (b) heat insulation films and (c) rear glass
sides was measured using FTIR and then the emissivityvalue of each component was obtained by ISO 10292 asshown in Table 2 It can be seen that as the surfaces ofthe semitransparent PV modules and rear glass were not allcoated by a film the emissivity values for the exterior andinterior sides were 084 While the heat insulation filmswere mainly composed of PET material there was no filmcoating the interior surface of the film so the emissivityvalues were all 076 Meanwhile the exterior surfaces of theheat insulation films all had a multilayer metal coating sothe surface emissivity values were lower than the surfaceemissivity values on the indoor side The surface emissivity
of heat insulation film C is 0033 which is thus categorized asa Low-E film
Table 3 shows the thermal performances of the three typesof PVmodules and the nine types of HISGs with the SHGCsshading coefficients and overall heat transfer coefficients (119880-values) The results indicate that the multilayer structureof the HISG reduced the solar direct transmittance andsince the heat insulation films were coated with transparentmetal films this reflected the solar radiation heat promptingthe SHGCs to be reduced to half the levels seen with thesemitransparent PVmodulesThismeans that the quantity ofsolar radiation heat passing through the HISG was half that
International Journal of Photoenergy 9
0
2
4
6
8
10
12
545
478
103
208
535
639
1024
25
535
723
1017
407
00 0001
527
84
1007
709
UV
tran
smitt
ance
Visib
le li
ght
refle
ctan
ce
Visib
le li
ght
tran
smitt
ance
Sola
r rad
iatio
nre
flect
ance
Sola
r rad
iatio
ntr
ansm
ittan
ce
Tran
smitt
ance
and
refle
ctan
ce (
)
Tandem laser moduleTandem laser-A HISG
Tandem laser-B HISGTandem laser-C HISG
(a)
0
2
4
6
8
10
12
14
16
18
20
0 00001
515515515515
123166
18822
821788744
679516
626
1034
1833
UV
tran
smitt
ance
Visib
le li
ght
refle
ctan
ce
Visib
le li
ght
tran
smitt
ance
Sola
r rad
iatio
nre
flect
ance
Sola
r rad
iatio
ntr
ansm
ittan
ce
Tran
smitt
ance
and
refle
ctan
ce (
)Tandem TCO moduleTandem TCO-A HISG
Tandem TCO-B HISGTandem TCO-C HISG
(b)
02468
101214161820222426
000001
517514
514512
243329
372435
964909
83773
662803
1326
2349
UV
tran
smitt
ance
Visib
le li
ght
refle
ctan
ce
Visib
le li
ght
tran
smitt
ance
Sola
r rad
iatio
nre
flect
ance
Sola
r rad
iatio
ntr
ansm
ittan
ce
Tran
smitt
ance
and
refle
ctan
ce (
)
a-Si TCO modulea-Si TCO-A HISG
a-Si TCO-B HISGa-Si TCO-C HISG
(c)
Figure 6 Optical properties of the HISGs (a) tandem laser module (b) tandem TCOmodule and (c) a-Si TCO module
passing through the semitransparent PV modules In termsof the 119880-value since all the semitransparent PV moduleswere assembled with 4mm times 4mm laminated glass the 119880-values based on ISO 10292 for all modules were 563Wm2-K The addition of heat insulation films and dual air gaps toform a multilayer structure greatly reduced the 119880-values oftheHISGs (1755Wm2-Kndash1824Wm2-K)Moreover havingheat insulation films with different emissivity values is one
of the main causes of the decline in the 119880-value Since heatinsulation film C had the lowest surface emissivity theHISGs assembled using film C also possessed lower119880-values(1755Wm2-K)
33 Power Generation Gain Performance The power genera-tion test results for the front and back sides of each semitrans-parent PV module are shown in Table 4 The measurement
10 International Journal of Photoenergy
Table 2 Emissivity of each component
Item Emissivity ofindoor side
Emissivity ofoutdoor side
Tandem laser module 084 084Tandem TCOmodule 084 084a-Si TCO module 084 084Heat insulation film A 076 0135Heat insulation film B 076 0045Heat insulation film C 076 0033Rear glass 084 084
Table 3Thermal properties of the semitransparent PVmodules andHISGs
ModuleItem
SHGC Shadingcoefficient 119880-value
Tandem lasermodule 03 0345 563
Tandem laser-AHISG 0151 0174 1824
Tandem laser-BHISG 0135 0155 1757
Tandem laser-CHISG 0129 0148 1755
Tandem TCOmodule 038 0437 563
Tandem TCO-AHISG 0218 025 1824
Tandem TCO-BHISG 0184 0211 1757
Tandem TCO-CHISG 0171 0196 1755
a-Si TCOmodule 041 0471 563
a-Si TCO-AHISG 0249 0286 1824
a-Si TCO-BHISG 0207 0238 1757
a-Si TCO-CHISG 019 0218 1755
results show that the power output for the front side of thetandem laser module was 126029W with an efficiency of8184 while that of the back side was only 1019W Thereason for this is the cell structure of the tandem lasermoduleas the bottom back-contact conductive layer is Al whichdoes not possess power generation characteristicsThereforeafter being illuminated by direct light there should not be apower generation effect However because the tandem lasermodule was subjected to transverse laser cutting during themanufacturing process light can pass through from the backsideThe light could then undergo refraction or transmissionat the rear glass so some of the light is able to enter the power-generating layer from the laser cut slits and so the back side
Table 4 Results of tests of electrical characteristics in STC for initialstates of the original transparent PV module (a) front side and (b)back side
(a)
Test itemTandemlaser
module
TandemTCO
module
a-SiTCO
moduleModule efficiency () 8184 811 778Maximum power output(W) 126029 124843 119796
Open circuit voltage (V) 167382 171629 111606Short circuit current (A) 1133 1038 1595Maximum voltage (V) 131026 140561 86939Maximum electric current(A) 0962 0888 1378
Fill factor 06644 07008 06731
(b)
Test itemTandemlaser
module
TandemTCO
module
a-SiTCO
moduleModule efficiency () 0066 0723 5361Maximum power output(W) 1019 11134 82566
Open circuit voltage (V) 109965 156555 108648Short circuit current (A) 0026 0108 1213Maximum voltage (V) 40348 132561 83918Maximum electric current(A) 0025 0084 0984
Fill factor 03506 06576 06264
of the tandem laser module also possesses a slight powergeneration effect
The power output of the front side of the tandem TCOmodule was 124843W with an efficiency of 811 whereasthat of the back side was only 11134W The reason why theefficiency from back-side illumination is low is due to lightabsorption in the lower bandgap 120583c-Si cell which allowslimited light into the a-Si cell The current output would belimited by the smaller current value from the a-Si and so alower efficiency is generated
The front-side power output of the a-Si TCOmodule was119796W with an efficiency of 778 whereas the back-sidepower output of the a-Si TCO module reached 82566WThe power-generating layer of the a-Si TCO module is thea-Si layer which is also classified as a cell structure withdual-surface power generation characteristics so the back-side power output was higher compared to that of the formertwo modules However the reason for the difference in thefront-side and back-side power outputs of the a-Si TCOmodule is that the materials of the front and rear glasswere different The front glass was ultraclear glass with morethan 90 visible light transmittance Meanwhile in orderto increase the loading strength of the BIPV the rear glasswas mostly tempered glass or heat-strengthened glass with
International Journal of Photoenergy 11
lower transmissivity In addition before entering the power-generating layer from the back side the light still needs to passthrough a layer of EVA plastic film which will also reduce thesolar irradianceThe back-side power output of the a-Si TCOmodule was thus only 69 of the front-side power output
The results of the electrical tests of each semitransparentPV module and each combination of HISGs are shown inTable 5 The results for power generation gain are shownin Table 6 The experimental results indicated that boththe power generation and efficiency of tandem laser HISGexhibited slightly increasing trends the power generationincreased by around 001ndash013 and the efficiency increasedby around 0001ndash001 However the power generationand efficiency of tandem TCO HISG and a-Si TCO HISGdisplayed increasing trends For the tandem TCO HISGthe power generation improved by around 327ndash1006 andthe efficiency increased by around 027ndash082 For the a-SiTCOHISG the power generation increased by around 094ndash307 and the efficiency increased by around 007ndash024The power-generating layer of the tandem TCOmodule is a-Si120583c-Si but that of the a-Si TCO module is a single layer ofa-Si The absorption spectrum of the tandem TCO module(300 nmndash1100 nm) is wider than that of the a-Si TCOmodule(300 nmndash750 nm) The back side of the tandem TCO HISGcan thus absorb higher effective irradiance than the a-Si TCOHISG This means that the efficiency enhanced rate of thetandemTCOHISG is higher than that of the a-Si TCOHISGIt is also worth noting that selecting an appropriate heatinsulation film in order to absorb a larger amount of reflectivesolar radiation by the back side of theHISG can lead to greaterenhancement of power generation
34 Simulation of Energy-Saving Performance The simula-tion results for the power generation of each HISG installedin the buildings and the energy consumption of the heatingventilation and air-conditioning (HVAC) system are shownin Table 7 As Tainan is located in a subtropical region inTaiwan where there is sufficient sunlight the annual powergeneration of each module was higher than that of themodules in London and the power outputs ranged between16328 kW and 18727 kW London is located in a temperatezone with mostly cloudy weather and thus the annual powergeneration only ranged between 8493 kWand 9741 kWTheseresults show that different climate zones andweather patternsare the main factors affecting the power generation of BIPVmodules
The simulation results in Table 7 also show that the poweroutputs of each HISG were larger than those of the originalsemitransparent PV modules That is the power enhance-ments of the tandem laser HISG were around 001ndash012those of the tandem TCO HISG were around 327ndash1006and those of the a-Si TCO HISG were around 094ndash307The simulated results also reveal that the percentage gainsin power generation for each HISG installed on the roofs ofbuildings as BIPV roofs are consistent with the experimentalresults under STC from IEC 61646 Therefore adding heatinsulation films onto semitransparent PV modules to forma HISG in order to enhance the power output of the modulesis beneficial in reducing the EPBT of the entire BIPV system
The simulation results for the energy consumption of theHVAC systems of buildings in Tainan Taiwan and LondonUK are shown in Tables 8 and 9 respectively As Tainan islocated in a subtropical region the use of a heater is lesscommon and the HVAC system is mostly used for coolingso the energy consumption for the latter is much higher thanthat for heating On the other hand London is located in atemperate region and the HVAC system is mainly used forheating so the energy consumption for this is much higherthan that for cooling
Furthermore the main factors affecting the energy con-sumption of theHVAC system are the shading coefficient andthe 119880-value of the envelope The shading coefficient and 119880-value of each HISG are lower than those of the semitrans-parent PV modules During summer solar radiation cannotenter the room easily through the HISG so cooling energycan be saved During winter the 119880-value of the HISG isvery low owing to the multilayer structure and althoughsolar radiation cannot enter the room easily the heat will beretained inside the room and will not dissipate easily andhence the amount of energy used for heating can also bereduced Therefore the simulation results for the HISGs allindicate greater energy-saving performance in the annualenergy consumption of the HVAC system The results showthat the HISG can save 2911ndash3219 of cooling energy 4734ndash4815 of heating energy and 3268ndash3575 of the totalenergy consumption of the HVAC system in subtropicalregions and 3727ndash4412 of cooling energy 3905ndash3986 ofheating energy and 3905ndash3986 of total energy consump-tion of the HVAC system in temperate regions Among all theHISGs the HISG encapsulated version using heat insulationfilm C had the best energy-saving performance
As seen in the simulation results given above the HISGcan not only enhance the power generation but also becauseof the better heat insulation performance shorten the EPBTof the entire HISG BIPV application on a building
4 Conclusion
The concepts of net zero energy zero energy and passiveenergy are becoming more important as part of the energyconservation policies adopted by the construction industryBIPV technology currently has great potential for effectivedevelopment of solar module techniques Theoretically if aBIPV module is combined with building materials it caneffectively reduce overall construction costs save energymodulate the indoor temperature and shorten the energypayback time (EPBT)
In this work the authors adopted three different types ofsemitransparent PV modules and combined three differenttypes of high-reflectivity films to encapsulate HISG BIPVsystems The optical and thermal properties and the overallpower generation effects of each HISG were investigated Inaddition Autodesk software was used to calculate the powergeneration and energy-saving effects of each HISG as appliedto actual buildings in Taiwan with a subtropical climate andEngland with a temperate climate As a result due to thethree-layer structure of the HISGwith a high-reflectivity heatinsulation film the heat insulation performance (SHGC and
12 International Journal of Photoenergy
Table5Testresults
forthe
vario
usBIPV
mod
ules
andHISGsu
nder
STC
Testitem
Tand
emlaser
mod
ule
Tand
emlaser-A
HISG
Tand
emlaser-BHISG
Tand
emlaser-CHISG
Tand
emTC
Omod
ule
Tand
emTC
O-A
HISG
Tand
emTC
O-B
HISG
Tand
emTC
O-C
HISG
a-SiTC
Omod
ule
a-Si
TCO-A
HISG
a-SiTC
O-B
HISG
a-Si
TCO-C
HISG
Efficiency
()
8184
8185
8189
8194
811
837
874
892
778
785
787
802
Maxim
umpo
wer
output
(W)
126029
12604
2126105
126187
124843
128926
134658
137399
119796
120921
121125
123475
Opencircuit
voltage
(V)
1673
821672
531672
81167313
1716
291716
441718
86172036
1116
061115
971116
131117
10
Shortcirc
uit
current(A)
1133
1134
1133
1134
1038
1074
1125
1150
1595
1612
1615
1650
Maxim
umvoltage
(V)
1310
261294
33130098
1292
07140561
1391
73138796
138027
86939
8733
787341
84561
Maxim
umele
ctric
current(A)
0962
0974
0969
0977
0888
0926
0970
0995
1378
1385
1387
1460
Fillfactor
066
44066
4606654
06651
07008
06996
06964
06944
06731
06721
06719
06698
International Journal of Photoenergy 13
Table 6 Results of power generation gain tests of the semitransparent PV modules and each combination of HISG under STC
ModuleItem
Power generation (W) Power generationenhancement () Module efficiency () Module efficiency
enhancement ()Tandem laser module 126029 mdash 8184 mdashTandem laser-A HISG 126042 001 8185 0001Tandem laser-B HISG 126105 006 8189 0005Tandem laser-C HISG 126187 013 8194 0010Tandem TCOmodule 124843 mdash 811 mdashTandem TCO-A HISG 128926 327 837 027Tandem TCO-B HISG 134658 786 874 064Tandem TCO-C HISG 137399 1006 892 082a-Si TCO module 119796 mdash 778 mdasha-Si TCO-A HISG 120921 094 785 007a-Si TCO-B HISG 121125 111 787 009a-Si TCO-C HISG 123475 307 802 024
Table 7 Power generation results for building body simulations
Module LocationTainan Taiwan (kW) Power enhancement () London UK (kW) Power enhancement ()
Tandem laser module 17178 mdash 8935 mdashTandem laser-A HISG 17179 001 8936 001Tandem laser-B HISG 17188 006 8940 006Tandem laser-C HISG 17199 012 8946 012Tandem TCOmodule 17016 mdash 8851 mdashTandem TCO-A HISG 17573 327 9141 327Tandem TCO-B HISG 18354 786 9547 786Tandem TCO-C HISG 18727 1006 9741 1006a-Si TCO module 16328 mdash 8493 mdasha-Si TCO-A HISG 16481 094 8573 094a-Si TCO-B HISG 16509 111 8587 111a-Si TCO-C HISG 16830 307 8754 307
Table 8 Simulation results for energy consumption of HVAC systems for the building body in the Tainan region of Taiwan
Module Cooling energyconsumption (kW)
Cooling energysaving ()
Heating energyconsumption
(kW)
Heating energysaving ()
Total HVAC systemenergy consumption
(kW)
Total HVACenergy saving
()Tandem laser module 28632 mdash 6924 mdash 35556 mdashTandem laser-A HISG 20296 2911 3639 4744 23935 3268Tandem laser-B HISG 20053 2996 3590 4815 23643 3350Tandem laser-C HISG 19958 3029 3591 4814 23549 3377Tandem TCOmodule 29495 mdash 6894 mdash 36390 mdashTandem TCO-A HISG 20793 2950 3623 4745 24415 3291Tandem TCO-B HISG 20412 3080 3576 4813 23988 3408Tandem TCO-C HISG 20201 3151 3583 4803 23784 3464a-Si TCO module 30368 mdash 6869 mdash 37236 mdasha-Si TCO-A HISG 20952 3101 3617 4734 24569 3402a-Si TCO-B HISG 20593 3219 3568 4806 24161 3511a-Si TCO-C HISG 20347 3300 3577 4793 23924 3575
14 International Journal of Photoenergy
Table 9 Simulation results for energy consumption of HVAC systems for the building body in London UK
ModuleCooling energyconsumption
(kW)
Cooling energysaving ()
Heating energyconsumption
(kW)
Heating energysaving ()
Total HVAC system energyconsumption (kW)
Total HVACenergy saving
()Tandem laser module 306 mdash 116818 mdash 117123 mdashTandem laser-A HISG 181 4085 71203 3905 71384 3905Tandem laser-B HISG 171 4412 70570 3959 70741 3960Tandem laser-C HISG 173 4346 70491 3966 70664 3967Tandem TCOmodule 271 mdash 117612 mdash 117883 mdashTandem TCO-A HISG 170 3727 71497 3921 71667 3920Tandem TCO-B HISG 164 3948 70753 3984 70917 3984Tandem TCO-C HISG 165 3911 70734 3986 70899 3986a-Si TCO module 287 mdash 117214 mdash 117501 mdasha-Si TCO-A HISG 175 3902 71273 3919 71448 3919a-Si TCO-B HISG 172 4007 70640 3973 70812 3973a-Si TCO-C HISG 171 4042 70566 3980 70737 3980
119880-value) showed an improvement Although the multilayerstructure of HISG would affect the visible light transmit-tance in practice it does not have a significant impact onthe view through the glass Moreover although the solardirect reflectance values all showed improving trends thevisible light reflectance was only around 5 which will notnecessarily cause environmental light pollution Comparedto the original modules the power generation and moduleefficiency of all HISGs were found to have increased Of allthe combinations of HISGs the gain in power generation ofthe tandem TCO-C HISG was the highest as the power gen-eration was improved by 1006 and the module efficiencywas improved by 082The results of the simulation showeda very similar trendwith regard to the level of electrical powergeneration based on experimental data that was obtainedusing the standard test conditions (STC) for measurementcontained in IEC 61646The simulation results also indicatedthat theHISG has a significant effect on the amount of energythat can be saved when using the HVAC system in bothsubtropical and temperate regions
This paper thus provides valuable information for renew-able energy planners and architectural designers who areinterested in using HISG BIPV systems
Competing Interests
The authors declare that there are no competing interestsregarding the publication of this paper
Acknowledgments
This study was supported by the Ministry of Science andTechnology of Taiwan under Projects MOST 105-3113-F-011-001 and MOST 105-3113-E-006-006-CC2
References
[1] M van der Hoeven Energy and Climate ChangemdashWorld EnergyOutlook Special Report International Energy Agency 2015
[2] P Jones S S Hou and X Li ldquoTowards zero carbon designin offices integrating smart facades ventilation and surfaceheating and coolingrdquoRenewable Energy vol 73 pp 69ndash76 2015
[3] W Pan ldquoSystem boundaries of zero carbon buildingsrdquo Renew-able and Sustainable Energy Reviews vol 37 pp 424ndash434 2014
[4] S Berry K Davidson and W Saman ldquoDefining zero carbonand zero energy homes from a performance-based regulatoryperspectiverdquo Energy Efficiency vol 7 no 2 pp 303ndash322 2014
[5] G P Hammond H A Harajli C I Jones and A B WinnettldquoWhole systems appraisal of a UK Building Integrated Photo-voltaic (BIPV) system energy environmental and economicevaluationsrdquo Energy Policy vol 40 no 1 pp 219ndash230 2012
[6] G A Keoleian and GM Lewis ldquoModeling the life cycle energyand environmental performance of amorphous silicon BIPVroofing in the USrdquo Renewable Energy vol 28 no 2 pp 271ndash2932003
[7] L Lu andHX Yang ldquoEnvironmental payback time analysis of aroof-mounted building-integrated photovoltaic (BIPV) systemin Hong Kongrdquo Applied Energy vol 87 no 12 pp 3625ndash36312010
[8] L Y Seng G Lalchand and G M Sow Lin ldquoEconomicalenvironmental and technical analysis of building integratedphotovoltaic systems in Malaysiardquo Energy Policy vol 36 no 6pp 2130ndash2142 2008
[9] M Oliver and T Jackson ldquoEnergy and economic evaluation ofbuilding-integrated photovoltaicsrdquo Energy vol 26 no 4 pp431ndash439 2001
[10] L Sabnani A Skumanich E Ryabova and R Noufi Devel-oping Market Opportunities for Flexible Rooftop Applicationsof PV Using Flexible CIGS Technology Market ConsiderationsNational Renewable Energy Laboratory (NREL) Golden ColoUSA 2011
[11] M A Green K Emery Y Hishikawa W Warta and E DDunlop ldquoSolar cell efficiency tables (version 47)rdquo Progress inPhotovoltaics Research and Applications vol 24 no 1 pp 3ndash112016
[12] G Y Yun M McEvoy and K Steemers ldquoDesign and overallenergy performance of a ventilated photovoltaic facaderdquo SolarEnergy vol 81 no 3 pp 383ndash394 2007
International Journal of Photoenergy 15
[13] PWWong Y ShimodaM NonakaM Inoue andMMizunoldquoSemi-transparent PV thermal performance power generationdaylight modelling and energy saving potential in a residentialapplicationrdquo Renewable Energy vol 33 no 5 pp 1024ndash10362008
[14] D H W Li T N T Lam W W H Chan and A H L MakldquoEnergy and cost analysis of semi-transparent photovoltaic inoffice buildingsrdquo Applied Energy vol 86 no 5 pp 722ndash7292009
[15] H Radhi ldquoEnergy analysis of facade-integrated photovoltaicsystems applied to UAE commercial buildingsrdquo Solar Energyvol 84 no 12 pp 2009ndash2021 2010
[16] E L Didone and A Wagner ldquoSemi-transparent PV windowsa study for office buildings in Brazilrdquo Energy and Buildings vol67 pp 136ndash142 2013
[17] P K Ng and N Mithraratne ldquoLifetime performance of semi-transparent building-integrated photovoltaic (BIPV) glazingsystems in the tropicsrdquo Renewable and Sustainable EnergyReviews vol 31 pp 736ndash745 2014
[18] C H Young Y L Chen and P C Chen ldquoHeat insulation solarglass and application on energy efficiency buildingsrdquo Energyand Buildings vol 78 pp 66ndash78 2014
[19] International Organization for Standardization ISO 9050 Glassin BuildingmdashDetermination of Light Transmittance Solar DirectTransmittance Total Solar Energy Transmittance UltravioletTransmittance and Related Glazing Factors International Orga-nization for Standardization Basel Switzerland 2003
[20] International Organization for Standardization ldquoISO10292glass in buildingmdashcalculation of steady-state U values (thermaltransmittance) of multiple glazingrdquo Tech Rep InternationalOrganization for Standardization Geneva Switzerland 1994
[21] International Standard ldquoThin-film terrestrial photovoltaic (pv)modulesmdashdesign qualification and type approvalrdquo IEC 616462008
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Inorganic ChemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Carbohydrate Chemistry
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
Physical Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom
Analytical Methods in Chemistry
Journal of
Volume 2014
Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
SpectroscopyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Medicinal ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chromatography Research International
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Applied ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Theoretical ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Spectroscopy
Analytical ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Quantum Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Organic Chemistry International
ElectrochemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CatalystsJournal of
International Journal of Photoenergy 5
the spectral reflectance of the third (inner) pane measured inthe opposite direction of incident radiation
222 Solar Direct Transmittance 120591119890 and Reflectance 120588
119890 of
Triple Glazing Thesolar direct transmittance and reflectanceare obtained as follows
120591119890=
sum2500
780
119878120582times 120591 (120582) times Δ120582
sum2500
780
119878120582times Δ120582
120588119890=
sum2500
780
119878120582times 120588 (120582) times Δ120582
sum2500
780
119878120582times Δ120582
(3)
where 119878120582is the relative spectral distribution of the solar radi-
ation
223 UV Transmittance UV transmittance is obtained asfollows
120591119890=
sum380
300
119878120582times 120591 (120582) times Δ120582
sum380
300
119878120582times Δ120582
(4)
224 119880-Value Calculation The thermal transmittance ofglazing also known as the119880-value is the rate of heat transferthrough one squaremeter of glazing divided by the differencebetween the ambient temperatures on each side The methodspecified by ISO 10292 is based on a calculation from thefollowing equation
1
119880
=
1
ℎ119905
+
1
ℎ119890
+
1
ℎ119894
(5)
where ℎ119894is the interior heat transfer coefficient ℎ
119890is the
exterior heat transfer coefficient ℎ119905is the conductance of the
multiple glazing unit
225 Total Solar Energy Transmittance The total solarenergy transmittance (also known as solar heat gain coeffi-cient) is the sum of the solar direct transmittance 120591
119890and the
secondary heat transfer factor 119902119894towards the inside
119892 = 120591119890+ 119902119894 (6)
The secondary heat transfer factor results from heat transferby convection and longwave IR-radiation of that part of theincident solar radiation which has been absorbed by theglazingThe secondary heat transfer factor towards the insideof triple glazing is calculated using the following formula
119902119894
=
((1205721198901+ 1205721198902+ 1205721198903) ℎ119890+ (1205721198902+ 1205721198903) Λ12+ 1205721198903Λ23)
1ℎ119894+ 1ℎ119890+ 1Λ
12+ 1Λ
23
(7)
where 1205721198901is the solar direct absorptance of the outer (first)
pane within the triple glazing 1205721198902is the solar direct absorp-
tance of the second pane within the triple glazing 1205721198903is the
solar direct absorptance of the third pane of the triple glazingΛ12is the thermal conductance between the outer surface of
the outer (first) pane and the center of the second pane Λ23
is the thermal conductance between the center of the secondpane and the center of the third pane
226 Shading Coefficient (SC) The shading coefficient ofglass is a measure of the total amount of heat passing throughthe glazing compared with that through single clear glass Itis approximately equal to the SHGC divided by 087
23 Test of Gains in Power Generation Performance Tests ofthe gain in power generation were made based on the stan-dard test conditions (STC) in the test standard given by theInternational Electrotechnical Commission IEC 61646 [21]for a thin-film PV module in order to explore the powergeneration characteristics of the nine types ofHISGdescribedabove The effects of each combination of materials on thegain in power generation capacity of the semitransparent PVmodule were then analyzed and compared
24 Assessment of Energy-Saving Performance In this studyAutodesk Ecotect Analysis was adopted to conduct simula-tions of building power generation and energy by adoptingthe results of the power generation test optical test andthermal test as the material parameters and choosing Tainanin Taiwan and London in the United Kingdom as the simu-lated locations The simulation was used to obtain the powergeneration capacity and energy consumption performanceof the HISGs in real-world applications on buildings insubtropical and temperate regions
241 BuildingModel Ecotect was used in this study tomodela single building The building body consists of a roof andfour walls to form an enclosed space in order to facilitatethe simulation of air-conditioning energy consumption Themain body of the building is facing south The roof has amonopitched roof structure with an incline angle of 235∘ andis composed of 10 piecestimes 10 pieces giving a total of 100 piecesof PV modules with a size of approximately 14m times 11m Theoverall dimensions of the building body are approximately14m times 10m times 83m as illustrated in Figure 3
242 Setting Parameters for the Simulation In terms of thematerial parameters the four surrounding walls are definedas being constructed of composite materials (110mm brickoutside plus 75mm timber frame with 10mm plasterboardinside) with a 119880-value of 177WmK whereas values forthe material parameters of each PV module come from theresults of the power generation and optical and thermal testsin this paper For the air-conditioning energy consumptionthis study uses a mixed-mode air-conditioning system forcooling and heating The usage time is 24 hours the comforttemperature range is 20∘Cndash26∘C the startup temperaturesetting for a cold room is 26∘C and the startup temperaturesetting for a warm room is 18∘C The simulation of the air-conditioning energy consumption was conducted for a wholeyear
3 Results and Discussion
31 Optical Properties The transmittance and reflectancecoefficient versus wavelength of each component are shownin Figures 4 and 5 respectively Table 1 shows the optical
6 International Journal of Photoenergy
Table 1 Optical properties of each component and HISGs
ModuleItem
Solar directtransmittance
Solar directreflectance
Visible lighttransmittance
Visible lightreflectance
UVtransmittance
Tandem laser module 709 1007 84 527 001Tandem TCOmodule 1833 679 220 515 001a-Si TCO module 2349 730 435 512 001Heat insulation film A 6814 1688 9532 483 175Heat insulation film B 4063 3089 8412 601 136Heat insulation film C 3315 4071 6104 2233 100Rear glass 8115 504 8885 566 6239Tandem laser-A HISG 407 1017 723 535 0Tandem laser-B HISG 25 1024 639 535 0Tandem laser-C HISG 208 1030 478 545 0Tandem TCO-A HISG 1034 744 188 515 0Tandem TCO-B HISG 626 788 166 515 0Tandem TCO-C HISG 516 821 123 515 0a-Si TCO-A HISG 1326 837 372 514 0a-Si TCO-B HISG 803 909 329 514 0a-Si TCO-C HISG 662 964 243 517 0
1400m
833
m
1009m
1100m110m
395
m
140m
Figure 3 The 3D model of the building body
properties of each component based on ISO 9050The valuesof lighting transmittance for the three PV modules were inthe 709ndash2349 range and those for the three heat insulationfilms were in the range of 3315ndash6814 The measurementresults show that the tandem lasermodule and heat insulationfilm C had better heat insulation effects They could thusbe used in hot climates where there is a need to reducesolar heat transmission especially in buildings where largetransparent surfaces are fitted Furthermore the tandem lasermodule and heat insulation filmA had better visibilities eventhoughwith the former the back-contact electrodematerial isopaque Part of the power-generating layers and back-contactelectrode layer in the tandem laser module were removed
using a transverse laser cutting method to enable the moduleto be light-transmissible It is also worth noting that the lowervisible light transmittance in other modules is mainly due toabsorption of the TCO layers The UV transmittances of thePVmodule and heat insulation film are less than 2meaningthat the performances of the HISGs with regard to isolatingUV light were very good
In the cell structure of the tandem TCO module thematerials of the power-generating layers are the same as thoseof the tandem laser module but in terms of the back-contactelectrode a TCO material with good light transmission andconduction properties was adopted Though TCO has highoptical transparency it does decrease light transmission fromUV to IR Therefore the tandem TCO module has a light-transmissible property and its insulation of solar thermalenergy is poorer than that of the tandem laser module Inaddition as the color of transmitted light tends to be winered part of its visible light transmittance was poorer Thematerial of the rear electrode in the cell structure of the a-Si TCO module was the same as that of the tandem TCOmoduleAs such it also has a light-transmissible property andthe transmitted light color tends to be orange red Howeverin the power-generating layer the a-Si TCO module had asingle-layer structure without a layer of 120583c-Si so its visiblelight transmittance was slightly better than that of the tandemTCOmodule Furthermore as it has no 120583c-Si layer to absorbthe solar light its solar radiation transmittance was slightlypoorer than that of the tandem TCOmodule
As shown in Figure 6 the measurement results for thesolar direct transmittance indicated that the addition ofa reflective layer reduces the transmittance of HISGs Forthe tandem laser tandem TCO and a-Si TCO modulethe solar direct transmittance was originally 709 1833
International Journal of Photoenergy 7
0
10
20
30
40
50Tr
ansm
ittan
ce (
)
Wavelength (nm)
Tandem laser moduleTandem TCO modulea-Si TCO module
300 600 900 1200 1500 1800 2100 2400
(a)
0
10
20
30
40
50
60
70
80
90
100
Tran
smitt
ance
()
Wavelength (nm)300 600 900 1200 1500 1800 2100 2400
Heat insulation film AHeat insulation film BHeat insulation film C
(b)
0
20
40
60
80
100
Tran
smitt
ance
()
Wavelength (nm)500 1000 1500 2000 2500
Glass
(c)
Figure 4 Transmittance spectra of each component (a) semitransparent PV module (b) heat insulation film and (c) rear glass
and 2349 but after being encapsulated into the HISGit dropped to 208ndash407 516ndash1034 and 662ndash1326respectively The visible light transmittance was originally84 22 and 435 but after being encapsulated into theHISG it dropped to 478ndash723 123ndash188 and 243ndash372respectively
After the various semitransparent PVmodules were inte-grated into the HISG with the various heat insulation filmsall their solar direct reflectance values increased slightly sothe encapsulationwas slightly beneficial to the heat insulatingeffect of the HISGs Moreover after being encapsulated intothe HISGs the effects on the visible light reflectance were allless severe falling to around 5 Therefore the HISGs willnot necessarily cause environmental light pollution
With regard to the UV transmittance since most of theUV light is absorbed by the semitransparent PV moduleand the heat insulation film the UV transmittance valuesof all the HISGs are 0 This means that the UV isolationperformances are very good and able to protect interiorfurnishings from aging and the skin from damage caused byUV radiation
32 Thermal Properties The surface emissivity of an objectrefers to its ability to release heat via thermal radiation afterabsorbing solar radiation The surface emissivity of eachcomponent is thus an important parameter affecting the heatinsulation performance of a HISG In this paper the spectralreflectance of each component on the exterior and interior
8 International Journal of Photoenergy
02468
101214161820222426
Refle
ctan
ce (
)
Wavelength (nm)
Tandem laser moduleTandem TCO modulea-Si TCO module
300 600 900 1200 1500 1800 2100 2400
(a)
0
10
20
30
40
50
60
70
Refle
ctan
ce (
)
Wavelength (nm)300 600 900 1200 1500 1800 2100 2400
Heat insulation film AHeat insulation film BHeat insulation film C
(b)
0
10
20
30
40
50
60
70
80
90
100
Refle
ctan
ce (
)
Wavelength (nm)
Glass
300 600 900 1200 1500 1800 2100 2400
(c)
Figure 5 Reflectance spectra of each component (a) semitransparent PV modules (b) heat insulation films and (c) rear glass
sides was measured using FTIR and then the emissivityvalue of each component was obtained by ISO 10292 asshown in Table 2 It can be seen that as the surfaces ofthe semitransparent PV modules and rear glass were not allcoated by a film the emissivity values for the exterior andinterior sides were 084 While the heat insulation filmswere mainly composed of PET material there was no filmcoating the interior surface of the film so the emissivityvalues were all 076 Meanwhile the exterior surfaces of theheat insulation films all had a multilayer metal coating sothe surface emissivity values were lower than the surfaceemissivity values on the indoor side The surface emissivity
of heat insulation film C is 0033 which is thus categorized asa Low-E film
Table 3 shows the thermal performances of the three typesof PVmodules and the nine types of HISGs with the SHGCsshading coefficients and overall heat transfer coefficients (119880-values) The results indicate that the multilayer structureof the HISG reduced the solar direct transmittance andsince the heat insulation films were coated with transparentmetal films this reflected the solar radiation heat promptingthe SHGCs to be reduced to half the levels seen with thesemitransparent PVmodulesThismeans that the quantity ofsolar radiation heat passing through the HISG was half that
International Journal of Photoenergy 9
0
2
4
6
8
10
12
545
478
103
208
535
639
1024
25
535
723
1017
407
00 0001
527
84
1007
709
UV
tran
smitt
ance
Visib
le li
ght
refle
ctan
ce
Visib
le li
ght
tran
smitt
ance
Sola
r rad
iatio
nre
flect
ance
Sola
r rad
iatio
ntr
ansm
ittan
ce
Tran
smitt
ance
and
refle
ctan
ce (
)
Tandem laser moduleTandem laser-A HISG
Tandem laser-B HISGTandem laser-C HISG
(a)
0
2
4
6
8
10
12
14
16
18
20
0 00001
515515515515
123166
18822
821788744
679516
626
1034
1833
UV
tran
smitt
ance
Visib
le li
ght
refle
ctan
ce
Visib
le li
ght
tran
smitt
ance
Sola
r rad
iatio
nre
flect
ance
Sola
r rad
iatio
ntr
ansm
ittan
ce
Tran
smitt
ance
and
refle
ctan
ce (
)Tandem TCO moduleTandem TCO-A HISG
Tandem TCO-B HISGTandem TCO-C HISG
(b)
02468
101214161820222426
000001
517514
514512
243329
372435
964909
83773
662803
1326
2349
UV
tran
smitt
ance
Visib
le li
ght
refle
ctan
ce
Visib
le li
ght
tran
smitt
ance
Sola
r rad
iatio
nre
flect
ance
Sola
r rad
iatio
ntr
ansm
ittan
ce
Tran
smitt
ance
and
refle
ctan
ce (
)
a-Si TCO modulea-Si TCO-A HISG
a-Si TCO-B HISGa-Si TCO-C HISG
(c)
Figure 6 Optical properties of the HISGs (a) tandem laser module (b) tandem TCOmodule and (c) a-Si TCO module
passing through the semitransparent PV modules In termsof the 119880-value since all the semitransparent PV moduleswere assembled with 4mm times 4mm laminated glass the 119880-values based on ISO 10292 for all modules were 563Wm2-K The addition of heat insulation films and dual air gaps toform a multilayer structure greatly reduced the 119880-values oftheHISGs (1755Wm2-Kndash1824Wm2-K)Moreover havingheat insulation films with different emissivity values is one
of the main causes of the decline in the 119880-value Since heatinsulation film C had the lowest surface emissivity theHISGs assembled using film C also possessed lower119880-values(1755Wm2-K)
33 Power Generation Gain Performance The power genera-tion test results for the front and back sides of each semitrans-parent PV module are shown in Table 4 The measurement
10 International Journal of Photoenergy
Table 2 Emissivity of each component
Item Emissivity ofindoor side
Emissivity ofoutdoor side
Tandem laser module 084 084Tandem TCOmodule 084 084a-Si TCO module 084 084Heat insulation film A 076 0135Heat insulation film B 076 0045Heat insulation film C 076 0033Rear glass 084 084
Table 3Thermal properties of the semitransparent PVmodules andHISGs
ModuleItem
SHGC Shadingcoefficient 119880-value
Tandem lasermodule 03 0345 563
Tandem laser-AHISG 0151 0174 1824
Tandem laser-BHISG 0135 0155 1757
Tandem laser-CHISG 0129 0148 1755
Tandem TCOmodule 038 0437 563
Tandem TCO-AHISG 0218 025 1824
Tandem TCO-BHISG 0184 0211 1757
Tandem TCO-CHISG 0171 0196 1755
a-Si TCOmodule 041 0471 563
a-Si TCO-AHISG 0249 0286 1824
a-Si TCO-BHISG 0207 0238 1757
a-Si TCO-CHISG 019 0218 1755
results show that the power output for the front side of thetandem laser module was 126029W with an efficiency of8184 while that of the back side was only 1019W Thereason for this is the cell structure of the tandem lasermoduleas the bottom back-contact conductive layer is Al whichdoes not possess power generation characteristicsThereforeafter being illuminated by direct light there should not be apower generation effect However because the tandem lasermodule was subjected to transverse laser cutting during themanufacturing process light can pass through from the backsideThe light could then undergo refraction or transmissionat the rear glass so some of the light is able to enter the power-generating layer from the laser cut slits and so the back side
Table 4 Results of tests of electrical characteristics in STC for initialstates of the original transparent PV module (a) front side and (b)back side
(a)
Test itemTandemlaser
module
TandemTCO
module
a-SiTCO
moduleModule efficiency () 8184 811 778Maximum power output(W) 126029 124843 119796
Open circuit voltage (V) 167382 171629 111606Short circuit current (A) 1133 1038 1595Maximum voltage (V) 131026 140561 86939Maximum electric current(A) 0962 0888 1378
Fill factor 06644 07008 06731
(b)
Test itemTandemlaser
module
TandemTCO
module
a-SiTCO
moduleModule efficiency () 0066 0723 5361Maximum power output(W) 1019 11134 82566
Open circuit voltage (V) 109965 156555 108648Short circuit current (A) 0026 0108 1213Maximum voltage (V) 40348 132561 83918Maximum electric current(A) 0025 0084 0984
Fill factor 03506 06576 06264
of the tandem laser module also possesses a slight powergeneration effect
The power output of the front side of the tandem TCOmodule was 124843W with an efficiency of 811 whereasthat of the back side was only 11134W The reason why theefficiency from back-side illumination is low is due to lightabsorption in the lower bandgap 120583c-Si cell which allowslimited light into the a-Si cell The current output would belimited by the smaller current value from the a-Si and so alower efficiency is generated
The front-side power output of the a-Si TCOmodule was119796W with an efficiency of 778 whereas the back-sidepower output of the a-Si TCO module reached 82566WThe power-generating layer of the a-Si TCO module is thea-Si layer which is also classified as a cell structure withdual-surface power generation characteristics so the back-side power output was higher compared to that of the formertwo modules However the reason for the difference in thefront-side and back-side power outputs of the a-Si TCOmodule is that the materials of the front and rear glasswere different The front glass was ultraclear glass with morethan 90 visible light transmittance Meanwhile in orderto increase the loading strength of the BIPV the rear glasswas mostly tempered glass or heat-strengthened glass with
International Journal of Photoenergy 11
lower transmissivity In addition before entering the power-generating layer from the back side the light still needs to passthrough a layer of EVA plastic film which will also reduce thesolar irradianceThe back-side power output of the a-Si TCOmodule was thus only 69 of the front-side power output
The results of the electrical tests of each semitransparentPV module and each combination of HISGs are shown inTable 5 The results for power generation gain are shownin Table 6 The experimental results indicated that boththe power generation and efficiency of tandem laser HISGexhibited slightly increasing trends the power generationincreased by around 001ndash013 and the efficiency increasedby around 0001ndash001 However the power generationand efficiency of tandem TCO HISG and a-Si TCO HISGdisplayed increasing trends For the tandem TCO HISGthe power generation improved by around 327ndash1006 andthe efficiency increased by around 027ndash082 For the a-SiTCOHISG the power generation increased by around 094ndash307 and the efficiency increased by around 007ndash024The power-generating layer of the tandem TCOmodule is a-Si120583c-Si but that of the a-Si TCO module is a single layer ofa-Si The absorption spectrum of the tandem TCO module(300 nmndash1100 nm) is wider than that of the a-Si TCOmodule(300 nmndash750 nm) The back side of the tandem TCO HISGcan thus absorb higher effective irradiance than the a-Si TCOHISG This means that the efficiency enhanced rate of thetandemTCOHISG is higher than that of the a-Si TCOHISGIt is also worth noting that selecting an appropriate heatinsulation film in order to absorb a larger amount of reflectivesolar radiation by the back side of theHISG can lead to greaterenhancement of power generation
34 Simulation of Energy-Saving Performance The simula-tion results for the power generation of each HISG installedin the buildings and the energy consumption of the heatingventilation and air-conditioning (HVAC) system are shownin Table 7 As Tainan is located in a subtropical region inTaiwan where there is sufficient sunlight the annual powergeneration of each module was higher than that of themodules in London and the power outputs ranged between16328 kW and 18727 kW London is located in a temperatezone with mostly cloudy weather and thus the annual powergeneration only ranged between 8493 kWand 9741 kWTheseresults show that different climate zones andweather patternsare the main factors affecting the power generation of BIPVmodules
The simulation results in Table 7 also show that the poweroutputs of each HISG were larger than those of the originalsemitransparent PV modules That is the power enhance-ments of the tandem laser HISG were around 001ndash012those of the tandem TCO HISG were around 327ndash1006and those of the a-Si TCO HISG were around 094ndash307The simulated results also reveal that the percentage gainsin power generation for each HISG installed on the roofs ofbuildings as BIPV roofs are consistent with the experimentalresults under STC from IEC 61646 Therefore adding heatinsulation films onto semitransparent PV modules to forma HISG in order to enhance the power output of the modulesis beneficial in reducing the EPBT of the entire BIPV system
The simulation results for the energy consumption of theHVAC systems of buildings in Tainan Taiwan and LondonUK are shown in Tables 8 and 9 respectively As Tainan islocated in a subtropical region the use of a heater is lesscommon and the HVAC system is mostly used for coolingso the energy consumption for the latter is much higher thanthat for heating On the other hand London is located in atemperate region and the HVAC system is mainly used forheating so the energy consumption for this is much higherthan that for cooling
Furthermore the main factors affecting the energy con-sumption of theHVAC system are the shading coefficient andthe 119880-value of the envelope The shading coefficient and 119880-value of each HISG are lower than those of the semitrans-parent PV modules During summer solar radiation cannotenter the room easily through the HISG so cooling energycan be saved During winter the 119880-value of the HISG isvery low owing to the multilayer structure and althoughsolar radiation cannot enter the room easily the heat will beretained inside the room and will not dissipate easily andhence the amount of energy used for heating can also bereduced Therefore the simulation results for the HISGs allindicate greater energy-saving performance in the annualenergy consumption of the HVAC system The results showthat the HISG can save 2911ndash3219 of cooling energy 4734ndash4815 of heating energy and 3268ndash3575 of the totalenergy consumption of the HVAC system in subtropicalregions and 3727ndash4412 of cooling energy 3905ndash3986 ofheating energy and 3905ndash3986 of total energy consump-tion of the HVAC system in temperate regions Among all theHISGs the HISG encapsulated version using heat insulationfilm C had the best energy-saving performance
As seen in the simulation results given above the HISGcan not only enhance the power generation but also becauseof the better heat insulation performance shorten the EPBTof the entire HISG BIPV application on a building
4 Conclusion
The concepts of net zero energy zero energy and passiveenergy are becoming more important as part of the energyconservation policies adopted by the construction industryBIPV technology currently has great potential for effectivedevelopment of solar module techniques Theoretically if aBIPV module is combined with building materials it caneffectively reduce overall construction costs save energymodulate the indoor temperature and shorten the energypayback time (EPBT)
In this work the authors adopted three different types ofsemitransparent PV modules and combined three differenttypes of high-reflectivity films to encapsulate HISG BIPVsystems The optical and thermal properties and the overallpower generation effects of each HISG were investigated Inaddition Autodesk software was used to calculate the powergeneration and energy-saving effects of each HISG as appliedto actual buildings in Taiwan with a subtropical climate andEngland with a temperate climate As a result due to thethree-layer structure of the HISGwith a high-reflectivity heatinsulation film the heat insulation performance (SHGC and
12 International Journal of Photoenergy
Table5Testresults
forthe
vario
usBIPV
mod
ules
andHISGsu
nder
STC
Testitem
Tand
emlaser
mod
ule
Tand
emlaser-A
HISG
Tand
emlaser-BHISG
Tand
emlaser-CHISG
Tand
emTC
Omod
ule
Tand
emTC
O-A
HISG
Tand
emTC
O-B
HISG
Tand
emTC
O-C
HISG
a-SiTC
Omod
ule
a-Si
TCO-A
HISG
a-SiTC
O-B
HISG
a-Si
TCO-C
HISG
Efficiency
()
8184
8185
8189
8194
811
837
874
892
778
785
787
802
Maxim
umpo
wer
output
(W)
126029
12604
2126105
126187
124843
128926
134658
137399
119796
120921
121125
123475
Opencircuit
voltage
(V)
1673
821672
531672
81167313
1716
291716
441718
86172036
1116
061115
971116
131117
10
Shortcirc
uit
current(A)
1133
1134
1133
1134
1038
1074
1125
1150
1595
1612
1615
1650
Maxim
umvoltage
(V)
1310
261294
33130098
1292
07140561
1391
73138796
138027
86939
8733
787341
84561
Maxim
umele
ctric
current(A)
0962
0974
0969
0977
0888
0926
0970
0995
1378
1385
1387
1460
Fillfactor
066
44066
4606654
06651
07008
06996
06964
06944
06731
06721
06719
06698
International Journal of Photoenergy 13
Table 6 Results of power generation gain tests of the semitransparent PV modules and each combination of HISG under STC
ModuleItem
Power generation (W) Power generationenhancement () Module efficiency () Module efficiency
enhancement ()Tandem laser module 126029 mdash 8184 mdashTandem laser-A HISG 126042 001 8185 0001Tandem laser-B HISG 126105 006 8189 0005Tandem laser-C HISG 126187 013 8194 0010Tandem TCOmodule 124843 mdash 811 mdashTandem TCO-A HISG 128926 327 837 027Tandem TCO-B HISG 134658 786 874 064Tandem TCO-C HISG 137399 1006 892 082a-Si TCO module 119796 mdash 778 mdasha-Si TCO-A HISG 120921 094 785 007a-Si TCO-B HISG 121125 111 787 009a-Si TCO-C HISG 123475 307 802 024
Table 7 Power generation results for building body simulations
Module LocationTainan Taiwan (kW) Power enhancement () London UK (kW) Power enhancement ()
Tandem laser module 17178 mdash 8935 mdashTandem laser-A HISG 17179 001 8936 001Tandem laser-B HISG 17188 006 8940 006Tandem laser-C HISG 17199 012 8946 012Tandem TCOmodule 17016 mdash 8851 mdashTandem TCO-A HISG 17573 327 9141 327Tandem TCO-B HISG 18354 786 9547 786Tandem TCO-C HISG 18727 1006 9741 1006a-Si TCO module 16328 mdash 8493 mdasha-Si TCO-A HISG 16481 094 8573 094a-Si TCO-B HISG 16509 111 8587 111a-Si TCO-C HISG 16830 307 8754 307
Table 8 Simulation results for energy consumption of HVAC systems for the building body in the Tainan region of Taiwan
Module Cooling energyconsumption (kW)
Cooling energysaving ()
Heating energyconsumption
(kW)
Heating energysaving ()
Total HVAC systemenergy consumption
(kW)
Total HVACenergy saving
()Tandem laser module 28632 mdash 6924 mdash 35556 mdashTandem laser-A HISG 20296 2911 3639 4744 23935 3268Tandem laser-B HISG 20053 2996 3590 4815 23643 3350Tandem laser-C HISG 19958 3029 3591 4814 23549 3377Tandem TCOmodule 29495 mdash 6894 mdash 36390 mdashTandem TCO-A HISG 20793 2950 3623 4745 24415 3291Tandem TCO-B HISG 20412 3080 3576 4813 23988 3408Tandem TCO-C HISG 20201 3151 3583 4803 23784 3464a-Si TCO module 30368 mdash 6869 mdash 37236 mdasha-Si TCO-A HISG 20952 3101 3617 4734 24569 3402a-Si TCO-B HISG 20593 3219 3568 4806 24161 3511a-Si TCO-C HISG 20347 3300 3577 4793 23924 3575
14 International Journal of Photoenergy
Table 9 Simulation results for energy consumption of HVAC systems for the building body in London UK
ModuleCooling energyconsumption
(kW)
Cooling energysaving ()
Heating energyconsumption
(kW)
Heating energysaving ()
Total HVAC system energyconsumption (kW)
Total HVACenergy saving
()Tandem laser module 306 mdash 116818 mdash 117123 mdashTandem laser-A HISG 181 4085 71203 3905 71384 3905Tandem laser-B HISG 171 4412 70570 3959 70741 3960Tandem laser-C HISG 173 4346 70491 3966 70664 3967Tandem TCOmodule 271 mdash 117612 mdash 117883 mdashTandem TCO-A HISG 170 3727 71497 3921 71667 3920Tandem TCO-B HISG 164 3948 70753 3984 70917 3984Tandem TCO-C HISG 165 3911 70734 3986 70899 3986a-Si TCO module 287 mdash 117214 mdash 117501 mdasha-Si TCO-A HISG 175 3902 71273 3919 71448 3919a-Si TCO-B HISG 172 4007 70640 3973 70812 3973a-Si TCO-C HISG 171 4042 70566 3980 70737 3980
119880-value) showed an improvement Although the multilayerstructure of HISG would affect the visible light transmit-tance in practice it does not have a significant impact onthe view through the glass Moreover although the solardirect reflectance values all showed improving trends thevisible light reflectance was only around 5 which will notnecessarily cause environmental light pollution Comparedto the original modules the power generation and moduleefficiency of all HISGs were found to have increased Of allthe combinations of HISGs the gain in power generation ofthe tandem TCO-C HISG was the highest as the power gen-eration was improved by 1006 and the module efficiencywas improved by 082The results of the simulation showeda very similar trendwith regard to the level of electrical powergeneration based on experimental data that was obtainedusing the standard test conditions (STC) for measurementcontained in IEC 61646The simulation results also indicatedthat theHISG has a significant effect on the amount of energythat can be saved when using the HVAC system in bothsubtropical and temperate regions
This paper thus provides valuable information for renew-able energy planners and architectural designers who areinterested in using HISG BIPV systems
Competing Interests
The authors declare that there are no competing interestsregarding the publication of this paper
Acknowledgments
This study was supported by the Ministry of Science andTechnology of Taiwan under Projects MOST 105-3113-F-011-001 and MOST 105-3113-E-006-006-CC2
References
[1] M van der Hoeven Energy and Climate ChangemdashWorld EnergyOutlook Special Report International Energy Agency 2015
[2] P Jones S S Hou and X Li ldquoTowards zero carbon designin offices integrating smart facades ventilation and surfaceheating and coolingrdquoRenewable Energy vol 73 pp 69ndash76 2015
[3] W Pan ldquoSystem boundaries of zero carbon buildingsrdquo Renew-able and Sustainable Energy Reviews vol 37 pp 424ndash434 2014
[4] S Berry K Davidson and W Saman ldquoDefining zero carbonand zero energy homes from a performance-based regulatoryperspectiverdquo Energy Efficiency vol 7 no 2 pp 303ndash322 2014
[5] G P Hammond H A Harajli C I Jones and A B WinnettldquoWhole systems appraisal of a UK Building Integrated Photo-voltaic (BIPV) system energy environmental and economicevaluationsrdquo Energy Policy vol 40 no 1 pp 219ndash230 2012
[6] G A Keoleian and GM Lewis ldquoModeling the life cycle energyand environmental performance of amorphous silicon BIPVroofing in the USrdquo Renewable Energy vol 28 no 2 pp 271ndash2932003
[7] L Lu andHX Yang ldquoEnvironmental payback time analysis of aroof-mounted building-integrated photovoltaic (BIPV) systemin Hong Kongrdquo Applied Energy vol 87 no 12 pp 3625ndash36312010
[8] L Y Seng G Lalchand and G M Sow Lin ldquoEconomicalenvironmental and technical analysis of building integratedphotovoltaic systems in Malaysiardquo Energy Policy vol 36 no 6pp 2130ndash2142 2008
[9] M Oliver and T Jackson ldquoEnergy and economic evaluation ofbuilding-integrated photovoltaicsrdquo Energy vol 26 no 4 pp431ndash439 2001
[10] L Sabnani A Skumanich E Ryabova and R Noufi Devel-oping Market Opportunities for Flexible Rooftop Applicationsof PV Using Flexible CIGS Technology Market ConsiderationsNational Renewable Energy Laboratory (NREL) Golden ColoUSA 2011
[11] M A Green K Emery Y Hishikawa W Warta and E DDunlop ldquoSolar cell efficiency tables (version 47)rdquo Progress inPhotovoltaics Research and Applications vol 24 no 1 pp 3ndash112016
[12] G Y Yun M McEvoy and K Steemers ldquoDesign and overallenergy performance of a ventilated photovoltaic facaderdquo SolarEnergy vol 81 no 3 pp 383ndash394 2007
International Journal of Photoenergy 15
[13] PWWong Y ShimodaM NonakaM Inoue andMMizunoldquoSemi-transparent PV thermal performance power generationdaylight modelling and energy saving potential in a residentialapplicationrdquo Renewable Energy vol 33 no 5 pp 1024ndash10362008
[14] D H W Li T N T Lam W W H Chan and A H L MakldquoEnergy and cost analysis of semi-transparent photovoltaic inoffice buildingsrdquo Applied Energy vol 86 no 5 pp 722ndash7292009
[15] H Radhi ldquoEnergy analysis of facade-integrated photovoltaicsystems applied to UAE commercial buildingsrdquo Solar Energyvol 84 no 12 pp 2009ndash2021 2010
[16] E L Didone and A Wagner ldquoSemi-transparent PV windowsa study for office buildings in Brazilrdquo Energy and Buildings vol67 pp 136ndash142 2013
[17] P K Ng and N Mithraratne ldquoLifetime performance of semi-transparent building-integrated photovoltaic (BIPV) glazingsystems in the tropicsrdquo Renewable and Sustainable EnergyReviews vol 31 pp 736ndash745 2014
[18] C H Young Y L Chen and P C Chen ldquoHeat insulation solarglass and application on energy efficiency buildingsrdquo Energyand Buildings vol 78 pp 66ndash78 2014
[19] International Organization for Standardization ISO 9050 Glassin BuildingmdashDetermination of Light Transmittance Solar DirectTransmittance Total Solar Energy Transmittance UltravioletTransmittance and Related Glazing Factors International Orga-nization for Standardization Basel Switzerland 2003
[20] International Organization for Standardization ldquoISO10292glass in buildingmdashcalculation of steady-state U values (thermaltransmittance) of multiple glazingrdquo Tech Rep InternationalOrganization for Standardization Geneva Switzerland 1994
[21] International Standard ldquoThin-film terrestrial photovoltaic (pv)modulesmdashdesign qualification and type approvalrdquo IEC 616462008
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Inorganic ChemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Carbohydrate Chemistry
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
Physical Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom
Analytical Methods in Chemistry
Journal of
Volume 2014
Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
SpectroscopyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Medicinal ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chromatography Research International
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Applied ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Theoretical ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Spectroscopy
Analytical ChemistryInternational Journal of
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Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Quantum Chemistry
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Organic Chemistry International
ElectrochemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CatalystsJournal of
6 International Journal of Photoenergy
Table 1 Optical properties of each component and HISGs
ModuleItem
Solar directtransmittance
Solar directreflectance
Visible lighttransmittance
Visible lightreflectance
UVtransmittance
Tandem laser module 709 1007 84 527 001Tandem TCOmodule 1833 679 220 515 001a-Si TCO module 2349 730 435 512 001Heat insulation film A 6814 1688 9532 483 175Heat insulation film B 4063 3089 8412 601 136Heat insulation film C 3315 4071 6104 2233 100Rear glass 8115 504 8885 566 6239Tandem laser-A HISG 407 1017 723 535 0Tandem laser-B HISG 25 1024 639 535 0Tandem laser-C HISG 208 1030 478 545 0Tandem TCO-A HISG 1034 744 188 515 0Tandem TCO-B HISG 626 788 166 515 0Tandem TCO-C HISG 516 821 123 515 0a-Si TCO-A HISG 1326 837 372 514 0a-Si TCO-B HISG 803 909 329 514 0a-Si TCO-C HISG 662 964 243 517 0
1400m
833
m
1009m
1100m110m
395
m
140m
Figure 3 The 3D model of the building body
properties of each component based on ISO 9050The valuesof lighting transmittance for the three PV modules were inthe 709ndash2349 range and those for the three heat insulationfilms were in the range of 3315ndash6814 The measurementresults show that the tandem lasermodule and heat insulationfilm C had better heat insulation effects They could thusbe used in hot climates where there is a need to reducesolar heat transmission especially in buildings where largetransparent surfaces are fitted Furthermore the tandem lasermodule and heat insulation filmA had better visibilities eventhoughwith the former the back-contact electrodematerial isopaque Part of the power-generating layers and back-contactelectrode layer in the tandem laser module were removed
using a transverse laser cutting method to enable the moduleto be light-transmissible It is also worth noting that the lowervisible light transmittance in other modules is mainly due toabsorption of the TCO layers The UV transmittances of thePVmodule and heat insulation film are less than 2meaningthat the performances of the HISGs with regard to isolatingUV light were very good
In the cell structure of the tandem TCO module thematerials of the power-generating layers are the same as thoseof the tandem laser module but in terms of the back-contactelectrode a TCO material with good light transmission andconduction properties was adopted Though TCO has highoptical transparency it does decrease light transmission fromUV to IR Therefore the tandem TCO module has a light-transmissible property and its insulation of solar thermalenergy is poorer than that of the tandem laser module Inaddition as the color of transmitted light tends to be winered part of its visible light transmittance was poorer Thematerial of the rear electrode in the cell structure of the a-Si TCO module was the same as that of the tandem TCOmoduleAs such it also has a light-transmissible property andthe transmitted light color tends to be orange red Howeverin the power-generating layer the a-Si TCO module had asingle-layer structure without a layer of 120583c-Si so its visiblelight transmittance was slightly better than that of the tandemTCOmodule Furthermore as it has no 120583c-Si layer to absorbthe solar light its solar radiation transmittance was slightlypoorer than that of the tandem TCOmodule
As shown in Figure 6 the measurement results for thesolar direct transmittance indicated that the addition ofa reflective layer reduces the transmittance of HISGs Forthe tandem laser tandem TCO and a-Si TCO modulethe solar direct transmittance was originally 709 1833
International Journal of Photoenergy 7
0
10
20
30
40
50Tr
ansm
ittan
ce (
)
Wavelength (nm)
Tandem laser moduleTandem TCO modulea-Si TCO module
300 600 900 1200 1500 1800 2100 2400
(a)
0
10
20
30
40
50
60
70
80
90
100
Tran
smitt
ance
()
Wavelength (nm)300 600 900 1200 1500 1800 2100 2400
Heat insulation film AHeat insulation film BHeat insulation film C
(b)
0
20
40
60
80
100
Tran
smitt
ance
()
Wavelength (nm)500 1000 1500 2000 2500
Glass
(c)
Figure 4 Transmittance spectra of each component (a) semitransparent PV module (b) heat insulation film and (c) rear glass
and 2349 but after being encapsulated into the HISGit dropped to 208ndash407 516ndash1034 and 662ndash1326respectively The visible light transmittance was originally84 22 and 435 but after being encapsulated into theHISG it dropped to 478ndash723 123ndash188 and 243ndash372respectively
After the various semitransparent PVmodules were inte-grated into the HISG with the various heat insulation filmsall their solar direct reflectance values increased slightly sothe encapsulationwas slightly beneficial to the heat insulatingeffect of the HISGs Moreover after being encapsulated intothe HISGs the effects on the visible light reflectance were allless severe falling to around 5 Therefore the HISGs willnot necessarily cause environmental light pollution
With regard to the UV transmittance since most of theUV light is absorbed by the semitransparent PV moduleand the heat insulation film the UV transmittance valuesof all the HISGs are 0 This means that the UV isolationperformances are very good and able to protect interiorfurnishings from aging and the skin from damage caused byUV radiation
32 Thermal Properties The surface emissivity of an objectrefers to its ability to release heat via thermal radiation afterabsorbing solar radiation The surface emissivity of eachcomponent is thus an important parameter affecting the heatinsulation performance of a HISG In this paper the spectralreflectance of each component on the exterior and interior
8 International Journal of Photoenergy
02468
101214161820222426
Refle
ctan
ce (
)
Wavelength (nm)
Tandem laser moduleTandem TCO modulea-Si TCO module
300 600 900 1200 1500 1800 2100 2400
(a)
0
10
20
30
40
50
60
70
Refle
ctan
ce (
)
Wavelength (nm)300 600 900 1200 1500 1800 2100 2400
Heat insulation film AHeat insulation film BHeat insulation film C
(b)
0
10
20
30
40
50
60
70
80
90
100
Refle
ctan
ce (
)
Wavelength (nm)
Glass
300 600 900 1200 1500 1800 2100 2400
(c)
Figure 5 Reflectance spectra of each component (a) semitransparent PV modules (b) heat insulation films and (c) rear glass
sides was measured using FTIR and then the emissivityvalue of each component was obtained by ISO 10292 asshown in Table 2 It can be seen that as the surfaces ofthe semitransparent PV modules and rear glass were not allcoated by a film the emissivity values for the exterior andinterior sides were 084 While the heat insulation filmswere mainly composed of PET material there was no filmcoating the interior surface of the film so the emissivityvalues were all 076 Meanwhile the exterior surfaces of theheat insulation films all had a multilayer metal coating sothe surface emissivity values were lower than the surfaceemissivity values on the indoor side The surface emissivity
of heat insulation film C is 0033 which is thus categorized asa Low-E film
Table 3 shows the thermal performances of the three typesof PVmodules and the nine types of HISGs with the SHGCsshading coefficients and overall heat transfer coefficients (119880-values) The results indicate that the multilayer structureof the HISG reduced the solar direct transmittance andsince the heat insulation films were coated with transparentmetal films this reflected the solar radiation heat promptingthe SHGCs to be reduced to half the levels seen with thesemitransparent PVmodulesThismeans that the quantity ofsolar radiation heat passing through the HISG was half that
International Journal of Photoenergy 9
0
2
4
6
8
10
12
545
478
103
208
535
639
1024
25
535
723
1017
407
00 0001
527
84
1007
709
UV
tran
smitt
ance
Visib
le li
ght
refle
ctan
ce
Visib
le li
ght
tran
smitt
ance
Sola
r rad
iatio
nre
flect
ance
Sola
r rad
iatio
ntr
ansm
ittan
ce
Tran
smitt
ance
and
refle
ctan
ce (
)
Tandem laser moduleTandem laser-A HISG
Tandem laser-B HISGTandem laser-C HISG
(a)
0
2
4
6
8
10
12
14
16
18
20
0 00001
515515515515
123166
18822
821788744
679516
626
1034
1833
UV
tran
smitt
ance
Visib
le li
ght
refle
ctan
ce
Visib
le li
ght
tran
smitt
ance
Sola
r rad
iatio
nre
flect
ance
Sola
r rad
iatio
ntr
ansm
ittan
ce
Tran
smitt
ance
and
refle
ctan
ce (
)Tandem TCO moduleTandem TCO-A HISG
Tandem TCO-B HISGTandem TCO-C HISG
(b)
02468
101214161820222426
000001
517514
514512
243329
372435
964909
83773
662803
1326
2349
UV
tran
smitt
ance
Visib
le li
ght
refle
ctan
ce
Visib
le li
ght
tran
smitt
ance
Sola
r rad
iatio
nre
flect
ance
Sola
r rad
iatio
ntr
ansm
ittan
ce
Tran
smitt
ance
and
refle
ctan
ce (
)
a-Si TCO modulea-Si TCO-A HISG
a-Si TCO-B HISGa-Si TCO-C HISG
(c)
Figure 6 Optical properties of the HISGs (a) tandem laser module (b) tandem TCOmodule and (c) a-Si TCO module
passing through the semitransparent PV modules In termsof the 119880-value since all the semitransparent PV moduleswere assembled with 4mm times 4mm laminated glass the 119880-values based on ISO 10292 for all modules were 563Wm2-K The addition of heat insulation films and dual air gaps toform a multilayer structure greatly reduced the 119880-values oftheHISGs (1755Wm2-Kndash1824Wm2-K)Moreover havingheat insulation films with different emissivity values is one
of the main causes of the decline in the 119880-value Since heatinsulation film C had the lowest surface emissivity theHISGs assembled using film C also possessed lower119880-values(1755Wm2-K)
33 Power Generation Gain Performance The power genera-tion test results for the front and back sides of each semitrans-parent PV module are shown in Table 4 The measurement
10 International Journal of Photoenergy
Table 2 Emissivity of each component
Item Emissivity ofindoor side
Emissivity ofoutdoor side
Tandem laser module 084 084Tandem TCOmodule 084 084a-Si TCO module 084 084Heat insulation film A 076 0135Heat insulation film B 076 0045Heat insulation film C 076 0033Rear glass 084 084
Table 3Thermal properties of the semitransparent PVmodules andHISGs
ModuleItem
SHGC Shadingcoefficient 119880-value
Tandem lasermodule 03 0345 563
Tandem laser-AHISG 0151 0174 1824
Tandem laser-BHISG 0135 0155 1757
Tandem laser-CHISG 0129 0148 1755
Tandem TCOmodule 038 0437 563
Tandem TCO-AHISG 0218 025 1824
Tandem TCO-BHISG 0184 0211 1757
Tandem TCO-CHISG 0171 0196 1755
a-Si TCOmodule 041 0471 563
a-Si TCO-AHISG 0249 0286 1824
a-Si TCO-BHISG 0207 0238 1757
a-Si TCO-CHISG 019 0218 1755
results show that the power output for the front side of thetandem laser module was 126029W with an efficiency of8184 while that of the back side was only 1019W Thereason for this is the cell structure of the tandem lasermoduleas the bottom back-contact conductive layer is Al whichdoes not possess power generation characteristicsThereforeafter being illuminated by direct light there should not be apower generation effect However because the tandem lasermodule was subjected to transverse laser cutting during themanufacturing process light can pass through from the backsideThe light could then undergo refraction or transmissionat the rear glass so some of the light is able to enter the power-generating layer from the laser cut slits and so the back side
Table 4 Results of tests of electrical characteristics in STC for initialstates of the original transparent PV module (a) front side and (b)back side
(a)
Test itemTandemlaser
module
TandemTCO
module
a-SiTCO
moduleModule efficiency () 8184 811 778Maximum power output(W) 126029 124843 119796
Open circuit voltage (V) 167382 171629 111606Short circuit current (A) 1133 1038 1595Maximum voltage (V) 131026 140561 86939Maximum electric current(A) 0962 0888 1378
Fill factor 06644 07008 06731
(b)
Test itemTandemlaser
module
TandemTCO
module
a-SiTCO
moduleModule efficiency () 0066 0723 5361Maximum power output(W) 1019 11134 82566
Open circuit voltage (V) 109965 156555 108648Short circuit current (A) 0026 0108 1213Maximum voltage (V) 40348 132561 83918Maximum electric current(A) 0025 0084 0984
Fill factor 03506 06576 06264
of the tandem laser module also possesses a slight powergeneration effect
The power output of the front side of the tandem TCOmodule was 124843W with an efficiency of 811 whereasthat of the back side was only 11134W The reason why theefficiency from back-side illumination is low is due to lightabsorption in the lower bandgap 120583c-Si cell which allowslimited light into the a-Si cell The current output would belimited by the smaller current value from the a-Si and so alower efficiency is generated
The front-side power output of the a-Si TCOmodule was119796W with an efficiency of 778 whereas the back-sidepower output of the a-Si TCO module reached 82566WThe power-generating layer of the a-Si TCO module is thea-Si layer which is also classified as a cell structure withdual-surface power generation characteristics so the back-side power output was higher compared to that of the formertwo modules However the reason for the difference in thefront-side and back-side power outputs of the a-Si TCOmodule is that the materials of the front and rear glasswere different The front glass was ultraclear glass with morethan 90 visible light transmittance Meanwhile in orderto increase the loading strength of the BIPV the rear glasswas mostly tempered glass or heat-strengthened glass with
International Journal of Photoenergy 11
lower transmissivity In addition before entering the power-generating layer from the back side the light still needs to passthrough a layer of EVA plastic film which will also reduce thesolar irradianceThe back-side power output of the a-Si TCOmodule was thus only 69 of the front-side power output
The results of the electrical tests of each semitransparentPV module and each combination of HISGs are shown inTable 5 The results for power generation gain are shownin Table 6 The experimental results indicated that boththe power generation and efficiency of tandem laser HISGexhibited slightly increasing trends the power generationincreased by around 001ndash013 and the efficiency increasedby around 0001ndash001 However the power generationand efficiency of tandem TCO HISG and a-Si TCO HISGdisplayed increasing trends For the tandem TCO HISGthe power generation improved by around 327ndash1006 andthe efficiency increased by around 027ndash082 For the a-SiTCOHISG the power generation increased by around 094ndash307 and the efficiency increased by around 007ndash024The power-generating layer of the tandem TCOmodule is a-Si120583c-Si but that of the a-Si TCO module is a single layer ofa-Si The absorption spectrum of the tandem TCO module(300 nmndash1100 nm) is wider than that of the a-Si TCOmodule(300 nmndash750 nm) The back side of the tandem TCO HISGcan thus absorb higher effective irradiance than the a-Si TCOHISG This means that the efficiency enhanced rate of thetandemTCOHISG is higher than that of the a-Si TCOHISGIt is also worth noting that selecting an appropriate heatinsulation film in order to absorb a larger amount of reflectivesolar radiation by the back side of theHISG can lead to greaterenhancement of power generation
34 Simulation of Energy-Saving Performance The simula-tion results for the power generation of each HISG installedin the buildings and the energy consumption of the heatingventilation and air-conditioning (HVAC) system are shownin Table 7 As Tainan is located in a subtropical region inTaiwan where there is sufficient sunlight the annual powergeneration of each module was higher than that of themodules in London and the power outputs ranged between16328 kW and 18727 kW London is located in a temperatezone with mostly cloudy weather and thus the annual powergeneration only ranged between 8493 kWand 9741 kWTheseresults show that different climate zones andweather patternsare the main factors affecting the power generation of BIPVmodules
The simulation results in Table 7 also show that the poweroutputs of each HISG were larger than those of the originalsemitransparent PV modules That is the power enhance-ments of the tandem laser HISG were around 001ndash012those of the tandem TCO HISG were around 327ndash1006and those of the a-Si TCO HISG were around 094ndash307The simulated results also reveal that the percentage gainsin power generation for each HISG installed on the roofs ofbuildings as BIPV roofs are consistent with the experimentalresults under STC from IEC 61646 Therefore adding heatinsulation films onto semitransparent PV modules to forma HISG in order to enhance the power output of the modulesis beneficial in reducing the EPBT of the entire BIPV system
The simulation results for the energy consumption of theHVAC systems of buildings in Tainan Taiwan and LondonUK are shown in Tables 8 and 9 respectively As Tainan islocated in a subtropical region the use of a heater is lesscommon and the HVAC system is mostly used for coolingso the energy consumption for the latter is much higher thanthat for heating On the other hand London is located in atemperate region and the HVAC system is mainly used forheating so the energy consumption for this is much higherthan that for cooling
Furthermore the main factors affecting the energy con-sumption of theHVAC system are the shading coefficient andthe 119880-value of the envelope The shading coefficient and 119880-value of each HISG are lower than those of the semitrans-parent PV modules During summer solar radiation cannotenter the room easily through the HISG so cooling energycan be saved During winter the 119880-value of the HISG isvery low owing to the multilayer structure and althoughsolar radiation cannot enter the room easily the heat will beretained inside the room and will not dissipate easily andhence the amount of energy used for heating can also bereduced Therefore the simulation results for the HISGs allindicate greater energy-saving performance in the annualenergy consumption of the HVAC system The results showthat the HISG can save 2911ndash3219 of cooling energy 4734ndash4815 of heating energy and 3268ndash3575 of the totalenergy consumption of the HVAC system in subtropicalregions and 3727ndash4412 of cooling energy 3905ndash3986 ofheating energy and 3905ndash3986 of total energy consump-tion of the HVAC system in temperate regions Among all theHISGs the HISG encapsulated version using heat insulationfilm C had the best energy-saving performance
As seen in the simulation results given above the HISGcan not only enhance the power generation but also becauseof the better heat insulation performance shorten the EPBTof the entire HISG BIPV application on a building
4 Conclusion
The concepts of net zero energy zero energy and passiveenergy are becoming more important as part of the energyconservation policies adopted by the construction industryBIPV technology currently has great potential for effectivedevelopment of solar module techniques Theoretically if aBIPV module is combined with building materials it caneffectively reduce overall construction costs save energymodulate the indoor temperature and shorten the energypayback time (EPBT)
In this work the authors adopted three different types ofsemitransparent PV modules and combined three differenttypes of high-reflectivity films to encapsulate HISG BIPVsystems The optical and thermal properties and the overallpower generation effects of each HISG were investigated Inaddition Autodesk software was used to calculate the powergeneration and energy-saving effects of each HISG as appliedto actual buildings in Taiwan with a subtropical climate andEngland with a temperate climate As a result due to thethree-layer structure of the HISGwith a high-reflectivity heatinsulation film the heat insulation performance (SHGC and
12 International Journal of Photoenergy
Table5Testresults
forthe
vario
usBIPV
mod
ules
andHISGsu
nder
STC
Testitem
Tand
emlaser
mod
ule
Tand
emlaser-A
HISG
Tand
emlaser-BHISG
Tand
emlaser-CHISG
Tand
emTC
Omod
ule
Tand
emTC
O-A
HISG
Tand
emTC
O-B
HISG
Tand
emTC
O-C
HISG
a-SiTC
Omod
ule
a-Si
TCO-A
HISG
a-SiTC
O-B
HISG
a-Si
TCO-C
HISG
Efficiency
()
8184
8185
8189
8194
811
837
874
892
778
785
787
802
Maxim
umpo
wer
output
(W)
126029
12604
2126105
126187
124843
128926
134658
137399
119796
120921
121125
123475
Opencircuit
voltage
(V)
1673
821672
531672
81167313
1716
291716
441718
86172036
1116
061115
971116
131117
10
Shortcirc
uit
current(A)
1133
1134
1133
1134
1038
1074
1125
1150
1595
1612
1615
1650
Maxim
umvoltage
(V)
1310
261294
33130098
1292
07140561
1391
73138796
138027
86939
8733
787341
84561
Maxim
umele
ctric
current(A)
0962
0974
0969
0977
0888
0926
0970
0995
1378
1385
1387
1460
Fillfactor
066
44066
4606654
06651
07008
06996
06964
06944
06731
06721
06719
06698
International Journal of Photoenergy 13
Table 6 Results of power generation gain tests of the semitransparent PV modules and each combination of HISG under STC
ModuleItem
Power generation (W) Power generationenhancement () Module efficiency () Module efficiency
enhancement ()Tandem laser module 126029 mdash 8184 mdashTandem laser-A HISG 126042 001 8185 0001Tandem laser-B HISG 126105 006 8189 0005Tandem laser-C HISG 126187 013 8194 0010Tandem TCOmodule 124843 mdash 811 mdashTandem TCO-A HISG 128926 327 837 027Tandem TCO-B HISG 134658 786 874 064Tandem TCO-C HISG 137399 1006 892 082a-Si TCO module 119796 mdash 778 mdasha-Si TCO-A HISG 120921 094 785 007a-Si TCO-B HISG 121125 111 787 009a-Si TCO-C HISG 123475 307 802 024
Table 7 Power generation results for building body simulations
Module LocationTainan Taiwan (kW) Power enhancement () London UK (kW) Power enhancement ()
Tandem laser module 17178 mdash 8935 mdashTandem laser-A HISG 17179 001 8936 001Tandem laser-B HISG 17188 006 8940 006Tandem laser-C HISG 17199 012 8946 012Tandem TCOmodule 17016 mdash 8851 mdashTandem TCO-A HISG 17573 327 9141 327Tandem TCO-B HISG 18354 786 9547 786Tandem TCO-C HISG 18727 1006 9741 1006a-Si TCO module 16328 mdash 8493 mdasha-Si TCO-A HISG 16481 094 8573 094a-Si TCO-B HISG 16509 111 8587 111a-Si TCO-C HISG 16830 307 8754 307
Table 8 Simulation results for energy consumption of HVAC systems for the building body in the Tainan region of Taiwan
Module Cooling energyconsumption (kW)
Cooling energysaving ()
Heating energyconsumption
(kW)
Heating energysaving ()
Total HVAC systemenergy consumption
(kW)
Total HVACenergy saving
()Tandem laser module 28632 mdash 6924 mdash 35556 mdashTandem laser-A HISG 20296 2911 3639 4744 23935 3268Tandem laser-B HISG 20053 2996 3590 4815 23643 3350Tandem laser-C HISG 19958 3029 3591 4814 23549 3377Tandem TCOmodule 29495 mdash 6894 mdash 36390 mdashTandem TCO-A HISG 20793 2950 3623 4745 24415 3291Tandem TCO-B HISG 20412 3080 3576 4813 23988 3408Tandem TCO-C HISG 20201 3151 3583 4803 23784 3464a-Si TCO module 30368 mdash 6869 mdash 37236 mdasha-Si TCO-A HISG 20952 3101 3617 4734 24569 3402a-Si TCO-B HISG 20593 3219 3568 4806 24161 3511a-Si TCO-C HISG 20347 3300 3577 4793 23924 3575
14 International Journal of Photoenergy
Table 9 Simulation results for energy consumption of HVAC systems for the building body in London UK
ModuleCooling energyconsumption
(kW)
Cooling energysaving ()
Heating energyconsumption
(kW)
Heating energysaving ()
Total HVAC system energyconsumption (kW)
Total HVACenergy saving
()Tandem laser module 306 mdash 116818 mdash 117123 mdashTandem laser-A HISG 181 4085 71203 3905 71384 3905Tandem laser-B HISG 171 4412 70570 3959 70741 3960Tandem laser-C HISG 173 4346 70491 3966 70664 3967Tandem TCOmodule 271 mdash 117612 mdash 117883 mdashTandem TCO-A HISG 170 3727 71497 3921 71667 3920Tandem TCO-B HISG 164 3948 70753 3984 70917 3984Tandem TCO-C HISG 165 3911 70734 3986 70899 3986a-Si TCO module 287 mdash 117214 mdash 117501 mdasha-Si TCO-A HISG 175 3902 71273 3919 71448 3919a-Si TCO-B HISG 172 4007 70640 3973 70812 3973a-Si TCO-C HISG 171 4042 70566 3980 70737 3980
119880-value) showed an improvement Although the multilayerstructure of HISG would affect the visible light transmit-tance in practice it does not have a significant impact onthe view through the glass Moreover although the solardirect reflectance values all showed improving trends thevisible light reflectance was only around 5 which will notnecessarily cause environmental light pollution Comparedto the original modules the power generation and moduleefficiency of all HISGs were found to have increased Of allthe combinations of HISGs the gain in power generation ofthe tandem TCO-C HISG was the highest as the power gen-eration was improved by 1006 and the module efficiencywas improved by 082The results of the simulation showeda very similar trendwith regard to the level of electrical powergeneration based on experimental data that was obtainedusing the standard test conditions (STC) for measurementcontained in IEC 61646The simulation results also indicatedthat theHISG has a significant effect on the amount of energythat can be saved when using the HVAC system in bothsubtropical and temperate regions
This paper thus provides valuable information for renew-able energy planners and architectural designers who areinterested in using HISG BIPV systems
Competing Interests
The authors declare that there are no competing interestsregarding the publication of this paper
Acknowledgments
This study was supported by the Ministry of Science andTechnology of Taiwan under Projects MOST 105-3113-F-011-001 and MOST 105-3113-E-006-006-CC2
References
[1] M van der Hoeven Energy and Climate ChangemdashWorld EnergyOutlook Special Report International Energy Agency 2015
[2] P Jones S S Hou and X Li ldquoTowards zero carbon designin offices integrating smart facades ventilation and surfaceheating and coolingrdquoRenewable Energy vol 73 pp 69ndash76 2015
[3] W Pan ldquoSystem boundaries of zero carbon buildingsrdquo Renew-able and Sustainable Energy Reviews vol 37 pp 424ndash434 2014
[4] S Berry K Davidson and W Saman ldquoDefining zero carbonand zero energy homes from a performance-based regulatoryperspectiverdquo Energy Efficiency vol 7 no 2 pp 303ndash322 2014
[5] G P Hammond H A Harajli C I Jones and A B WinnettldquoWhole systems appraisal of a UK Building Integrated Photo-voltaic (BIPV) system energy environmental and economicevaluationsrdquo Energy Policy vol 40 no 1 pp 219ndash230 2012
[6] G A Keoleian and GM Lewis ldquoModeling the life cycle energyand environmental performance of amorphous silicon BIPVroofing in the USrdquo Renewable Energy vol 28 no 2 pp 271ndash2932003
[7] L Lu andHX Yang ldquoEnvironmental payback time analysis of aroof-mounted building-integrated photovoltaic (BIPV) systemin Hong Kongrdquo Applied Energy vol 87 no 12 pp 3625ndash36312010
[8] L Y Seng G Lalchand and G M Sow Lin ldquoEconomicalenvironmental and technical analysis of building integratedphotovoltaic systems in Malaysiardquo Energy Policy vol 36 no 6pp 2130ndash2142 2008
[9] M Oliver and T Jackson ldquoEnergy and economic evaluation ofbuilding-integrated photovoltaicsrdquo Energy vol 26 no 4 pp431ndash439 2001
[10] L Sabnani A Skumanich E Ryabova and R Noufi Devel-oping Market Opportunities for Flexible Rooftop Applicationsof PV Using Flexible CIGS Technology Market ConsiderationsNational Renewable Energy Laboratory (NREL) Golden ColoUSA 2011
[11] M A Green K Emery Y Hishikawa W Warta and E DDunlop ldquoSolar cell efficiency tables (version 47)rdquo Progress inPhotovoltaics Research and Applications vol 24 no 1 pp 3ndash112016
[12] G Y Yun M McEvoy and K Steemers ldquoDesign and overallenergy performance of a ventilated photovoltaic facaderdquo SolarEnergy vol 81 no 3 pp 383ndash394 2007
International Journal of Photoenergy 15
[13] PWWong Y ShimodaM NonakaM Inoue andMMizunoldquoSemi-transparent PV thermal performance power generationdaylight modelling and energy saving potential in a residentialapplicationrdquo Renewable Energy vol 33 no 5 pp 1024ndash10362008
[14] D H W Li T N T Lam W W H Chan and A H L MakldquoEnergy and cost analysis of semi-transparent photovoltaic inoffice buildingsrdquo Applied Energy vol 86 no 5 pp 722ndash7292009
[15] H Radhi ldquoEnergy analysis of facade-integrated photovoltaicsystems applied to UAE commercial buildingsrdquo Solar Energyvol 84 no 12 pp 2009ndash2021 2010
[16] E L Didone and A Wagner ldquoSemi-transparent PV windowsa study for office buildings in Brazilrdquo Energy and Buildings vol67 pp 136ndash142 2013
[17] P K Ng and N Mithraratne ldquoLifetime performance of semi-transparent building-integrated photovoltaic (BIPV) glazingsystems in the tropicsrdquo Renewable and Sustainable EnergyReviews vol 31 pp 736ndash745 2014
[18] C H Young Y L Chen and P C Chen ldquoHeat insulation solarglass and application on energy efficiency buildingsrdquo Energyand Buildings vol 78 pp 66ndash78 2014
[19] International Organization for Standardization ISO 9050 Glassin BuildingmdashDetermination of Light Transmittance Solar DirectTransmittance Total Solar Energy Transmittance UltravioletTransmittance and Related Glazing Factors International Orga-nization for Standardization Basel Switzerland 2003
[20] International Organization for Standardization ldquoISO10292glass in buildingmdashcalculation of steady-state U values (thermaltransmittance) of multiple glazingrdquo Tech Rep InternationalOrganization for Standardization Geneva Switzerland 1994
[21] International Standard ldquoThin-film terrestrial photovoltaic (pv)modulesmdashdesign qualification and type approvalrdquo IEC 616462008
Submit your manuscripts athttpwwwhindawicom
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International Journal ofPhotoenergy
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CatalystsJournal of
International Journal of Photoenergy 7
0
10
20
30
40
50Tr
ansm
ittan
ce (
)
Wavelength (nm)
Tandem laser moduleTandem TCO modulea-Si TCO module
300 600 900 1200 1500 1800 2100 2400
(a)
0
10
20
30
40
50
60
70
80
90
100
Tran
smitt
ance
()
Wavelength (nm)300 600 900 1200 1500 1800 2100 2400
Heat insulation film AHeat insulation film BHeat insulation film C
(b)
0
20
40
60
80
100
Tran
smitt
ance
()
Wavelength (nm)500 1000 1500 2000 2500
Glass
(c)
Figure 4 Transmittance spectra of each component (a) semitransparent PV module (b) heat insulation film and (c) rear glass
and 2349 but after being encapsulated into the HISGit dropped to 208ndash407 516ndash1034 and 662ndash1326respectively The visible light transmittance was originally84 22 and 435 but after being encapsulated into theHISG it dropped to 478ndash723 123ndash188 and 243ndash372respectively
After the various semitransparent PVmodules were inte-grated into the HISG with the various heat insulation filmsall their solar direct reflectance values increased slightly sothe encapsulationwas slightly beneficial to the heat insulatingeffect of the HISGs Moreover after being encapsulated intothe HISGs the effects on the visible light reflectance were allless severe falling to around 5 Therefore the HISGs willnot necessarily cause environmental light pollution
With regard to the UV transmittance since most of theUV light is absorbed by the semitransparent PV moduleand the heat insulation film the UV transmittance valuesof all the HISGs are 0 This means that the UV isolationperformances are very good and able to protect interiorfurnishings from aging and the skin from damage caused byUV radiation
32 Thermal Properties The surface emissivity of an objectrefers to its ability to release heat via thermal radiation afterabsorbing solar radiation The surface emissivity of eachcomponent is thus an important parameter affecting the heatinsulation performance of a HISG In this paper the spectralreflectance of each component on the exterior and interior
8 International Journal of Photoenergy
02468
101214161820222426
Refle
ctan
ce (
)
Wavelength (nm)
Tandem laser moduleTandem TCO modulea-Si TCO module
300 600 900 1200 1500 1800 2100 2400
(a)
0
10
20
30
40
50
60
70
Refle
ctan
ce (
)
Wavelength (nm)300 600 900 1200 1500 1800 2100 2400
Heat insulation film AHeat insulation film BHeat insulation film C
(b)
0
10
20
30
40
50
60
70
80
90
100
Refle
ctan
ce (
)
Wavelength (nm)
Glass
300 600 900 1200 1500 1800 2100 2400
(c)
Figure 5 Reflectance spectra of each component (a) semitransparent PV modules (b) heat insulation films and (c) rear glass
sides was measured using FTIR and then the emissivityvalue of each component was obtained by ISO 10292 asshown in Table 2 It can be seen that as the surfaces ofthe semitransparent PV modules and rear glass were not allcoated by a film the emissivity values for the exterior andinterior sides were 084 While the heat insulation filmswere mainly composed of PET material there was no filmcoating the interior surface of the film so the emissivityvalues were all 076 Meanwhile the exterior surfaces of theheat insulation films all had a multilayer metal coating sothe surface emissivity values were lower than the surfaceemissivity values on the indoor side The surface emissivity
of heat insulation film C is 0033 which is thus categorized asa Low-E film
Table 3 shows the thermal performances of the three typesof PVmodules and the nine types of HISGs with the SHGCsshading coefficients and overall heat transfer coefficients (119880-values) The results indicate that the multilayer structureof the HISG reduced the solar direct transmittance andsince the heat insulation films were coated with transparentmetal films this reflected the solar radiation heat promptingthe SHGCs to be reduced to half the levels seen with thesemitransparent PVmodulesThismeans that the quantity ofsolar radiation heat passing through the HISG was half that
International Journal of Photoenergy 9
0
2
4
6
8
10
12
545
478
103
208
535
639
1024
25
535
723
1017
407
00 0001
527
84
1007
709
UV
tran
smitt
ance
Visib
le li
ght
refle
ctan
ce
Visib
le li
ght
tran
smitt
ance
Sola
r rad
iatio
nre
flect
ance
Sola
r rad
iatio
ntr
ansm
ittan
ce
Tran
smitt
ance
and
refle
ctan
ce (
)
Tandem laser moduleTandem laser-A HISG
Tandem laser-B HISGTandem laser-C HISG
(a)
0
2
4
6
8
10
12
14
16
18
20
0 00001
515515515515
123166
18822
821788744
679516
626
1034
1833
UV
tran
smitt
ance
Visib
le li
ght
refle
ctan
ce
Visib
le li
ght
tran
smitt
ance
Sola
r rad
iatio
nre
flect
ance
Sola
r rad
iatio
ntr
ansm
ittan
ce
Tran
smitt
ance
and
refle
ctan
ce (
)Tandem TCO moduleTandem TCO-A HISG
Tandem TCO-B HISGTandem TCO-C HISG
(b)
02468
101214161820222426
000001
517514
514512
243329
372435
964909
83773
662803
1326
2349
UV
tran
smitt
ance
Visib
le li
ght
refle
ctan
ce
Visib
le li
ght
tran
smitt
ance
Sola
r rad
iatio
nre
flect
ance
Sola
r rad
iatio
ntr
ansm
ittan
ce
Tran
smitt
ance
and
refle
ctan
ce (
)
a-Si TCO modulea-Si TCO-A HISG
a-Si TCO-B HISGa-Si TCO-C HISG
(c)
Figure 6 Optical properties of the HISGs (a) tandem laser module (b) tandem TCOmodule and (c) a-Si TCO module
passing through the semitransparent PV modules In termsof the 119880-value since all the semitransparent PV moduleswere assembled with 4mm times 4mm laminated glass the 119880-values based on ISO 10292 for all modules were 563Wm2-K The addition of heat insulation films and dual air gaps toform a multilayer structure greatly reduced the 119880-values oftheHISGs (1755Wm2-Kndash1824Wm2-K)Moreover havingheat insulation films with different emissivity values is one
of the main causes of the decline in the 119880-value Since heatinsulation film C had the lowest surface emissivity theHISGs assembled using film C also possessed lower119880-values(1755Wm2-K)
33 Power Generation Gain Performance The power genera-tion test results for the front and back sides of each semitrans-parent PV module are shown in Table 4 The measurement
10 International Journal of Photoenergy
Table 2 Emissivity of each component
Item Emissivity ofindoor side
Emissivity ofoutdoor side
Tandem laser module 084 084Tandem TCOmodule 084 084a-Si TCO module 084 084Heat insulation film A 076 0135Heat insulation film B 076 0045Heat insulation film C 076 0033Rear glass 084 084
Table 3Thermal properties of the semitransparent PVmodules andHISGs
ModuleItem
SHGC Shadingcoefficient 119880-value
Tandem lasermodule 03 0345 563
Tandem laser-AHISG 0151 0174 1824
Tandem laser-BHISG 0135 0155 1757
Tandem laser-CHISG 0129 0148 1755
Tandem TCOmodule 038 0437 563
Tandem TCO-AHISG 0218 025 1824
Tandem TCO-BHISG 0184 0211 1757
Tandem TCO-CHISG 0171 0196 1755
a-Si TCOmodule 041 0471 563
a-Si TCO-AHISG 0249 0286 1824
a-Si TCO-BHISG 0207 0238 1757
a-Si TCO-CHISG 019 0218 1755
results show that the power output for the front side of thetandem laser module was 126029W with an efficiency of8184 while that of the back side was only 1019W Thereason for this is the cell structure of the tandem lasermoduleas the bottom back-contact conductive layer is Al whichdoes not possess power generation characteristicsThereforeafter being illuminated by direct light there should not be apower generation effect However because the tandem lasermodule was subjected to transverse laser cutting during themanufacturing process light can pass through from the backsideThe light could then undergo refraction or transmissionat the rear glass so some of the light is able to enter the power-generating layer from the laser cut slits and so the back side
Table 4 Results of tests of electrical characteristics in STC for initialstates of the original transparent PV module (a) front side and (b)back side
(a)
Test itemTandemlaser
module
TandemTCO
module
a-SiTCO
moduleModule efficiency () 8184 811 778Maximum power output(W) 126029 124843 119796
Open circuit voltage (V) 167382 171629 111606Short circuit current (A) 1133 1038 1595Maximum voltage (V) 131026 140561 86939Maximum electric current(A) 0962 0888 1378
Fill factor 06644 07008 06731
(b)
Test itemTandemlaser
module
TandemTCO
module
a-SiTCO
moduleModule efficiency () 0066 0723 5361Maximum power output(W) 1019 11134 82566
Open circuit voltage (V) 109965 156555 108648Short circuit current (A) 0026 0108 1213Maximum voltage (V) 40348 132561 83918Maximum electric current(A) 0025 0084 0984
Fill factor 03506 06576 06264
of the tandem laser module also possesses a slight powergeneration effect
The power output of the front side of the tandem TCOmodule was 124843W with an efficiency of 811 whereasthat of the back side was only 11134W The reason why theefficiency from back-side illumination is low is due to lightabsorption in the lower bandgap 120583c-Si cell which allowslimited light into the a-Si cell The current output would belimited by the smaller current value from the a-Si and so alower efficiency is generated
The front-side power output of the a-Si TCOmodule was119796W with an efficiency of 778 whereas the back-sidepower output of the a-Si TCO module reached 82566WThe power-generating layer of the a-Si TCO module is thea-Si layer which is also classified as a cell structure withdual-surface power generation characteristics so the back-side power output was higher compared to that of the formertwo modules However the reason for the difference in thefront-side and back-side power outputs of the a-Si TCOmodule is that the materials of the front and rear glasswere different The front glass was ultraclear glass with morethan 90 visible light transmittance Meanwhile in orderto increase the loading strength of the BIPV the rear glasswas mostly tempered glass or heat-strengthened glass with
International Journal of Photoenergy 11
lower transmissivity In addition before entering the power-generating layer from the back side the light still needs to passthrough a layer of EVA plastic film which will also reduce thesolar irradianceThe back-side power output of the a-Si TCOmodule was thus only 69 of the front-side power output
The results of the electrical tests of each semitransparentPV module and each combination of HISGs are shown inTable 5 The results for power generation gain are shownin Table 6 The experimental results indicated that boththe power generation and efficiency of tandem laser HISGexhibited slightly increasing trends the power generationincreased by around 001ndash013 and the efficiency increasedby around 0001ndash001 However the power generationand efficiency of tandem TCO HISG and a-Si TCO HISGdisplayed increasing trends For the tandem TCO HISGthe power generation improved by around 327ndash1006 andthe efficiency increased by around 027ndash082 For the a-SiTCOHISG the power generation increased by around 094ndash307 and the efficiency increased by around 007ndash024The power-generating layer of the tandem TCOmodule is a-Si120583c-Si but that of the a-Si TCO module is a single layer ofa-Si The absorption spectrum of the tandem TCO module(300 nmndash1100 nm) is wider than that of the a-Si TCOmodule(300 nmndash750 nm) The back side of the tandem TCO HISGcan thus absorb higher effective irradiance than the a-Si TCOHISG This means that the efficiency enhanced rate of thetandemTCOHISG is higher than that of the a-Si TCOHISGIt is also worth noting that selecting an appropriate heatinsulation film in order to absorb a larger amount of reflectivesolar radiation by the back side of theHISG can lead to greaterenhancement of power generation
34 Simulation of Energy-Saving Performance The simula-tion results for the power generation of each HISG installedin the buildings and the energy consumption of the heatingventilation and air-conditioning (HVAC) system are shownin Table 7 As Tainan is located in a subtropical region inTaiwan where there is sufficient sunlight the annual powergeneration of each module was higher than that of themodules in London and the power outputs ranged between16328 kW and 18727 kW London is located in a temperatezone with mostly cloudy weather and thus the annual powergeneration only ranged between 8493 kWand 9741 kWTheseresults show that different climate zones andweather patternsare the main factors affecting the power generation of BIPVmodules
The simulation results in Table 7 also show that the poweroutputs of each HISG were larger than those of the originalsemitransparent PV modules That is the power enhance-ments of the tandem laser HISG were around 001ndash012those of the tandem TCO HISG were around 327ndash1006and those of the a-Si TCO HISG were around 094ndash307The simulated results also reveal that the percentage gainsin power generation for each HISG installed on the roofs ofbuildings as BIPV roofs are consistent with the experimentalresults under STC from IEC 61646 Therefore adding heatinsulation films onto semitransparent PV modules to forma HISG in order to enhance the power output of the modulesis beneficial in reducing the EPBT of the entire BIPV system
The simulation results for the energy consumption of theHVAC systems of buildings in Tainan Taiwan and LondonUK are shown in Tables 8 and 9 respectively As Tainan islocated in a subtropical region the use of a heater is lesscommon and the HVAC system is mostly used for coolingso the energy consumption for the latter is much higher thanthat for heating On the other hand London is located in atemperate region and the HVAC system is mainly used forheating so the energy consumption for this is much higherthan that for cooling
Furthermore the main factors affecting the energy con-sumption of theHVAC system are the shading coefficient andthe 119880-value of the envelope The shading coefficient and 119880-value of each HISG are lower than those of the semitrans-parent PV modules During summer solar radiation cannotenter the room easily through the HISG so cooling energycan be saved During winter the 119880-value of the HISG isvery low owing to the multilayer structure and althoughsolar radiation cannot enter the room easily the heat will beretained inside the room and will not dissipate easily andhence the amount of energy used for heating can also bereduced Therefore the simulation results for the HISGs allindicate greater energy-saving performance in the annualenergy consumption of the HVAC system The results showthat the HISG can save 2911ndash3219 of cooling energy 4734ndash4815 of heating energy and 3268ndash3575 of the totalenergy consumption of the HVAC system in subtropicalregions and 3727ndash4412 of cooling energy 3905ndash3986 ofheating energy and 3905ndash3986 of total energy consump-tion of the HVAC system in temperate regions Among all theHISGs the HISG encapsulated version using heat insulationfilm C had the best energy-saving performance
As seen in the simulation results given above the HISGcan not only enhance the power generation but also becauseof the better heat insulation performance shorten the EPBTof the entire HISG BIPV application on a building
4 Conclusion
The concepts of net zero energy zero energy and passiveenergy are becoming more important as part of the energyconservation policies adopted by the construction industryBIPV technology currently has great potential for effectivedevelopment of solar module techniques Theoretically if aBIPV module is combined with building materials it caneffectively reduce overall construction costs save energymodulate the indoor temperature and shorten the energypayback time (EPBT)
In this work the authors adopted three different types ofsemitransparent PV modules and combined three differenttypes of high-reflectivity films to encapsulate HISG BIPVsystems The optical and thermal properties and the overallpower generation effects of each HISG were investigated Inaddition Autodesk software was used to calculate the powergeneration and energy-saving effects of each HISG as appliedto actual buildings in Taiwan with a subtropical climate andEngland with a temperate climate As a result due to thethree-layer structure of the HISGwith a high-reflectivity heatinsulation film the heat insulation performance (SHGC and
12 International Journal of Photoenergy
Table5Testresults
forthe
vario
usBIPV
mod
ules
andHISGsu
nder
STC
Testitem
Tand
emlaser
mod
ule
Tand
emlaser-A
HISG
Tand
emlaser-BHISG
Tand
emlaser-CHISG
Tand
emTC
Omod
ule
Tand
emTC
O-A
HISG
Tand
emTC
O-B
HISG
Tand
emTC
O-C
HISG
a-SiTC
Omod
ule
a-Si
TCO-A
HISG
a-SiTC
O-B
HISG
a-Si
TCO-C
HISG
Efficiency
()
8184
8185
8189
8194
811
837
874
892
778
785
787
802
Maxim
umpo
wer
output
(W)
126029
12604
2126105
126187
124843
128926
134658
137399
119796
120921
121125
123475
Opencircuit
voltage
(V)
1673
821672
531672
81167313
1716
291716
441718
86172036
1116
061115
971116
131117
10
Shortcirc
uit
current(A)
1133
1134
1133
1134
1038
1074
1125
1150
1595
1612
1615
1650
Maxim
umvoltage
(V)
1310
261294
33130098
1292
07140561
1391
73138796
138027
86939
8733
787341
84561
Maxim
umele
ctric
current(A)
0962
0974
0969
0977
0888
0926
0970
0995
1378
1385
1387
1460
Fillfactor
066
44066
4606654
06651
07008
06996
06964
06944
06731
06721
06719
06698
International Journal of Photoenergy 13
Table 6 Results of power generation gain tests of the semitransparent PV modules and each combination of HISG under STC
ModuleItem
Power generation (W) Power generationenhancement () Module efficiency () Module efficiency
enhancement ()Tandem laser module 126029 mdash 8184 mdashTandem laser-A HISG 126042 001 8185 0001Tandem laser-B HISG 126105 006 8189 0005Tandem laser-C HISG 126187 013 8194 0010Tandem TCOmodule 124843 mdash 811 mdashTandem TCO-A HISG 128926 327 837 027Tandem TCO-B HISG 134658 786 874 064Tandem TCO-C HISG 137399 1006 892 082a-Si TCO module 119796 mdash 778 mdasha-Si TCO-A HISG 120921 094 785 007a-Si TCO-B HISG 121125 111 787 009a-Si TCO-C HISG 123475 307 802 024
Table 7 Power generation results for building body simulations
Module LocationTainan Taiwan (kW) Power enhancement () London UK (kW) Power enhancement ()
Tandem laser module 17178 mdash 8935 mdashTandem laser-A HISG 17179 001 8936 001Tandem laser-B HISG 17188 006 8940 006Tandem laser-C HISG 17199 012 8946 012Tandem TCOmodule 17016 mdash 8851 mdashTandem TCO-A HISG 17573 327 9141 327Tandem TCO-B HISG 18354 786 9547 786Tandem TCO-C HISG 18727 1006 9741 1006a-Si TCO module 16328 mdash 8493 mdasha-Si TCO-A HISG 16481 094 8573 094a-Si TCO-B HISG 16509 111 8587 111a-Si TCO-C HISG 16830 307 8754 307
Table 8 Simulation results for energy consumption of HVAC systems for the building body in the Tainan region of Taiwan
Module Cooling energyconsumption (kW)
Cooling energysaving ()
Heating energyconsumption
(kW)
Heating energysaving ()
Total HVAC systemenergy consumption
(kW)
Total HVACenergy saving
()Tandem laser module 28632 mdash 6924 mdash 35556 mdashTandem laser-A HISG 20296 2911 3639 4744 23935 3268Tandem laser-B HISG 20053 2996 3590 4815 23643 3350Tandem laser-C HISG 19958 3029 3591 4814 23549 3377Tandem TCOmodule 29495 mdash 6894 mdash 36390 mdashTandem TCO-A HISG 20793 2950 3623 4745 24415 3291Tandem TCO-B HISG 20412 3080 3576 4813 23988 3408Tandem TCO-C HISG 20201 3151 3583 4803 23784 3464a-Si TCO module 30368 mdash 6869 mdash 37236 mdasha-Si TCO-A HISG 20952 3101 3617 4734 24569 3402a-Si TCO-B HISG 20593 3219 3568 4806 24161 3511a-Si TCO-C HISG 20347 3300 3577 4793 23924 3575
14 International Journal of Photoenergy
Table 9 Simulation results for energy consumption of HVAC systems for the building body in London UK
ModuleCooling energyconsumption
(kW)
Cooling energysaving ()
Heating energyconsumption
(kW)
Heating energysaving ()
Total HVAC system energyconsumption (kW)
Total HVACenergy saving
()Tandem laser module 306 mdash 116818 mdash 117123 mdashTandem laser-A HISG 181 4085 71203 3905 71384 3905Tandem laser-B HISG 171 4412 70570 3959 70741 3960Tandem laser-C HISG 173 4346 70491 3966 70664 3967Tandem TCOmodule 271 mdash 117612 mdash 117883 mdashTandem TCO-A HISG 170 3727 71497 3921 71667 3920Tandem TCO-B HISG 164 3948 70753 3984 70917 3984Tandem TCO-C HISG 165 3911 70734 3986 70899 3986a-Si TCO module 287 mdash 117214 mdash 117501 mdasha-Si TCO-A HISG 175 3902 71273 3919 71448 3919a-Si TCO-B HISG 172 4007 70640 3973 70812 3973a-Si TCO-C HISG 171 4042 70566 3980 70737 3980
119880-value) showed an improvement Although the multilayerstructure of HISG would affect the visible light transmit-tance in practice it does not have a significant impact onthe view through the glass Moreover although the solardirect reflectance values all showed improving trends thevisible light reflectance was only around 5 which will notnecessarily cause environmental light pollution Comparedto the original modules the power generation and moduleefficiency of all HISGs were found to have increased Of allthe combinations of HISGs the gain in power generation ofthe tandem TCO-C HISG was the highest as the power gen-eration was improved by 1006 and the module efficiencywas improved by 082The results of the simulation showeda very similar trendwith regard to the level of electrical powergeneration based on experimental data that was obtainedusing the standard test conditions (STC) for measurementcontained in IEC 61646The simulation results also indicatedthat theHISG has a significant effect on the amount of energythat can be saved when using the HVAC system in bothsubtropical and temperate regions
This paper thus provides valuable information for renew-able energy planners and architectural designers who areinterested in using HISG BIPV systems
Competing Interests
The authors declare that there are no competing interestsregarding the publication of this paper
Acknowledgments
This study was supported by the Ministry of Science andTechnology of Taiwan under Projects MOST 105-3113-F-011-001 and MOST 105-3113-E-006-006-CC2
References
[1] M van der Hoeven Energy and Climate ChangemdashWorld EnergyOutlook Special Report International Energy Agency 2015
[2] P Jones S S Hou and X Li ldquoTowards zero carbon designin offices integrating smart facades ventilation and surfaceheating and coolingrdquoRenewable Energy vol 73 pp 69ndash76 2015
[3] W Pan ldquoSystem boundaries of zero carbon buildingsrdquo Renew-able and Sustainable Energy Reviews vol 37 pp 424ndash434 2014
[4] S Berry K Davidson and W Saman ldquoDefining zero carbonand zero energy homes from a performance-based regulatoryperspectiverdquo Energy Efficiency vol 7 no 2 pp 303ndash322 2014
[5] G P Hammond H A Harajli C I Jones and A B WinnettldquoWhole systems appraisal of a UK Building Integrated Photo-voltaic (BIPV) system energy environmental and economicevaluationsrdquo Energy Policy vol 40 no 1 pp 219ndash230 2012
[6] G A Keoleian and GM Lewis ldquoModeling the life cycle energyand environmental performance of amorphous silicon BIPVroofing in the USrdquo Renewable Energy vol 28 no 2 pp 271ndash2932003
[7] L Lu andHX Yang ldquoEnvironmental payback time analysis of aroof-mounted building-integrated photovoltaic (BIPV) systemin Hong Kongrdquo Applied Energy vol 87 no 12 pp 3625ndash36312010
[8] L Y Seng G Lalchand and G M Sow Lin ldquoEconomicalenvironmental and technical analysis of building integratedphotovoltaic systems in Malaysiardquo Energy Policy vol 36 no 6pp 2130ndash2142 2008
[9] M Oliver and T Jackson ldquoEnergy and economic evaluation ofbuilding-integrated photovoltaicsrdquo Energy vol 26 no 4 pp431ndash439 2001
[10] L Sabnani A Skumanich E Ryabova and R Noufi Devel-oping Market Opportunities for Flexible Rooftop Applicationsof PV Using Flexible CIGS Technology Market ConsiderationsNational Renewable Energy Laboratory (NREL) Golden ColoUSA 2011
[11] M A Green K Emery Y Hishikawa W Warta and E DDunlop ldquoSolar cell efficiency tables (version 47)rdquo Progress inPhotovoltaics Research and Applications vol 24 no 1 pp 3ndash112016
[12] G Y Yun M McEvoy and K Steemers ldquoDesign and overallenergy performance of a ventilated photovoltaic facaderdquo SolarEnergy vol 81 no 3 pp 383ndash394 2007
International Journal of Photoenergy 15
[13] PWWong Y ShimodaM NonakaM Inoue andMMizunoldquoSemi-transparent PV thermal performance power generationdaylight modelling and energy saving potential in a residentialapplicationrdquo Renewable Energy vol 33 no 5 pp 1024ndash10362008
[14] D H W Li T N T Lam W W H Chan and A H L MakldquoEnergy and cost analysis of semi-transparent photovoltaic inoffice buildingsrdquo Applied Energy vol 86 no 5 pp 722ndash7292009
[15] H Radhi ldquoEnergy analysis of facade-integrated photovoltaicsystems applied to UAE commercial buildingsrdquo Solar Energyvol 84 no 12 pp 2009ndash2021 2010
[16] E L Didone and A Wagner ldquoSemi-transparent PV windowsa study for office buildings in Brazilrdquo Energy and Buildings vol67 pp 136ndash142 2013
[17] P K Ng and N Mithraratne ldquoLifetime performance of semi-transparent building-integrated photovoltaic (BIPV) glazingsystems in the tropicsrdquo Renewable and Sustainable EnergyReviews vol 31 pp 736ndash745 2014
[18] C H Young Y L Chen and P C Chen ldquoHeat insulation solarglass and application on energy efficiency buildingsrdquo Energyand Buildings vol 78 pp 66ndash78 2014
[19] International Organization for Standardization ISO 9050 Glassin BuildingmdashDetermination of Light Transmittance Solar DirectTransmittance Total Solar Energy Transmittance UltravioletTransmittance and Related Glazing Factors International Orga-nization for Standardization Basel Switzerland 2003
[20] International Organization for Standardization ldquoISO10292glass in buildingmdashcalculation of steady-state U values (thermaltransmittance) of multiple glazingrdquo Tech Rep InternationalOrganization for Standardization Geneva Switzerland 1994
[21] International Standard ldquoThin-film terrestrial photovoltaic (pv)modulesmdashdesign qualification and type approvalrdquo IEC 616462008
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Inorganic ChemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Carbohydrate Chemistry
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
Physical Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom
Analytical Methods in Chemistry
Journal of
Volume 2014
Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
SpectroscopyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Medicinal ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chromatography Research International
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Applied ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Theoretical ChemistryJournal of
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Journal of
Spectroscopy
Analytical ChemistryInternational Journal of
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Quantum Chemistry
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Organic Chemistry International
ElectrochemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CatalystsJournal of
8 International Journal of Photoenergy
02468
101214161820222426
Refle
ctan
ce (
)
Wavelength (nm)
Tandem laser moduleTandem TCO modulea-Si TCO module
300 600 900 1200 1500 1800 2100 2400
(a)
0
10
20
30
40
50
60
70
Refle
ctan
ce (
)
Wavelength (nm)300 600 900 1200 1500 1800 2100 2400
Heat insulation film AHeat insulation film BHeat insulation film C
(b)
0
10
20
30
40
50
60
70
80
90
100
Refle
ctan
ce (
)
Wavelength (nm)
Glass
300 600 900 1200 1500 1800 2100 2400
(c)
Figure 5 Reflectance spectra of each component (a) semitransparent PV modules (b) heat insulation films and (c) rear glass
sides was measured using FTIR and then the emissivityvalue of each component was obtained by ISO 10292 asshown in Table 2 It can be seen that as the surfaces ofthe semitransparent PV modules and rear glass were not allcoated by a film the emissivity values for the exterior andinterior sides were 084 While the heat insulation filmswere mainly composed of PET material there was no filmcoating the interior surface of the film so the emissivityvalues were all 076 Meanwhile the exterior surfaces of theheat insulation films all had a multilayer metal coating sothe surface emissivity values were lower than the surfaceemissivity values on the indoor side The surface emissivity
of heat insulation film C is 0033 which is thus categorized asa Low-E film
Table 3 shows the thermal performances of the three typesof PVmodules and the nine types of HISGs with the SHGCsshading coefficients and overall heat transfer coefficients (119880-values) The results indicate that the multilayer structureof the HISG reduced the solar direct transmittance andsince the heat insulation films were coated with transparentmetal films this reflected the solar radiation heat promptingthe SHGCs to be reduced to half the levels seen with thesemitransparent PVmodulesThismeans that the quantity ofsolar radiation heat passing through the HISG was half that
International Journal of Photoenergy 9
0
2
4
6
8
10
12
545
478
103
208
535
639
1024
25
535
723
1017
407
00 0001
527
84
1007
709
UV
tran
smitt
ance
Visib
le li
ght
refle
ctan
ce
Visib
le li
ght
tran
smitt
ance
Sola
r rad
iatio
nre
flect
ance
Sola
r rad
iatio
ntr
ansm
ittan
ce
Tran
smitt
ance
and
refle
ctan
ce (
)
Tandem laser moduleTandem laser-A HISG
Tandem laser-B HISGTandem laser-C HISG
(a)
0
2
4
6
8
10
12
14
16
18
20
0 00001
515515515515
123166
18822
821788744
679516
626
1034
1833
UV
tran
smitt
ance
Visib
le li
ght
refle
ctan
ce
Visib
le li
ght
tran
smitt
ance
Sola
r rad
iatio
nre
flect
ance
Sola
r rad
iatio
ntr
ansm
ittan
ce
Tran
smitt
ance
and
refle
ctan
ce (
)Tandem TCO moduleTandem TCO-A HISG
Tandem TCO-B HISGTandem TCO-C HISG
(b)
02468
101214161820222426
000001
517514
514512
243329
372435
964909
83773
662803
1326
2349
UV
tran
smitt
ance
Visib
le li
ght
refle
ctan
ce
Visib
le li
ght
tran
smitt
ance
Sola
r rad
iatio
nre
flect
ance
Sola
r rad
iatio
ntr
ansm
ittan
ce
Tran
smitt
ance
and
refle
ctan
ce (
)
a-Si TCO modulea-Si TCO-A HISG
a-Si TCO-B HISGa-Si TCO-C HISG
(c)
Figure 6 Optical properties of the HISGs (a) tandem laser module (b) tandem TCOmodule and (c) a-Si TCO module
passing through the semitransparent PV modules In termsof the 119880-value since all the semitransparent PV moduleswere assembled with 4mm times 4mm laminated glass the 119880-values based on ISO 10292 for all modules were 563Wm2-K The addition of heat insulation films and dual air gaps toform a multilayer structure greatly reduced the 119880-values oftheHISGs (1755Wm2-Kndash1824Wm2-K)Moreover havingheat insulation films with different emissivity values is one
of the main causes of the decline in the 119880-value Since heatinsulation film C had the lowest surface emissivity theHISGs assembled using film C also possessed lower119880-values(1755Wm2-K)
33 Power Generation Gain Performance The power genera-tion test results for the front and back sides of each semitrans-parent PV module are shown in Table 4 The measurement
10 International Journal of Photoenergy
Table 2 Emissivity of each component
Item Emissivity ofindoor side
Emissivity ofoutdoor side
Tandem laser module 084 084Tandem TCOmodule 084 084a-Si TCO module 084 084Heat insulation film A 076 0135Heat insulation film B 076 0045Heat insulation film C 076 0033Rear glass 084 084
Table 3Thermal properties of the semitransparent PVmodules andHISGs
ModuleItem
SHGC Shadingcoefficient 119880-value
Tandem lasermodule 03 0345 563
Tandem laser-AHISG 0151 0174 1824
Tandem laser-BHISG 0135 0155 1757
Tandem laser-CHISG 0129 0148 1755
Tandem TCOmodule 038 0437 563
Tandem TCO-AHISG 0218 025 1824
Tandem TCO-BHISG 0184 0211 1757
Tandem TCO-CHISG 0171 0196 1755
a-Si TCOmodule 041 0471 563
a-Si TCO-AHISG 0249 0286 1824
a-Si TCO-BHISG 0207 0238 1757
a-Si TCO-CHISG 019 0218 1755
results show that the power output for the front side of thetandem laser module was 126029W with an efficiency of8184 while that of the back side was only 1019W Thereason for this is the cell structure of the tandem lasermoduleas the bottom back-contact conductive layer is Al whichdoes not possess power generation characteristicsThereforeafter being illuminated by direct light there should not be apower generation effect However because the tandem lasermodule was subjected to transverse laser cutting during themanufacturing process light can pass through from the backsideThe light could then undergo refraction or transmissionat the rear glass so some of the light is able to enter the power-generating layer from the laser cut slits and so the back side
Table 4 Results of tests of electrical characteristics in STC for initialstates of the original transparent PV module (a) front side and (b)back side
(a)
Test itemTandemlaser
module
TandemTCO
module
a-SiTCO
moduleModule efficiency () 8184 811 778Maximum power output(W) 126029 124843 119796
Open circuit voltage (V) 167382 171629 111606Short circuit current (A) 1133 1038 1595Maximum voltage (V) 131026 140561 86939Maximum electric current(A) 0962 0888 1378
Fill factor 06644 07008 06731
(b)
Test itemTandemlaser
module
TandemTCO
module
a-SiTCO
moduleModule efficiency () 0066 0723 5361Maximum power output(W) 1019 11134 82566
Open circuit voltage (V) 109965 156555 108648Short circuit current (A) 0026 0108 1213Maximum voltage (V) 40348 132561 83918Maximum electric current(A) 0025 0084 0984
Fill factor 03506 06576 06264
of the tandem laser module also possesses a slight powergeneration effect
The power output of the front side of the tandem TCOmodule was 124843W with an efficiency of 811 whereasthat of the back side was only 11134W The reason why theefficiency from back-side illumination is low is due to lightabsorption in the lower bandgap 120583c-Si cell which allowslimited light into the a-Si cell The current output would belimited by the smaller current value from the a-Si and so alower efficiency is generated
The front-side power output of the a-Si TCOmodule was119796W with an efficiency of 778 whereas the back-sidepower output of the a-Si TCO module reached 82566WThe power-generating layer of the a-Si TCO module is thea-Si layer which is also classified as a cell structure withdual-surface power generation characteristics so the back-side power output was higher compared to that of the formertwo modules However the reason for the difference in thefront-side and back-side power outputs of the a-Si TCOmodule is that the materials of the front and rear glasswere different The front glass was ultraclear glass with morethan 90 visible light transmittance Meanwhile in orderto increase the loading strength of the BIPV the rear glasswas mostly tempered glass or heat-strengthened glass with
International Journal of Photoenergy 11
lower transmissivity In addition before entering the power-generating layer from the back side the light still needs to passthrough a layer of EVA plastic film which will also reduce thesolar irradianceThe back-side power output of the a-Si TCOmodule was thus only 69 of the front-side power output
The results of the electrical tests of each semitransparentPV module and each combination of HISGs are shown inTable 5 The results for power generation gain are shownin Table 6 The experimental results indicated that boththe power generation and efficiency of tandem laser HISGexhibited slightly increasing trends the power generationincreased by around 001ndash013 and the efficiency increasedby around 0001ndash001 However the power generationand efficiency of tandem TCO HISG and a-Si TCO HISGdisplayed increasing trends For the tandem TCO HISGthe power generation improved by around 327ndash1006 andthe efficiency increased by around 027ndash082 For the a-SiTCOHISG the power generation increased by around 094ndash307 and the efficiency increased by around 007ndash024The power-generating layer of the tandem TCOmodule is a-Si120583c-Si but that of the a-Si TCO module is a single layer ofa-Si The absorption spectrum of the tandem TCO module(300 nmndash1100 nm) is wider than that of the a-Si TCOmodule(300 nmndash750 nm) The back side of the tandem TCO HISGcan thus absorb higher effective irradiance than the a-Si TCOHISG This means that the efficiency enhanced rate of thetandemTCOHISG is higher than that of the a-Si TCOHISGIt is also worth noting that selecting an appropriate heatinsulation film in order to absorb a larger amount of reflectivesolar radiation by the back side of theHISG can lead to greaterenhancement of power generation
34 Simulation of Energy-Saving Performance The simula-tion results for the power generation of each HISG installedin the buildings and the energy consumption of the heatingventilation and air-conditioning (HVAC) system are shownin Table 7 As Tainan is located in a subtropical region inTaiwan where there is sufficient sunlight the annual powergeneration of each module was higher than that of themodules in London and the power outputs ranged between16328 kW and 18727 kW London is located in a temperatezone with mostly cloudy weather and thus the annual powergeneration only ranged between 8493 kWand 9741 kWTheseresults show that different climate zones andweather patternsare the main factors affecting the power generation of BIPVmodules
The simulation results in Table 7 also show that the poweroutputs of each HISG were larger than those of the originalsemitransparent PV modules That is the power enhance-ments of the tandem laser HISG were around 001ndash012those of the tandem TCO HISG were around 327ndash1006and those of the a-Si TCO HISG were around 094ndash307The simulated results also reveal that the percentage gainsin power generation for each HISG installed on the roofs ofbuildings as BIPV roofs are consistent with the experimentalresults under STC from IEC 61646 Therefore adding heatinsulation films onto semitransparent PV modules to forma HISG in order to enhance the power output of the modulesis beneficial in reducing the EPBT of the entire BIPV system
The simulation results for the energy consumption of theHVAC systems of buildings in Tainan Taiwan and LondonUK are shown in Tables 8 and 9 respectively As Tainan islocated in a subtropical region the use of a heater is lesscommon and the HVAC system is mostly used for coolingso the energy consumption for the latter is much higher thanthat for heating On the other hand London is located in atemperate region and the HVAC system is mainly used forheating so the energy consumption for this is much higherthan that for cooling
Furthermore the main factors affecting the energy con-sumption of theHVAC system are the shading coefficient andthe 119880-value of the envelope The shading coefficient and 119880-value of each HISG are lower than those of the semitrans-parent PV modules During summer solar radiation cannotenter the room easily through the HISG so cooling energycan be saved During winter the 119880-value of the HISG isvery low owing to the multilayer structure and althoughsolar radiation cannot enter the room easily the heat will beretained inside the room and will not dissipate easily andhence the amount of energy used for heating can also bereduced Therefore the simulation results for the HISGs allindicate greater energy-saving performance in the annualenergy consumption of the HVAC system The results showthat the HISG can save 2911ndash3219 of cooling energy 4734ndash4815 of heating energy and 3268ndash3575 of the totalenergy consumption of the HVAC system in subtropicalregions and 3727ndash4412 of cooling energy 3905ndash3986 ofheating energy and 3905ndash3986 of total energy consump-tion of the HVAC system in temperate regions Among all theHISGs the HISG encapsulated version using heat insulationfilm C had the best energy-saving performance
As seen in the simulation results given above the HISGcan not only enhance the power generation but also becauseof the better heat insulation performance shorten the EPBTof the entire HISG BIPV application on a building
4 Conclusion
The concepts of net zero energy zero energy and passiveenergy are becoming more important as part of the energyconservation policies adopted by the construction industryBIPV technology currently has great potential for effectivedevelopment of solar module techniques Theoretically if aBIPV module is combined with building materials it caneffectively reduce overall construction costs save energymodulate the indoor temperature and shorten the energypayback time (EPBT)
In this work the authors adopted three different types ofsemitransparent PV modules and combined three differenttypes of high-reflectivity films to encapsulate HISG BIPVsystems The optical and thermal properties and the overallpower generation effects of each HISG were investigated Inaddition Autodesk software was used to calculate the powergeneration and energy-saving effects of each HISG as appliedto actual buildings in Taiwan with a subtropical climate andEngland with a temperate climate As a result due to thethree-layer structure of the HISGwith a high-reflectivity heatinsulation film the heat insulation performance (SHGC and
12 International Journal of Photoenergy
Table5Testresults
forthe
vario
usBIPV
mod
ules
andHISGsu
nder
STC
Testitem
Tand
emlaser
mod
ule
Tand
emlaser-A
HISG
Tand
emlaser-BHISG
Tand
emlaser-CHISG
Tand
emTC
Omod
ule
Tand
emTC
O-A
HISG
Tand
emTC
O-B
HISG
Tand
emTC
O-C
HISG
a-SiTC
Omod
ule
a-Si
TCO-A
HISG
a-SiTC
O-B
HISG
a-Si
TCO-C
HISG
Efficiency
()
8184
8185
8189
8194
811
837
874
892
778
785
787
802
Maxim
umpo
wer
output
(W)
126029
12604
2126105
126187
124843
128926
134658
137399
119796
120921
121125
123475
Opencircuit
voltage
(V)
1673
821672
531672
81167313
1716
291716
441718
86172036
1116
061115
971116
131117
10
Shortcirc
uit
current(A)
1133
1134
1133
1134
1038
1074
1125
1150
1595
1612
1615
1650
Maxim
umvoltage
(V)
1310
261294
33130098
1292
07140561
1391
73138796
138027
86939
8733
787341
84561
Maxim
umele
ctric
current(A)
0962
0974
0969
0977
0888
0926
0970
0995
1378
1385
1387
1460
Fillfactor
066
44066
4606654
06651
07008
06996
06964
06944
06731
06721
06719
06698
International Journal of Photoenergy 13
Table 6 Results of power generation gain tests of the semitransparent PV modules and each combination of HISG under STC
ModuleItem
Power generation (W) Power generationenhancement () Module efficiency () Module efficiency
enhancement ()Tandem laser module 126029 mdash 8184 mdashTandem laser-A HISG 126042 001 8185 0001Tandem laser-B HISG 126105 006 8189 0005Tandem laser-C HISG 126187 013 8194 0010Tandem TCOmodule 124843 mdash 811 mdashTandem TCO-A HISG 128926 327 837 027Tandem TCO-B HISG 134658 786 874 064Tandem TCO-C HISG 137399 1006 892 082a-Si TCO module 119796 mdash 778 mdasha-Si TCO-A HISG 120921 094 785 007a-Si TCO-B HISG 121125 111 787 009a-Si TCO-C HISG 123475 307 802 024
Table 7 Power generation results for building body simulations
Module LocationTainan Taiwan (kW) Power enhancement () London UK (kW) Power enhancement ()
Tandem laser module 17178 mdash 8935 mdashTandem laser-A HISG 17179 001 8936 001Tandem laser-B HISG 17188 006 8940 006Tandem laser-C HISG 17199 012 8946 012Tandem TCOmodule 17016 mdash 8851 mdashTandem TCO-A HISG 17573 327 9141 327Tandem TCO-B HISG 18354 786 9547 786Tandem TCO-C HISG 18727 1006 9741 1006a-Si TCO module 16328 mdash 8493 mdasha-Si TCO-A HISG 16481 094 8573 094a-Si TCO-B HISG 16509 111 8587 111a-Si TCO-C HISG 16830 307 8754 307
Table 8 Simulation results for energy consumption of HVAC systems for the building body in the Tainan region of Taiwan
Module Cooling energyconsumption (kW)
Cooling energysaving ()
Heating energyconsumption
(kW)
Heating energysaving ()
Total HVAC systemenergy consumption
(kW)
Total HVACenergy saving
()Tandem laser module 28632 mdash 6924 mdash 35556 mdashTandem laser-A HISG 20296 2911 3639 4744 23935 3268Tandem laser-B HISG 20053 2996 3590 4815 23643 3350Tandem laser-C HISG 19958 3029 3591 4814 23549 3377Tandem TCOmodule 29495 mdash 6894 mdash 36390 mdashTandem TCO-A HISG 20793 2950 3623 4745 24415 3291Tandem TCO-B HISG 20412 3080 3576 4813 23988 3408Tandem TCO-C HISG 20201 3151 3583 4803 23784 3464a-Si TCO module 30368 mdash 6869 mdash 37236 mdasha-Si TCO-A HISG 20952 3101 3617 4734 24569 3402a-Si TCO-B HISG 20593 3219 3568 4806 24161 3511a-Si TCO-C HISG 20347 3300 3577 4793 23924 3575
14 International Journal of Photoenergy
Table 9 Simulation results for energy consumption of HVAC systems for the building body in London UK
ModuleCooling energyconsumption
(kW)
Cooling energysaving ()
Heating energyconsumption
(kW)
Heating energysaving ()
Total HVAC system energyconsumption (kW)
Total HVACenergy saving
()Tandem laser module 306 mdash 116818 mdash 117123 mdashTandem laser-A HISG 181 4085 71203 3905 71384 3905Tandem laser-B HISG 171 4412 70570 3959 70741 3960Tandem laser-C HISG 173 4346 70491 3966 70664 3967Tandem TCOmodule 271 mdash 117612 mdash 117883 mdashTandem TCO-A HISG 170 3727 71497 3921 71667 3920Tandem TCO-B HISG 164 3948 70753 3984 70917 3984Tandem TCO-C HISG 165 3911 70734 3986 70899 3986a-Si TCO module 287 mdash 117214 mdash 117501 mdasha-Si TCO-A HISG 175 3902 71273 3919 71448 3919a-Si TCO-B HISG 172 4007 70640 3973 70812 3973a-Si TCO-C HISG 171 4042 70566 3980 70737 3980
119880-value) showed an improvement Although the multilayerstructure of HISG would affect the visible light transmit-tance in practice it does not have a significant impact onthe view through the glass Moreover although the solardirect reflectance values all showed improving trends thevisible light reflectance was only around 5 which will notnecessarily cause environmental light pollution Comparedto the original modules the power generation and moduleefficiency of all HISGs were found to have increased Of allthe combinations of HISGs the gain in power generation ofthe tandem TCO-C HISG was the highest as the power gen-eration was improved by 1006 and the module efficiencywas improved by 082The results of the simulation showeda very similar trendwith regard to the level of electrical powergeneration based on experimental data that was obtainedusing the standard test conditions (STC) for measurementcontained in IEC 61646The simulation results also indicatedthat theHISG has a significant effect on the amount of energythat can be saved when using the HVAC system in bothsubtropical and temperate regions
This paper thus provides valuable information for renew-able energy planners and architectural designers who areinterested in using HISG BIPV systems
Competing Interests
The authors declare that there are no competing interestsregarding the publication of this paper
Acknowledgments
This study was supported by the Ministry of Science andTechnology of Taiwan under Projects MOST 105-3113-F-011-001 and MOST 105-3113-E-006-006-CC2
References
[1] M van der Hoeven Energy and Climate ChangemdashWorld EnergyOutlook Special Report International Energy Agency 2015
[2] P Jones S S Hou and X Li ldquoTowards zero carbon designin offices integrating smart facades ventilation and surfaceheating and coolingrdquoRenewable Energy vol 73 pp 69ndash76 2015
[3] W Pan ldquoSystem boundaries of zero carbon buildingsrdquo Renew-able and Sustainable Energy Reviews vol 37 pp 424ndash434 2014
[4] S Berry K Davidson and W Saman ldquoDefining zero carbonand zero energy homes from a performance-based regulatoryperspectiverdquo Energy Efficiency vol 7 no 2 pp 303ndash322 2014
[5] G P Hammond H A Harajli C I Jones and A B WinnettldquoWhole systems appraisal of a UK Building Integrated Photo-voltaic (BIPV) system energy environmental and economicevaluationsrdquo Energy Policy vol 40 no 1 pp 219ndash230 2012
[6] G A Keoleian and GM Lewis ldquoModeling the life cycle energyand environmental performance of amorphous silicon BIPVroofing in the USrdquo Renewable Energy vol 28 no 2 pp 271ndash2932003
[7] L Lu andHX Yang ldquoEnvironmental payback time analysis of aroof-mounted building-integrated photovoltaic (BIPV) systemin Hong Kongrdquo Applied Energy vol 87 no 12 pp 3625ndash36312010
[8] L Y Seng G Lalchand and G M Sow Lin ldquoEconomicalenvironmental and technical analysis of building integratedphotovoltaic systems in Malaysiardquo Energy Policy vol 36 no 6pp 2130ndash2142 2008
[9] M Oliver and T Jackson ldquoEnergy and economic evaluation ofbuilding-integrated photovoltaicsrdquo Energy vol 26 no 4 pp431ndash439 2001
[10] L Sabnani A Skumanich E Ryabova and R Noufi Devel-oping Market Opportunities for Flexible Rooftop Applicationsof PV Using Flexible CIGS Technology Market ConsiderationsNational Renewable Energy Laboratory (NREL) Golden ColoUSA 2011
[11] M A Green K Emery Y Hishikawa W Warta and E DDunlop ldquoSolar cell efficiency tables (version 47)rdquo Progress inPhotovoltaics Research and Applications vol 24 no 1 pp 3ndash112016
[12] G Y Yun M McEvoy and K Steemers ldquoDesign and overallenergy performance of a ventilated photovoltaic facaderdquo SolarEnergy vol 81 no 3 pp 383ndash394 2007
International Journal of Photoenergy 15
[13] PWWong Y ShimodaM NonakaM Inoue andMMizunoldquoSemi-transparent PV thermal performance power generationdaylight modelling and energy saving potential in a residentialapplicationrdquo Renewable Energy vol 33 no 5 pp 1024ndash10362008
[14] D H W Li T N T Lam W W H Chan and A H L MakldquoEnergy and cost analysis of semi-transparent photovoltaic inoffice buildingsrdquo Applied Energy vol 86 no 5 pp 722ndash7292009
[15] H Radhi ldquoEnergy analysis of facade-integrated photovoltaicsystems applied to UAE commercial buildingsrdquo Solar Energyvol 84 no 12 pp 2009ndash2021 2010
[16] E L Didone and A Wagner ldquoSemi-transparent PV windowsa study for office buildings in Brazilrdquo Energy and Buildings vol67 pp 136ndash142 2013
[17] P K Ng and N Mithraratne ldquoLifetime performance of semi-transparent building-integrated photovoltaic (BIPV) glazingsystems in the tropicsrdquo Renewable and Sustainable EnergyReviews vol 31 pp 736ndash745 2014
[18] C H Young Y L Chen and P C Chen ldquoHeat insulation solarglass and application on energy efficiency buildingsrdquo Energyand Buildings vol 78 pp 66ndash78 2014
[19] International Organization for Standardization ISO 9050 Glassin BuildingmdashDetermination of Light Transmittance Solar DirectTransmittance Total Solar Energy Transmittance UltravioletTransmittance and Related Glazing Factors International Orga-nization for Standardization Basel Switzerland 2003
[20] International Organization for Standardization ldquoISO10292glass in buildingmdashcalculation of steady-state U values (thermaltransmittance) of multiple glazingrdquo Tech Rep InternationalOrganization for Standardization Geneva Switzerland 1994
[21] International Standard ldquoThin-film terrestrial photovoltaic (pv)modulesmdashdesign qualification and type approvalrdquo IEC 616462008
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Inorganic ChemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Carbohydrate Chemistry
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
Physical Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom
Analytical Methods in Chemistry
Journal of
Volume 2014
Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
SpectroscopyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Medicinal ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chromatography Research International
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Applied ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Theoretical ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Spectroscopy
Analytical ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Quantum Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Organic Chemistry International
ElectrochemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CatalystsJournal of
International Journal of Photoenergy 9
0
2
4
6
8
10
12
545
478
103
208
535
639
1024
25
535
723
1017
407
00 0001
527
84
1007
709
UV
tran
smitt
ance
Visib
le li
ght
refle
ctan
ce
Visib
le li
ght
tran
smitt
ance
Sola
r rad
iatio
nre
flect
ance
Sola
r rad
iatio
ntr
ansm
ittan
ce
Tran
smitt
ance
and
refle
ctan
ce (
)
Tandem laser moduleTandem laser-A HISG
Tandem laser-B HISGTandem laser-C HISG
(a)
0
2
4
6
8
10
12
14
16
18
20
0 00001
515515515515
123166
18822
821788744
679516
626
1034
1833
UV
tran
smitt
ance
Visib
le li
ght
refle
ctan
ce
Visib
le li
ght
tran
smitt
ance
Sola
r rad
iatio
nre
flect
ance
Sola
r rad
iatio
ntr
ansm
ittan
ce
Tran
smitt
ance
and
refle
ctan
ce (
)Tandem TCO moduleTandem TCO-A HISG
Tandem TCO-B HISGTandem TCO-C HISG
(b)
02468
101214161820222426
000001
517514
514512
243329
372435
964909
83773
662803
1326
2349
UV
tran
smitt
ance
Visib
le li
ght
refle
ctan
ce
Visib
le li
ght
tran
smitt
ance
Sola
r rad
iatio
nre
flect
ance
Sola
r rad
iatio
ntr
ansm
ittan
ce
Tran
smitt
ance
and
refle
ctan
ce (
)
a-Si TCO modulea-Si TCO-A HISG
a-Si TCO-B HISGa-Si TCO-C HISG
(c)
Figure 6 Optical properties of the HISGs (a) tandem laser module (b) tandem TCOmodule and (c) a-Si TCO module
passing through the semitransparent PV modules In termsof the 119880-value since all the semitransparent PV moduleswere assembled with 4mm times 4mm laminated glass the 119880-values based on ISO 10292 for all modules were 563Wm2-K The addition of heat insulation films and dual air gaps toform a multilayer structure greatly reduced the 119880-values oftheHISGs (1755Wm2-Kndash1824Wm2-K)Moreover havingheat insulation films with different emissivity values is one
of the main causes of the decline in the 119880-value Since heatinsulation film C had the lowest surface emissivity theHISGs assembled using film C also possessed lower119880-values(1755Wm2-K)
33 Power Generation Gain Performance The power genera-tion test results for the front and back sides of each semitrans-parent PV module are shown in Table 4 The measurement
10 International Journal of Photoenergy
Table 2 Emissivity of each component
Item Emissivity ofindoor side
Emissivity ofoutdoor side
Tandem laser module 084 084Tandem TCOmodule 084 084a-Si TCO module 084 084Heat insulation film A 076 0135Heat insulation film B 076 0045Heat insulation film C 076 0033Rear glass 084 084
Table 3Thermal properties of the semitransparent PVmodules andHISGs
ModuleItem
SHGC Shadingcoefficient 119880-value
Tandem lasermodule 03 0345 563
Tandem laser-AHISG 0151 0174 1824
Tandem laser-BHISG 0135 0155 1757
Tandem laser-CHISG 0129 0148 1755
Tandem TCOmodule 038 0437 563
Tandem TCO-AHISG 0218 025 1824
Tandem TCO-BHISG 0184 0211 1757
Tandem TCO-CHISG 0171 0196 1755
a-Si TCOmodule 041 0471 563
a-Si TCO-AHISG 0249 0286 1824
a-Si TCO-BHISG 0207 0238 1757
a-Si TCO-CHISG 019 0218 1755
results show that the power output for the front side of thetandem laser module was 126029W with an efficiency of8184 while that of the back side was only 1019W Thereason for this is the cell structure of the tandem lasermoduleas the bottom back-contact conductive layer is Al whichdoes not possess power generation characteristicsThereforeafter being illuminated by direct light there should not be apower generation effect However because the tandem lasermodule was subjected to transverse laser cutting during themanufacturing process light can pass through from the backsideThe light could then undergo refraction or transmissionat the rear glass so some of the light is able to enter the power-generating layer from the laser cut slits and so the back side
Table 4 Results of tests of electrical characteristics in STC for initialstates of the original transparent PV module (a) front side and (b)back side
(a)
Test itemTandemlaser
module
TandemTCO
module
a-SiTCO
moduleModule efficiency () 8184 811 778Maximum power output(W) 126029 124843 119796
Open circuit voltage (V) 167382 171629 111606Short circuit current (A) 1133 1038 1595Maximum voltage (V) 131026 140561 86939Maximum electric current(A) 0962 0888 1378
Fill factor 06644 07008 06731
(b)
Test itemTandemlaser
module
TandemTCO
module
a-SiTCO
moduleModule efficiency () 0066 0723 5361Maximum power output(W) 1019 11134 82566
Open circuit voltage (V) 109965 156555 108648Short circuit current (A) 0026 0108 1213Maximum voltage (V) 40348 132561 83918Maximum electric current(A) 0025 0084 0984
Fill factor 03506 06576 06264
of the tandem laser module also possesses a slight powergeneration effect
The power output of the front side of the tandem TCOmodule was 124843W with an efficiency of 811 whereasthat of the back side was only 11134W The reason why theefficiency from back-side illumination is low is due to lightabsorption in the lower bandgap 120583c-Si cell which allowslimited light into the a-Si cell The current output would belimited by the smaller current value from the a-Si and so alower efficiency is generated
The front-side power output of the a-Si TCOmodule was119796W with an efficiency of 778 whereas the back-sidepower output of the a-Si TCO module reached 82566WThe power-generating layer of the a-Si TCO module is thea-Si layer which is also classified as a cell structure withdual-surface power generation characteristics so the back-side power output was higher compared to that of the formertwo modules However the reason for the difference in thefront-side and back-side power outputs of the a-Si TCOmodule is that the materials of the front and rear glasswere different The front glass was ultraclear glass with morethan 90 visible light transmittance Meanwhile in orderto increase the loading strength of the BIPV the rear glasswas mostly tempered glass or heat-strengthened glass with
International Journal of Photoenergy 11
lower transmissivity In addition before entering the power-generating layer from the back side the light still needs to passthrough a layer of EVA plastic film which will also reduce thesolar irradianceThe back-side power output of the a-Si TCOmodule was thus only 69 of the front-side power output
The results of the electrical tests of each semitransparentPV module and each combination of HISGs are shown inTable 5 The results for power generation gain are shownin Table 6 The experimental results indicated that boththe power generation and efficiency of tandem laser HISGexhibited slightly increasing trends the power generationincreased by around 001ndash013 and the efficiency increasedby around 0001ndash001 However the power generationand efficiency of tandem TCO HISG and a-Si TCO HISGdisplayed increasing trends For the tandem TCO HISGthe power generation improved by around 327ndash1006 andthe efficiency increased by around 027ndash082 For the a-SiTCOHISG the power generation increased by around 094ndash307 and the efficiency increased by around 007ndash024The power-generating layer of the tandem TCOmodule is a-Si120583c-Si but that of the a-Si TCO module is a single layer ofa-Si The absorption spectrum of the tandem TCO module(300 nmndash1100 nm) is wider than that of the a-Si TCOmodule(300 nmndash750 nm) The back side of the tandem TCO HISGcan thus absorb higher effective irradiance than the a-Si TCOHISG This means that the efficiency enhanced rate of thetandemTCOHISG is higher than that of the a-Si TCOHISGIt is also worth noting that selecting an appropriate heatinsulation film in order to absorb a larger amount of reflectivesolar radiation by the back side of theHISG can lead to greaterenhancement of power generation
34 Simulation of Energy-Saving Performance The simula-tion results for the power generation of each HISG installedin the buildings and the energy consumption of the heatingventilation and air-conditioning (HVAC) system are shownin Table 7 As Tainan is located in a subtropical region inTaiwan where there is sufficient sunlight the annual powergeneration of each module was higher than that of themodules in London and the power outputs ranged between16328 kW and 18727 kW London is located in a temperatezone with mostly cloudy weather and thus the annual powergeneration only ranged between 8493 kWand 9741 kWTheseresults show that different climate zones andweather patternsare the main factors affecting the power generation of BIPVmodules
The simulation results in Table 7 also show that the poweroutputs of each HISG were larger than those of the originalsemitransparent PV modules That is the power enhance-ments of the tandem laser HISG were around 001ndash012those of the tandem TCO HISG were around 327ndash1006and those of the a-Si TCO HISG were around 094ndash307The simulated results also reveal that the percentage gainsin power generation for each HISG installed on the roofs ofbuildings as BIPV roofs are consistent with the experimentalresults under STC from IEC 61646 Therefore adding heatinsulation films onto semitransparent PV modules to forma HISG in order to enhance the power output of the modulesis beneficial in reducing the EPBT of the entire BIPV system
The simulation results for the energy consumption of theHVAC systems of buildings in Tainan Taiwan and LondonUK are shown in Tables 8 and 9 respectively As Tainan islocated in a subtropical region the use of a heater is lesscommon and the HVAC system is mostly used for coolingso the energy consumption for the latter is much higher thanthat for heating On the other hand London is located in atemperate region and the HVAC system is mainly used forheating so the energy consumption for this is much higherthan that for cooling
Furthermore the main factors affecting the energy con-sumption of theHVAC system are the shading coefficient andthe 119880-value of the envelope The shading coefficient and 119880-value of each HISG are lower than those of the semitrans-parent PV modules During summer solar radiation cannotenter the room easily through the HISG so cooling energycan be saved During winter the 119880-value of the HISG isvery low owing to the multilayer structure and althoughsolar radiation cannot enter the room easily the heat will beretained inside the room and will not dissipate easily andhence the amount of energy used for heating can also bereduced Therefore the simulation results for the HISGs allindicate greater energy-saving performance in the annualenergy consumption of the HVAC system The results showthat the HISG can save 2911ndash3219 of cooling energy 4734ndash4815 of heating energy and 3268ndash3575 of the totalenergy consumption of the HVAC system in subtropicalregions and 3727ndash4412 of cooling energy 3905ndash3986 ofheating energy and 3905ndash3986 of total energy consump-tion of the HVAC system in temperate regions Among all theHISGs the HISG encapsulated version using heat insulationfilm C had the best energy-saving performance
As seen in the simulation results given above the HISGcan not only enhance the power generation but also becauseof the better heat insulation performance shorten the EPBTof the entire HISG BIPV application on a building
4 Conclusion
The concepts of net zero energy zero energy and passiveenergy are becoming more important as part of the energyconservation policies adopted by the construction industryBIPV technology currently has great potential for effectivedevelopment of solar module techniques Theoretically if aBIPV module is combined with building materials it caneffectively reduce overall construction costs save energymodulate the indoor temperature and shorten the energypayback time (EPBT)
In this work the authors adopted three different types ofsemitransparent PV modules and combined three differenttypes of high-reflectivity films to encapsulate HISG BIPVsystems The optical and thermal properties and the overallpower generation effects of each HISG were investigated Inaddition Autodesk software was used to calculate the powergeneration and energy-saving effects of each HISG as appliedto actual buildings in Taiwan with a subtropical climate andEngland with a temperate climate As a result due to thethree-layer structure of the HISGwith a high-reflectivity heatinsulation film the heat insulation performance (SHGC and
12 International Journal of Photoenergy
Table5Testresults
forthe
vario
usBIPV
mod
ules
andHISGsu
nder
STC
Testitem
Tand
emlaser
mod
ule
Tand
emlaser-A
HISG
Tand
emlaser-BHISG
Tand
emlaser-CHISG
Tand
emTC
Omod
ule
Tand
emTC
O-A
HISG
Tand
emTC
O-B
HISG
Tand
emTC
O-C
HISG
a-SiTC
Omod
ule
a-Si
TCO-A
HISG
a-SiTC
O-B
HISG
a-Si
TCO-C
HISG
Efficiency
()
8184
8185
8189
8194
811
837
874
892
778
785
787
802
Maxim
umpo
wer
output
(W)
126029
12604
2126105
126187
124843
128926
134658
137399
119796
120921
121125
123475
Opencircuit
voltage
(V)
1673
821672
531672
81167313
1716
291716
441718
86172036
1116
061115
971116
131117
10
Shortcirc
uit
current(A)
1133
1134
1133
1134
1038
1074
1125
1150
1595
1612
1615
1650
Maxim
umvoltage
(V)
1310
261294
33130098
1292
07140561
1391
73138796
138027
86939
8733
787341
84561
Maxim
umele
ctric
current(A)
0962
0974
0969
0977
0888
0926
0970
0995
1378
1385
1387
1460
Fillfactor
066
44066
4606654
06651
07008
06996
06964
06944
06731
06721
06719
06698
International Journal of Photoenergy 13
Table 6 Results of power generation gain tests of the semitransparent PV modules and each combination of HISG under STC
ModuleItem
Power generation (W) Power generationenhancement () Module efficiency () Module efficiency
enhancement ()Tandem laser module 126029 mdash 8184 mdashTandem laser-A HISG 126042 001 8185 0001Tandem laser-B HISG 126105 006 8189 0005Tandem laser-C HISG 126187 013 8194 0010Tandem TCOmodule 124843 mdash 811 mdashTandem TCO-A HISG 128926 327 837 027Tandem TCO-B HISG 134658 786 874 064Tandem TCO-C HISG 137399 1006 892 082a-Si TCO module 119796 mdash 778 mdasha-Si TCO-A HISG 120921 094 785 007a-Si TCO-B HISG 121125 111 787 009a-Si TCO-C HISG 123475 307 802 024
Table 7 Power generation results for building body simulations
Module LocationTainan Taiwan (kW) Power enhancement () London UK (kW) Power enhancement ()
Tandem laser module 17178 mdash 8935 mdashTandem laser-A HISG 17179 001 8936 001Tandem laser-B HISG 17188 006 8940 006Tandem laser-C HISG 17199 012 8946 012Tandem TCOmodule 17016 mdash 8851 mdashTandem TCO-A HISG 17573 327 9141 327Tandem TCO-B HISG 18354 786 9547 786Tandem TCO-C HISG 18727 1006 9741 1006a-Si TCO module 16328 mdash 8493 mdasha-Si TCO-A HISG 16481 094 8573 094a-Si TCO-B HISG 16509 111 8587 111a-Si TCO-C HISG 16830 307 8754 307
Table 8 Simulation results for energy consumption of HVAC systems for the building body in the Tainan region of Taiwan
Module Cooling energyconsumption (kW)
Cooling energysaving ()
Heating energyconsumption
(kW)
Heating energysaving ()
Total HVAC systemenergy consumption
(kW)
Total HVACenergy saving
()Tandem laser module 28632 mdash 6924 mdash 35556 mdashTandem laser-A HISG 20296 2911 3639 4744 23935 3268Tandem laser-B HISG 20053 2996 3590 4815 23643 3350Tandem laser-C HISG 19958 3029 3591 4814 23549 3377Tandem TCOmodule 29495 mdash 6894 mdash 36390 mdashTandem TCO-A HISG 20793 2950 3623 4745 24415 3291Tandem TCO-B HISG 20412 3080 3576 4813 23988 3408Tandem TCO-C HISG 20201 3151 3583 4803 23784 3464a-Si TCO module 30368 mdash 6869 mdash 37236 mdasha-Si TCO-A HISG 20952 3101 3617 4734 24569 3402a-Si TCO-B HISG 20593 3219 3568 4806 24161 3511a-Si TCO-C HISG 20347 3300 3577 4793 23924 3575
14 International Journal of Photoenergy
Table 9 Simulation results for energy consumption of HVAC systems for the building body in London UK
ModuleCooling energyconsumption
(kW)
Cooling energysaving ()
Heating energyconsumption
(kW)
Heating energysaving ()
Total HVAC system energyconsumption (kW)
Total HVACenergy saving
()Tandem laser module 306 mdash 116818 mdash 117123 mdashTandem laser-A HISG 181 4085 71203 3905 71384 3905Tandem laser-B HISG 171 4412 70570 3959 70741 3960Tandem laser-C HISG 173 4346 70491 3966 70664 3967Tandem TCOmodule 271 mdash 117612 mdash 117883 mdashTandem TCO-A HISG 170 3727 71497 3921 71667 3920Tandem TCO-B HISG 164 3948 70753 3984 70917 3984Tandem TCO-C HISG 165 3911 70734 3986 70899 3986a-Si TCO module 287 mdash 117214 mdash 117501 mdasha-Si TCO-A HISG 175 3902 71273 3919 71448 3919a-Si TCO-B HISG 172 4007 70640 3973 70812 3973a-Si TCO-C HISG 171 4042 70566 3980 70737 3980
119880-value) showed an improvement Although the multilayerstructure of HISG would affect the visible light transmit-tance in practice it does not have a significant impact onthe view through the glass Moreover although the solardirect reflectance values all showed improving trends thevisible light reflectance was only around 5 which will notnecessarily cause environmental light pollution Comparedto the original modules the power generation and moduleefficiency of all HISGs were found to have increased Of allthe combinations of HISGs the gain in power generation ofthe tandem TCO-C HISG was the highest as the power gen-eration was improved by 1006 and the module efficiencywas improved by 082The results of the simulation showeda very similar trendwith regard to the level of electrical powergeneration based on experimental data that was obtainedusing the standard test conditions (STC) for measurementcontained in IEC 61646The simulation results also indicatedthat theHISG has a significant effect on the amount of energythat can be saved when using the HVAC system in bothsubtropical and temperate regions
This paper thus provides valuable information for renew-able energy planners and architectural designers who areinterested in using HISG BIPV systems
Competing Interests
The authors declare that there are no competing interestsregarding the publication of this paper
Acknowledgments
This study was supported by the Ministry of Science andTechnology of Taiwan under Projects MOST 105-3113-F-011-001 and MOST 105-3113-E-006-006-CC2
References
[1] M van der Hoeven Energy and Climate ChangemdashWorld EnergyOutlook Special Report International Energy Agency 2015
[2] P Jones S S Hou and X Li ldquoTowards zero carbon designin offices integrating smart facades ventilation and surfaceheating and coolingrdquoRenewable Energy vol 73 pp 69ndash76 2015
[3] W Pan ldquoSystem boundaries of zero carbon buildingsrdquo Renew-able and Sustainable Energy Reviews vol 37 pp 424ndash434 2014
[4] S Berry K Davidson and W Saman ldquoDefining zero carbonand zero energy homes from a performance-based regulatoryperspectiverdquo Energy Efficiency vol 7 no 2 pp 303ndash322 2014
[5] G P Hammond H A Harajli C I Jones and A B WinnettldquoWhole systems appraisal of a UK Building Integrated Photo-voltaic (BIPV) system energy environmental and economicevaluationsrdquo Energy Policy vol 40 no 1 pp 219ndash230 2012
[6] G A Keoleian and GM Lewis ldquoModeling the life cycle energyand environmental performance of amorphous silicon BIPVroofing in the USrdquo Renewable Energy vol 28 no 2 pp 271ndash2932003
[7] L Lu andHX Yang ldquoEnvironmental payback time analysis of aroof-mounted building-integrated photovoltaic (BIPV) systemin Hong Kongrdquo Applied Energy vol 87 no 12 pp 3625ndash36312010
[8] L Y Seng G Lalchand and G M Sow Lin ldquoEconomicalenvironmental and technical analysis of building integratedphotovoltaic systems in Malaysiardquo Energy Policy vol 36 no 6pp 2130ndash2142 2008
[9] M Oliver and T Jackson ldquoEnergy and economic evaluation ofbuilding-integrated photovoltaicsrdquo Energy vol 26 no 4 pp431ndash439 2001
[10] L Sabnani A Skumanich E Ryabova and R Noufi Devel-oping Market Opportunities for Flexible Rooftop Applicationsof PV Using Flexible CIGS Technology Market ConsiderationsNational Renewable Energy Laboratory (NREL) Golden ColoUSA 2011
[11] M A Green K Emery Y Hishikawa W Warta and E DDunlop ldquoSolar cell efficiency tables (version 47)rdquo Progress inPhotovoltaics Research and Applications vol 24 no 1 pp 3ndash112016
[12] G Y Yun M McEvoy and K Steemers ldquoDesign and overallenergy performance of a ventilated photovoltaic facaderdquo SolarEnergy vol 81 no 3 pp 383ndash394 2007
International Journal of Photoenergy 15
[13] PWWong Y ShimodaM NonakaM Inoue andMMizunoldquoSemi-transparent PV thermal performance power generationdaylight modelling and energy saving potential in a residentialapplicationrdquo Renewable Energy vol 33 no 5 pp 1024ndash10362008
[14] D H W Li T N T Lam W W H Chan and A H L MakldquoEnergy and cost analysis of semi-transparent photovoltaic inoffice buildingsrdquo Applied Energy vol 86 no 5 pp 722ndash7292009
[15] H Radhi ldquoEnergy analysis of facade-integrated photovoltaicsystems applied to UAE commercial buildingsrdquo Solar Energyvol 84 no 12 pp 2009ndash2021 2010
[16] E L Didone and A Wagner ldquoSemi-transparent PV windowsa study for office buildings in Brazilrdquo Energy and Buildings vol67 pp 136ndash142 2013
[17] P K Ng and N Mithraratne ldquoLifetime performance of semi-transparent building-integrated photovoltaic (BIPV) glazingsystems in the tropicsrdquo Renewable and Sustainable EnergyReviews vol 31 pp 736ndash745 2014
[18] C H Young Y L Chen and P C Chen ldquoHeat insulation solarglass and application on energy efficiency buildingsrdquo Energyand Buildings vol 78 pp 66ndash78 2014
[19] International Organization for Standardization ISO 9050 Glassin BuildingmdashDetermination of Light Transmittance Solar DirectTransmittance Total Solar Energy Transmittance UltravioletTransmittance and Related Glazing Factors International Orga-nization for Standardization Basel Switzerland 2003
[20] International Organization for Standardization ldquoISO10292glass in buildingmdashcalculation of steady-state U values (thermaltransmittance) of multiple glazingrdquo Tech Rep InternationalOrganization for Standardization Geneva Switzerland 1994
[21] International Standard ldquoThin-film terrestrial photovoltaic (pv)modulesmdashdesign qualification and type approvalrdquo IEC 616462008
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Inorganic ChemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Carbohydrate Chemistry
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
Physical Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom
Analytical Methods in Chemistry
Journal of
Volume 2014
Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
SpectroscopyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Medicinal ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chromatography Research International
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Applied ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Theoretical ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Spectroscopy
Analytical ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Quantum Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Organic Chemistry International
ElectrochemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CatalystsJournal of
10 International Journal of Photoenergy
Table 2 Emissivity of each component
Item Emissivity ofindoor side
Emissivity ofoutdoor side
Tandem laser module 084 084Tandem TCOmodule 084 084a-Si TCO module 084 084Heat insulation film A 076 0135Heat insulation film B 076 0045Heat insulation film C 076 0033Rear glass 084 084
Table 3Thermal properties of the semitransparent PVmodules andHISGs
ModuleItem
SHGC Shadingcoefficient 119880-value
Tandem lasermodule 03 0345 563
Tandem laser-AHISG 0151 0174 1824
Tandem laser-BHISG 0135 0155 1757
Tandem laser-CHISG 0129 0148 1755
Tandem TCOmodule 038 0437 563
Tandem TCO-AHISG 0218 025 1824
Tandem TCO-BHISG 0184 0211 1757
Tandem TCO-CHISG 0171 0196 1755
a-Si TCOmodule 041 0471 563
a-Si TCO-AHISG 0249 0286 1824
a-Si TCO-BHISG 0207 0238 1757
a-Si TCO-CHISG 019 0218 1755
results show that the power output for the front side of thetandem laser module was 126029W with an efficiency of8184 while that of the back side was only 1019W Thereason for this is the cell structure of the tandem lasermoduleas the bottom back-contact conductive layer is Al whichdoes not possess power generation characteristicsThereforeafter being illuminated by direct light there should not be apower generation effect However because the tandem lasermodule was subjected to transverse laser cutting during themanufacturing process light can pass through from the backsideThe light could then undergo refraction or transmissionat the rear glass so some of the light is able to enter the power-generating layer from the laser cut slits and so the back side
Table 4 Results of tests of electrical characteristics in STC for initialstates of the original transparent PV module (a) front side and (b)back side
(a)
Test itemTandemlaser
module
TandemTCO
module
a-SiTCO
moduleModule efficiency () 8184 811 778Maximum power output(W) 126029 124843 119796
Open circuit voltage (V) 167382 171629 111606Short circuit current (A) 1133 1038 1595Maximum voltage (V) 131026 140561 86939Maximum electric current(A) 0962 0888 1378
Fill factor 06644 07008 06731
(b)
Test itemTandemlaser
module
TandemTCO
module
a-SiTCO
moduleModule efficiency () 0066 0723 5361Maximum power output(W) 1019 11134 82566
Open circuit voltage (V) 109965 156555 108648Short circuit current (A) 0026 0108 1213Maximum voltage (V) 40348 132561 83918Maximum electric current(A) 0025 0084 0984
Fill factor 03506 06576 06264
of the tandem laser module also possesses a slight powergeneration effect
The power output of the front side of the tandem TCOmodule was 124843W with an efficiency of 811 whereasthat of the back side was only 11134W The reason why theefficiency from back-side illumination is low is due to lightabsorption in the lower bandgap 120583c-Si cell which allowslimited light into the a-Si cell The current output would belimited by the smaller current value from the a-Si and so alower efficiency is generated
The front-side power output of the a-Si TCOmodule was119796W with an efficiency of 778 whereas the back-sidepower output of the a-Si TCO module reached 82566WThe power-generating layer of the a-Si TCO module is thea-Si layer which is also classified as a cell structure withdual-surface power generation characteristics so the back-side power output was higher compared to that of the formertwo modules However the reason for the difference in thefront-side and back-side power outputs of the a-Si TCOmodule is that the materials of the front and rear glasswere different The front glass was ultraclear glass with morethan 90 visible light transmittance Meanwhile in orderto increase the loading strength of the BIPV the rear glasswas mostly tempered glass or heat-strengthened glass with
International Journal of Photoenergy 11
lower transmissivity In addition before entering the power-generating layer from the back side the light still needs to passthrough a layer of EVA plastic film which will also reduce thesolar irradianceThe back-side power output of the a-Si TCOmodule was thus only 69 of the front-side power output
The results of the electrical tests of each semitransparentPV module and each combination of HISGs are shown inTable 5 The results for power generation gain are shownin Table 6 The experimental results indicated that boththe power generation and efficiency of tandem laser HISGexhibited slightly increasing trends the power generationincreased by around 001ndash013 and the efficiency increasedby around 0001ndash001 However the power generationand efficiency of tandem TCO HISG and a-Si TCO HISGdisplayed increasing trends For the tandem TCO HISGthe power generation improved by around 327ndash1006 andthe efficiency increased by around 027ndash082 For the a-SiTCOHISG the power generation increased by around 094ndash307 and the efficiency increased by around 007ndash024The power-generating layer of the tandem TCOmodule is a-Si120583c-Si but that of the a-Si TCO module is a single layer ofa-Si The absorption spectrum of the tandem TCO module(300 nmndash1100 nm) is wider than that of the a-Si TCOmodule(300 nmndash750 nm) The back side of the tandem TCO HISGcan thus absorb higher effective irradiance than the a-Si TCOHISG This means that the efficiency enhanced rate of thetandemTCOHISG is higher than that of the a-Si TCOHISGIt is also worth noting that selecting an appropriate heatinsulation film in order to absorb a larger amount of reflectivesolar radiation by the back side of theHISG can lead to greaterenhancement of power generation
34 Simulation of Energy-Saving Performance The simula-tion results for the power generation of each HISG installedin the buildings and the energy consumption of the heatingventilation and air-conditioning (HVAC) system are shownin Table 7 As Tainan is located in a subtropical region inTaiwan where there is sufficient sunlight the annual powergeneration of each module was higher than that of themodules in London and the power outputs ranged between16328 kW and 18727 kW London is located in a temperatezone with mostly cloudy weather and thus the annual powergeneration only ranged between 8493 kWand 9741 kWTheseresults show that different climate zones andweather patternsare the main factors affecting the power generation of BIPVmodules
The simulation results in Table 7 also show that the poweroutputs of each HISG were larger than those of the originalsemitransparent PV modules That is the power enhance-ments of the tandem laser HISG were around 001ndash012those of the tandem TCO HISG were around 327ndash1006and those of the a-Si TCO HISG were around 094ndash307The simulated results also reveal that the percentage gainsin power generation for each HISG installed on the roofs ofbuildings as BIPV roofs are consistent with the experimentalresults under STC from IEC 61646 Therefore adding heatinsulation films onto semitransparent PV modules to forma HISG in order to enhance the power output of the modulesis beneficial in reducing the EPBT of the entire BIPV system
The simulation results for the energy consumption of theHVAC systems of buildings in Tainan Taiwan and LondonUK are shown in Tables 8 and 9 respectively As Tainan islocated in a subtropical region the use of a heater is lesscommon and the HVAC system is mostly used for coolingso the energy consumption for the latter is much higher thanthat for heating On the other hand London is located in atemperate region and the HVAC system is mainly used forheating so the energy consumption for this is much higherthan that for cooling
Furthermore the main factors affecting the energy con-sumption of theHVAC system are the shading coefficient andthe 119880-value of the envelope The shading coefficient and 119880-value of each HISG are lower than those of the semitrans-parent PV modules During summer solar radiation cannotenter the room easily through the HISG so cooling energycan be saved During winter the 119880-value of the HISG isvery low owing to the multilayer structure and althoughsolar radiation cannot enter the room easily the heat will beretained inside the room and will not dissipate easily andhence the amount of energy used for heating can also bereduced Therefore the simulation results for the HISGs allindicate greater energy-saving performance in the annualenergy consumption of the HVAC system The results showthat the HISG can save 2911ndash3219 of cooling energy 4734ndash4815 of heating energy and 3268ndash3575 of the totalenergy consumption of the HVAC system in subtropicalregions and 3727ndash4412 of cooling energy 3905ndash3986 ofheating energy and 3905ndash3986 of total energy consump-tion of the HVAC system in temperate regions Among all theHISGs the HISG encapsulated version using heat insulationfilm C had the best energy-saving performance
As seen in the simulation results given above the HISGcan not only enhance the power generation but also becauseof the better heat insulation performance shorten the EPBTof the entire HISG BIPV application on a building
4 Conclusion
The concepts of net zero energy zero energy and passiveenergy are becoming more important as part of the energyconservation policies adopted by the construction industryBIPV technology currently has great potential for effectivedevelopment of solar module techniques Theoretically if aBIPV module is combined with building materials it caneffectively reduce overall construction costs save energymodulate the indoor temperature and shorten the energypayback time (EPBT)
In this work the authors adopted three different types ofsemitransparent PV modules and combined three differenttypes of high-reflectivity films to encapsulate HISG BIPVsystems The optical and thermal properties and the overallpower generation effects of each HISG were investigated Inaddition Autodesk software was used to calculate the powergeneration and energy-saving effects of each HISG as appliedto actual buildings in Taiwan with a subtropical climate andEngland with a temperate climate As a result due to thethree-layer structure of the HISGwith a high-reflectivity heatinsulation film the heat insulation performance (SHGC and
12 International Journal of Photoenergy
Table5Testresults
forthe
vario
usBIPV
mod
ules
andHISGsu
nder
STC
Testitem
Tand
emlaser
mod
ule
Tand
emlaser-A
HISG
Tand
emlaser-BHISG
Tand
emlaser-CHISG
Tand
emTC
Omod
ule
Tand
emTC
O-A
HISG
Tand
emTC
O-B
HISG
Tand
emTC
O-C
HISG
a-SiTC
Omod
ule
a-Si
TCO-A
HISG
a-SiTC
O-B
HISG
a-Si
TCO-C
HISG
Efficiency
()
8184
8185
8189
8194
811
837
874
892
778
785
787
802
Maxim
umpo
wer
output
(W)
126029
12604
2126105
126187
124843
128926
134658
137399
119796
120921
121125
123475
Opencircuit
voltage
(V)
1673
821672
531672
81167313
1716
291716
441718
86172036
1116
061115
971116
131117
10
Shortcirc
uit
current(A)
1133
1134
1133
1134
1038
1074
1125
1150
1595
1612
1615
1650
Maxim
umvoltage
(V)
1310
261294
33130098
1292
07140561
1391
73138796
138027
86939
8733
787341
84561
Maxim
umele
ctric
current(A)
0962
0974
0969
0977
0888
0926
0970
0995
1378
1385
1387
1460
Fillfactor
066
44066
4606654
06651
07008
06996
06964
06944
06731
06721
06719
06698
International Journal of Photoenergy 13
Table 6 Results of power generation gain tests of the semitransparent PV modules and each combination of HISG under STC
ModuleItem
Power generation (W) Power generationenhancement () Module efficiency () Module efficiency
enhancement ()Tandem laser module 126029 mdash 8184 mdashTandem laser-A HISG 126042 001 8185 0001Tandem laser-B HISG 126105 006 8189 0005Tandem laser-C HISG 126187 013 8194 0010Tandem TCOmodule 124843 mdash 811 mdashTandem TCO-A HISG 128926 327 837 027Tandem TCO-B HISG 134658 786 874 064Tandem TCO-C HISG 137399 1006 892 082a-Si TCO module 119796 mdash 778 mdasha-Si TCO-A HISG 120921 094 785 007a-Si TCO-B HISG 121125 111 787 009a-Si TCO-C HISG 123475 307 802 024
Table 7 Power generation results for building body simulations
Module LocationTainan Taiwan (kW) Power enhancement () London UK (kW) Power enhancement ()
Tandem laser module 17178 mdash 8935 mdashTandem laser-A HISG 17179 001 8936 001Tandem laser-B HISG 17188 006 8940 006Tandem laser-C HISG 17199 012 8946 012Tandem TCOmodule 17016 mdash 8851 mdashTandem TCO-A HISG 17573 327 9141 327Tandem TCO-B HISG 18354 786 9547 786Tandem TCO-C HISG 18727 1006 9741 1006a-Si TCO module 16328 mdash 8493 mdasha-Si TCO-A HISG 16481 094 8573 094a-Si TCO-B HISG 16509 111 8587 111a-Si TCO-C HISG 16830 307 8754 307
Table 8 Simulation results for energy consumption of HVAC systems for the building body in the Tainan region of Taiwan
Module Cooling energyconsumption (kW)
Cooling energysaving ()
Heating energyconsumption
(kW)
Heating energysaving ()
Total HVAC systemenergy consumption
(kW)
Total HVACenergy saving
()Tandem laser module 28632 mdash 6924 mdash 35556 mdashTandem laser-A HISG 20296 2911 3639 4744 23935 3268Tandem laser-B HISG 20053 2996 3590 4815 23643 3350Tandem laser-C HISG 19958 3029 3591 4814 23549 3377Tandem TCOmodule 29495 mdash 6894 mdash 36390 mdashTandem TCO-A HISG 20793 2950 3623 4745 24415 3291Tandem TCO-B HISG 20412 3080 3576 4813 23988 3408Tandem TCO-C HISG 20201 3151 3583 4803 23784 3464a-Si TCO module 30368 mdash 6869 mdash 37236 mdasha-Si TCO-A HISG 20952 3101 3617 4734 24569 3402a-Si TCO-B HISG 20593 3219 3568 4806 24161 3511a-Si TCO-C HISG 20347 3300 3577 4793 23924 3575
14 International Journal of Photoenergy
Table 9 Simulation results for energy consumption of HVAC systems for the building body in London UK
ModuleCooling energyconsumption
(kW)
Cooling energysaving ()
Heating energyconsumption
(kW)
Heating energysaving ()
Total HVAC system energyconsumption (kW)
Total HVACenergy saving
()Tandem laser module 306 mdash 116818 mdash 117123 mdashTandem laser-A HISG 181 4085 71203 3905 71384 3905Tandem laser-B HISG 171 4412 70570 3959 70741 3960Tandem laser-C HISG 173 4346 70491 3966 70664 3967Tandem TCOmodule 271 mdash 117612 mdash 117883 mdashTandem TCO-A HISG 170 3727 71497 3921 71667 3920Tandem TCO-B HISG 164 3948 70753 3984 70917 3984Tandem TCO-C HISG 165 3911 70734 3986 70899 3986a-Si TCO module 287 mdash 117214 mdash 117501 mdasha-Si TCO-A HISG 175 3902 71273 3919 71448 3919a-Si TCO-B HISG 172 4007 70640 3973 70812 3973a-Si TCO-C HISG 171 4042 70566 3980 70737 3980
119880-value) showed an improvement Although the multilayerstructure of HISG would affect the visible light transmit-tance in practice it does not have a significant impact onthe view through the glass Moreover although the solardirect reflectance values all showed improving trends thevisible light reflectance was only around 5 which will notnecessarily cause environmental light pollution Comparedto the original modules the power generation and moduleefficiency of all HISGs were found to have increased Of allthe combinations of HISGs the gain in power generation ofthe tandem TCO-C HISG was the highest as the power gen-eration was improved by 1006 and the module efficiencywas improved by 082The results of the simulation showeda very similar trendwith regard to the level of electrical powergeneration based on experimental data that was obtainedusing the standard test conditions (STC) for measurementcontained in IEC 61646The simulation results also indicatedthat theHISG has a significant effect on the amount of energythat can be saved when using the HVAC system in bothsubtropical and temperate regions
This paper thus provides valuable information for renew-able energy planners and architectural designers who areinterested in using HISG BIPV systems
Competing Interests
The authors declare that there are no competing interestsregarding the publication of this paper
Acknowledgments
This study was supported by the Ministry of Science andTechnology of Taiwan under Projects MOST 105-3113-F-011-001 and MOST 105-3113-E-006-006-CC2
References
[1] M van der Hoeven Energy and Climate ChangemdashWorld EnergyOutlook Special Report International Energy Agency 2015
[2] P Jones S S Hou and X Li ldquoTowards zero carbon designin offices integrating smart facades ventilation and surfaceheating and coolingrdquoRenewable Energy vol 73 pp 69ndash76 2015
[3] W Pan ldquoSystem boundaries of zero carbon buildingsrdquo Renew-able and Sustainable Energy Reviews vol 37 pp 424ndash434 2014
[4] S Berry K Davidson and W Saman ldquoDefining zero carbonand zero energy homes from a performance-based regulatoryperspectiverdquo Energy Efficiency vol 7 no 2 pp 303ndash322 2014
[5] G P Hammond H A Harajli C I Jones and A B WinnettldquoWhole systems appraisal of a UK Building Integrated Photo-voltaic (BIPV) system energy environmental and economicevaluationsrdquo Energy Policy vol 40 no 1 pp 219ndash230 2012
[6] G A Keoleian and GM Lewis ldquoModeling the life cycle energyand environmental performance of amorphous silicon BIPVroofing in the USrdquo Renewable Energy vol 28 no 2 pp 271ndash2932003
[7] L Lu andHX Yang ldquoEnvironmental payback time analysis of aroof-mounted building-integrated photovoltaic (BIPV) systemin Hong Kongrdquo Applied Energy vol 87 no 12 pp 3625ndash36312010
[8] L Y Seng G Lalchand and G M Sow Lin ldquoEconomicalenvironmental and technical analysis of building integratedphotovoltaic systems in Malaysiardquo Energy Policy vol 36 no 6pp 2130ndash2142 2008
[9] M Oliver and T Jackson ldquoEnergy and economic evaluation ofbuilding-integrated photovoltaicsrdquo Energy vol 26 no 4 pp431ndash439 2001
[10] L Sabnani A Skumanich E Ryabova and R Noufi Devel-oping Market Opportunities for Flexible Rooftop Applicationsof PV Using Flexible CIGS Technology Market ConsiderationsNational Renewable Energy Laboratory (NREL) Golden ColoUSA 2011
[11] M A Green K Emery Y Hishikawa W Warta and E DDunlop ldquoSolar cell efficiency tables (version 47)rdquo Progress inPhotovoltaics Research and Applications vol 24 no 1 pp 3ndash112016
[12] G Y Yun M McEvoy and K Steemers ldquoDesign and overallenergy performance of a ventilated photovoltaic facaderdquo SolarEnergy vol 81 no 3 pp 383ndash394 2007
International Journal of Photoenergy 15
[13] PWWong Y ShimodaM NonakaM Inoue andMMizunoldquoSemi-transparent PV thermal performance power generationdaylight modelling and energy saving potential in a residentialapplicationrdquo Renewable Energy vol 33 no 5 pp 1024ndash10362008
[14] D H W Li T N T Lam W W H Chan and A H L MakldquoEnergy and cost analysis of semi-transparent photovoltaic inoffice buildingsrdquo Applied Energy vol 86 no 5 pp 722ndash7292009
[15] H Radhi ldquoEnergy analysis of facade-integrated photovoltaicsystems applied to UAE commercial buildingsrdquo Solar Energyvol 84 no 12 pp 2009ndash2021 2010
[16] E L Didone and A Wagner ldquoSemi-transparent PV windowsa study for office buildings in Brazilrdquo Energy and Buildings vol67 pp 136ndash142 2013
[17] P K Ng and N Mithraratne ldquoLifetime performance of semi-transparent building-integrated photovoltaic (BIPV) glazingsystems in the tropicsrdquo Renewable and Sustainable EnergyReviews vol 31 pp 736ndash745 2014
[18] C H Young Y L Chen and P C Chen ldquoHeat insulation solarglass and application on energy efficiency buildingsrdquo Energyand Buildings vol 78 pp 66ndash78 2014
[19] International Organization for Standardization ISO 9050 Glassin BuildingmdashDetermination of Light Transmittance Solar DirectTransmittance Total Solar Energy Transmittance UltravioletTransmittance and Related Glazing Factors International Orga-nization for Standardization Basel Switzerland 2003
[20] International Organization for Standardization ldquoISO10292glass in buildingmdashcalculation of steady-state U values (thermaltransmittance) of multiple glazingrdquo Tech Rep InternationalOrganization for Standardization Geneva Switzerland 1994
[21] International Standard ldquoThin-film terrestrial photovoltaic (pv)modulesmdashdesign qualification and type approvalrdquo IEC 616462008
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Inorganic ChemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Carbohydrate Chemistry
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
Physical Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom
Analytical Methods in Chemistry
Journal of
Volume 2014
Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
SpectroscopyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Medicinal ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chromatography Research International
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Applied ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Theoretical ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Spectroscopy
Analytical ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Quantum Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Organic Chemistry International
ElectrochemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CatalystsJournal of
International Journal of Photoenergy 11
lower transmissivity In addition before entering the power-generating layer from the back side the light still needs to passthrough a layer of EVA plastic film which will also reduce thesolar irradianceThe back-side power output of the a-Si TCOmodule was thus only 69 of the front-side power output
The results of the electrical tests of each semitransparentPV module and each combination of HISGs are shown inTable 5 The results for power generation gain are shownin Table 6 The experimental results indicated that boththe power generation and efficiency of tandem laser HISGexhibited slightly increasing trends the power generationincreased by around 001ndash013 and the efficiency increasedby around 0001ndash001 However the power generationand efficiency of tandem TCO HISG and a-Si TCO HISGdisplayed increasing trends For the tandem TCO HISGthe power generation improved by around 327ndash1006 andthe efficiency increased by around 027ndash082 For the a-SiTCOHISG the power generation increased by around 094ndash307 and the efficiency increased by around 007ndash024The power-generating layer of the tandem TCOmodule is a-Si120583c-Si but that of the a-Si TCO module is a single layer ofa-Si The absorption spectrum of the tandem TCO module(300 nmndash1100 nm) is wider than that of the a-Si TCOmodule(300 nmndash750 nm) The back side of the tandem TCO HISGcan thus absorb higher effective irradiance than the a-Si TCOHISG This means that the efficiency enhanced rate of thetandemTCOHISG is higher than that of the a-Si TCOHISGIt is also worth noting that selecting an appropriate heatinsulation film in order to absorb a larger amount of reflectivesolar radiation by the back side of theHISG can lead to greaterenhancement of power generation
34 Simulation of Energy-Saving Performance The simula-tion results for the power generation of each HISG installedin the buildings and the energy consumption of the heatingventilation and air-conditioning (HVAC) system are shownin Table 7 As Tainan is located in a subtropical region inTaiwan where there is sufficient sunlight the annual powergeneration of each module was higher than that of themodules in London and the power outputs ranged between16328 kW and 18727 kW London is located in a temperatezone with mostly cloudy weather and thus the annual powergeneration only ranged between 8493 kWand 9741 kWTheseresults show that different climate zones andweather patternsare the main factors affecting the power generation of BIPVmodules
The simulation results in Table 7 also show that the poweroutputs of each HISG were larger than those of the originalsemitransparent PV modules That is the power enhance-ments of the tandem laser HISG were around 001ndash012those of the tandem TCO HISG were around 327ndash1006and those of the a-Si TCO HISG were around 094ndash307The simulated results also reveal that the percentage gainsin power generation for each HISG installed on the roofs ofbuildings as BIPV roofs are consistent with the experimentalresults under STC from IEC 61646 Therefore adding heatinsulation films onto semitransparent PV modules to forma HISG in order to enhance the power output of the modulesis beneficial in reducing the EPBT of the entire BIPV system
The simulation results for the energy consumption of theHVAC systems of buildings in Tainan Taiwan and LondonUK are shown in Tables 8 and 9 respectively As Tainan islocated in a subtropical region the use of a heater is lesscommon and the HVAC system is mostly used for coolingso the energy consumption for the latter is much higher thanthat for heating On the other hand London is located in atemperate region and the HVAC system is mainly used forheating so the energy consumption for this is much higherthan that for cooling
Furthermore the main factors affecting the energy con-sumption of theHVAC system are the shading coefficient andthe 119880-value of the envelope The shading coefficient and 119880-value of each HISG are lower than those of the semitrans-parent PV modules During summer solar radiation cannotenter the room easily through the HISG so cooling energycan be saved During winter the 119880-value of the HISG isvery low owing to the multilayer structure and althoughsolar radiation cannot enter the room easily the heat will beretained inside the room and will not dissipate easily andhence the amount of energy used for heating can also bereduced Therefore the simulation results for the HISGs allindicate greater energy-saving performance in the annualenergy consumption of the HVAC system The results showthat the HISG can save 2911ndash3219 of cooling energy 4734ndash4815 of heating energy and 3268ndash3575 of the totalenergy consumption of the HVAC system in subtropicalregions and 3727ndash4412 of cooling energy 3905ndash3986 ofheating energy and 3905ndash3986 of total energy consump-tion of the HVAC system in temperate regions Among all theHISGs the HISG encapsulated version using heat insulationfilm C had the best energy-saving performance
As seen in the simulation results given above the HISGcan not only enhance the power generation but also becauseof the better heat insulation performance shorten the EPBTof the entire HISG BIPV application on a building
4 Conclusion
The concepts of net zero energy zero energy and passiveenergy are becoming more important as part of the energyconservation policies adopted by the construction industryBIPV technology currently has great potential for effectivedevelopment of solar module techniques Theoretically if aBIPV module is combined with building materials it caneffectively reduce overall construction costs save energymodulate the indoor temperature and shorten the energypayback time (EPBT)
In this work the authors adopted three different types ofsemitransparent PV modules and combined three differenttypes of high-reflectivity films to encapsulate HISG BIPVsystems The optical and thermal properties and the overallpower generation effects of each HISG were investigated Inaddition Autodesk software was used to calculate the powergeneration and energy-saving effects of each HISG as appliedto actual buildings in Taiwan with a subtropical climate andEngland with a temperate climate As a result due to thethree-layer structure of the HISGwith a high-reflectivity heatinsulation film the heat insulation performance (SHGC and
12 International Journal of Photoenergy
Table5Testresults
forthe
vario
usBIPV
mod
ules
andHISGsu
nder
STC
Testitem
Tand
emlaser
mod
ule
Tand
emlaser-A
HISG
Tand
emlaser-BHISG
Tand
emlaser-CHISG
Tand
emTC
Omod
ule
Tand
emTC
O-A
HISG
Tand
emTC
O-B
HISG
Tand
emTC
O-C
HISG
a-SiTC
Omod
ule
a-Si
TCO-A
HISG
a-SiTC
O-B
HISG
a-Si
TCO-C
HISG
Efficiency
()
8184
8185
8189
8194
811
837
874
892
778
785
787
802
Maxim
umpo
wer
output
(W)
126029
12604
2126105
126187
124843
128926
134658
137399
119796
120921
121125
123475
Opencircuit
voltage
(V)
1673
821672
531672
81167313
1716
291716
441718
86172036
1116
061115
971116
131117
10
Shortcirc
uit
current(A)
1133
1134
1133
1134
1038
1074
1125
1150
1595
1612
1615
1650
Maxim
umvoltage
(V)
1310
261294
33130098
1292
07140561
1391
73138796
138027
86939
8733
787341
84561
Maxim
umele
ctric
current(A)
0962
0974
0969
0977
0888
0926
0970
0995
1378
1385
1387
1460
Fillfactor
066
44066
4606654
06651
07008
06996
06964
06944
06731
06721
06719
06698
International Journal of Photoenergy 13
Table 6 Results of power generation gain tests of the semitransparent PV modules and each combination of HISG under STC
ModuleItem
Power generation (W) Power generationenhancement () Module efficiency () Module efficiency
enhancement ()Tandem laser module 126029 mdash 8184 mdashTandem laser-A HISG 126042 001 8185 0001Tandem laser-B HISG 126105 006 8189 0005Tandem laser-C HISG 126187 013 8194 0010Tandem TCOmodule 124843 mdash 811 mdashTandem TCO-A HISG 128926 327 837 027Tandem TCO-B HISG 134658 786 874 064Tandem TCO-C HISG 137399 1006 892 082a-Si TCO module 119796 mdash 778 mdasha-Si TCO-A HISG 120921 094 785 007a-Si TCO-B HISG 121125 111 787 009a-Si TCO-C HISG 123475 307 802 024
Table 7 Power generation results for building body simulations
Module LocationTainan Taiwan (kW) Power enhancement () London UK (kW) Power enhancement ()
Tandem laser module 17178 mdash 8935 mdashTandem laser-A HISG 17179 001 8936 001Tandem laser-B HISG 17188 006 8940 006Tandem laser-C HISG 17199 012 8946 012Tandem TCOmodule 17016 mdash 8851 mdashTandem TCO-A HISG 17573 327 9141 327Tandem TCO-B HISG 18354 786 9547 786Tandem TCO-C HISG 18727 1006 9741 1006a-Si TCO module 16328 mdash 8493 mdasha-Si TCO-A HISG 16481 094 8573 094a-Si TCO-B HISG 16509 111 8587 111a-Si TCO-C HISG 16830 307 8754 307
Table 8 Simulation results for energy consumption of HVAC systems for the building body in the Tainan region of Taiwan
Module Cooling energyconsumption (kW)
Cooling energysaving ()
Heating energyconsumption
(kW)
Heating energysaving ()
Total HVAC systemenergy consumption
(kW)
Total HVACenergy saving
()Tandem laser module 28632 mdash 6924 mdash 35556 mdashTandem laser-A HISG 20296 2911 3639 4744 23935 3268Tandem laser-B HISG 20053 2996 3590 4815 23643 3350Tandem laser-C HISG 19958 3029 3591 4814 23549 3377Tandem TCOmodule 29495 mdash 6894 mdash 36390 mdashTandem TCO-A HISG 20793 2950 3623 4745 24415 3291Tandem TCO-B HISG 20412 3080 3576 4813 23988 3408Tandem TCO-C HISG 20201 3151 3583 4803 23784 3464a-Si TCO module 30368 mdash 6869 mdash 37236 mdasha-Si TCO-A HISG 20952 3101 3617 4734 24569 3402a-Si TCO-B HISG 20593 3219 3568 4806 24161 3511a-Si TCO-C HISG 20347 3300 3577 4793 23924 3575
14 International Journal of Photoenergy
Table 9 Simulation results for energy consumption of HVAC systems for the building body in London UK
ModuleCooling energyconsumption
(kW)
Cooling energysaving ()
Heating energyconsumption
(kW)
Heating energysaving ()
Total HVAC system energyconsumption (kW)
Total HVACenergy saving
()Tandem laser module 306 mdash 116818 mdash 117123 mdashTandem laser-A HISG 181 4085 71203 3905 71384 3905Tandem laser-B HISG 171 4412 70570 3959 70741 3960Tandem laser-C HISG 173 4346 70491 3966 70664 3967Tandem TCOmodule 271 mdash 117612 mdash 117883 mdashTandem TCO-A HISG 170 3727 71497 3921 71667 3920Tandem TCO-B HISG 164 3948 70753 3984 70917 3984Tandem TCO-C HISG 165 3911 70734 3986 70899 3986a-Si TCO module 287 mdash 117214 mdash 117501 mdasha-Si TCO-A HISG 175 3902 71273 3919 71448 3919a-Si TCO-B HISG 172 4007 70640 3973 70812 3973a-Si TCO-C HISG 171 4042 70566 3980 70737 3980
119880-value) showed an improvement Although the multilayerstructure of HISG would affect the visible light transmit-tance in practice it does not have a significant impact onthe view through the glass Moreover although the solardirect reflectance values all showed improving trends thevisible light reflectance was only around 5 which will notnecessarily cause environmental light pollution Comparedto the original modules the power generation and moduleefficiency of all HISGs were found to have increased Of allthe combinations of HISGs the gain in power generation ofthe tandem TCO-C HISG was the highest as the power gen-eration was improved by 1006 and the module efficiencywas improved by 082The results of the simulation showeda very similar trendwith regard to the level of electrical powergeneration based on experimental data that was obtainedusing the standard test conditions (STC) for measurementcontained in IEC 61646The simulation results also indicatedthat theHISG has a significant effect on the amount of energythat can be saved when using the HVAC system in bothsubtropical and temperate regions
This paper thus provides valuable information for renew-able energy planners and architectural designers who areinterested in using HISG BIPV systems
Competing Interests
The authors declare that there are no competing interestsregarding the publication of this paper
Acknowledgments
This study was supported by the Ministry of Science andTechnology of Taiwan under Projects MOST 105-3113-F-011-001 and MOST 105-3113-E-006-006-CC2
References
[1] M van der Hoeven Energy and Climate ChangemdashWorld EnergyOutlook Special Report International Energy Agency 2015
[2] P Jones S S Hou and X Li ldquoTowards zero carbon designin offices integrating smart facades ventilation and surfaceheating and coolingrdquoRenewable Energy vol 73 pp 69ndash76 2015
[3] W Pan ldquoSystem boundaries of zero carbon buildingsrdquo Renew-able and Sustainable Energy Reviews vol 37 pp 424ndash434 2014
[4] S Berry K Davidson and W Saman ldquoDefining zero carbonand zero energy homes from a performance-based regulatoryperspectiverdquo Energy Efficiency vol 7 no 2 pp 303ndash322 2014
[5] G P Hammond H A Harajli C I Jones and A B WinnettldquoWhole systems appraisal of a UK Building Integrated Photo-voltaic (BIPV) system energy environmental and economicevaluationsrdquo Energy Policy vol 40 no 1 pp 219ndash230 2012
[6] G A Keoleian and GM Lewis ldquoModeling the life cycle energyand environmental performance of amorphous silicon BIPVroofing in the USrdquo Renewable Energy vol 28 no 2 pp 271ndash2932003
[7] L Lu andHX Yang ldquoEnvironmental payback time analysis of aroof-mounted building-integrated photovoltaic (BIPV) systemin Hong Kongrdquo Applied Energy vol 87 no 12 pp 3625ndash36312010
[8] L Y Seng G Lalchand and G M Sow Lin ldquoEconomicalenvironmental and technical analysis of building integratedphotovoltaic systems in Malaysiardquo Energy Policy vol 36 no 6pp 2130ndash2142 2008
[9] M Oliver and T Jackson ldquoEnergy and economic evaluation ofbuilding-integrated photovoltaicsrdquo Energy vol 26 no 4 pp431ndash439 2001
[10] L Sabnani A Skumanich E Ryabova and R Noufi Devel-oping Market Opportunities for Flexible Rooftop Applicationsof PV Using Flexible CIGS Technology Market ConsiderationsNational Renewable Energy Laboratory (NREL) Golden ColoUSA 2011
[11] M A Green K Emery Y Hishikawa W Warta and E DDunlop ldquoSolar cell efficiency tables (version 47)rdquo Progress inPhotovoltaics Research and Applications vol 24 no 1 pp 3ndash112016
[12] G Y Yun M McEvoy and K Steemers ldquoDesign and overallenergy performance of a ventilated photovoltaic facaderdquo SolarEnergy vol 81 no 3 pp 383ndash394 2007
International Journal of Photoenergy 15
[13] PWWong Y ShimodaM NonakaM Inoue andMMizunoldquoSemi-transparent PV thermal performance power generationdaylight modelling and energy saving potential in a residentialapplicationrdquo Renewable Energy vol 33 no 5 pp 1024ndash10362008
[14] D H W Li T N T Lam W W H Chan and A H L MakldquoEnergy and cost analysis of semi-transparent photovoltaic inoffice buildingsrdquo Applied Energy vol 86 no 5 pp 722ndash7292009
[15] H Radhi ldquoEnergy analysis of facade-integrated photovoltaicsystems applied to UAE commercial buildingsrdquo Solar Energyvol 84 no 12 pp 2009ndash2021 2010
[16] E L Didone and A Wagner ldquoSemi-transparent PV windowsa study for office buildings in Brazilrdquo Energy and Buildings vol67 pp 136ndash142 2013
[17] P K Ng and N Mithraratne ldquoLifetime performance of semi-transparent building-integrated photovoltaic (BIPV) glazingsystems in the tropicsrdquo Renewable and Sustainable EnergyReviews vol 31 pp 736ndash745 2014
[18] C H Young Y L Chen and P C Chen ldquoHeat insulation solarglass and application on energy efficiency buildingsrdquo Energyand Buildings vol 78 pp 66ndash78 2014
[19] International Organization for Standardization ISO 9050 Glassin BuildingmdashDetermination of Light Transmittance Solar DirectTransmittance Total Solar Energy Transmittance UltravioletTransmittance and Related Glazing Factors International Orga-nization for Standardization Basel Switzerland 2003
[20] International Organization for Standardization ldquoISO10292glass in buildingmdashcalculation of steady-state U values (thermaltransmittance) of multiple glazingrdquo Tech Rep InternationalOrganization for Standardization Geneva Switzerland 1994
[21] International Standard ldquoThin-film terrestrial photovoltaic (pv)modulesmdashdesign qualification and type approvalrdquo IEC 616462008
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Inorganic ChemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Carbohydrate Chemistry
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
Physical Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom
Analytical Methods in Chemistry
Journal of
Volume 2014
Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
SpectroscopyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Medicinal ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chromatography Research International
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Applied ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Theoretical ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Spectroscopy
Analytical ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Quantum Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Organic Chemistry International
ElectrochemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CatalystsJournal of
12 International Journal of Photoenergy
Table5Testresults
forthe
vario
usBIPV
mod
ules
andHISGsu
nder
STC
Testitem
Tand
emlaser
mod
ule
Tand
emlaser-A
HISG
Tand
emlaser-BHISG
Tand
emlaser-CHISG
Tand
emTC
Omod
ule
Tand
emTC
O-A
HISG
Tand
emTC
O-B
HISG
Tand
emTC
O-C
HISG
a-SiTC
Omod
ule
a-Si
TCO-A
HISG
a-SiTC
O-B
HISG
a-Si
TCO-C
HISG
Efficiency
()
8184
8185
8189
8194
811
837
874
892
778
785
787
802
Maxim
umpo
wer
output
(W)
126029
12604
2126105
126187
124843
128926
134658
137399
119796
120921
121125
123475
Opencircuit
voltage
(V)
1673
821672
531672
81167313
1716
291716
441718
86172036
1116
061115
971116
131117
10
Shortcirc
uit
current(A)
1133
1134
1133
1134
1038
1074
1125
1150
1595
1612
1615
1650
Maxim
umvoltage
(V)
1310
261294
33130098
1292
07140561
1391
73138796
138027
86939
8733
787341
84561
Maxim
umele
ctric
current(A)
0962
0974
0969
0977
0888
0926
0970
0995
1378
1385
1387
1460
Fillfactor
066
44066
4606654
06651
07008
06996
06964
06944
06731
06721
06719
06698
International Journal of Photoenergy 13
Table 6 Results of power generation gain tests of the semitransparent PV modules and each combination of HISG under STC
ModuleItem
Power generation (W) Power generationenhancement () Module efficiency () Module efficiency
enhancement ()Tandem laser module 126029 mdash 8184 mdashTandem laser-A HISG 126042 001 8185 0001Tandem laser-B HISG 126105 006 8189 0005Tandem laser-C HISG 126187 013 8194 0010Tandem TCOmodule 124843 mdash 811 mdashTandem TCO-A HISG 128926 327 837 027Tandem TCO-B HISG 134658 786 874 064Tandem TCO-C HISG 137399 1006 892 082a-Si TCO module 119796 mdash 778 mdasha-Si TCO-A HISG 120921 094 785 007a-Si TCO-B HISG 121125 111 787 009a-Si TCO-C HISG 123475 307 802 024
Table 7 Power generation results for building body simulations
Module LocationTainan Taiwan (kW) Power enhancement () London UK (kW) Power enhancement ()
Tandem laser module 17178 mdash 8935 mdashTandem laser-A HISG 17179 001 8936 001Tandem laser-B HISG 17188 006 8940 006Tandem laser-C HISG 17199 012 8946 012Tandem TCOmodule 17016 mdash 8851 mdashTandem TCO-A HISG 17573 327 9141 327Tandem TCO-B HISG 18354 786 9547 786Tandem TCO-C HISG 18727 1006 9741 1006a-Si TCO module 16328 mdash 8493 mdasha-Si TCO-A HISG 16481 094 8573 094a-Si TCO-B HISG 16509 111 8587 111a-Si TCO-C HISG 16830 307 8754 307
Table 8 Simulation results for energy consumption of HVAC systems for the building body in the Tainan region of Taiwan
Module Cooling energyconsumption (kW)
Cooling energysaving ()
Heating energyconsumption
(kW)
Heating energysaving ()
Total HVAC systemenergy consumption
(kW)
Total HVACenergy saving
()Tandem laser module 28632 mdash 6924 mdash 35556 mdashTandem laser-A HISG 20296 2911 3639 4744 23935 3268Tandem laser-B HISG 20053 2996 3590 4815 23643 3350Tandem laser-C HISG 19958 3029 3591 4814 23549 3377Tandem TCOmodule 29495 mdash 6894 mdash 36390 mdashTandem TCO-A HISG 20793 2950 3623 4745 24415 3291Tandem TCO-B HISG 20412 3080 3576 4813 23988 3408Tandem TCO-C HISG 20201 3151 3583 4803 23784 3464a-Si TCO module 30368 mdash 6869 mdash 37236 mdasha-Si TCO-A HISG 20952 3101 3617 4734 24569 3402a-Si TCO-B HISG 20593 3219 3568 4806 24161 3511a-Si TCO-C HISG 20347 3300 3577 4793 23924 3575
14 International Journal of Photoenergy
Table 9 Simulation results for energy consumption of HVAC systems for the building body in London UK
ModuleCooling energyconsumption
(kW)
Cooling energysaving ()
Heating energyconsumption
(kW)
Heating energysaving ()
Total HVAC system energyconsumption (kW)
Total HVACenergy saving
()Tandem laser module 306 mdash 116818 mdash 117123 mdashTandem laser-A HISG 181 4085 71203 3905 71384 3905Tandem laser-B HISG 171 4412 70570 3959 70741 3960Tandem laser-C HISG 173 4346 70491 3966 70664 3967Tandem TCOmodule 271 mdash 117612 mdash 117883 mdashTandem TCO-A HISG 170 3727 71497 3921 71667 3920Tandem TCO-B HISG 164 3948 70753 3984 70917 3984Tandem TCO-C HISG 165 3911 70734 3986 70899 3986a-Si TCO module 287 mdash 117214 mdash 117501 mdasha-Si TCO-A HISG 175 3902 71273 3919 71448 3919a-Si TCO-B HISG 172 4007 70640 3973 70812 3973a-Si TCO-C HISG 171 4042 70566 3980 70737 3980
119880-value) showed an improvement Although the multilayerstructure of HISG would affect the visible light transmit-tance in practice it does not have a significant impact onthe view through the glass Moreover although the solardirect reflectance values all showed improving trends thevisible light reflectance was only around 5 which will notnecessarily cause environmental light pollution Comparedto the original modules the power generation and moduleefficiency of all HISGs were found to have increased Of allthe combinations of HISGs the gain in power generation ofthe tandem TCO-C HISG was the highest as the power gen-eration was improved by 1006 and the module efficiencywas improved by 082The results of the simulation showeda very similar trendwith regard to the level of electrical powergeneration based on experimental data that was obtainedusing the standard test conditions (STC) for measurementcontained in IEC 61646The simulation results also indicatedthat theHISG has a significant effect on the amount of energythat can be saved when using the HVAC system in bothsubtropical and temperate regions
This paper thus provides valuable information for renew-able energy planners and architectural designers who areinterested in using HISG BIPV systems
Competing Interests
The authors declare that there are no competing interestsregarding the publication of this paper
Acknowledgments
This study was supported by the Ministry of Science andTechnology of Taiwan under Projects MOST 105-3113-F-011-001 and MOST 105-3113-E-006-006-CC2
References
[1] M van der Hoeven Energy and Climate ChangemdashWorld EnergyOutlook Special Report International Energy Agency 2015
[2] P Jones S S Hou and X Li ldquoTowards zero carbon designin offices integrating smart facades ventilation and surfaceheating and coolingrdquoRenewable Energy vol 73 pp 69ndash76 2015
[3] W Pan ldquoSystem boundaries of zero carbon buildingsrdquo Renew-able and Sustainable Energy Reviews vol 37 pp 424ndash434 2014
[4] S Berry K Davidson and W Saman ldquoDefining zero carbonand zero energy homes from a performance-based regulatoryperspectiverdquo Energy Efficiency vol 7 no 2 pp 303ndash322 2014
[5] G P Hammond H A Harajli C I Jones and A B WinnettldquoWhole systems appraisal of a UK Building Integrated Photo-voltaic (BIPV) system energy environmental and economicevaluationsrdquo Energy Policy vol 40 no 1 pp 219ndash230 2012
[6] G A Keoleian and GM Lewis ldquoModeling the life cycle energyand environmental performance of amorphous silicon BIPVroofing in the USrdquo Renewable Energy vol 28 no 2 pp 271ndash2932003
[7] L Lu andHX Yang ldquoEnvironmental payback time analysis of aroof-mounted building-integrated photovoltaic (BIPV) systemin Hong Kongrdquo Applied Energy vol 87 no 12 pp 3625ndash36312010
[8] L Y Seng G Lalchand and G M Sow Lin ldquoEconomicalenvironmental and technical analysis of building integratedphotovoltaic systems in Malaysiardquo Energy Policy vol 36 no 6pp 2130ndash2142 2008
[9] M Oliver and T Jackson ldquoEnergy and economic evaluation ofbuilding-integrated photovoltaicsrdquo Energy vol 26 no 4 pp431ndash439 2001
[10] L Sabnani A Skumanich E Ryabova and R Noufi Devel-oping Market Opportunities for Flexible Rooftop Applicationsof PV Using Flexible CIGS Technology Market ConsiderationsNational Renewable Energy Laboratory (NREL) Golden ColoUSA 2011
[11] M A Green K Emery Y Hishikawa W Warta and E DDunlop ldquoSolar cell efficiency tables (version 47)rdquo Progress inPhotovoltaics Research and Applications vol 24 no 1 pp 3ndash112016
[12] G Y Yun M McEvoy and K Steemers ldquoDesign and overallenergy performance of a ventilated photovoltaic facaderdquo SolarEnergy vol 81 no 3 pp 383ndash394 2007
International Journal of Photoenergy 15
[13] PWWong Y ShimodaM NonakaM Inoue andMMizunoldquoSemi-transparent PV thermal performance power generationdaylight modelling and energy saving potential in a residentialapplicationrdquo Renewable Energy vol 33 no 5 pp 1024ndash10362008
[14] D H W Li T N T Lam W W H Chan and A H L MakldquoEnergy and cost analysis of semi-transparent photovoltaic inoffice buildingsrdquo Applied Energy vol 86 no 5 pp 722ndash7292009
[15] H Radhi ldquoEnergy analysis of facade-integrated photovoltaicsystems applied to UAE commercial buildingsrdquo Solar Energyvol 84 no 12 pp 2009ndash2021 2010
[16] E L Didone and A Wagner ldquoSemi-transparent PV windowsa study for office buildings in Brazilrdquo Energy and Buildings vol67 pp 136ndash142 2013
[17] P K Ng and N Mithraratne ldquoLifetime performance of semi-transparent building-integrated photovoltaic (BIPV) glazingsystems in the tropicsrdquo Renewable and Sustainable EnergyReviews vol 31 pp 736ndash745 2014
[18] C H Young Y L Chen and P C Chen ldquoHeat insulation solarglass and application on energy efficiency buildingsrdquo Energyand Buildings vol 78 pp 66ndash78 2014
[19] International Organization for Standardization ISO 9050 Glassin BuildingmdashDetermination of Light Transmittance Solar DirectTransmittance Total Solar Energy Transmittance UltravioletTransmittance and Related Glazing Factors International Orga-nization for Standardization Basel Switzerland 2003
[20] International Organization for Standardization ldquoISO10292glass in buildingmdashcalculation of steady-state U values (thermaltransmittance) of multiple glazingrdquo Tech Rep InternationalOrganization for Standardization Geneva Switzerland 1994
[21] International Standard ldquoThin-film terrestrial photovoltaic (pv)modulesmdashdesign qualification and type approvalrdquo IEC 616462008
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Inorganic ChemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Carbohydrate Chemistry
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
Physical Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom
Analytical Methods in Chemistry
Journal of
Volume 2014
Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
SpectroscopyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Medicinal ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chromatography Research International
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Applied ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Theoretical ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Spectroscopy
Analytical ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Quantum Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Organic Chemistry International
ElectrochemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CatalystsJournal of
International Journal of Photoenergy 13
Table 6 Results of power generation gain tests of the semitransparent PV modules and each combination of HISG under STC
ModuleItem
Power generation (W) Power generationenhancement () Module efficiency () Module efficiency
enhancement ()Tandem laser module 126029 mdash 8184 mdashTandem laser-A HISG 126042 001 8185 0001Tandem laser-B HISG 126105 006 8189 0005Tandem laser-C HISG 126187 013 8194 0010Tandem TCOmodule 124843 mdash 811 mdashTandem TCO-A HISG 128926 327 837 027Tandem TCO-B HISG 134658 786 874 064Tandem TCO-C HISG 137399 1006 892 082a-Si TCO module 119796 mdash 778 mdasha-Si TCO-A HISG 120921 094 785 007a-Si TCO-B HISG 121125 111 787 009a-Si TCO-C HISG 123475 307 802 024
Table 7 Power generation results for building body simulations
Module LocationTainan Taiwan (kW) Power enhancement () London UK (kW) Power enhancement ()
Tandem laser module 17178 mdash 8935 mdashTandem laser-A HISG 17179 001 8936 001Tandem laser-B HISG 17188 006 8940 006Tandem laser-C HISG 17199 012 8946 012Tandem TCOmodule 17016 mdash 8851 mdashTandem TCO-A HISG 17573 327 9141 327Tandem TCO-B HISG 18354 786 9547 786Tandem TCO-C HISG 18727 1006 9741 1006a-Si TCO module 16328 mdash 8493 mdasha-Si TCO-A HISG 16481 094 8573 094a-Si TCO-B HISG 16509 111 8587 111a-Si TCO-C HISG 16830 307 8754 307
Table 8 Simulation results for energy consumption of HVAC systems for the building body in the Tainan region of Taiwan
Module Cooling energyconsumption (kW)
Cooling energysaving ()
Heating energyconsumption
(kW)
Heating energysaving ()
Total HVAC systemenergy consumption
(kW)
Total HVACenergy saving
()Tandem laser module 28632 mdash 6924 mdash 35556 mdashTandem laser-A HISG 20296 2911 3639 4744 23935 3268Tandem laser-B HISG 20053 2996 3590 4815 23643 3350Tandem laser-C HISG 19958 3029 3591 4814 23549 3377Tandem TCOmodule 29495 mdash 6894 mdash 36390 mdashTandem TCO-A HISG 20793 2950 3623 4745 24415 3291Tandem TCO-B HISG 20412 3080 3576 4813 23988 3408Tandem TCO-C HISG 20201 3151 3583 4803 23784 3464a-Si TCO module 30368 mdash 6869 mdash 37236 mdasha-Si TCO-A HISG 20952 3101 3617 4734 24569 3402a-Si TCO-B HISG 20593 3219 3568 4806 24161 3511a-Si TCO-C HISG 20347 3300 3577 4793 23924 3575
14 International Journal of Photoenergy
Table 9 Simulation results for energy consumption of HVAC systems for the building body in London UK
ModuleCooling energyconsumption
(kW)
Cooling energysaving ()
Heating energyconsumption
(kW)
Heating energysaving ()
Total HVAC system energyconsumption (kW)
Total HVACenergy saving
()Tandem laser module 306 mdash 116818 mdash 117123 mdashTandem laser-A HISG 181 4085 71203 3905 71384 3905Tandem laser-B HISG 171 4412 70570 3959 70741 3960Tandem laser-C HISG 173 4346 70491 3966 70664 3967Tandem TCOmodule 271 mdash 117612 mdash 117883 mdashTandem TCO-A HISG 170 3727 71497 3921 71667 3920Tandem TCO-B HISG 164 3948 70753 3984 70917 3984Tandem TCO-C HISG 165 3911 70734 3986 70899 3986a-Si TCO module 287 mdash 117214 mdash 117501 mdasha-Si TCO-A HISG 175 3902 71273 3919 71448 3919a-Si TCO-B HISG 172 4007 70640 3973 70812 3973a-Si TCO-C HISG 171 4042 70566 3980 70737 3980
119880-value) showed an improvement Although the multilayerstructure of HISG would affect the visible light transmit-tance in practice it does not have a significant impact onthe view through the glass Moreover although the solardirect reflectance values all showed improving trends thevisible light reflectance was only around 5 which will notnecessarily cause environmental light pollution Comparedto the original modules the power generation and moduleefficiency of all HISGs were found to have increased Of allthe combinations of HISGs the gain in power generation ofthe tandem TCO-C HISG was the highest as the power gen-eration was improved by 1006 and the module efficiencywas improved by 082The results of the simulation showeda very similar trendwith regard to the level of electrical powergeneration based on experimental data that was obtainedusing the standard test conditions (STC) for measurementcontained in IEC 61646The simulation results also indicatedthat theHISG has a significant effect on the amount of energythat can be saved when using the HVAC system in bothsubtropical and temperate regions
This paper thus provides valuable information for renew-able energy planners and architectural designers who areinterested in using HISG BIPV systems
Competing Interests
The authors declare that there are no competing interestsregarding the publication of this paper
Acknowledgments
This study was supported by the Ministry of Science andTechnology of Taiwan under Projects MOST 105-3113-F-011-001 and MOST 105-3113-E-006-006-CC2
References
[1] M van der Hoeven Energy and Climate ChangemdashWorld EnergyOutlook Special Report International Energy Agency 2015
[2] P Jones S S Hou and X Li ldquoTowards zero carbon designin offices integrating smart facades ventilation and surfaceheating and coolingrdquoRenewable Energy vol 73 pp 69ndash76 2015
[3] W Pan ldquoSystem boundaries of zero carbon buildingsrdquo Renew-able and Sustainable Energy Reviews vol 37 pp 424ndash434 2014
[4] S Berry K Davidson and W Saman ldquoDefining zero carbonand zero energy homes from a performance-based regulatoryperspectiverdquo Energy Efficiency vol 7 no 2 pp 303ndash322 2014
[5] G P Hammond H A Harajli C I Jones and A B WinnettldquoWhole systems appraisal of a UK Building Integrated Photo-voltaic (BIPV) system energy environmental and economicevaluationsrdquo Energy Policy vol 40 no 1 pp 219ndash230 2012
[6] G A Keoleian and GM Lewis ldquoModeling the life cycle energyand environmental performance of amorphous silicon BIPVroofing in the USrdquo Renewable Energy vol 28 no 2 pp 271ndash2932003
[7] L Lu andHX Yang ldquoEnvironmental payback time analysis of aroof-mounted building-integrated photovoltaic (BIPV) systemin Hong Kongrdquo Applied Energy vol 87 no 12 pp 3625ndash36312010
[8] L Y Seng G Lalchand and G M Sow Lin ldquoEconomicalenvironmental and technical analysis of building integratedphotovoltaic systems in Malaysiardquo Energy Policy vol 36 no 6pp 2130ndash2142 2008
[9] M Oliver and T Jackson ldquoEnergy and economic evaluation ofbuilding-integrated photovoltaicsrdquo Energy vol 26 no 4 pp431ndash439 2001
[10] L Sabnani A Skumanich E Ryabova and R Noufi Devel-oping Market Opportunities for Flexible Rooftop Applicationsof PV Using Flexible CIGS Technology Market ConsiderationsNational Renewable Energy Laboratory (NREL) Golden ColoUSA 2011
[11] M A Green K Emery Y Hishikawa W Warta and E DDunlop ldquoSolar cell efficiency tables (version 47)rdquo Progress inPhotovoltaics Research and Applications vol 24 no 1 pp 3ndash112016
[12] G Y Yun M McEvoy and K Steemers ldquoDesign and overallenergy performance of a ventilated photovoltaic facaderdquo SolarEnergy vol 81 no 3 pp 383ndash394 2007
International Journal of Photoenergy 15
[13] PWWong Y ShimodaM NonakaM Inoue andMMizunoldquoSemi-transparent PV thermal performance power generationdaylight modelling and energy saving potential in a residentialapplicationrdquo Renewable Energy vol 33 no 5 pp 1024ndash10362008
[14] D H W Li T N T Lam W W H Chan and A H L MakldquoEnergy and cost analysis of semi-transparent photovoltaic inoffice buildingsrdquo Applied Energy vol 86 no 5 pp 722ndash7292009
[15] H Radhi ldquoEnergy analysis of facade-integrated photovoltaicsystems applied to UAE commercial buildingsrdquo Solar Energyvol 84 no 12 pp 2009ndash2021 2010
[16] E L Didone and A Wagner ldquoSemi-transparent PV windowsa study for office buildings in Brazilrdquo Energy and Buildings vol67 pp 136ndash142 2013
[17] P K Ng and N Mithraratne ldquoLifetime performance of semi-transparent building-integrated photovoltaic (BIPV) glazingsystems in the tropicsrdquo Renewable and Sustainable EnergyReviews vol 31 pp 736ndash745 2014
[18] C H Young Y L Chen and P C Chen ldquoHeat insulation solarglass and application on energy efficiency buildingsrdquo Energyand Buildings vol 78 pp 66ndash78 2014
[19] International Organization for Standardization ISO 9050 Glassin BuildingmdashDetermination of Light Transmittance Solar DirectTransmittance Total Solar Energy Transmittance UltravioletTransmittance and Related Glazing Factors International Orga-nization for Standardization Basel Switzerland 2003
[20] International Organization for Standardization ldquoISO10292glass in buildingmdashcalculation of steady-state U values (thermaltransmittance) of multiple glazingrdquo Tech Rep InternationalOrganization for Standardization Geneva Switzerland 1994
[21] International Standard ldquoThin-film terrestrial photovoltaic (pv)modulesmdashdesign qualification and type approvalrdquo IEC 616462008
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Inorganic ChemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Carbohydrate Chemistry
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
Physical Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom
Analytical Methods in Chemistry
Journal of
Volume 2014
Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
SpectroscopyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Medicinal ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chromatography Research International
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Applied ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Theoretical ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Spectroscopy
Analytical ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Quantum Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Organic Chemistry International
ElectrochemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CatalystsJournal of
14 International Journal of Photoenergy
Table 9 Simulation results for energy consumption of HVAC systems for the building body in London UK
ModuleCooling energyconsumption
(kW)
Cooling energysaving ()
Heating energyconsumption
(kW)
Heating energysaving ()
Total HVAC system energyconsumption (kW)
Total HVACenergy saving
()Tandem laser module 306 mdash 116818 mdash 117123 mdashTandem laser-A HISG 181 4085 71203 3905 71384 3905Tandem laser-B HISG 171 4412 70570 3959 70741 3960Tandem laser-C HISG 173 4346 70491 3966 70664 3967Tandem TCOmodule 271 mdash 117612 mdash 117883 mdashTandem TCO-A HISG 170 3727 71497 3921 71667 3920Tandem TCO-B HISG 164 3948 70753 3984 70917 3984Tandem TCO-C HISG 165 3911 70734 3986 70899 3986a-Si TCO module 287 mdash 117214 mdash 117501 mdasha-Si TCO-A HISG 175 3902 71273 3919 71448 3919a-Si TCO-B HISG 172 4007 70640 3973 70812 3973a-Si TCO-C HISG 171 4042 70566 3980 70737 3980
119880-value) showed an improvement Although the multilayerstructure of HISG would affect the visible light transmit-tance in practice it does not have a significant impact onthe view through the glass Moreover although the solardirect reflectance values all showed improving trends thevisible light reflectance was only around 5 which will notnecessarily cause environmental light pollution Comparedto the original modules the power generation and moduleefficiency of all HISGs were found to have increased Of allthe combinations of HISGs the gain in power generation ofthe tandem TCO-C HISG was the highest as the power gen-eration was improved by 1006 and the module efficiencywas improved by 082The results of the simulation showeda very similar trendwith regard to the level of electrical powergeneration based on experimental data that was obtainedusing the standard test conditions (STC) for measurementcontained in IEC 61646The simulation results also indicatedthat theHISG has a significant effect on the amount of energythat can be saved when using the HVAC system in bothsubtropical and temperate regions
This paper thus provides valuable information for renew-able energy planners and architectural designers who areinterested in using HISG BIPV systems
Competing Interests
The authors declare that there are no competing interestsregarding the publication of this paper
Acknowledgments
This study was supported by the Ministry of Science andTechnology of Taiwan under Projects MOST 105-3113-F-011-001 and MOST 105-3113-E-006-006-CC2
References
[1] M van der Hoeven Energy and Climate ChangemdashWorld EnergyOutlook Special Report International Energy Agency 2015
[2] P Jones S S Hou and X Li ldquoTowards zero carbon designin offices integrating smart facades ventilation and surfaceheating and coolingrdquoRenewable Energy vol 73 pp 69ndash76 2015
[3] W Pan ldquoSystem boundaries of zero carbon buildingsrdquo Renew-able and Sustainable Energy Reviews vol 37 pp 424ndash434 2014
[4] S Berry K Davidson and W Saman ldquoDefining zero carbonand zero energy homes from a performance-based regulatoryperspectiverdquo Energy Efficiency vol 7 no 2 pp 303ndash322 2014
[5] G P Hammond H A Harajli C I Jones and A B WinnettldquoWhole systems appraisal of a UK Building Integrated Photo-voltaic (BIPV) system energy environmental and economicevaluationsrdquo Energy Policy vol 40 no 1 pp 219ndash230 2012
[6] G A Keoleian and GM Lewis ldquoModeling the life cycle energyand environmental performance of amorphous silicon BIPVroofing in the USrdquo Renewable Energy vol 28 no 2 pp 271ndash2932003
[7] L Lu andHX Yang ldquoEnvironmental payback time analysis of aroof-mounted building-integrated photovoltaic (BIPV) systemin Hong Kongrdquo Applied Energy vol 87 no 12 pp 3625ndash36312010
[8] L Y Seng G Lalchand and G M Sow Lin ldquoEconomicalenvironmental and technical analysis of building integratedphotovoltaic systems in Malaysiardquo Energy Policy vol 36 no 6pp 2130ndash2142 2008
[9] M Oliver and T Jackson ldquoEnergy and economic evaluation ofbuilding-integrated photovoltaicsrdquo Energy vol 26 no 4 pp431ndash439 2001
[10] L Sabnani A Skumanich E Ryabova and R Noufi Devel-oping Market Opportunities for Flexible Rooftop Applicationsof PV Using Flexible CIGS Technology Market ConsiderationsNational Renewable Energy Laboratory (NREL) Golden ColoUSA 2011
[11] M A Green K Emery Y Hishikawa W Warta and E DDunlop ldquoSolar cell efficiency tables (version 47)rdquo Progress inPhotovoltaics Research and Applications vol 24 no 1 pp 3ndash112016
[12] G Y Yun M McEvoy and K Steemers ldquoDesign and overallenergy performance of a ventilated photovoltaic facaderdquo SolarEnergy vol 81 no 3 pp 383ndash394 2007
International Journal of Photoenergy 15
[13] PWWong Y ShimodaM NonakaM Inoue andMMizunoldquoSemi-transparent PV thermal performance power generationdaylight modelling and energy saving potential in a residentialapplicationrdquo Renewable Energy vol 33 no 5 pp 1024ndash10362008
[14] D H W Li T N T Lam W W H Chan and A H L MakldquoEnergy and cost analysis of semi-transparent photovoltaic inoffice buildingsrdquo Applied Energy vol 86 no 5 pp 722ndash7292009
[15] H Radhi ldquoEnergy analysis of facade-integrated photovoltaicsystems applied to UAE commercial buildingsrdquo Solar Energyvol 84 no 12 pp 2009ndash2021 2010
[16] E L Didone and A Wagner ldquoSemi-transparent PV windowsa study for office buildings in Brazilrdquo Energy and Buildings vol67 pp 136ndash142 2013
[17] P K Ng and N Mithraratne ldquoLifetime performance of semi-transparent building-integrated photovoltaic (BIPV) glazingsystems in the tropicsrdquo Renewable and Sustainable EnergyReviews vol 31 pp 736ndash745 2014
[18] C H Young Y L Chen and P C Chen ldquoHeat insulation solarglass and application on energy efficiency buildingsrdquo Energyand Buildings vol 78 pp 66ndash78 2014
[19] International Organization for Standardization ISO 9050 Glassin BuildingmdashDetermination of Light Transmittance Solar DirectTransmittance Total Solar Energy Transmittance UltravioletTransmittance and Related Glazing Factors International Orga-nization for Standardization Basel Switzerland 2003
[20] International Organization for Standardization ldquoISO10292glass in buildingmdashcalculation of steady-state U values (thermaltransmittance) of multiple glazingrdquo Tech Rep InternationalOrganization for Standardization Geneva Switzerland 1994
[21] International Standard ldquoThin-film terrestrial photovoltaic (pv)modulesmdashdesign qualification and type approvalrdquo IEC 616462008
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Inorganic ChemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Carbohydrate Chemistry
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
Physical Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom
Analytical Methods in Chemistry
Journal of
Volume 2014
Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
SpectroscopyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Medicinal ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chromatography Research International
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Applied ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Theoretical ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Spectroscopy
Analytical ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Quantum Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Organic Chemistry International
ElectrochemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CatalystsJournal of
International Journal of Photoenergy 15
[13] PWWong Y ShimodaM NonakaM Inoue andMMizunoldquoSemi-transparent PV thermal performance power generationdaylight modelling and energy saving potential in a residentialapplicationrdquo Renewable Energy vol 33 no 5 pp 1024ndash10362008
[14] D H W Li T N T Lam W W H Chan and A H L MakldquoEnergy and cost analysis of semi-transparent photovoltaic inoffice buildingsrdquo Applied Energy vol 86 no 5 pp 722ndash7292009
[15] H Radhi ldquoEnergy analysis of facade-integrated photovoltaicsystems applied to UAE commercial buildingsrdquo Solar Energyvol 84 no 12 pp 2009ndash2021 2010
[16] E L Didone and A Wagner ldquoSemi-transparent PV windowsa study for office buildings in Brazilrdquo Energy and Buildings vol67 pp 136ndash142 2013
[17] P K Ng and N Mithraratne ldquoLifetime performance of semi-transparent building-integrated photovoltaic (BIPV) glazingsystems in the tropicsrdquo Renewable and Sustainable EnergyReviews vol 31 pp 736ndash745 2014
[18] C H Young Y L Chen and P C Chen ldquoHeat insulation solarglass and application on energy efficiency buildingsrdquo Energyand Buildings vol 78 pp 66ndash78 2014
[19] International Organization for Standardization ISO 9050 Glassin BuildingmdashDetermination of Light Transmittance Solar DirectTransmittance Total Solar Energy Transmittance UltravioletTransmittance and Related Glazing Factors International Orga-nization for Standardization Basel Switzerland 2003
[20] International Organization for Standardization ldquoISO10292glass in buildingmdashcalculation of steady-state U values (thermaltransmittance) of multiple glazingrdquo Tech Rep InternationalOrganization for Standardization Geneva Switzerland 1994
[21] International Standard ldquoThin-film terrestrial photovoltaic (pv)modulesmdashdesign qualification and type approvalrdquo IEC 616462008
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Inorganic ChemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Carbohydrate Chemistry
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
Physical Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom
Analytical Methods in Chemistry
Journal of
Volume 2014
Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
SpectroscopyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Medicinal ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chromatography Research International
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Applied ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Theoretical ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Spectroscopy
Analytical ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Quantum Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Organic Chemistry International
ElectrochemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CatalystsJournal of
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Inorganic ChemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Carbohydrate Chemistry
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
Physical Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom
Analytical Methods in Chemistry
Journal of
Volume 2014
Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
SpectroscopyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Medicinal ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chromatography Research International
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Applied ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Theoretical ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Spectroscopy
Analytical ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Quantum Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Organic Chemistry International
ElectrochemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CatalystsJournal of