Energy Savings Obtainable Through Passive Solar Techniques

8/14/2019 Energy Savings Obtainable Through Passive Solar Techniques

1/14


2/14

TITLE : ENERGY ShVIN(Ki C)IWAINAHIJ: 7111{)1](:11PASSTVH SOT,A1{ 1IKIIN1 QIIES

AUTHOR(S): J. 1}. lhllcomh

SUBMITTED TO: ll)t.cr]l.1(.ioll,ll. Crmgn!:::: m I llli 1c l.i II \ I II :n(wly MClrldf.l(mwnt1OVChl 11! Vil~:%j.l!l, lO~kll$J(llNny 12-1(1, 1)NO

.. -. -

J)lscIAMl~--

[

.,.,.,

,.,. _-,--- ,..- . . -...-. ....-.

cdq -C

8..-

!ii!!!i!!!fi!?!?al{lll-IPJII Il. li 1!.1

! !1. ml, Ai:l! l

I .t Ill

l lv iP :l l l ,l, ll l( , l ll tll l l l ll tl t, llT, I :wp ll lll l,l lw I l, lll lll lldw 111,11I I,,(1. !; . ( ; I IVIVIIIIWI Il, l,nl l, l ll lc*l ll~*ll ll ! lv, ., ll ly, ll lv ll l lF.l ll I, ll \l l

I( 1 I lll ll ll dl 111 lql f( lf hl l~ l b Il !l ldl dl ,11 I (l lt ll ( II Il l, i 411 .1111!11,111)11 ,ll I ll T lh lw I ll ll l, l, ! I I! 1111+11 ,h ll ( J, !; l i l l , , , , , l l u l mv l l1 1 11~ 11 1, , 1 - !

Ilw Icli AIJIIIIH ::lWIIIIIII I nll,ll.llt ll~ 1.,11 !1,,,1. 111,11111,,11111Ilillw 111,$11111) 111. 1 1 1 1 11 1 , ,1 ,Wllh 11,,1101111,,[1.1111,,11:, , ,,11,,1111,., ( If 111P11!; llql,lllllPwl ( If I Il,,llly

LOS ALAIMOS SCIENTIFIC LABORATORY

{I FIIIII)UIA II-,Ill I,nlllh!l H! Ill t Ill l)!, \tllllllt Aa I w 1411%I film 110

,1


3/14

Etf FU2Y)AVIKS C8TAItWLE TFWLIIH PA5SIVE W-AR TECHNIQUL5J, Ooqlas 6alcomb

Los Alamos Scientific Lahorat,)ryLOS Alarms, New Mexico, 87545, Lk4

ABSTRACT

A passive solar energy system is me lrl which the tkr,nal energy flow is byn~tural means, that is by radiation, contict.ion, or natural convection. Thepurpose of tk peper 1s to provide a surv~?y of passive sokr heatlw experience,especially in the U.S. Design approaches are revipwed and exa~les shown.M!.sc~ceptions are fliscuSSed. Advantages are listed, The I.OS Alarm program ofperformar~ce simulation and evaluation is described and a si~lified method orr3erformnce estlmaticm is cutlinedm

IN7RCflLCTION

Ou,inq the period of 1976-1979 passive solar heating of lxilclirys emerged rathersuddenly within the Lhitecl States from tk status of a curlnsity to recugnltlulas one OF the rtust practical and effective means of using solar energy, Many O!the factors which have caused this to ha~en are dlsd present in Portyal and itwuld seem that such an awakenirq might also be possibl! I_ert?. Passive solarofters a shrple, eccmmlcal, comfortable am rellable rr:ans of bulldlly Ileatillgthat 1s particularly suitable to the range of latltucits where rrost ot theI%rtuquese pqulation resides, lhe bulk of the heatlrw loads can be easliyoffset hy solar g~lns through effective architectural use of rrrdterials normallyenpluyecl in construction.

@yc areful consideration of building orlentatlcml treatment of glazlly, sturagcof exces~ I]eat. !n building mass, shading, ati ventilation, a I)u!lding Carl IJL,designed to be ~lte cllmatlcnlly aUaptlve, #mJrbiry solar gulns during ;Iwinter day and storinq through tn the night and yet rejectlq sumnwr sun,Passive crwllng effects cm also be achieved by ccmtrol of radiaLirxl losses,evapor~tlon, ventilation, and especially tkx+ u st! of buildify mas% heat capwltyto flveragr rtlurnal tmpxature Swlriqs thus rcducirq ufterlluoll overtledll~i

T}K U.S. EXFTRIEtW

Ily l~K FI h anriflll nf experlmentHl hulldlng$ had hccrl twllt IMISU.LI H1veryexpllclt IJassIvc solar heatlnq ~orw?pts. ThL?:;(?w~~~ l~oliit~ll iitd nlmrxil


4/14

indepencknt designs based rmre cm physical lntuitim than mthemticalanalysis. They were located in such varied places as the Pyrenees of southernFrance, the NewEngland and %dthwestern parts of the U.S. anLYLiverpool,

Emjland. There hqcl been several prior passive bulldiqs by Morse inMassachusetts, Keck In the miduest U.j., and the M.I.T. researchers but ttwy hadgone largely w,heeded.

The period from 1973 to 1976 saw an inter.se interest in a CL I V e SOI Z I renergyd?velopmnt In response to energy curtailments and a sudd?n general awareness ofthe finiteness of mrlci energy mpplles. This led to ma~or U.5. federalgovernment expenditures in solar energy and tlw emergerce of a solar industrycomprised prtmarlly of srmll business. By the end of 1978 the total rutier ofsu!ar Installations was estimated to be lW,CIJD dcminated by swlrruning Pool anddomestic hot inter heating appllcaticms. However, little nule was taken otpassive solar approaches in a rush to ccmwrercialize solar through theestablishment of an in~stry tiith saw little to gain through prormtion ofpassive concepts.

Almost in parallel with the active system effort , a small but aetermlned groupbegan an investigation of p~ssive solar t@proaches. A s e r i e s of threeW1l-attencfed rrational passive solar conferences was held in the U.3. in May1976 (Albuquerque, New MexlcoJ, in March ]979 (Philadelphia, Pennsyl#ania), andJanuary 1979 (San Jose, CallfrJrn~a). Ths proceedlys of these ccmferences(1,7,3) Plus several papers given at annual crmferences of the 1X5, AmricanSection (L, 5) cc.mtaln a vealth of sclentitlc ~nforma!lon m passive systemanalyse~ &nd performa,xe evallJation:, Secund and third generaticm p d SSi V e SOl i - I rtvJildings h?ve been bdlt and reported. A growlrg enthusiasm for passiveapprmrhes has emerged strorqly su~orted by regional solar energy assoclaticns,amhlterts, qla~sroots and alternative eneray groups, Wpropriate tcctnologyenthusiasts, and ecologist.

The last few yearf have been characterl?cd by ir piethora ot enerqy studies anupolir./ ,Wvlews, Virtually every such study reported in 1979, irtiludjng themuch-vaunted Qovernrrn?ntal Intemgency Dormstic Pollcy Re{ iew, iid~ ;tmnglyrecommended that major attention be given to passive solar twatlng. IlkDepartment of Energy (~E) has slmglt?l out tom solHr tectnologles to be~nhaslzea in a major c~rrwrclallzathm prrgrarn: w~ter heatlry and pds~lvt!sDacc heating. The lkpa:tment of Housing km Urban Development conwcted aspr=clal Passive 5olHI Oe;lgn lcnpetltlon for residential hcusi~ ar)~ awarded$1,~,~ lnpriz~~ tr 1620f the 5513appllcanlr th~t ~aliflcci, The resetircl]

and rh?velopmen!. buckjrt for passive solur heiitl~ and cooi~rg has grown trom$135,~ in 1975, to Wo,an in 1976, to $2,8CU,LW in 197H to til,lcmwd $4,2m!lllnn in 1979, ml $16.7 rnllllon in 1980.


5/14

TW cifferent schemes for classifyirq aassive solar systems have been used. Oneis 8 fmctional or generic classification in which tl_e relationship of solargain, thermal stnrage, ad tlw? Fn2atd *ace are classified Gccorclim to tlkcategories: 1) direct, 2) indirect, and 3) isolated. A second cla.%ificati~nschemn?, *ich has been used nmre often, defines passive system types accordiryto tht= ptysical configuration. In this *hem the buildiys are identifiedaccording to the categories, a) direct g~n, b) twrlmal storage wall, c)attached sun space, d) thermal storaw roof, and e) convective looP. bothclassificatim scherres are very useful and can augment rne anotbr; usedtogetmr they form a poherful vocabulary for describing varicrus passive designapproaches. These tm classiflcat.icn sctn?rres are described in more Cletall below.

PJfsJral Categories

Fig. 1. Direct Gain. Sunlightenters the heated space, lSCOn\2rtedto heat at *sotiirq surfaces, Mndis dispersed throughout the Waceand to the various enclosing ur-faces md room cor}tcnls.

L.MIW!wall

Flqm 3. At t n c hf l l h ~ S@CF , ? 1 1 1 s1s acn,jlblmtlrm of cllrect qaln and tlwrmalstornqe ml 1 ap+lroflctm. IIP t)uildlnrj

Fig. 2. Thermal Storage wall. Sunlightpenetrates glazing and 1s absorbed andconverted to heat at a wall Wrfhce in-terposed between the glaziy and theFn3ated Wace. THe wali is usuallymasonry (Trunk wall) or containersfilled with water (water wall), altkrughlt might contain phase-charye material.

% ~ -u W-

{

11(J, 4. Tt-,erml btoragc Roof. l t l l , ; *similar to tk L k r mi i l :tSralJl w~ll ex -ce~]t that the ir,terpowu th?lmd]

I


6/14

Fig. 5. Convective Loop. lhis approachis most akin to conventional acivesystems in that there is a separatecollector and separate !hermal storage.It is a passive approach, however, be-cause the thermal energy flow is bynatural convection.

GENERICCATEG~IES

1. Direct . Same as above, Fig. 1.

2. Indirect. tillght 1s absorbed and stored by a mass interposed betwen theglaz-the Condithned space. The conditioned spat? is partially emlosedand hounded by the thermal storage mss so that a stron~ natural (anduncontrolled) th?rmal comliy is achleveci. Exanples of the lnuirect a~roachare the thermal storage wall, thermal storage roof , and th? northerly room or theattachec! sunspace, as deplctsd ~n Figs. 2, 3, and 4.

3. Isolated. This is an indirect ~ystem except that ttw?re is a cristirrt thermalwpa~fby means of either insulation or physical separation) between thethermal storage md the heated space. The ctmvectlve loop, as depicted in Fig.S, 1s in this category. The thermal storage wall, thermml storage roof, andattach~ mnspace approaclws can also be mede into i~latr?d systems by insulatingbetween thermal storage and the heated Wace.

Dlscussim

TM physical categories listed above are frequently used in ,~escriptimls ofpassive system because they are easily visualized and most quickly convey thecmcepts and fhysical principles errhcdied in the most ronmm passive designs.However, they lack generality and a large catalog of different ap~ruaclws aridassociated ohysical de%crlptims can be expected to ermerys, The genericca?eqorles are SCIgeneral in nature t,nt they can be expected to survive asuseful nays of describing quite a brrm range of calcepts. Furttvsrmure, they

n~ly with equal nase to natural coolirm cmcepts as WC1l RS solar heatin,qlwhrreas all the physical categories Ii, III abcwe, except the tkrrnd~ sturagerocf, are specifically solar heatlrq curu,@s. ReJucthm lrl cxIollIy load, IJUIIto added rmss lr the building, rmy tell b, an addL@ benefit, but this does notusda:]y drive th? design, Addition of verlli]ation crJrJIIIq by means of i lthermally drlvl?n rmtural ccxnvccticm chirrncy muy also I)e lrrnrpordtrd.

These descriptive categorIzntlons overl~ but carl tJc useil Lugetlwr. Fur (,xiwruIle,me :nuld ensi.~y refer to a mlx of isolatfli thermirl stor~gr wutl:r Willl ::Ih]conve,:tlve looII -such a c~hlr~t~~ hflq, ill fn~t. , lwww Illtlt qrld 5I1OWI!o wurkM?ll.

w!LKwk!?!2

if


7/14

MYTHS

Passive salar is mt much mderstood and a nunber of misconceptims have grrJwn uparomd false notions. Among these are:

1. . Passive solar will mti well mly in privileged regions, such as theArmsrican southwest. Both experieme and analysis refute this. Successfulappllcatlcns have heen demonstrated in frigid Wyoming, C1OUCIYild cGld NewEngland and cloudy, grey Liverpool, Ergland. Calculations for a 45 cm Trombewll, Wed with night insulatim, indfcate the following energy savi@s:

B@stcO, MassachusettsAlbuq@rq@, New Mr?xicoMadison, WiscmsinSeattle, Washington

The area of the wall 1scoefficient of 2.1 w/et

Heati~ load Solar Heatiy Net YieldLatitude Oc-days Fraction kwhr/m2-yr

4:@ 3130 4B% 3033:jo 2420 71% 346450 4370 &a 37U490 2460 54% 26B

1/4 rf the floor area of the house which has a total lossDIII SQ meter of floor area (exclusive of the Tronbe

wall) and rmintal,wd within t,hc range of 21.1C to 26,7C. bui!ding internalheat sources (pecple, lights, appliances, etc.) are assumed to account tox2.7oC of the tenperat~re increase.

7. Cmupants of passive solar bdildings nmt sacrifice comfort. Temperatures~lrgs ore excessive and uncontrollable. Although this certainly can be thecase, gccd design practjce can prevent it. If a large ml.ar fract.ia is desiredin e cold clirrate, a direct gtiin buildinq can be expected to experience clear-dayswir~s of at least 5C and nmrr likely 10C. However, a thick (45 cm +)Irnvent,ed Tranbe wall wit:, t~rmostatic auxiliary back~ can provide a very stablelnter~l mvironment and at the =me time a 70-80% solar Contribtirm. [he veryeffective design appr~ach is to separate the bulldimg into two zones as shownbelow.

IDIRECT OAII@Po ACC

I .SUNACr II

The Cllrect-gdn Zaw 1 will experiencelarge temperature swings (10 to 15Con a clear day) hut provides a very sult-nhle space for an Q1 lock entrymey, a

trmsit ~ren, an atrium or a greenhouse,Zcne 2, by crntrust, cm be very stableIn tPrrp~rHtllrr and I!; rmre suitable as ahlqh-crm,iort l~vlnq zalc,

II VA .~-WJ1H ~MWwu

Even flntr mninq can he used to locute closets, parlttles, bedrooms, and llvir~rmms r+ccord!rq to lndlvlchiul cc,lfort requirements.

3, ~~~nt~ of I%I!i%ive ~lar bull(IkJs ~~t k Wry ~rlvolved h) tl~ (~JUhIl]of ttm s)~t.~m, Aqriln, tills 1s u miter of cholcc. Lkw car) ciIwirjII lrl11.nnd.npcrntecl rmvdllt? lWilll13LlWl, fOI t?Xf l171 . )k! , (II l)UrlI&ChSdJIC VI?ntS. llmy curl,hnw~wr, IIP m)t.nrmtwl on H t,lwrmwwt or nr]t u!;d, Most l]ulldlIw:; Lt] rrly onopmllrx] wlnrhwn for vrrltilatlrm nm!lng tiirlr~ w+tm, surwy ~rlrlg HIhl full dUyLlult. ~)115 1,; ;I n,)tllrnl ml(l foml~lnr n?iwrt of nw;t lmusL\:;,


8/14


9/14

Direct Gain $20-120/m2 Thermal storage mof$80-20fl/m2

$lCIJ-280/m2Thermal storage w-all Convective loopAttached wn spat.s $50-160/m2

$ 50-80/m2

These costs vary @penCling on where and how the buildirg is constructed, thefi~terials used, the workmanship and finishing, and wheth?r or mt some means areprovided to insulate agai nSt 10SSeS at night. The cost of night. insulationitself is generally in the range of $20 tc $UII per sq meter and is ircluaetl inthe ranges given above.

Cne of the reasons that costs tend to be low for passive systems is becwse thematerials are available, the infrastructure rcquiled for the manufacture anddistribution r these fIBt e r i a lS i s in place, md builders are familiar with theiruse. The most ccnmmn of these materials are glass, oth?r glazings, and mason-ry. Armtl?er reason that costs are low is that the passive elements fr~q,jentlyserve two fum tlons so that their cost can be written off aijainst both r unctions.

Ease of Natural Operatim

Hic;l reliability of passive solar designs is attributable to the lack of rmvi~parts and the use of conventional materials. Since t~re is very little~C~iCal eqUip~nt tkre iS very little tO go wrong. Most of the materialswhich are assaci~ted with passive solar desi~ll are normal construction materialsused within the.,r normal operating range whch have already been long and welltested. The two most ccnnron materials, glass and masonry, are the elements otthe building which can be expected to last the longest mder normal canditicms.

Thermal Canfor R

Perhaps the rrost comfortable way to heat a buildiy is with a large racllant paneloperating at luw temperature. Heat fluxes am relatively low, there are no hotspots or cold Wets to be expected, draftS are eliminated, and there is nonoise. A well insulated room car] be heated easily by maintaining any one of theside or floor surfaces at a temperature no greater than 27C. A particularbenefit of radiant heating frchn a side wall surface is the natural convection ofalr witnin the room which occurs between the heated surface and tile otherslightly cooler surfaces. The convective current is so slow as to beimperceptible t o the occupants of the room but sufficiently strong to maintaingood mixi~ of the air and prevent stratlflcatlon. This type of radiant h ea t i n gis normally associated with the thermal storage kall and direct gain passivea~roaches.

It is also nell established that it is mre efficient to tiat a space radiantlythan by Eeatlng the air. The effective canfort temperature 1s made ~ abuutequally hy the man radiant temperature and by tlw air temperature. Thus it tl~.mean radiant ttnperature can be maintained high then the ai r temperature can bemaintained relatively low and still achieve a comfortable cmluitim. Thus theheating of air which infiltrates the build~ng, which accounts for a verySi g r l ~ f i Ci Yl tfracticm of the energy requirements of a f tnderr t il l- insul~te~huildlng, will he slgnificmtly lcwer in a ~ace which 1s !,eated predcnninantly t.IYradial,t energy,

One mst hc careful h passive SOlar des.lgns to avoid large cold Surtaces withint~ rcom in order to avoid ttw o~oslte effect described above. Large glassareas seem especially cold in a room and require relatively hlyh air te~cratL]resto offset tnelr depression on tlw radiant envlronmnt. Thus ttw designer Ofdirect gain systems 1s led to consider mov~le insulation syst.ems, drapes, tripleglazlng, or other means of protr!ctlng the rocnn m-~nnts from cold glabs sur!aces,

I


10/14

Few Needs for Cert if icat im

For all of the reasons given ?hve there are few need5 fcr Cert.iiicaticm of

equipment used in p a SS i v e systems. Procetires for certification have alreadybeen =t~lished fOr most of the comnm Const.ructlm mt iYia lS used. And Mthirqabout the awlicatim of these materiais in passive systems SFN3U1.d require anextenslcm of the certiflcatims now LOneffect.

However, new passive Sdlar CO@CmentS will be developed--such as glazingassemblies, mxable insulatim a?.setilies, and other packagd devices--which willn?quire established cert if icat ions.

Aesthetic Appeal

Although passive solar buildings my look different than their more cmventicmalneighbors, their aw=rence is generally Considered a~ealing. The nation hasbecome accustomed ta the use of large expanses of glass and often chooses such adesign for aesthetic reasons. Many architectural features such as picture orclerestmm windo~s and massive fireplace sectims ir a btildimg can be turned togOOd t~rhl use simply by properly establishing their relationship to thebuilding gecmmtry and orient:t icn. Many thermally desirable features such asshadicg overhamgs and shutters can a d d to tlw buildings architect,Jral Variety

The availability of sunlight within the living space @ens the possibility ofadding growing plants to the space for tlv? simple Joy of their beauty, varietyand ever-changing characteristics.

Altkwwgh architectural design has never been static, We advent of passive CIes.approaches atis a whole new dimension and synergy to buildirg design which wilherald a revoluticm in architectural practice.

Indepenrknce

Even in the event of total failure of the backup heating S- I PPI Yand theelectrical service to he building, a well-desjgned passive solar buildify willremain moderately comfortable and will never freezt.

PEFFCRMAWESIt41LATICNAt@ EVALUATION

The Los Alamos Scientific Laboratory (LAY) program has been a cornerstone of theDepartment of Energy research and d!?velopment in passive solar heating. The

primary ob,~ectives are 1) to perform a detailed evaluatim of passive solarheaticg and 2) to provick? a quantitative proce~~ which will enable build!.ngdesigners to incorporate P a Ss l Ve solar heatiy into building deslgll. The prugr~mconsists of foJr key elements: a) experiments in passive solar test rooms,b) mnitorinq of passive salar buildings, c) co~uter siwlaticns and systema,lalysis of passive solar ccmceots , and d) ri?velopment of deslqn tools forlncurporatimg passive Wlar concepts into building design.

Test Fnnms -.

Fourteen passive solar test rooms have been cmstructed at LrIs AlcnrJs andck?tailrd data have been taken unckr very carefully controlleil conditions. basedm these results validatim of the computer simulatim ~el~ for L.ikrmal storagewall and direct gain test rooms has proceeded m schedule, 617 Future wrk wlliconcentra~.e on different design approaclws such as convective loops, attachedWvspaccs, and thermal stormy? ruofs, and m tht? extensim ot these e~erim~!ltsLo a variety of advancd concepts to impnve performa,lce,


11/14

Mmitored Buildinrjs

Instrumentation has been installed in 15 passive solar buildings and extensive

data have been taken c&ring two winters cperation. These buildings represent avariety of @sign approaches. Data taken m these buildings allow ths extensio(of the ccmputer model validation from siwle-room test situations to actualb u i l d i n g s h a v i n g a v a r i e t y o f c o n p l i c a t k g f ac t or s d e t o t he I KI r e Co i _@e xs t r u c t u r e md the ompancy. l%ta From three buildiqs have been analyzed andthe mdel validatim process has been successful.

carp uter Simulation and Systems Analyfi&

The experimental a n d mmitoring wrk i; tied together and made useful by conputersimulation and analysis. &Ily through these tools can tl_e results begeneralized, ck?sign milmds developed, and the effW2t of both cii~tic f a C: Or Sand design factors quantified. The mos: progress has been maae in thi- area.~:e faith has been %tablished in a rmtlwmatical modelirg spproach, then accmplex cmputer model can be assembleu representing a particular class ofbuildings and this nmdel useo for system:; Studies. These are of tvm types:climatic studies and parameter variations. lhese studies have been the backbonefor the LA51 effort.

The results of these studies have ccmfirmed thut passive solar heatiy ispractical throughmt the rarge of clirmtes within tl,e United States. Theperformance variation betwen different climate zones is less than might havebeen Imagined since passive solar is shcwn to work effectively in relativelydiffuse solar Ccmditions. when ccupled wit,) an economic evaluation, it has beenestablished that passive solar h~ating ccqwtes favorably in 1978 on a life-cyclebasis with electric Wace heating in nearly all parts of the United States, withoil in most places, anc with (regulated) nat~lral gas in some places.

Th e approach used is to pff:orm full-year hour-by-hour simulation of thebuildi~s for ari,,us desigrl possibilities Fe; 29 aifferen? climates tor whichLA.SLhas detailed weather and salar data. Th~ Imur-by-hour simulation techniquescan also be used to determine the influecce of various design parameters. Onthis basis important performance anu ecmonuc ,Iecisicms can be made in order tochoose the most awroprlate systems fr each climate ana to optimize the aesigns.

DEVEL@KNTw HIGN KJ3LS

LASL has made significant progress in using the ~:orrplex rrmdels to develop silrwledesign techniques. TO do this the results of mary hundreds of rxmr-by-houranalyses are used as a basis for determining corr?laticm. This has been carriedthrough to ccwpletion for two classes of passive designs and 1s uncerway for theadditional classes, The procedure was used Wccessfully as tile basis forevaluation of th recent Passive Solar Design Co~?titiun arid Denmnstratlon.

Simplif ied Method

The tectniqm employed is the LASLMcnthly Solar Loi,o Ratio mthod. Theproce~re 1.s to determine for each month of the heatiry season a dimensionlessSolar Load Ratio (S-R) defined as:

SLR = (nmthly Wlar radiation absorbed/(rmmthly load).

Th e mmthly solar rHctlatlon absorbed 1s ttn? total sol;r energy trmsmlttedthrwgh tile collection glozlng less any that 1s reflect:d back out. lhe mxlthly

lnrirl !5 the total mmthly heating requirement of the hdldlry in tt,e CIIISCIMWf


12/14

a n y w , h c l ud h g heat required to satisfy tlw steady-state load of the solarcol~ectfcm wall and building infiltration.

It h a s b e e n ~te.rmined that the rnnthly Solar Savir@s Fracticm (S5F) can be

successfully Correlated with AR, Since the monthly SS may vary statisticallyfor the sam value of 54-R, the reconmmded procedure is to esthste ~- cmaverages. Month-to-month variations will te,ld to average each other OU: and theQR mthm will provide a 9CtId estimate of the long-tern average. The methodcharacteristically prodces annual solar savings fraction estimates which fallwithin a 3.4% standard deviation of t;e hour-by-hour amdal Calculatic,ls.

The correlation mrves for S IS SLR c& not depend on climate (the correlationsare tine for 10 in 29 widely ciffering climates in the U.S. and Canada) but dodepend on system type. ~rre.ation curves have been generated for dir~ct gain,Tr omb e wlls, md water wallsj both with aild without night insulatim.E~orlential Pmctions have b e e n u s e d for t lw correlations.

Fo r each rmmth of the heating season, the ratio 5/CO :s determined, where 5 isthe total mmlthly solar radiation transmitted through one sqlrare meter of s o u t h -f ac t no , - . e r t i c a l d o t i l e g l a z h g a n d ~ L s t ns b a s e 1 8 . 3 C h e a t i ng d e g r ee d a y s .

Th e n t h e So l a r Savi@s F r ac t i o n ( S$ ) i s d e t e r mi n e dfor e a c h frnn?.h as fol lows:

ssF=l- K ( l - F) , wh e r eF=,qX, forX RF S 1.OCU for large X.

K = 1 + G/ LCRX = ( 5 / M) ) / ( L CSlxK)

(X is the 501ar Load Ratio)

building load coefficient, exclusive

LCR = of solar gla~i.nqsolar collecticm area

a nd wh e r e

( LCR i s the Load Collector Ratio)

Constants for tk various passive system types are as follows:

G R A B c D

m 10.6 0.5 IJ.5213 1.0133IXNI

1.06422.4 0.7 0.5420

0.69.27.9866 1.1479 0.9U97

Tw 3,6 C. b 0 , 3 6 9 8 1 . 0 4 0 8 1 . 0 7 9 7 U. 4 4 0 7TwNI 0 . 5 1 , 0 L I . 4 5 5 6 . 9 7 6 9 1 . 2 1 5 9 o . 8 4 b 9

Ww 5 , 0 1 , 3 0 , 4 0 2 5 . 9 8 7 2 1 . 5 0 5 > u . ! l J 54WWN1 0,7 1.2 0,4846 .9799 1,8495 1,2795

Th e ; mi n u a l SSF i s

t +? r e, LX, TW MI Ir es p ~ c t i v e l y . NI

then obtained f r o m t he s ums o t t h e omn t h l y v a l u e s , a s f o l l ows :

qMF i x mlAn n u a l 5 S =

- - - q%

WW Ml c n t e d i r e c t g a i n ,Tromhe wall, dnd water wall[ndici lte~ night ~ ns u l a t l c m,


13/14

Most passive designs ca}sist rrf a mixture ttw basic approaches. Few Trorrbewalls are wlthwt same direct gain conpme[lt. Most water walls are spread-aparttuhm or other cmt.ainers which allow some CJirect heating. The recomrrvmdedprocetire is to cmp-rte a siqle *R, based on tlw total solar gain through aliglazirq divided by the total thermal loadST.

, anc then compute a weighted-averageThis is detc:-{ned b y Conputing a separate 5* for each design approachand a v e r ag i n g Pi t we n t hem b a s e d m t he r el a t i v eproporL:.on of each glazed area.

Re f e r e nc e De s i g n s

Th e correlatim curves are determined for a set of reference COn f i 9 Ur 0 t k YM@ i n d as follows:

Oouble alazina, rnrmal transmittance = 0.7!!7 , 6.4 mmSpaciwNight i&ulat~6n (when used) is O 6 W/Cm2; 5:CIl pm to 8

3Thermal Storage = 92UC130J/C per m of glazlrqWater wall: equivalent to 216 nvr of waterTrombe wall: 450 mmthickness

Thermi?l ccr,dctivity . 1.73 W/mCTranbe wall has vents, upper and lower, each 3% of the hahaving backdrafl dampers,Oirect Gain . exQosed surface = 3 x glazed ?Lea

150 rrvnthicknessOttmr nuildirg mass 1s negligiblewall-to-:oom cmtictancr . 5.7 W/C m2

m-am

1 area,

hxlliaw maintains an interml bulldhj temperature above 18.3C. Heiit 1s~nv@ to rmintain the building tc.~eratur~ below 23.~C. No lntermlhu~ldimg heat generation.

Estlmatlcq ttw E!fect of Variations 111 Ocsign Parameters

The effect of cha:-,plrq a design parameter (dtlwr than the area of glazing) car~ beassessed by Gt..xlylnq the piidished result~ of huur-t]y-hour calcui;~tiuls in whichthe various parametl=rs are varied me at a time, These are giver, in Reterence 8.

REFEKNCE:

Proceed:lqs of tlw Conference m ?ass!ve 5olar Heatinq and Cooling;:kY, 1976). Albuquerque, N.M. 1.A-663:~-c; 355 pi; available from NiitTr=clmicul Inform:~tlm 5r?rvlce, .Sprir]gfield, VA, for $lJ.uJ tl.>.

ona

Fl~llad~lphia, PA, 949 pp; avallnble frum Mid-Atlantic !iolar Energy ll~mciatim,P77} uraYs }uyry Ave., Philndelphla, FA., 19146 for $2I,[lJ U.S.

5. Prnceedlws 01 the 3rd rlltialai PassIvc Sulur [lhlterr:rwe (January, 19/!!) m~.Jo\P, r A 111 pllllllcntlorl; LII 11P nvailahll: trnm, Amr l c a n .50cLiIJll, Irltl:r:mlionalSnlnr Ene;oy Soclcty (AS/ISES), PmO. liIIx 1416; Amrlcan i e c l l o l u q ~ c al l J r l ~ ve r s l L y ,Kllle rIl TX., 76541.

II, Procrcdlc-qt or the nS~15[.5 f l r l r n . l i r )Yx ~t r r [ ! r r n(Jwc, ]V//) L J r l d r l w) , [ L . ; M+ / pJ r ; O~ ;II ViIl];III]II r r l ~mA! i / l Y. 5 ( NY N f . 3 ) 0

9 . l l r ( , [ . ~ , y j l [ ~ ! ;f ~ ~ f l s , l l q s r l wl u a l l l M\ f l ! r ( l! l (N JiII!it, lV/tl) IJlvwt!l, [;(l, ;n v a l l i i l l ] p f r nm A5 / l * ! I ( wrrcf, 3).

II


14/14

6. J. D. Balcorrb, R, 0 . Mc Fa r l a n d , a n d 5 . W Wo r e , ( Ju n e 1 9 7 7 ) ~ l n u l a t i ~~ jAn a l y s i s Pa \ $ i v e s o l a r He a t e d L u , l i l i ng--~~arlscn with Test RrwmR esults~rese.lted at t h e AS/15Es Anrwal ~4eeting, (see ref. 4, aoove).

7. W, O. Wray and J. D. Balcomb, S.?nsltivlty of Direct Cain Space Heatin~Performance to Fmdamental Paramet~~t]ms, Solar Enerd(1

.. y, vol. 2979) .

3,-N0. 5

I?m J. D. 9alcomh md others, (January 1960). Passive Solar Ilesi n Ha nd bc o kVolune II: ~--assive Solar Oesl n Analvsis, U. S. Department o Energy,mE/c s-o127ri!. %r-vailable from Nat ma~eclnical Informatim Service,~ringfielrl, vA, f o r $ 1 4 . OJ U. 5 .

Energy Savings Obtainable Through Passive Solar Techniques

Documents

Transcript of Energy Savings Obtainable Through Passive Solar Techniques