G. Romero (1), J.F. Urchueguía (1), H. Witte (2), W. Cambien (1), T. Magraner (1)

Transcription

1 Proceedngs World Geothermal Congress 2005 Antalya, Turkey, Aprl 2005 Comparatve Study Between a Geothermal Heat Pump System and an Ar-to-Water Heat Pump System for Heatng and Coolng n Typcal Condtons of the European Medterranean Coast G. Romero (), J.F. Urchueguía (), H. Wtte (2), W. Camben (), T. Magraner () () Insttuto de Ingenería Energétca - IIE / Unversdad Poltécnca de Valenca -UPV / Camno de Vera, 4, Valenca, Span : (+34) , emal addr. : jfurchuegua@fs.upv.es (2 ) Groenholland B.V., Valschermkade 26, 059 CD, : (+3) (0) , Amsterdam, The Netherlands Keywords: Coolng, Heatng, Heat Pump, Ground Coupled Heat Exchanger, Performance. ABSTRACT To make a overall assessment of a Ground Coupled Heat Exchanger (GCHE) t s not only mportant to understand the behavour of the GCHE, but also to consder the system n whch t wll operate: ts loads and utlzaton factors (as a functon of clmate condtons and applcaton), effcency (whch also depends on the heat pump) and other system parameters, such as pumpng requrements, long term sol heat mbalance, etc. As part of the European project GEOCOOL [], ths paper shows the results of applyng a methodology developed for the comparatve study between a system combnng a waterto-water reversble heat pump of commercal sze wth a vertcal GCHE and an equvalent ar-to-water heat pump system n typcal condtons of the European Medterranean rm (of great mportance for coolng). For ths purpose, the seasonal system performance factors for heatng and coolng, and the temperature profles of the water n the GCHE for a 25 year perod were calculated for dfferent borehole confguratons and for dfferent backfll materals. In addton, an extensve study of relevant clmatologcal parameters of Valenca-Span was made. These results were transformed nto bn-hour data whch are used for calculatng the seasonal system performance factors for heatng and coolng for the ar-to-water heat pump system. The heat pump propertes have been calculated usng the IMST Group s ART software [2]. Fnally, a comparson was made between the GCHE-system and an ar-to-water heat pump showng the effcency mprovement obtaned for varous groutng materals, and for dfferent GCHE geometres.. INTRODUCTION In many applcatons, the ground temperature n wnter can be up to 5-20 degrees hgher than the ar temperature [3], ths ncreases the capacty and the effcency of a heat pump system. Dependng on the geographc localzaton, heat pump systems wth a ground heat exchanger can show an mprovement n the effcency of the system of 35% n heatng mode compared to the conventonal ar source heat pumps systems. Ths value reaches up to 40-60% n coolng performance. As a consequence of ths, the IMST team of UPV, have been developng ths relatvely new technology whch contrbutes towards energy effcency. The IMST works n assocaton wth other natonal and European nsttutons, and t s the man member n the European project GEOCOOL, whose man am s to show the advantages of usng Ground Heat Exchangers as an energy savng technology n Medterranean Europe. 2. PRE-DESIGN PARAMETERS Based on the energy demand of the GEOCOOL prototype faclty at the UPV, the performance data of the heat pump and the local geology and geo-hydrology, have resulted n a pre-desgn consstng of sx boreholes n a rectangular 3 x 2 confguraton, to a depth of 50 meters. When we consder the applcaton of the GEOCOOL concept for the whole regon, t s obvous that the sze and constructon of the borehole heat exchanger may dffer between regons, e.g. due to the need to use an ant-freeze soluton or due to legslaton requrng specfc backfll materals. To be able to defne proper szng rules and to extend the theoretcal work t has been decded to construct dfferent borehole confguratons for the GEOCOOL experment. The followng alternatve borehole completons wll be mplemented: backfll wth coarse sand wth spacers backfll wth fne sand wthout spacers, backfll wth fne sand wth spacers, backfll wth 0% bentonte n water wth spacers backfll wth 2% bentonte mxed wth fne sand wth spacers. Other parameters used n the pre-desgn process are: GROUND (test IN-SITU): Ground thermal conductvty:.6 W/m K, Volumetrc heat capacty: 2.4MJ/m3 K Ground surface temperature: 8.5 C. BOREHOLE: Confguraton: 6 : 3 x 2, rectangle, Borehole depth: 50 m, Borehole spacng: 3 m, Borehole dameter: 0.4 m, U-ppe dameter: Polyethylene PE00, DN ¼,PN 0. HEAT CARRIER FLUID: Water, HEAT PUMP: IZE70 (Catesa) [4], CIRCULATION PUMP: CH 4-20 (Grundfos). Addtonally, a study of heatng and coolng loads for the GEOCOOL buldng was done (Fgure ). It s mportant to

2 realze that the load calculated for the month of August s zero correspondng to the vacaton perod of the unversty. Fgure: Load Profle Geocool Buldng It can be seen n Fgure that the values of the thermal loads are gven n kwh, beng postve for heatng requrements and negatve for coolng requrements. The software used for the evaluaton of the heatng and coolng load profle s CALENER [5]. 3. RESULTS AND DISCUSSION 3. Water temperature profle n the GCHE 3.. Evoluton of the water temperature for dfferent backfll materals To nvestgate how the dfferent backfll materals nfluence the evoluton of the temperature of the water, calculatons have been made of the temperature response of the system to a steady peak load. The results are presented n Fgures 2 & 3). Fgure3: Modellng results for fve dfferent vertcal borehole confguratons n coolng condtons. As s evdent from the graphs, the man effect s the temperature dfference needed to overcome the thermal resstance of the borehole gven a specfc heat flux. The thermal conductvty vares from 0.7 W/m.K for the 0% bentonte n water flled borehole wth 0.083m spacers to 2.4 W/m.K for the borehole flled wth coarse sand. Ths gves a temperature dfference of 3.49 ºC durng heatng of the buldng (2.8 kw net load) and of 6.95 ºC durng the coolng load (7.6 kw net load). The dfferences are very pronounced for the system usng coarse sand as backfll materal and the system usng 0% bentonte n water as backfll materal. The use of spacers s especally useful n a borehole backflled wth bentonte, n whch case the dstance between the up- and down legs has a bg nfluence. The boreholes wth ntermedate conductvtes show only small effects of thermal resstance and spacers. These dfferences n temperature wll probably be dffcult to measure adequately as there wll be other perturbatons n the data whch may, mask the effect of fllng materal and spacers. It wll be very nterestng to see f these theoretcal calculatons are reproduced by the expermental data. Fgure 2: Modellng results for fve dfferent vertcal borehole confguratons n heatng condtons. Fgures 2 and 3 shows the senstvty of temperature evoluton to the type of groutng used and ts assocated thermal conductvty n heatng and coolng respectvely.. A 0% bentonte n water grout gves a poor thermal conductvty compared to the coarse sand grout. Fgure 4: Average temperature profle of the water n the GCHE Fgure 4 shows the average temperature profle of the water nsde the ground heat exchanger for a 25 years perod.. The desgn parameters gven above are used to do ths analyss, usng 0% bentonte n water as the backfll materal. Results shown here were obtaned usng two dfferent software packages, EED [6] and GLHEPRO [7]. It can be seen that the average temperature of the water over the years s ncreased by 2.6 ºC at the end of the 25 year perod because the annual coolng load s hgher than the annual heatng load. 2

3 As an example, Fgure 5 shows the peak temperature profle for the 5 dfferent backfll materals consdered for the 24 and 25th year, when the hghest temperatures are reached. Fgure 6: Maxmum and mnmum temperature profle of the water n the GCHE for some borehole confguratons. Fgure 5: Peak temperature profle for the water n the GCHE for 5 knds of backfll materals. Fgure 6 showsn that 0% bentonte n water s the backfll materal whch results n the hghest temperatures, reachng 4.27ºC n the 25th year supposng an 8 hour peak load. The analyss shows that the best behavour wth respect to the hghest temperature of the water s acheved wth coarse sand wth spacers (SS=0.083m) as a backfll materal where the temperature reaches the maxmum of 34.22ºC n the 25th year. Ths demonstrates the mportance of the thermal conductvty of the backfll materal n the nstallaton desgn. The thermal conductvty of the 0% bentonte n water s 0.7 W/mK whle ths value rses to 2. W/mK for the sand. It s also observed that ntermedate values among those mentoned above are obtaned wth other backfll materals for the same desgn condtons. Another very mportant factor s the use of spacers; for example, the maxmum temperature reaches 36.86ºC for coarse sand wthout spacers n the 25th year, whch s 2.54ºC hgher than the temperature obtaned wth the same backfll materal but usng spacers (Shank Spacng = 0.083m) Effect of dfferent borehole confguratons on the water temperature Once the effect of dfferent backfll materals on the water temperature was known, the effect of dfferent borehole confguratons was studed. Fve confguratons were compared: 2 n lne (5x and 6x) and 3 n rectangle (2x2, 3x2, 4x2). The same desgn parameters were assumed for all of them usng the worst backfll materal (0% bentonte n water) and a total heat exchanger length of 600 meters. 3.2 Estmaton of seasonal system performances for the GCHE of the Geocool system The Seasonal Performance Factor s the rato between the thermal energy provded to/extracted from the buldng (heatng/coolng thermal load) and the suppled electrcal energy used for heatng or coolng n a determned season. We dstngush between the HSPF Heatng Seasonal Performance Factor, as the performance factor of the system n wnter, and the CSPF Coolng Seasonal Performance Factor for the summer. In the calculaton of the SPF all energy nputs of the system must be taken nto account, such as heat pump consumpton, crculaton pumps, blowers, etc. In ths secton the results obtaned for the GEOCOOL project wll be descrbed, and HSPF and CSPF wll be calculated for dfferent borehole confguratons and for dfferent backfll materals. Moreover the study wll compare the performance of the GCHE system wth an equvalent ar-to-water heat pump system, calculatng HSPF and CSPF and showng the enhancements of the GCHE system compared to the ar-to-water heat pump system. A senstvty analyss of the dfferent optons n the desgn of the GEOCOOL GCHE system has been done wth the help of CALENDER, EED, GLHEPRO, ART, and other software tools. The parameters used for ths analyss are those gven n secton 2. Also the heat pump and crculaton pump propertes are taken n account. Results shown n the next graph were obtaned usng EED and GLHEPRO software, wth a dfference between them of only 0.4ºC for the values of the water temperature. As we can see n Fgure 6, the behavour of the mnmum temperature of the water n the GCHE s smlar among the rectangular confguratons 2x2 and 3x2, reachng the value 9.43ºC n the 3th month out of the whole 25 years perod of analyss. The maxmum value of the mnmum temperature s 0.2ºC n the 3th month for the 4x2 borehole confguraton. The rest of the borehole confguratons show a smlar behavour wth the water temperatures stayng wthn the range of values obtaned wth the borehole confguratons 2x2 and 4x2 presentng a maxmum dfference of 0.78ºC. Fgure 7: Interacton between the dfferent software packages 3

4 Fgure 7 shows the nteracton between the dfferent software packages that were used to model the global GEOCOOL system. Fgure 7 shows that the frst step n the modellng process s to calculate the GEOCOOL buldng s load profle (). To make ths calculaton the software package CALENER was used, enterng the thermal load data of the buldng and the desgn parameters mentoned n secton.2.. EED calculates the effectve thermal resstance of the borehole (2), and ART s used to model the heat pump (3). The electrcty consumpton s calculated usng GLHEPRO (4), and fnally the SPF model calculates the SPF both for heatng and for coolng for a perod of 25 years (5). Ths result s ntroduced nto EED agan as one of the desgn parameters, n order to recalculate the effectve thermal resstance of the borehole; ths teratve process leads to a hgher precson n the fnal result. EED and GLHEPRO calculate the water temperature n the GCHE for a perod of 25 years (6). Heat Pump (IZE70) As was mentoned before, the selected heat pump s CIATESA s IZE70, whch s a reversble water-to-water heat pump equpped wth a scroll compressor and usng R- 407c refrgerant. Thermal capacty and power curves are shown below. researchers also made ther own measurements of these propertes and checked them wth the catalogue nformaton. Addtonal data were calculated wth ART (Advanced Refrgeraton Technologes, of IMST-group, IIE, UPV) software. The characterstc curves for the HP are gven for a water flow rate of 2.9 m 3 /h and specfc temperature condtons n the nteror crcut n the buldng, therefore: For summer (coolng): Hot Temperature = load sde enterng water temperature at heat pump = 2 ºC Cold Temperature = load sde temperature of the water leavng the heat pump = 7 ºC For wnter (heatng): Hot Temperature = load sde temperature of the water leavng the heat pump = 50 ºC Cold Temperature = load sde enterng water temperature at heat pump = 45 ºC The crculaton pump For the desgn of the GCHE system a Grundfos CH 4-20 centrfugal crculatng pump was selected based on a hydraulc study of the system. Its pump curve s shown below: Fgure 8: Coolng capacty of the HP/Coolng Load vs enterng water temperature at the HP. Fgure 9: Electrcal power consumed by the HP/Coolng Load vs enterng temperature at the HP. Fgure 2: H-Q Curve for Grundfos CH 4-20 pump. Fgure 0: Heatng capacty of the HP/Heatng Load vs enterng water temperature at the HP. Fgure : Electrcal power consumed by the HP/Heatng Load vs enterng temperature at the HP. Data used n the curves below (see fgures 8, 9, 0 & ) are taken from the manufacturer s catalogue. The team of 4 Fgure 2 shows that the electrcal power consumpton of the pump for a 2.9 m 3 /h water flow s kw, whch must be added to the electrcal consumpton of the heat pump n order to obtan the total consumpton of the system. SPF calculaton for the GCHE system Once the desgn parameters are defned and ntroduced n the correspondng software EED and GLHEPRO, the average, mnmum and maxmum temperature profles of the water n the GCHE for a 25 years perod are obtaned, as well as the monthly average value of the heatng/coolng energy (wnter/summer) and the consumed energy of the system (heat pump + crculatng pump) for the same perod of tme. The Heatng Seasonal Performance Factor, HSPF [kwh/kwh], s defned as:

5 where: HSPF n Q H = = n E H = Q E H n H [] s the heatng thermal load for the month (n kwh) s the amount of heatng months per year s the electrcal power consumed by the system n the month (n kwh) Romero et al. Fgure 3 shows that 0% bentonte n water gves the lowest HSPF, whle coarse sand wth spacers gves the best. The dfference between both s after 25 years. Fgure 3 also shows that 0% bentonte n water gves the lowest CSPF agan, whle coarse sand wth spacers gves the best. The dfference between both s more pronounced than n the case of the HSPF, beng 0.54 after 25 years. The values of CSPF are hgher than those of HSPF, ths s a consequence of the fact that the heat pump n heatng mode works n hot water condtons of 45/50ºC HSPF and CSPF for dfferent GCHE geometres In ths secton we compare the HSPF and CSPF for 5 varants of the GEOCOOL concept wth dfferent borehole confguratons Smlarly, the Coolng Seasonal Performance Factor, CSPF [kwh/kwh], s determned by: CSPF n QC = = n E C = [2] where: Q C n E C s the coolng thermal load for the month (n kwh) s the amount of coolng months per year s the electrcal power consumed by the system n the month (n kwh) 3.2. Modelled values for HSPF and CSPF for a system wth a GCHE wth dfferent groutng materals In ths secton we wll comment on the HSPF and CSPF values found for the GEOCOOL concept; we wll compare these parameters for 5 dfferent groutng materals, n order to show whch grout s more favourable. (Total borehole length = 300 m) Fgure 4: HSPF and CSPF for dfferent borehole geometres As shown n Fgure 4 the hghest HSPF s obtaned wth a 4x2 confguraton, rsng to n year 25. The lowest HSPF s found for a 5x confguraton, gvng a dfference of % compared to the former geometry. Confguratons 6x and 2x2 behave very smlarly to 4x2, whle confguraton 3x2 gves a better yeld. These values were calculated usng the same total GCHE length (300m). Therefore the borehole depths may vary between dfferent confguratons. In practce the geometrc confguraton wll depend on constructon consderatons, such as avalable space, drllng equpment, cost per meter of borehole length, etc. In the same way the CSPF was calculated for dfferent geometrc arrangements of the boreholes. The best performance s found for confguraton 5x, beng 4.27 after 25 years, followed by confguraton 3x2 and fnally confguraton 4x2 wth a CSPF of 4.4. So dfferent geometrc confguratons wll be deal n summer than n wnter. (Fgure 6) Fgure 3: HSPF and CSPF for dfferent groutng materals n a rectangular confguraton (3x2) Seasonal Performance Factor (SPF) for the Ar-to- Water Heat Pump The Seasonal Performance Factor for the ar to water heat pump s the rato between the thermal energy suppled to or extracted from the buldng (heatng or coolng load), and the electrcal energy consumed, n a certan season. In ths case the devces that use energy are the heat pump s compressor and the axal fan.

6 In ths secton we wll descrbe the dfferent elements n the ar to water heat pump, the computng methodology and the results obtaned for the GEOCOOL project The Ar to Water Heat Pump The selected heat pump s a reversble IWD 80s, manufactured by CIATESA, featurng a scroll compressor and usng R-407c as refrgerant wth a coolng capacty of 5.9 kw and heatng capacty of 8 kw. The calculatons below are based on data from the manufacturer s catalogue, whch have been checked usng ART software and found relable. Hstogram Analyss 40 Temperature ntervals were defned, from 0ºC to 40ºC wth steps of ºC, n whch the values observed n the cty of Valenca were classfed. Fgures 5 and 6 show the hstograms for the months of January and July n the perod The mean temperatures n these months have been calculated usng the formula: T = n m b [3] The man nomnal characterstcs of ths heat pump are: Seres IWD 80s evaporator capacty () (kw) 5.9 electrcal power demand (C)(3) (kw) 6.9 condenser capacty (2) (kw) 8 where T the mean temperature n the total number of hours (744) m the mean of each nterval b the number of bn-hours correspondng to each nterval electrcal power demand (H)(4) (kw) 6.6 The data varance was calculated by means of the formula: () evaporator capacty for water leavng the heat pump at 7 ºC and an exteror ar temperature of 35 ºC (2) condenser capacty for water leavng the heat pump at 50 ºC and an exteror ar temperature of 6 ºC (3) compressor s and fan s jont electrcal power demand n nomnal coolng condtons (4) compressor s and fan s jont electrcal power demand n nomnal heatng condtons s = m T b n [4] Clmate Data A method to represent the temperature profle for a certan area n a certan perod s the bn-hours method. It conssts of addng up the number of hours that the outsde temperature les wthn a certan range, and repeatng ths calculaton for all temperature ranges that may occur. In ths way a temperature hstogram s obtaned. The nformaton needed to make ths hstogram s a database of hourly temperature observatons n the study area. In the case of Valenca, the Insttuto Naconal de Meteorología (Spansh Natonal Meteorologcal Insttute) suppled the raw data for the years 2000, 200 and Fgure 5: Hstogram of temperatures n Valenca n January ( ) Documentaton The data furnshed by the INM were compared wth data gathered n the Clmatc Atlas of Valenca (Atlas Clmátco de la Comundad Valencana). Ths book contans tables wth absolute mnmum temperatures, means of mnma, means, absolute maxmum temperatures and means of maxmums for each month n the perod A perod of 30 years s consdered as a statstcally representatve perod, therefore these values can be consdered as the expected values for Valenca. On the other hand data were avalable for the INM webste ( where means of mnma, means and means of maxmums are shown for the perod , for each month. 6 Fgure 6: Hstogram of temperatures n Valenca n July ( )

7 As can be observed the hstograms are not perfectly symmetrcal: they have a tal to the rght,.e. towards the hgher temperatures. Comparson wth data gathered n the Clmatc Atlas of Valenca The Atlas Clmátco de la Comundad Valencana unfortunately doesn t gve data varance. It does however gve nformaton about the mean values, but the mean s defned as follows: The annual mean s normally calculated on bass of daly means, whch are the average values of the daly maxmums and mnmums. Other methods to estmate the mean daly temperature exst as well, based on a contnuous record of temperatures durng the day or regular temperature measurements durng the day. Ths way of calculatng the mean daly temperature, and therefore the mean monthly temperature, does not correspond to the method explaned n the prevous chapter. Snce the hstograms are not symmetrcal, the average of the mnmum and maxmum temperatures (Tmed) wll be hgher than the mean temperature based on 24 daly observatons. Indeed, for the perod we fnd mportant dfferences, especally n the months of January: Comparson wth data provded by INM-webste We compare our hourly observatons wth the INM data for the perod Accordng to the data found on the INM webste for January s.5ºc. The mean mnmum and mean maxmum temperatures are respectvely 7 and 6. ºC. The average value of the Tmed for 2000, 200 and 2002 s the value that comes closer to,5ºc than any Tmed n these three years. Accordng to the data found on the INM webste T for July s 24.9ºC. The mean mnmum and mean maxmum temperatures are respectvely 20.8 y 29. ºC. However the months of July durng 2000, 200 and 2002 were all warmer; the most smlar year was Calculated HSPF and CSPF for the IWD 80s heat pump n the GEOCOOL Concept After havng analysed all clmatc nformaton, calculated the bn-hours for Valenca, modelled the IWD 80s heat pump wth ART, calculated the heatng and coolng load for the buldng of the GEOCOOL project and applyng the methodology proposed n the Standard ANSI/ASHRAE 6-995[8] and ARI Standard 20/ [9], the followng results were obtaned: T Table 2: SPF values for CIATESA s IWD 80s heat pump Table : Comparson wth data from the Atlas Clmátco de Valenca T T mn T max T med January July January July January July Means January Means July T The queston s: Do Tmed, and for the perod mn max correspond to the equvalent values for the perod ? Accordng to the atlas Tmed for January s.5ºc. The mean mnmum and maxmum temperatures are respectvely 7 and 5.9ºC. The average value of the Tmed for 2000, 200 and 2002 s the value that comes closer to.5ºc than any Tmed n these three years. Therefore the best way to model the temperatures n January n Valenca s takng the average values for these three years. Accordng to the atlas Tmed for July s 24.3ºC. The mean mnmum and maxmum temperatures are respectvely 20.5 and 28.7 ºC. However the months of July durng 2000, 200 and 2002 were all warmer; the most smlar year was Therefore the best way to model the temperatures n July n Valenca s takng the values of the year T The HSPF values are very smlar for the three years, havng an average value of The CSPF the 2002 has a slghtly hgher value than the other two years. Accordng to the clmatc study of Valenca, 2002 was the most representatve year f you compare t wth the last 25 years [0], whle the most representatve value for HSPF s the average of all three years. 3.4 Comparson between GCHE-system and Ar-to- Water Heat Pump Ths study compares two equvalent systems: the GCHEsystem and an Ar-to-Water Heat Pump wth smlar capactes n heatng (8 kw) and coolng (6 kw). The heat pumps where selected because they use smlar technology, both have a vapour compresson cycle usng R- 407c as a refrgerant, a Scroll compressor and plate heat exchangers at the applcaton sde. The man dfference between the two heat pumps s the normal workng temperature of the outsde crcut. In summer, the water n the external crcut wll have a lower temperature than the ar that cools the ar-to-water heat pump, whle n wnter t s warmer than the ar used to carry heat to the ar-to water heat pump. Therefore the COP of the water-to-water heat pump wll be hgher n both modes of operaton Wth the SPF calculated for the GCHE system (see 3.2) and for the Ar-to-water Heat Pump (see 3.3), the results can be compared to quantfy the effcency gan obtaned compared to a conventonal ar-to-water system. 7

8 3.4. Effcency mprovement obtaned for varous groutng materals In order to quantfy the mprovement of the GCHE versus a conventonal ar-to-water heat pump, heatng and coolng SPF values of several years were calculated. The results are shown below: Fgure 7 shows the percentage effcency gan n heatng mode of a GCHE system vs. an Ar-to-Water Heat Pump, for varous groutng materals. The grout that gves the hghest mprovement s coarse sand, followed by fne sand mxed wth 2% bentonte; whle 0% bentonte0% n water gves the least mprovement. The average mprovement over tme of the GEOCOOL concept usng coarse sand wth spacers as groutng materal s 35.4%. Also Fgure 9 shows the percentage effcency gan n coolng mode of a GCHE system vs. an Ar-to-Water Heat Pump, for varous groutng materals. The grout that gves the hghest mprovement s coarse sand, followed by fne sand mxed wth 2% bentonte; whle 0% bentonte n water gves the least mprovement. The average mprovement over tme of the GEOCOOL concept usng coarse sand wth spacers as groutng materal s 52.6%. Fgure 20: Heatng and Coolng Effcency Improvement GCHE vs. ar-to-water Heat Pump for varous borehole confguratons A possble explanaton for the opposte results n heatng and n coolng mode s that due to the mbalance between annual heatng load and annual coolng load (the former beng smaller than the latter), more and more heat s stored n the ground over tme. Ths leads to an ncreasng mprovement of the heatng effcency, but a loss of coolng effcency over tme. When a relatvely compact geometrcal borehole confguraton s chosen, such as a 4x2 rectangle, ths storage effect s enhanced; therefore ths confguraton gves a hgher mprovement n heatng and a lower mprovement n coolng. A lnear confguraton however, such as a 5x, wll favour heat dsspaton and therefore leads to a hgher yeld n coolng, but lower n heatng. Note that n heatng mode, the dfference between effcency gan n the best (4x2) and n the worst confguraton (5x) s.4%, whle n coolng the dfference s 4.6%. Fgure 7: Heatng and Coolng Effcency Improvement GCHE vs. ar-to-water Heat Pump for varous Groutng Materals Effcency mprovement obtaned for varous borehole confguratons Fgure 20 shows the percentage effcency gan n heatng mode of a GCHE system vs. an Ar-to-Water Heat Pump, for varous borehole confguratons. The geometrc confguraton that gves the hghest mprovement s 4x2 boreholes wth 36.5%, whle the 5x n-lne confguraton gves the least mprovement (34.7%). Also Fgure 8 shows the percentage effcency gan n coolng mode of a GCHE system vs. an Ar-to-Water Heat Pump, for varous borehole confguratons. The geometrcal confguraton that gves the hghest mprovement s 5x boreholes wth 50.4%, followed by 6x wth 49.8%, whle the 4x2 confguraton gves the least mprovement (45.8%). As was mentoned before, the modellng helps to choose the best groutng materal and geometrcal confguraton as far as the system effcency s concerned. However, constructon lmtatons, costs, etc are not taken nto account here. 4. CONCLUSIONS The advantages of the use of ground coupled heat pumps compared to conventonal ar source heat pumps were shown to be an energy savng technology n the European Medterranean area. In partcular the theoretcal mprovement n the seasonal coeffcent of performance for the heatng season has been shown to be about 32-36%, and the mprovement n the seasonal coeffcent of performance for the coolng season to be 50-60% over a 25 year perod of operaton. Other advantages of GCHE system compared to ar source n a costal regon are prmarly that the ground source heat pumps wll not be affected by salt corroson, the lower nose level, the lower mantenance cost because the heat pump s placed ndoors, the lower vsual mpact and the reducton n peak electrcal requrements. REFERENCES [] Geocool Geothermal Heat Pump for Coolng-and Heatng along South European Coastal Areas, NNE

9 00847, Fnanced by European Commsson. FP6 Sxth Framework Programme ( ). [2] J.M. Corberán, J. Gonzálvez, P. Montes, R. Blasco. ART: A computer code to assst the desgn of refrgeraton and A/C equpment, 8th Internatonal Refrgeraton Conference at Purdue Unversty, West Lafayette, IN, USA., (2000) p [3] Closed-Loop/Ground-Source Heat Pump Systems, Installaton Gude, Internatonal Ground Source Heat Pump Assocaton, Oklahoma State Unversty, 988. [4] CIATESA Notca Técnca Nº 700 A, Dcembre 200. Equpos agua-agua con compresor Scroll, sere IZE. Catálogo de fabrcante. [5] CALENER. Manual de Usuaro Versón 2.0. Grupo de Termotecna, Escuela Superor de Ingeneros, Unversdad de Sevlla. (200). [6] EED - Earth Energy Desgner, User manual, Verson 2.0. Dept. of Mathematcal Physcs, Lund Unversty, October 30, 2000 [7] Sptler, J.D. GLHEPRO - A Desgn Tool for Commercal Buldng Ground Loop Heat Exchangers. - Proceedngs of the Fourth Internatonal Heat Pumps n Cold Clmates Conference, Aylmer, Québec. August 7-8, [8] ANSI/ASHRAE 6-995, Methods of Testng for Ratng Seasonal Effcency of Untary Ar Condtoners and Heat Pumps. Amercan Socety of Heatng, Refrgeratng, and Ar-Condtonng Engneers, Inc. Atlanta, GA, 995 p [9] ARI Standard 20/ , Untary Ar-Condtonng and Ar-Source Heat Pump Equpment. Ar-Condtonng & refrgeraton Insttute. Arlngton, Vrgna, sect. 5., p [0] INM Insttuto Naconal de Meteorología, Datos clmátcos htpp:// 9