D7-arsenal-Feasibility of ground coupled heat pump technol… · 2014-08-11 · GROUND-REACH...

TECHNICAL, ENVIRONMENTAL AND ECONOMIC FEASIBILITY OF GROUND COUPLED HEAT PUMP TECHNOLOGIES UNDER DEFINED CONDITIONS

Deliverable 7 Ground-Reach

August 2008

“Reaching the Kyoto targets by means of a wide introduction of ground coupled heat pumps (GCHP) in the built environment”

Project GROUND-REACH Project supported by Contract No.: EIE/05/105/S12.420205

www.groundreach.eu

GROUND-REACH Technical, environmental and economic feasibility of ground coupled heat pump technologies under defined conditions, August 2008

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Technical, environmental and economic feasibility of ground coupled heat pump technologies under defined conditions About this Technical Report This report examines the potential of ground coupled heat pump to help reach the objective of Building Performance Directive1 to promote improvement of the energy performance of buildings within the community, taking into account outdoor climatic local conditions as well as indoor climate requirements and cost-effectiveness. Author/s Patrice Pinel arsenal research Vienna, Austria Telephone: +43 (0) 50 550-6373 Email: [email protected] Markus Brychta arsenal research Vienna, Austria Email: markus.brychta @arsenal.ac.at Editor Tim Selke arsenal research Vienna, Austria Telephone: +43 (0) 50 550-6651 Email: [email protected]

Date: August 2008 EC Contract EIE/05/105/S12.420205

www.groundreach.eu Project co-ordinator Centre for Renewable Energy Sources (CRES) 19th km Marathonos ave., 19009 Pikermi Attikis, Greece. http://www.cres.gr/ Dimitrios Mendrinos Tel.: +30.210.6603300 Fax: +30.210.6603301 [email protected]

Disclaimer The sole responsibility for the content of this publication lies with the authors. It does not represent the opinion of the Community. The authors and the European Commission are not responsible for any use that may be made of the information contained therein.


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Contents

Contents ............................................................................................................. 3

1 Introduction ................................................................................................... 5

2 Methodology.................................................................................................. 6

2.1 Buildings 6

2.2 Systems 6

2.3 Comparisons 7

3 Simulations Results ...................................................................................... 8

3.1 Building loads results 8 3.1.1 Design loads 8 3.1.2 Heating and cooling loads 10

3.2 Energy consumption for space conditioning 12 3.2.1 Energy consumption from heat pumps 12 3.2.2 Energy consumption from split systems 12 3.2.3 Energy consumption from boilers 13

3.3 Performances of space conditioning equipment 14

4 Comparison of environmental and economic impacts ............................ 16

4.1 CO2 emmissions 16

4.2 Primary energy savings 19

4.3 Operating costs 22

4.4 Life cycle costs 24

Conclusions ...................................................................................................... 29

References ....................................................................................................... 31

Project Description ......................................................................................... 34

Project partners .............................................................................................. 35

A.I Building Simulations Inputs....................................................................... 36

A.I.1 Buildings geometrical descriptions 37


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A.I.1.1 Single family house 37 A.I.1.2 Multi units residential building 39 A.I.1.3 Office & retail building 40 A.I.1.4 Hotel 41

A.I.2 Buildings energy efficiency 42 A.I.2.1 Insulation 42 A.I.2.2 Ventilation and infiltrations 43 A.I.2.3 Shading 43 A.I.2.4 B.5 Setbacks 43

A.I.3 Internal gains 44 A.I.3.1 Internal gains for simulations of single family houses 44 A.I.3.2 Internal gains for simulations of multi units residential buildings 46 A.I.3.3 Internal gains for simulations of office & retail buildings 47 A.I.3.4 Internal gains for simulations of hotels 49

A.II Systems Design ........................................................................................ 50

A.II.1 Heat Pump Systems 50 A.II.1.1 Heat Pumps 51 A.II.1.2 Buffers 51 A.II.1.3 Ground loops 52 A.II.1.4 Pumping 54

A.II.2 Boiler Systems 54

A.II.3 Split Systems 55

A.II.4 Fully electric systems 55


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1 Introduction It is the objective of the Buildings Performance Directive1 to promote the improvement of the energy performance of buildings within the Community, taking into account outdoor climatic and local conditions as well as indoor climate requirements and cost-effectiveness. This objective is based on the fact that buildings will have an impact on long-term energy consumption and buildings should therefore meet minimum energy performance requirements tailored to the local climate.

This work, part of Work Package 4 of the Ground-Reach project, refers to the following paragraphs of the Buildings Performance Directive: • “As the application of alternative energy supply systems is generally not explored to

its full potential, the technical, environmental and economic feasibility of alternative energy supply systems should be considered; this can be carried out once, by the Member State, through a study which produces a list of energy conservation measures, for average local market conditions, meeting cost-effectiveness criteria. Before construction starts, specific studies may be requested if the measure, or measures, is deemed feasible.” (L 1/64 (12))

• “New buildings. Member States shall take the necessary measures to ensure that new buildings meet the minimum energy performance requirements set by the Member States. For new buildings with a total useful floor area over 1 000 m2, Member States shall ensure that the technical, environmental and economic feasibility of alternative systems such as: − decentralised energy supply systems based on renewable energy, − CHP, − district or block heating or cooling, if available, − heat pumps, under certain conditions,

is considered and is taken into account before construction starts.” (Article 5, L 1/68)

This Directive defines “heat pump” as follows: “a device or installation that extracts heat at low temperature from air, water or earth and supplies the heat to the building.“ (Article 2, L 1/67)

The present report explores the potential of ground coupled heat pumps to help achieve this objective of the Building Performance Directive for different types of building and climates through the use of computer simulations. This potential is evaluated using comparisons with other systems commonly used to condition building space.

1 DIRECTIVE 2002/91/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 16 December 2002 on the energy performance of buildings (4.1.2003 L 1/66 Official Journal of the European Communities)


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2 Methodology In order to obtain comparisons which are representative of the whole of Europe, three climates are explored. These climates are assumed to be represented by the cities in brackets:

• Cold (Stockholm, Sweden) • Temperate (Frankfurt, Germany) • Warm (Athens, Greece)

2.1 Buildings Four building types are also explored to obtain comparisons indicative of the whole building stock:

• Single family house • Multi family house • Hotel (large building) • Building combining a Supermarket with Offices

Two levels of building energy efficiency are also assumed: a high level of insulation and air tightness, representative of more recent building constructions, and an average level of insulation and air tightness representative of older constructions with a certain concern for efficiency. It is assumed that any less energy efficient building that would be retrofitted to improve its energy consumption would also receive other energy efficiency upgrades and not just a replacement of the conditioning system. These buildings are modelled, with proper inputs representative of the climate and occupants behaviour for each of the three cities aforementioned, using the TRNBuild (Transsolar 2004) building modelling utility. The TRNSYS 16 (Klein et al., 2004) is then used to evaluate:

• The system design loads • The energy requirement for space heating and cooling

This results in 24 different space conditioning load profiles and design loads. Details of building constructions and simulation inputs are provided in Appendix A.I. Calculated heating and cooling loads are presented in Section 3.1.

2.2 Systems The design loads are then used to size ground coupled heat pumps and comparison systems. The design procedure and resulting systems are detailed in Appendix A.II.


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These systems are simulated using the TRNSYS environment resulting in the yearly energy consumption and SPF (Seasonal Performance Factor) of each system. Only low temperature heat pumps with no DHW (Domestic Hot Water) production are explored in the framework of Deliverable 7; high temperature distribution with DHW production is explored in Deliverable 8. The following table provides an overview of the compared systems. Energy consumptions calculated by the simulations are presented in Section 3.2. Table 2.1 Systems explored in the course of Deliverable 7

Climate HP system Comparison systems

Cold

1- NG boiler (Heating), Split system (cooling) 2- Oil boiler (Heating), Split system (cooling) 3- Split + Electric (Heating), Split system (cooling) 4- Electric (Heating), Split system (cooling)

Moderate

1- NG boiler (Heating), Split system (cooling) 2- Oil boiler (Heating), Split system (cooling) 3- Split system (heating & cooling) 4- Electric (Heating), Split system (cooling)

Warm

- Centralized - Low temperature heating - High temperature cooling - Boreholes ground exchanger

1- Oil Boiler (heating), split system (cooling) 2- Split system (heating & cooling) 3- Electric (Heating), Split system (cooling)

Note: Since Greece has no significant Natural Gas market according to Eurostat (2006), NG systems are not explored for warm climates.

2.3 Comparisons Finally, the resulting energy consumptions are used to compare different systems in different conditions, using a procedure outlined in Deliverable 3 (Forsén & Roots 2007) of the Ground-Reach project. The procedure and results are presented in Section 4 of the present report.


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3 Simulations Results This section presents results from the building and systems simulations. All results are expressed in values per square meter of used surface. As mentioned in Appendix A.I., the average surfaces of residential dwellings in the countries considered for the present analysis are:

• 91.6 m2 in Stockholm, • 89.7 m2 in Frankfurt, • 82.7 m2 in Athens.

Residential dwelling useful surfaces for other countries can be found in section 2.1 of the report Housing Statistics in the European Union (2005). For the commercial buildings, useful floor areas are:

• 1439 m2 for the combined office/retail building, • 5754 m2 for the hotel.

3.1 Building loads results

3.1.1 Design loads Figure 3.1 presents result from design loads calculations. For all figures presented in this section, the terms:

• “Low” and “High” stand for the lower and higher building energy efficiency cases previously defined;

• “Cold”, “Temp” and “Warm” stand for the cold, temperate and warm climates considered in the study;

• “SFH”, “MFH”, “Office-Retail” and “Hotel” stand for the different building types studied, SFH meaning Single Family House while MFH means Multiple Families House or Apartment Building.

These loads consider the steady state heat transfer from the building envelope and infiltrations, assuming the building temperature is at its set-point while the ambient is at a heating design temperature. Heating design temperatures used for these calculations are:

• -17.5 °C in Stockholm, • -9.9 °C in Frankfurt, • 1.8 °C in Athens.

This is a typical HVAC system methodology recommended by most building codes. It was used to design the systems studied in the present report.


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Low eff. High eff. Low eff. High eff. Low eff. High eff. Low eff. High eff.

SFH MFH Office-Retail Hotel

Des

ign

Hea

ting

Load

, W/m

²

ColdTemperateWarm

Figure 3.1 Design heating loads

Figure 3.2 presents the highest heating loads encountered during transient simulations of the buildings. As can be seen, “real” loads are generally smaller than design loads since the transient calculation also accounts for solar and internal gains. Nevertheless, it is bad practice to account on gains for design so the loads from figure 3.1 are used for design.

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Max

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ting

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, W/m

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ColdTemperateWarm

Figure 3.2 Maximum heating loads during simulations


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Since this study also deals with cooling loads, it is necessary to also ensure that the designed systems are capable of handling the cooling demands of the buildings. Evaluating cooling loads is often imprecise as they are very dependant on gains so it is preferable to evaluate these loads by looking at the results of the simulation and selecting the highest load. Figure 3.3 presents the highest cooling loads for each building and climate case.

0

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30

40

50

60

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80



Max

Coo

ling

Load

, W/m

²

ColdTemperateWarm

Figure 3.3 Maximum cooling loads during simulations

As can be seen, these loads are generally lower than the heating design loads of figure 3.1 so the heat pumps designed for heating should be capable of handling them. Cooling loads are higher only for the combination retail/office buildings in warm climate but these cases are compensated during simulations by the heat pump buffer so the systems can absorb these loads.

3.1.2 Heating and cooling demand Figure 3.4 and 3.5 present the total conditioning demands evaluated from the yearly simulations. As can be seen, different in insulation levels often result in heating demand being lower in the cold climate than in the temperate one. Another interesting result is the fact that the computed cooling demands in temperate and cold climates are higher for high efficiency buildings than for lower efficiency ones. This is due to the higher infiltration rates of lower efficiency buildings which removes some of the internal and solar gains from the buildings and indicates that natural


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ventilation is generally more efficient in these climates during cooling season than the heat recovery ventilation assumed for this work.

0

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60

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100

120

140



Hea

ting

Load

, kW

h/m

²

ColdTemperateWarm

Figure 3.4 Total heating demand from space conditioning

0

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45

50



Coo

ling

Load

, kW

h/m

²

ColdTemperateWarm

Figure 3.5 Total cooling demand from space conditioning


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3.2 Energy consumption for space conditioning This section presents the energy consumption by the heat pumps and comparison systems studied in the present report. In the case of boilers, this energy is oil or natural gas equivalent while in the case of heat pumps and split systems, that energy is electricity. 3.2.1 Energy consumption from heat pumps Figure 3.6 displays the electricity consumption of heat pumps used to condition the buildings. Since the performances of such systems evolve as there is accumulation or depletion of heat in the bore-field, results are presented for the 10th year of operation assumed to be around the mid-point of the system life. As can be seen, for the lower energy efficiency cases, heating consumption is lower in the cold climate than in the temperate one. This is due to the fact that buildings are better insulated in Sweden than Germany and is confirmed by figure 3.1 which shows that the loads are not only a direct function of climate.

Figure 3.6 Heat pumps electricity consumption 3.2.2 Energy consumption from split systems

Figure 3.7 shows the calculated electricity consumption of split systems. For the cold climate, electric resistance (100%) heating is assumed for temperatures below -18° C.

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Cold Temp. Warm Cold Temp. Warm Cold Temp. Warm Cold Temp. Warm


Heat

Pum

p E

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rici

ty C

onsu

mpt

ion,

kW

h/m

²

PumpingCoolingHeating


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Figure 3.7 Split systems electricity consumption

3.2.3 Energy consumption from boilers Figure 3.8 presents the energy consumption from boilers during the heating season.

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Boile

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Figure 3.8 Energy consumption from boilers

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3.3 Performances of space conditioning equipment The methodology used in chapter 4 of the current report to compare environmental and economic impacts of the systems requires the efficiency of the different systems. For the heat pump and split systems, efficiencies are presented in the form of SPFs (Seasonal Performance Factors), which are the ratio of the heat displaced over the electricity consumption over an entire season (heating or cooling). For boilers, the efficiency is expressed in the form of an AFUE (Annual Fuel Utilization Efficiency) which accounts for the steady state efficiency of the boiler as well as the efficiency losses due to cycling (turning the boiler on/off). The following figures (3.9 – 3.11) present the efficiencies observed during the simulations. The heat pumps SPFs expressed are for the entire system and therefore take into account pumping to the ground loop: these are slightly lower than the SPFs for the heat pumps alone. The subscripts “h” and “c” represent the heating and cooling season respectively.

Figure 3.9 Heat pump systems seasonal performance factors

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Figure 3.10 Split systems seasonal performance factors

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Figure 3.11 Boilers Annual Fuel Utilization Efficiency

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4 Comparison of environmental and economic impacts In the course of this work package, environmental impacts are compared considering CO2 emissions and primary energy consumption while and economic impacts are evaluated considering operating and life cycle costs of the systems. The methodologies used are explained in Deliverable 3 (Forsén & Roots 2007) of the Ground-Reach project.

4.1 CO2 emmissions According to equation 6 of Deliverable 3, the CO2 emissions savings, conv

HPcomph − , of

upgrading a space conditioning system with a heat pump can be expressed as:

⎥⎥⎦

⎤

⎢⎢⎣

⎡−+−=−

aux

compupaux

upcomp

comp

auxcompupel

upcomp

comp

elconvHPcomp ef

efexen

SPFefef

exenhηη

ηηη

ηη

)1(1 (4.1)

Where:

• exen is the fraction of the building’s heating energy consumption provided by the heat pump

• SPF is the heat pump system’s seasonal performance factor • compη is the efficiency of the compared system

• auxη is the efficiency of the auxiliary system

• elef is the emission factor for electricity

• compef is the emission factor for the compared source

• auxef is the emission factor for the auxiliary source

• upelη is the upstream efficiency for electricity (extraction, transformation and

transport) • up

compη is the upstream efficiency of the compared source

• upauxη is the upstream efficiency of the auxiliary source

Emission factors ⎟⎟⎠

⎞⎜⎜⎝

⎛up

efη

are provided in Deliverable 3:

• 0.33 kg/kWh for oil, • 0.238 kg/kWh for natural gas, • 0.878 kg/kWh for electricity in Greece, • 0.622 kg/kWh for electricity in Germany, • 0.077 kg/kWh for electricity in Sweden;


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Since: • the current work is only concerned with space heating and cooling, • the entire conditioning loads are supplied by heat pumps for heat pump systems, • all cooling is supplied by split systems for comparison systems, and therefore uses

electricity; equation 4.1 can be reformulated as:

( )⎥⎥⎦

⎤

⎢⎢⎣

⎡−+−=−

C

Cplit

H

Hcmpupel

upHcmp

Hcmp

elconvHPcmp SPF

SPFsHeatRatio

SPFefef

HeatRatioh ,,,

,

11η

ηη

(4.2)

Where: coolingheating

heating

loadloadload

HeatRatio+

=

The subscripts C and H stand for Cooling and Heating respectively Applying equation 4.2 to the efficiencies presented in section 3.3 yields the emissions savings factors presented in figure 4.1 and summarised as a function of climate and energy source in table 4.1. Note that, as previously mentioned, no natural gas results are presented for the warm climate since there is no significant market in Greece. The different comparisons presented in figure 4.1 are:

• Heat pump replacing Oil boiler (heating) and Split system (cooling) – Blue bars • Heat pump replacing Gas boiler (heating) and Split system (cooling) – Red bars • Heat pump replacing Electricity (heating) and Split system (cooling) – Yellow bars • Heat pump replacing Split system (heating and cooling) – Green bars

Figure 4.1 Emissions savings factors

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Table 4.1 Summary of relative CO2 emissions savings Country HP VS oil/split

% HP VS gas/split

% HP VS electricity/split

% HP VS split/split

% Sweden 85-95 83-93 66-71 37-43 Germany 46-67 32-54 59-70 23-33 Greece 23-40 NA 27-48 20-25 These relative emissions savings are very high for Sweden when replacing oil or natural gas boilers since Swedish electricity is almost emissions free. For Greece, where the electricity is not as clean and a more important fraction of conditioning is cooling which is handled by relatively efficient split systems, the savings are lower but still substantial. The building’s energy efficiency has little effect on the savings factors for Sweden since the heating/cooling load ratio remains similarly heavily biased toward heating. For warmer climates, relative savings are generally higher for lower energy efficiency buildings. This would indicate that there is high potential for CO2 reduction in upgrading the conditioning systems of older buildings in these countries. One should be careful when interpreting results for substitution of electricity based systems. Replacing an electricity/split based system in Greece may result in about a third of the relative savings observed in Sweden, but these relative savings apply to a much higher initial emissions rate in Greece. For example, for a low efficiency building in Greece the electricity consumption for space conditioning would be 76 kWh/m2 (60 for the electric heating + 16 for the split system cooling), while it would be 95 kWh/m2 (93 + 2) in Sweden. This would result in CO2 emissions of 7.3 kg/m2 (0.077 kg/kWh ) in Sweden and 67 kg/m2 (0.878 kg/kWh) in Greece. So the saving factors presented in figure 4.1 would result in savings of 4.9 kg/m2 (68% of 7.3) in Sweden and 30 kg/m2 (45% of 67) in Greece. Figure 4.2 presents the CO2 emissions savings in absolute form per area of conditioned floor while Table 4.2 summarises these values as a function of climate and replaced energy source. Results clearly show that replacing fossil fuel based systems in Sweden and Germany would yield higher absolute emissions savings than in Greece while replacing electricity based systems would yield higher savings in Germany, followed by Greece and finally by Sweden. Table 4.2 Summary of absolute CO2 emissions savings per area of conditioned floor Country HP VS oil/split

Kg/m2 HP VS gas/split

Kg/m2 HP VS electricity/split

Kg/m2 HP VS split/split

Kg/m2 Sweden 9-49 6-35 1-5 0.4-1.4 Germany 4-51 2-29 9-61 1.2-6.9 Greece 2-21 NA 5-41 1.4-5.4


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Figure 4.2 Absolute CO2 emissions savings per area of conditioned floor

4.2 Primary energy savings Deliverable 3 also proposes a relationship (equation 9 of the report) to evaluate primary energy savings:

⎥⎥⎦

⎤

⎢⎢⎣

⎡−+−=−

aux

compupaux

upcompcomp

upel

upcompenergyprim

HPcomp exenSPF

exenhηη

ηηη

ηη

)1(1_ (4.3)

It also proposes values of upstream efficiencies ηup:

• 84% for oil • 85% for natural gas • 37% for electricity in Greece • 33% for electricity in Germany • 44% for electricity in Sweden

Again, transforming this relationship to the space heating and cooling loads analysed in the present report yields:

( )⎥⎥⎦

⎤

⎢⎢⎣

⎡−+−=−

C

Csplit

H

Hcmpupel

upHcmpenergyprim

HPcmp SPFSPF

HeatRatioSPF

HeatRatioh ,,,_ 11η

ηη

(4.4)

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ving

s (k

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r) HP VS Oil/SplitHP VS NG/SplitHP VS Elec/SplitHP VS Split/Split


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Applying this relationship to the simulation results previously presented yields the primary energy savings presented in Figure 4.3 and summarised in table 4.3:

Figure 4.3 Primary energy savings factors Table 4.3 Summary of relative primary energy savings Country HP VS oil/split

% HP VS gas/split


% HP VS split/split

% Sweden 50-66 49-65 66-71 37-43 Germany 33-55 32-55 59-70 23-33 Greece 24-43 NA 27-48 20-25 Savings factors are the same as the CO2 emissions savings factors (section 4.1) for comparison with electricity based (split and electric heating) heating systems. This is normal since these use the same conditioning source (electricity) as the heat pump and so only the system efficiency intervenes in the computation of the savings factor. Once more, relative savings are higher in Sweden since the upstream efficiency of electricity is higher there. For the other climates, savings are higher in Germany despite the upstream efficiency being higher in Greece. This can be explained by the fact that loads in Germany are more biased toward heating, and so the efficiency gain of switching the conditioning system for a heat pump more than compensates for the lower upstream efficiency: it is more advantageous to switch boiler use (60-83%) or lower efficiency split systems used in heating (SPF ≈ 2.6) than to replace split systems with higher efficiency in Greece (SPF ≈ 2.8 in both heating and cooling).

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Figure 4.4 and Table 4.4 present these same results in absolute form per area of conditioned floor. Absolute primary energy savings are generally higher in Germany, which has relatively high conditioning loads, especially for replacement of electricity based system since Germany has the lowest electricity upstream efficiency.

Figure 4.4 Absolute primary energy savings per area of conditioned floor Table 4.4 Summary of absolute primary energy savings per area of conditioned floor Country HP VS oil/split

kWh/m2/year HP VS gas/split kWh/m2/year

HP VS electricity/split kWh/m2/year

HP VS split/split kWh/m2/year

Sweden 19-121 19-119 39-148 12-40 Germany 11-150 10-146 43-296 6-34 Greece 8-82 NA 17-126 4-17

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4.3 Operating costs Deliverable 3 proposes the following relationship to evaluate end use costs savings:

⎥⎥⎦

⎤

⎢⎢⎣

⎡−+−=−

aux

comp

comp

elcomp

comp

eltuseendHPcomp price

priceexen

SPFpriceprice

exenhηηη

)1(1cos__ (4.5)

According to Eurostat (2006), the prices of the different sources used for this analysis are: Table 4.5 End consumer prices of energy sources

Sources Application Sweden €/kWh

Germany €/kWh

Greece €/kWh

Oil All 0.1057 0.0630 0.0615 Residential 0.0934 0.0575 NA Natural Gas Commercial 0.0441 0.0417 NA Residential 0.1435 0.1832 0.0701 Electricity Commercial 0.0593 0.0994 0.0668

Note that, for this analysis, the residential prices are used for Single and Multi Family House buildings while the commercial prices are used for the Combination Retail/Office building and the Hotel. Adjusting equation 4.5 for the conditions encountered in the present work:

( )⎥⎥⎦

⎤

⎢⎢⎣

⎡−+−=−

C

Csplit

H

Hcmp

Hcmp

eltHPcmp SPF

SPFHeatRatio

SPFprpr

HeatRatioh ,,

,

cos 11η

(4.6)

Under these conditions, the simulation results convert to the following relative operating costs savings. Table 4.6 Summary of relative operating costs savings Country HP VS oil/split

% HP VS gas/split


% HP VS split/split

% Sweden 62-89 58-76 66-71 37-43 Germany 28-72 23-58 59-70 23-33 Greece 28-52 NA 27-48 20-25


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Figure 4.5 Economic savings factors. Relative operating costs savings are higher, especially for residential buildings, when boiler systems are replaced in Sweden where prices of fossil energy are higher. Savings are also higher for replacement of oil boilers in residential buildings in Greece than in Germany since Germany has the highest residential electricity price of all studied countries. Figure 4.6 and table 4.7 present the result in absolute form. As can be seen, replacing electricity based systems provides the most economic benefits in Germany where the cost of electricity is the highest. For replacement of fossil fuel based systems, the most benefits are encountered in Sweden where prices of fossil fuel are the highest. The low costs of energy results in relatively less economic incentive in Greece. Table 4.7 Summary of absolute operating costs savings per area of conditioned floor Country HP VS oil/split

€/m2/year HP VS gas/split

€/m2/year HP VS electricity/split

€/m2/year HP VS split/split

€/m2/year Sweden 2.67-12.54 0.88-10.48 1.03-9.35 0.32-2.52 Germany 0.87-6.93 0.41-5.65 1.41-17.88 0.19-2.03 Greece 0.46-5.23 NA 0.41-3.27 0.10-0.43

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Figure 4.6 Absolute operating costs savings per area of conditioned floor

4.4 Life cycle costs Initial equipment costs are assumed to be equal for all studied countries. They are approximated using typical data for countries where market for such equipment are relatively well developed. Prices for heat pumps are evaluated using the following relationship which was developed from Austrian data: PriceHP (€) = 4823 + 238 * Cap for Cap ≤ 25 kW PriceHP (€) = 9681 + 63.5 * Cap for Cap > 25 kW Prices for borehole exchangers are also evaluated from Austrian data where € 550 is the average cost for transporting the drilling equipment: PriceBore (€) = 550 + 45 * Lengthdrilling(m) The cost of boilers and split systems are evaluated using the following relationships which were derived from Greek data: Priceboiler, oil (€) = 380 + 16.7 * Cap Priceboiler, gas (€) = 1518 + 13.3 * Cap Pricesplit (€) = max(300, 269 * Cap – 1317)

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ts S

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gs (€

/m²/y

ear) HP VS Oil/Split

HP VS NG/SplitHP VS Elec/SplitHP VS Split/Split


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Under these conditions, all equipment costs per area of conditioned space used for the present study are as presented in Figure 4.7. As can be seen, the initial costs of heat pumps systems are much larger than the costs of compared systems. The study therefore consists mainly in comparing the cost of heat pump systems to their cost savings during operation presented in section 4.3.

Figure 4.7 Initial cost of equipment: a) Single and Multi family houses

Figure 4.7 Initial cost of equipment: b) Office-Retail building and Hotel

0

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t, €/

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Office-Retail Hotel

Equi

pmen

t Cos

t, €/

m²

Base Equipment

Split for Supplementary Cooling


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This life cycle cost analysis assumes that the conditioning equipment have a useful life (Life) of 30 years. Under this assumption, the direct (fixed energy prices and no interest on investment) life cycle cost (LCC) brought down on a yearly basis, resumes to: LCCA = Costequipment/Life + Costoperation The life cycle costs comparisons (savings provided by heat pumps) are provided for the different studied systems in figure 4.8 where negative values represent situations where the LCC of the compared system is lower than the one of the heat pump system. As can be seen, the low cost of energy in Greece makes alternative systems more advantageous than heat pump systems using this evaluation method. Furthermore, the lower costs and relatively good performance factor of split systems also make them more advantageous for all studied scenarios.

Figure 4.8 Direct LCC annual savings of heat pump systems If we assume that the price of energy increases each year by a constant factor (inc), the resulting annual LCC can now be evaluated by using the mean energy cost during the system’s life. LCCA = Costequipment/Life + Costoperation{1+(1+inc)Life}/2 The LCC comparisons shown in figure 4.8 are computed assuming a 3% annual increase in the price of energy during the 30 year life of the system. As can be seen, it is advantageous under this assumption to replace almost all systems, except split systems in Greece, by heat pumps.

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Figure 4.8 LCC comparisons assuming a 3% yearly increase in the cost of energy

It is also possible that the high initial costs of heat pumps systems result in eventual consumers having to use a financing mechanism in order to complete the acquisition of the system. In such a case, the investment (inv) would be reimbursed over a certain period (n years) and submitted to a certain interest rate (int). The sum of the payments required to reimburse that investment repartitioned over the system life can be expressed as:

And so the annual life cycle cost can now be expressed as:

If we assume that the system costs are repaid in a period of 5 years at an annual interest rate of 5%, the life cycle costs become as shown in Figure 4.9. As can be seen, this payment method makes heat pump systems slightly less attractive from the life cycle cost perspective.

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( )( ) 1int1

int1int−++××

×= n

ninvLifenPayment

( )( )

( )2

111int1int1int Life

operationn

n

AincCostinv

LifenLCC ++

+−++××

×=


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Figure 4.9 LCC comparisons assuming a 3% yearly energy cost increase, a 5% interest rate on the cost of equipment and a 5 year reimbursement period

It is hard to draw firm conclusions from this life-cycle cost analysis since results depend highly on inflation and the payment method of the initial investment, variables that are difficult to predict accurately. Results show that replacing fossil or purely electric based systems in Sweden and Germany is highly beneficial. For split systems in these locations and other alternative systems located in Greece, the analysis is less conclusive. For split systems located in Greece, the analysis indicates that split systems would have a lower life cycle cost than heat pumps.

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Conclusions The objective of the present study was to explore the potential of ground coupled heat pumps to help achieve this objective of the Building Performance Directive for different types of buildings and climates through the use of computer simulations. In order to achieve this objective, different buildings topologies were defined and simulated considering different climates representative of the whole of Europe. The resulting conditioning loads were used to design ground coupled heat pump and comparison systems. These space conditioning systems were also simulated in order to evaluate their respective annual energy consumption and efficiency. Results were compared to evaluate the relative and absolute savings achieved by replacing each compared system with a ground coupled heat pump regarding:

• CO2 emissions, • Primary energy savings, • Operating cost for the end consumer, • Life cycle costs.

Results regarding CO2 emissions Results show substantial CO2 emissions reductions (15 to 95%) could be achieved by substituting conventional space conditioning systems with heat pumps. They also show that replacing fossil fuel based systems would have the most impact in Sweden where the electricity mix is relatively clean and heating loads are higher but also a relatively high impact in Germany. Finally, replacing electricity based systems would have the most impact in Germany, followed by Greece, where the electricity mix is less clean than in Sweden. Results regarding primary energy savings Considerable primary energy consumption (15 to 71%) could also be achieved by replacing conventional conditioning systems with heat pumps. The most savings could be achieved in Germany and Sweden since these countries have higher heating loads. Replacing electricity based systems in Germany would provide the highest savings since electricity production upstream efficiency is the lowest observed in the countries studied in this report. Results regarding operating costs According to the calculations, end user operating cost reductions of 15 to 89% could be achieved with heat pumps upgrades. Replacing fossil based systems would have the most impact in Sweden while replacing electricity based systems would have the most impact in Germany where electricity prices are the highest. There are few economic incentives for replacement in Greece where the cost of energy is lower.


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Results regarding life cycle costs The analysis regarding life cycle costs showed that results are highly dependant on inflation rate considered as well as the payment/financing method used to acquire the conditioning equipment. Results indicate that heat pumps are highly beneficial compared to fossil based or purely electric systems in Sweden and Germany while split systems have lower life cycle costs in Greece. For fossil and purely electric systems in Greece, as well as split systems in Sweden and Germany, results are inconclusive.


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TESS (2004). Type 665:Air Source Heat Pump (Split System Heat Pump), Type 700:Simple Boiler with Efficiency Inputs, Type 668:Water-Water Heat Pump, Thermal Energy Systems Specialists

TRANSSOLAR (2004). Multizone Building modeling with Type56 and TRNBuild, TRNSYS User Manual Vol. 6, TRANSSOLAR Energietechnik GmbH, http://www.transsolar.com

VDI 4640 (1998). Richtlinie, Thermische Nutzung des Untergrundes, Erdgekoppelte Wärmepumpen. VDI-Gesellschaft Energietechnik, Düsseldorf; Beuth Verlag

VDI 6002 (2007). Solare Trinkwassererwärmung - Anwendungen in Studentenwohnheimen, Seniorenheimen, Krankenhäusern, Hallenbädern, und auf Campingplätzen, Düsseldorf; Beuth Verlag

Yavuzturk C. (1999). Modeling of Vertical Ground Loop Heat Exchangers for Ground Source Heat Pumps Systems. PhD Thesis. Oklahoma State University

Yavuzturk C., Spitler, J.D. (1999). A Short Time Step Response Factor Model for Vertical Ground Loop Heat Exchangers. ASHRAE Transactions, Volume 105, No. 2.

Yavuzturk C., Spitler, J.D. (2001). Field Validation of a Short Time Step Model for Vertical Ground-Loop Heat Exchangers. ASHRAE Transactions, Volume 107, No. 1.


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Project Description The GROUND-REACH project is expected to effectively assist EU policy towards both short and long term market penetration of ground coupled heat pumps, through analysing the market for ground coupled heat pumps and providing best practices, guidelines for local/regional authorities and key professional groups, conferences, meetings, website, brochure and other promotional tools. It will facilitate: A better understanding of ground coupled heat pumps merits and benefits and their importance towards Community policy objectives in relation to Kyoto targets and the buildings performance directive. An increased awareness and improved knowledge and perception of the ground coupled heat pumps technology among key European professional groups for short term market penetration. The work is grouped in the following work packages:

WP#1 – Project management

WP#2 - Estimating the potential of ground coupled heat pumps for reducing CO2 emissions and primary energy demand for heating and cooling purposes in the built environment: evaluation of available statistical information, definition of competing heating/cooling technologies, analysis of existing calculation tools, CO2 emissions calculation.

WP#3 - Compiling and evaluating existing ground coupled heat pumps best practice information in Europe: identifying and updating information from all European member states, including case studies, and technical guidelines.

WP#4 - Analysing the contribution of ground coupled heat pump technologies to reach the objectives of the Buildings Performance Directive: Analysis of the technical, environmental and economic feasibility of ground coupled heat pump technologies; Guideline for supporting planners and architects in detailed technical aspects and in general questions; Standards review, evaluation and proposals.

WP#5 - Defining measures to overcome barriers for broader market penetration and setting up a long term dissemination plan: identification of market barriers including legal/ regulatory, economical and technical, proposals for long term EU level interventions to overcome them, including a new directive on RES-Heat.

WP#6 - Launching a large scale promotional campaign at European level: brochure, poster, promotional text, presentations, interactive Internet site, setting-up the European Geothermal Heat Pump Committee, publications, international conference and exhibition, a series of regional meetings targeting key professional groups.

WP#7 - Common dissemination activities


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Project partners

Project Co-ordinators: Centre for Renewable Energy Sources (Greece)

European Geothermal Energy Council (EGEC)

European Heat Pump Association (EHPA)

Österreichisches Forschungs- und Prüfzentrum Arsenal Ges.m.b.H (ARSENAL)

Bureau de Recherches Géologiques et Minières (BRGM)

SVEP Information & Service AB (SVEP)

University of Oradea (UOR)

BESEL S.A. (BESEL)

COWI A/S (COWI)

Ellehauge & Kildemoes (E & K)

Flemish Institute for Technological Research (VITO)

Ecofys Netherlands b.v. (ECOFYS)

The Energy Efficiency Agency (EEA)

Escola Superior De Tecnologia De Setubal (ESTSetubal)

Fachinformationszentrum Karlsruhe Gesellschaft für wissenschaftlich-technische Information mbH

Geoteam Technisches Büro für Hydrogeologie, Geothermie und Umwelt Ges.m.b.H (GEOTEAM)

Associazione Rete di Punti Energia (PUNTI ENERGIA)

Agence de l'environnement et de la Maîtrise de l'energie (ADEME)

Narodowa Agencja Poszanowania Energii S.A. (NAPE)

EnPro Engineers Bureau Ltd (ENPRO)

GFE Energy Management (GFE)


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A.I Building Simulations Inputs

Deliverable 7 involves the study of many building types in different climates. The building types include:

• A single family house • A multi unit residential building • A combined retail and office building • A hotel

And the climates

• Cold (Sweden) • Temperate (Germany) • Warm (Greece)

Average buildings dimensions vary from country to country and it would be a large task to model a different building for every case studied. Therefore, only one version of each of these four buildings is modelled and results are presented in values of loads and gains per surface area instead of absolute values. This way, absolute loads can easily be extrapolated, without need to create new building models, by multiplying by the average floor area in each country. Furthermore, two versions of each of these buildings, which seem like the most susceptible to have heat pumps installed, are studied: a building with a certain age (described as the lower efficiency case) representing a large portion of the existing buildings stock - and a recent, more energy efficient building, which would represent the actual and future direction of building practices in Europe. Table AI.1 describes the characteristics of the two types of buildings selected. Details on how these values were determined are given in sections AI.2 and AI.3. The other sections describe these buildings and the various parameters used for simulations.


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Table AI.1 Characteristics of the buildings studied Lower energy efficiency Higher energy efficiency

Infiltrations (ACH)

0.5 0.15

Ventilation 2 ACH for retail/office None for other buildings

2 ACH for retail/office 0.5 ACH for other buildings

HRV Eff=70% @ 0°C Eff=75% @ -25°C Eff = 50% in cooling

U-Value (W/m2.K) Cold climatic zone Roof 0.20 0.13 Façade 0.30 0.17 Floor 0.20 0.17 Windows 1.60 1.33 Temperate climatic zone Roof 0.50 0.23 Façade 1.00 0.38 Floor 0.80 0.41 Windows 2.00 1.68 Warm climatic zone Roof 1.00 0.43 Façade 1.40 0.48 Floor 1.00 0.48 Windows 3.50 2.71

A.I.1 Buildings geometrical descriptions This section describes the geometries of the buildings modelled. Dimensions are provided but should not really be considered as directly representative of the particular regions studied since every input and output are expressed in relation to conditioned floor area. A.I.1.1 Single family house

The simulated single family house is illustrated in Figure AI.1. It is composed of an unconditioned basement (UG), two floors (AG0 and AG1) and an unconditioned attic (AT). Each floor has a 70 m2 area and the height of inhabited floors is 2.7 m. The house is assumed to be oriented to the south where its main window coverage is located. The resulting geometrical characteristics impacting heat exchanges are presented in Table AI.2.


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Figure AI.1 Single family house Table AI.2 Geometrical characteristics of the single family house

Zone UG E0 E1 AT Colour Red Orange Green White Gross Volume (m3) 190 190 190 95 Area exposed to ambient (m2) 164 94 94 145 Window area south (m2) 0 10.96 2.9 0 Window area east (m2) 0 4.84 2.86 0 Window area north (m2) 0 4.34 2.58 0 Window area west (m2) 0 2.42 1.43 0


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A.I.1.2 Multi units residential building The multi units residential building is illustrated in Figure AI.2. It is composed of 15 dwellings, resulting in a total conditioned floor area of 1290 m2. The building is oriented facing south-west, so two faces have sun exposure during most of a day. The resulting geometrical characteristics impacting heat exchanges are presented in Table AI.3.

Figure AI.2 Multi unit residential building Table AI.3 Geometrical characteristics of multi unit residential building

E0

E1

E2

Zone UG

Dwell. Public Dwell. public Dwell. public

AT

Colour Red orange Green Blue green brown green whiteGross Volume (m3) 1274 1146 127 1146 127 1146 127 670 Exposed Area (m2) 625 236 0 236 0 236 0 534 Window area SE (m2) 0 15.4 0 15.4 0 15.4 0 0 Window area SW (m2) 0 23.1 0 23.1 0 23.1 0 0 Window area NW (m2) 0 14 0 14 0 14 0 0 Window area NE (m2) 0 23.1 0 23.1 0 23.1 0 0


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A.I.1.3 Office & retail building This combined building is assumed to have the same shape and dimensions as the multi family residential building, only a different floor plan and window repartition. Figure AI.3 presents the different floor plans of the building. The retail part of the building (left image - ground floor), is based on a supermarket project simulated by arsenal research. The office part (right image - upper floors) is based on an office building modelled for Annex 48 of the IEA. The original dimensions of the IEA building are not used but the general characteristics like the floor area repartition, the fraction of the façade occupied by windows, etc. are reproduced. Table AI.4 presents the heat transfer geometrical characteristics of this building.

Figure AI.3 Office & retail building

Table AI.4 Geometrical characteristics of office & retail building

Floor UG Ground

Zone Regular Sales

Chilled Sales

Regular storage

Chilled storage Employee

Gross Volume (m3) 1274 828 204 153 38 51

Exposed Area (m2) 625 165 29 21 24

Window area SE (m2) 0 0 0 0 2

Window area SW (m2) 0 0 0 0 0

Window area NW (m2) 0 47 0 0 0

Window area NE (m2) 0 0 0 0 0

Floor 1st , 2nd Floors

Zone Office Meeting room Washrooms Circulation Attic

Gross Volume (m3) 764 268 38 204 670

Exposed Area (m2) 141 55 25 17 534

Window area SE (m2) 0 0 0 0 0

Window area SW (m2) 19 18 0 0 0

Window area NW (m2) 0 0 0 0 0

Window area NE (m2) 31 0 2.5 2.5 0


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A.I.1.4 Hotel The building used to simulate the behaviour of a hotel is presented in figure AI.4. The zone repartition is based on a relatively large low budget hotel with no restaurant, pool, training, etc. facilities: only rooms, a reception on the ground floor and circulation zones. The geometry and characteristics are similar to the multi-units residential building presented in section AI.1.2 except that building dimensions are doubled (floor area quadrupled) in order to obtain higher conditioning loads. Table AI.5 presents its heat transfer geometrical characteristics.

Figure AI4 Hotel (left = ground floor, right = upper floors)

Table B5 Geometrical characteristics of hotel

Floor UG Ground Floor

Zone Reception Rooms Wash-rooms Circulation

Gross Volume (m3) 5096 1019 2548 510 1019

Exposed Area (m2) 0 107 278 93

Window area SE (m2) 0 13 0 16

Window area SW (m2) 0 0 36 10

Window area NW (m2) 0 0 27 3

Window area NE (m2) 0 21 26 0

Floor 1st, 2nd Floor Attic

Zone Rooms Wash-rooms Circulation

Gross Volume (m3) 3822 764 510 2680

Exposed Area (m2) 459 19 2136

Window area SE (m2) 27 3 0

Window area SW (m2) 47 0 0

Window area NW (m2) 27 3 0

Window area NE (m2) 47 0 0


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A.I.2 Buildings energy efficiency As previously mentioned, two levels of energy efficiency are modelled for each building. The lower level of energy efficiency involves lower insulation values and higher infiltrations. The higher level involves better insulation and air tightness as well as heat recovery ventilation. A.I.2.1 Insulation

U-values of building components were obtained from Table 6 of Deliverable 1 (Lindner & Bhar, 2007). Since there is no distinction regarding the building applications in that table (the table is for all building stock), these U-Values are used for all buildings studied in the course of the present work package. U-Values for different building components in different climates are presented in Table 2.2 and explained in the following paragraphs. It is assumed that older buildings susceptible to have a heat pump installed would probably also have some degrees of retrofitting. Values in Table 6 of Deliverable 1 for buildings built before 1975 and renovated are very similar to values for buildings built between 1975 and 1990. Therefore these values are used for the lower efficiency scenario since they cover a large share of the building stock. In recent years, there has been a strong push for more energy efficient buildings and it seems to be the way building construction is headed in Europe. Since it is hard to predict the future, this work will not use some of the extreme U-values proposed elsewhere but high standards currently used on a large scale, which are represented in Table 6 of Deliverable 1 as the buildings built or retrofitted after 2006. Meanwhile, we will keep in mind that they are probably destined to improve in the near/medium future. Table 2.2 U-values used in the course of Work Package 4 U-Value W/m2.K

Lower energy efficiency Higher energy efficiency

Cold climatic zone Roof 0.20 0.13 Façade 0.30 0.17 Floor 0.20 0.17 Windows 1.60 1.33 Temperate climatic zone Roof 0.50 0.23 Façade 1.00 0.38 Floor 0.80 0.41 Windows 2.00 1.68 Warm climatic zone Roof 1.00 0.43 Façade 1.40 0.48 Floor 1.00 0.48 Windows 3.50 2.71


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A.I.2.2 Ventilation and infiltrations It has been customary in the past to allow a certain amount of infiltrations in small buildings in order to ensure good indoor air quality: a technique called passive or natural ventilation. According to a number of sources, typical air infiltrations rates for current buildings are around 0.45 ACH (air changes per hour). This results in relatively good air quality and do not warrant the use of mechanically assisted ventilation for residential applications. Therefore, this strategy is used for the lower energy efficiency standard modelled except for the combination office/retail building which requires 2 ACH supplementary ventilation since it is more densely occupied. Heat recovery is assumed for this ventilation rate since it would make no sense to invest in a heat pump without first investing in a recovery system considering that the main heating loads come from the ventilation for these cases. For the high efficiency case, many sources state a maximum around 0.15 ACH. Petersdorff & al., for example, use 0.1 ACH for the residential sector and 0.2 ACH for offices for their calculations. The present work uses 0.15 ACH. This infiltration rate is not sufficient to ensure good air quality and has to be assisted with mechanical ventilation. Since the main reason to replace infiltrations with ventilation is energy efficiency, the ventilation system is equipped with a typical heat recovery exchanger. Ventilation rates used are 2 ACH for the combination office/retail building and 0.5 ACH for all other buildings. Ventilation is assumed to be continuous since optimising ventilation strategy is outside the scope of the current work. A.I.2.3 Shading

Shading of the building façade is a complex topic and depends on a wide range of environmental factors (building location, urban density, vegetation, etc). Shading of the windows also depends on occupants behaviours. Seriously taking into account shading would be a major study in itself and is not the goal of the Ground-Reach project. Therefore, all building façades are assumed to have a view factor to the sky of 0.5. Shading of south facing windows is assumed to be operative, only for residential buildings, offices and hotels, when solar radiation is in excess of 600 W/m2 on the horizontal plane. This results in 2066 hr/year of shading for Greece, 953 hr/year for Germany and 327 hr/year for Sweden. Window shading devices are assumed to be on the exterior of windows for the residential sector and on the inside of the windows for hotels. The devices are also assumed to block 50% of the incoming radiation. A.I.2.4 B.5 Setbacks

Although they have been proven to be a very efficient way to reduce energy consumption of buildings, and should definitely be considered in the frame of Buildings Performance Directive1, no setbacks on the temperatures are accounted for in the simulations and temperature setpoints are assumed to be 21°C in heating mode and 26°C in cooling mode.


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Optimizing the setback strategy of a building is a relatively time consuming task and not the objective of Work Package 4.

A.I.3 Internal gains Internal gains are divided in three categories: people (occupancy), lighting and equipment. Occupancy data for the residential sector are provided in table 3 of Ground-Reach Deliverable 1 (2007). For Germany and Sweden, they are respectively 2.2 and 2.1 occupants per dwelling. Since table 3 contained no data for Greece, an occupancy of 2.8 is assumed based on data for the year 2000 in section 1.9 of the source used for D1, Housing Statistics in the European Union (2005). All other data and schedules regarding internal gains are based on the National Calculation Method (NCM, BRE, 2007) database. This well researched database is used extensively for energy calculations of different types of buildings. The following sections describe the internal loads and schedules used for this work. A.I.3.1 Internal gains for simulations of single family houses

Occupancy

Since results are expressed in values per square meters of dwelling area, the number of occupants per dwelling previously mentioned is converted in a number of occupants per square meter in order to obtain the same relative heat generation effect on the building. According to section 2.1 of the report Housing Statistics in the European Union (2005), the average useful floor area per dwelling is: 89.7 m2 in Germany, 82.7 m2 in Greece and 91.6 m2 in Sweden. This yields, using values of occupants per dwelling previously mentioned:

• 0.0245 occupants/m2 for Germany • 0.0339 occupants/m2 for Greece • 0.0229 occupants/m2 for Sweden

Each occupant is assumed to emit 150 W of heat (ISO 7730 value for seated occupants doing light work), 75 W sensible and 75 W latent. According to ASHRAE (2000), a sleeping occupant produces about 70 W of heat. Since the simulation software allows for only one type of occupant, it was assumed that sleeping individuals account for 0.47 occupants each. For the course of this work, the following assumptions are made about the repartition of floor area in the house:

• Ground floor: Living room (50%), Dining room (40%), Kitchen (10%) • First floor: Bedrooms (90%), Washroom (10%)

These yields, taking into account the schedules proposed by the NCM database for occupancy in each of these zones, which are not reproduced here for compactness sake, the following occupancy schedule for the two floors.


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Occupancy, Weekdays (area & activity weighted)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

1 3 5 7 9 11 13 15 17 19 21 23

Hour of Day

Occ

upoa

ncy

Frac

tion

Ground FloorFirst Floor

Occupancy, Weekends (area & activity weighted)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

1 3 5 7 9 11 13 15 17 19 21 23

Hour of Day

Occ

upoa

ncy

Frac

tion


Figure AI.5 Occupancy for single family houses

Lighting

The NCM database recommends light intensities (lux) for different zones in residential buildings. For the course of this work, an efficient lighting system which would generate about 3.3 W/m2/100 lux, 20% of which is radiant, is assumed. The NCM database also proposes schedules for lighting. Adjusting them for light intensity and areas of the different zones yields:

Lighting, Weekdays (area & intensity weighted)

0

1

2

3

4

5

6

1 3 5 7 9 11 13 15 17 19 21 23

Hour of Day

Ligh

ting,

W/m

2


Lighting, Weekends (area & intensity weighted)

0

1

2

3

4

5

6

7

8

9

1 3 5 7 9 11 13 15 17 19 21 23

Hour of Day

Ligh

ting,

W/m

2


Figure AI.6 Lighting for single family houses

Since it is customary to shut down electric lights in the residential sector when natural light is sufficient, they are assumed to be close them when solar radiation on the horizontal plane is higher than 50 W/m2. Equipment

The NCM database also recommends intensities (W/ m2) and schedules for heat generated from equipments in the different zones of a residential building. Weighting these values for the different zones previously defined yields:


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Equipment, Weekdays (area & intensity weighted)

0

1

2

3

4

5

6

7

8

9

1 3 5 7 9 11 13 15 17 19 21 23

Hour of Day

Equi

pmen

t, W

/m2


Equipment, Weekends (area & intensity weighted)

0

1

2

3

4

5

6

7

8

9

1 3 5 7 9 11 13 15 17 19 21 23

Hour of Day

Equi

pmen

t, W

/m2


Figure AI.7 Equipment for single family houses

A.I.3.2 Internal gains for simulations of multi units residential buildings

Occupancy Using the same data and methodology as in section A.I.3.1, but assuming this time that all zones are located on the same floor, yields the following occupancy schedules.

Occupancy (area & activity weighted)

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

1 3 5 7 9 11 13 15 17 19 21 23

Hour of Day

Occ

upoa

ncy

Frac

tion

WeekdaysWeekends

Figure AI.8 Occupancy for multi units residential buildings

Lighting Again, the data and methodology are the same as in section A.I.3.1 since they also concern the residential sector. This yields:


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Lighting (area & intensity weighted)

0

1

2

3

4

5

6

7

1 3 5 7 9 11 13 15 17 19 21 23

Hour of Day

Ligh

ting,

W/m

2

WeekdaysWeekends

Figure AI.9 Lighting for multi units residential buildings

Equipment Using the same data and methodology as in section A.I.3.1 yields:

Equipment (area & intensity weighted)

0

1

2

3

4

5

6

7

8

9

1 3 5 7 9 11 13 15 17 19 21 23

Hour of Day

Equi

pmen

t, W

/m2

WeekdaysWeekend

Figure AI.10 Equipment for multi units residential buildings

A.I.3.3 Internal gains for simulations of office & retail buildings

The following area repartition is based on a supermarket simulated by Arsenal in the course of a project and an office building previously used in the course of Annex 48 of the IEA (Ransquin, 2008):

• Upper floors (offices): Circulation (16%), Offices (60%), Meeting rooms (21%), Washrooms (3%)

• Ground floor (retail): Regular sales (65%), Chilled sales (16%), Regular storage (12%), Chilled storage (3%), Employees rooms (4%)


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Occupancy The NCM database recommends intensities and schedules for occupancy of the zones previously defined. Once adjusted for the area repartitions, these result in the following occupancy:


0

0.02

0.04

0.06

0.08

0.1

0.12

1 3 5 7 9 11 13 15 17 19 21 23

Hour of Day

Occ

upoa

nts/

m2

WeekdaysWeekends


0

0.01

0.020.03

0.04

0.05

0.06

0.070.08

0.09

0.1

1 3 5 7 9 11 13 15 17 19 21 23

Hour of DayO

ccup

oant

s/m

2

WeekdaysSaturdaySunday

Figure AI.11 Occupancy for office (left) & retail (right) floors

Lighting Using the same procedure as in section A.I.3.1 and the NCM data for offices and retail zones yields:


0

2

4

6

8

10

12

14

1 3 5 7 9 11 13 15 17 19 21 23

Hour of Day

Ligh

ting,

W/m

2

WeekdaysWeekends


0

24

6

810

12

14

1618

20

1 3 5 7 9 11 13 15 17 19 21 23

Hour of Day

Ligh

ting,

W/m

2


Figure AI.12 Lighting for office (left) & retail (right) floors

Equipment The same procedure results in the following heat generation from equipments:


0

2

4

6

8

10

12

1 3 5 7 9 11 13 15 17 19 21 23

Hour of Day

Equ

ipm

ent,

W/m

2

WeekdaysWeekend


0

12

3

45

6

7

89

10

1 3 5 7 9 11 13 15 17 19 21 23

Hour of Day

Equi

pmen

t, W

/m2


Figure A.I.13 Equipment for office (left) & retail (right) floors


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A.I.3.4 Internal gains for simulations of hotels The following zone repartition is assumed for simulation of a hotel:

• Ground Floor: Reception (20%), Rooms (50%), Washrooms (10%), Public (20%) • Upper floors: Rooms (75%), Washrooms (15%), Public spaces (10%)

Following the same method as in section A.I.3.3 with this zone repartition and the NCM data for hotels yields: Occupancy

Occupancy (area & activity weighted)- Ground floor

0

0.005

0.010.015

0.02

0.025

0.03

0.0350.04

0.045

0.05

1 3 5 7 9 11 13 15 17 19 21 23

Hour of Day

Occ

upoa

nts/

m2

WeekdaysWeekends

Occupancy (area & activity weighted)- Other floors

0

0.005

0.01

0.015

0.020.025

0.03

0.035

0.04

0.045

0.05

1 3 5 7 9 11 13 15 17 19 21 23

Hour of Day

Occ

upoa

nts/

m2

WeekdaysWeekends

Figure AI.14 Occupancy for hotels

Lighting Lighting (area & intensity weighted)- Ground floor

0

0.5

1

1.5

2

2.5

3

3.5

4

1 3 5 7 9 11 13 15 17 19 21 23

Hour of Day

Ligh

ting,

W/m

2

WeekdaysWeekends

Lighting (area & intensity weighted)- Other floors

0

0.5

1

1.5

2

2.5

3

3.5

4

1 3 5 7 9 11 13 15 17 19 21 23

Hour of Day

Ligh

ting,

W/m

2

WeekdaysWeekends

Figure AI.15 Lighting for hotels

Equipment

Equipment (area & intens. weighted)- Ground floor

0

1

2

3

4

5

6

7

1 3 5 7 9 11 13 15 17 19 21 23

Hour of Day

Equi

pmen

t, W

/m2

WeekdaysWeekend

Equipment (area & intens. weighted)- Other floors

0

1

2

3

4

5

6

7

1 3 5 7 9 11 13 15 17 19 21 23

Hour of Day

Equi

pmen

t, W

/m2

WeekdaysWeekend

Figure AI.16 Equipment for hotels


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A.II Systems Design This section describes the design procedure used to conceive all the systems simulated in the course of this work. Design starts from the heating design loads presented in section 3.1.1 which are used to determine the required capacity. From there all components are sized according to procedures presented in the following sections.

A.II.1 Heat Pump Systems Heat pump systems are assumed to include:

• A heat pump; • A buffer on the load side; • A vertical ground loop; • A pump for the ground loop.

Pumping on the load side is not considered since there are too many unknown about distribution and the pumping would be required no matter what conditioning system is used. The design of each component is described in the following sections. The resulting systems are described in Table AII.1. Table AII.1 Heat pump systems Building Climate Efficiency Heat Pump

kW Buffer Litres

Ground Loop Boreholes: nX x nY x Length

Low 7 245 2 x 1 x 81 Cold

High 5 175 1 x 1 x 104 Low 10 350 2 x 1 x 81

Temperate High 5 175 1 x 1 x 85 Low 10 350 3 x 1 x 76

SFH

Warm High 5 175 2 x 1 x 74 Low 50 1750 4 x 3 x 113

Cold High 25 875 3 x 3 x 91 Low 60 2100 4 x 3 x 96


MFH




Office Retail




Hotel

Warm High 80 2800 6 x 5 x 85


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A.II.1.1 Heat Pumps Heat pumps are sized according to the heating design loads presented in figure 3.1. The flows circulating through the heat pump are water on the load side and a 30% solution of water and ethylene-glycol on the source side. Flows of these heat transport fluids are fixed in order to obtain temperature differences of 6°C for water at the condenser and 4° C for water/glycol at the evaporator. Assuming a COP of 4.5, the resulting flow rates are:

• 145 l/hr/ kWHP at condenser • 210 l/hr/ kWHP at evaporator

Where kWHP is the installed heat pump capacity. The heat pump model used for simulations is Type 668 of the TESS HVAC library (TESS 2004) which simulates a water-water heat pump. Type 668 is a simple manufacturer inputs based model which interpolates the heat pump performances from a set of inputs. The heat pump is switched on and off and told whether it is operating in heating or cooling mode by control signals. Data used for simulations come from measurements made at arsenal research on a relatively efficient model. The COP (Coefficient Of Performance) obtained during those measurements are presented in Figure AII.1.

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

-10 -5 0 5 10 15 20

Source Temperature, °C

CO

P H

P H

eatin

g TLoad=10TLoad=20TLoad=35TLoad=40TLoad=45TLoad=55

2.0

2.5

3.0

3.5

4.0

4.5

0 10 20 30 40 50

Source Temperature, °C

CO

P H

P C

oolin

g

TLoad=0TLoad=5TLoad=15

Figure AII.1 Heat Pumps COP: Heating (Left) and Cooling (Right)

A.II.1.2 Buffers Buffers are sized according to the criteria of 35 l/kWHP (Bundesamt für Energie, 2002) where kWHP is the installed heat pump capacity. Temperature control of the buffer will be made by switching the heat pump on when temperature at the bottom of the buffer tank (heat pump condenser inlet) is lower than 24°C and switching it off when that temperature exceeds 29°C. All tanks are assumed to have optimized dimensions to reduce heat losses. This means that the area/volume ratio is minimized, resulting in the following dimensions:


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31

2⎟⎠⎞

⎜⎝⎛=π

Vr 2rVH×

=π

Where H is the height of the tank (m), r is its radius (m) and V is its volume (m3). Tanks are also assumed to be located in the building’s basement where they do not influence the conditioning loads. Furthermore, they are assumed to have 80 mm PU insulation for sizes smaller than 750 liters and 100 mm for larger tanks. A.II.1.3 Ground loops Ground loops are originally sized using a procedure explained in Bernier et al. (2000a and 2008). The method is an extension of the work of Kavanaugh and Rafferty (1997) and consists in designing the loop to be capable of handling successively 10 years of average annual loads, followed by 1 month of monthly peak load and, finally, 6 hours of hourly peak load. Readers are referred to the Bernier et al. article for details of the calculation. Since the method requires the heat pump COP which is not always easy to estimate, the boreholes are designed using this procedure, simulated and then redesigned using an extrapolation of the lowest/highest temperature encountered during the simulation to the design value. This extrapolation has the form:

heatingdesignFF

simulationFFfinitialheat TT

TTLL

,

min,

−

−= For the heating length

FFcoolingdesign

FFsimulationfinitialcool TT

TTLL

−

−=

,

max, For the cooling length

Where: • The final length is the maximum of Lheat and Lcool (m) • TFF is the undisturbed ground (far field) temperature (°C) • Tmin,simulation and Tmax,simulation ar the maximum and minimum return temperature from

the bore-field encountered during the simulation (°C) • Tdesign,heating and Tdesign,cooling are the maximum and minimum return temperature the

considered acceptable by the system designer (°C). Values used for the present work are:

o -5 °C heating, 30 °C cooling for cold climate; o -5 °C heating, 30 °C cooling for temperate climate; o 0 °C heating, 35 °C cooling for the warm climate.

Systems are simulated using a model similar to the one described in Pinel (2003) and Bernier & al. (2004). The model consists in resolving the local heat transfer around a borehole using the cylindrical heat source equation (Carslaw & Jaeger 1947, Ingersoll et al. 1954), and superposing a temperature penalty, evaluated using the finite volume method (Patankar, 1980), to take into account thermal interactions among boreholes. The main differences between the model developed for this Ground-Reach work package and the previous work of


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Pinel is that the new model is tri-dimensional and has adiabatic boundaries which can be moved to simulate another neighbouring system, while the original model by Pinel was two-dimensional and had fixed boundaries assumed to be at the far field temperature. Many inputs had to be fixed in order to complete this project. Table AII.2 provides an overview of the borehole field design. Table AII.2 Bore-field assumptions

Parameter Assumption NB_X Number of boreholes in the X direction NB_Y Number of boreholes in the Y direction

Set to maintain borehole length at around 100 m See last column of Table AII.1 for values

Distance between boreholes in the X direction Distance between boreholes in the Y direction 8 m

Length of each borehole (top to bottom of the boreholes) See last column of Table AII.1

Depth of the boreholes (distance from ground surface to top of the boreholes) 2 m

Depth at which the water table is located 500 m Distance from the last borehole to the adiabatic far field in each direction (East, West, North, South)

500 m

Borehole diameter 15 cm Number of boreholes connected in series in each parallel branch 1

Tubes dimensions 25 mm SDR-11 Number of U-Tubes in each borehole 1

Location of the U-Tubes in the boreholes Both U-Tube legs located midway between borehole centre and wall

Far field temperature

Average ambient temperature Cold: 5.31°C Temperate: 9.67°C Warm: 17.61°C

Thermal conductivity of the grout or backfill 10% Bentonite (k = 0.73 W/m°C) Thermal conductivity of the tubes HDPE (k = 0.4 W/m°C)

Thermal properties of the ground around the boreholes

Typical soil (limestone) 2.7 W/m°C ρ = 2550 Kg/m3 Cp = 880 J/kg°C

Thermal properties of the ground in the region located on top of the boreholes Same as for the rest of the ground

Thermal properties of the heat transport fluid

Water/Glycol (30%) K = 0.49 W/m°C ρ =1057 Kg/m3 Cp=3726 J/kg°C Mu=0.0035 Kg/ms


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A.II.1.4 Pumping Pumping electricity consumption can be estimated by the relation:

pumpmotorpump

qghQηη

ρ×

×××=

1000&

Where: • h is the pumping head (m) • q& is the flow of heat transfer fluid (l/s) • g is the universal acceleration constant (9.81 m/s2) • ρ is the density of the heat transfer fluid (kg/m3) • ηmotor is the efficiency of the pump’s motor • ηpump is the pumping efficiency

Efficiency can be assumed constant if the pump is consistently working under its design conditions (identical flow and head). So the use of constant efficiencies is valid for this study and the pumping system does not require to be sized for the evaluation of its energy consumption. Combined motor and pump efficiency is assumed to be 0.3 according to EN 1451 part 3 (CEN, 2004). Pumping head is evaluated using the following relation which was derived for the tubes used from procedures and data from Kavanaugh & Rafferty (1997):

6.404.0/

0205.0/

2679.02

+×+⎟⎟

⎠

⎞

⎜⎜

⎝

⎛+⎟⎟

⎠

⎞⎜⎜⎝

⎛= header

seriesboreholesseriesboreholesboreholepump L

nnq

nnqLh

&& (5.4)

Where nseries is the number of boreholes connected in series, q& is the total flow at the evaporator of the heat pump and Lheader is the total header length (twice the distance from the heat pump to the last borehole).

A.II.2 Boiler Systems Boiler efficiencies are often expressed as AFUE (Annual Fuel Usage Efficiency). This seasonal efficiency takes into account part load boiler operation, i.e. the efficiency losses when a boiler has to switch on and off and must therefore constantly warm itself before contributing to space heating. Typical AFUEs for boilers are (Defra 2008):

• 55% for old heavy weight model • 65% for old lightweight model • 78% for new non-condensing model • 88% for new condensing model


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Efficiencies of boilers vary significantly, meaning that guesses have to be made on boiler efficiency. Furthermore, WP4 is only interested with annual energy consumptions, not precise transient behaviour. Therefore, no effort is made to model part-load operation to estimate the transient behaviour of boilers at every time step and values of AFUE are used directly to convert the heating load to energy consumption. Lower efficiency buildings are assumed to be equipped with older boilers while higher efficiency buildings are assumed to have newer ones. Since it would be difficult to guess which technology is present in every building, average values are used for each boiler age. This result in AFUEs of:

• 60% for lower efficiency cases • 83% for higher efficiency cases

A.II.3 Split Systems Split systems, like heat pump systems, are simulated using a manufacturer based model: Type 665 of the TESS HVAC library (TESS 2004). Figure AII.2 presents the COPs assumed for simulation. When the split system operates in heating mode, its performances can be assumed to be a function of ambient dry bulb alone. When it operates in cooling mode, the indoor (load) wet bulb temperature also affects performances. For Work Package 4, indoor humidity is assumed to be constant at 50% RH.

2.0

2.2

2.4

2.6

2.8

3.0

3.2

3.4

3.6

3.8

4.0

-30 -20 -10 0 10 20 30

Ambient Temperature, °C

CO

P S

plit

Hea

ting

2.0

2.2

2.4

2.6

2.8

3.0

3.2

3.4

20 25 30 35 40 45 50

Ambient Temperature, °C

CO

P S

plit

Coo

ling

WBin=15WBin=17.2WBin=19.4WBin=21.7

Figure AII.2 Split systems COP: Heating (Left) and Cooling (Right)

A.II.4 Fully electric systems Fully electric systems are assumed to have a 100% efficiency.

GROUND-REACH

Project Description The GROUND-REACH project is expected to effectively assist EU policy towards both short and long term market penetration of ground coupled heat pumps, through analysing the market for ground coupled heat pumps and providing best practices, guidelines for local/regional authorities and key professional groups, conferences, meetings, website, brochure and other promotional tools. It will facilitate: A better understanding of ground coupled heat pumps merits and benefits and their importance towards Community policy objectives in relation to Kyoto targets and the buildings performance directive. An increased awareness and improved knowledge and perception of the ground coupled heat pumps technology among key European professional groups for short term market penetration. The work is grouped in the following work packages:

WP#1 – Project management

WP#2 - Estimating the potential of ground coupled heat pumps for reducing CO2 emissions and primary energy demand for heating and cooling purposes in the built environment: evaluation of available statistical information, definition of competing heating/cooling technologies, analysis of existing calculation tools, CO2 emissions calculation.

WP#3 - Compiling and evaluating existing ground coupled heat pumps best practice information in Europe: identifying and updating information from all European member states, including case studies, and technical guidelines.

WP#4 - Analysing the contribution of ground coupled heat pump technologies to reach the objectives of the Buildings Performance Directive: Analysis of the technical, environmental and economic feasibility of ground coupled heat pump technologies; Guideline for supporting planners and architects in detailed technical aspects and in general questions; Standards review, evaluation and proposals.

WP#5 - Defining measures to overcome barriers for broader market penetration and setting up a long term dissemination plan: identification of market barriers including legal/ regulatory, economical and technical, proposals for long term EU level interventions to overcome them, including a new directive on RES-Heat.

WP#6 - Launching a large scale promotional campaign at European level: brochure, poster, promotional text, presentations, interactive Internet site, setting-up the European Geothermal Heat Pump Committee, publications, international conference and exhibition, a series of regional meetings targeting key professional groups.

WP#7 - Common dissemination activities

Project partners

Project Coordinator: Centre for Renewable Energy Sources (CRES)

European Geothermal Energy Council (EGEC)

European Heat Pump Association (EHPA)

Österreichisches Forschungs- und Prüfzentrum Arsenal Ges.m.b.H (ARSENAL)

Bureau de Recherches Géologiques et Minières (BRGM)

SVEP Information & Service AB (SVEP)

University of Oradea (UOR)

BESEL S.A. (BESEL)

COWI A/S (COWI)

Ellehauge & Kildemoes (E & K)

Flemish Institute for Technological Research (VITO)

Ecofys Netherlands b.v. (ECOFYS)

The Energy Efficiency Agency (EEA)

Escola Superior De Tecnologia De Setubal (ESTSetubal)

Fachinformationszentrum Karlsruhe G mbH

Geoteam Technisches Büro für Hydrogeologie, Geothermie und Umwelt Ges.m.b.H (GEOTEAM)

Cestec SpA

Agence de l'environnement et de la Maîtrise de l'energie (ADEME)

Narodowa Agencja Poszanowania Energii S.A. (NAPE)

EnPro Engineers Bureau Ltd (ENPRO)

TERA Energy S.r.l. (TERA)

D7-arsenal-Feasibility of ground coupled heat pump technol… · 2014-08-11 · GROUND-REACH...

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