Influence of Ground-source Heat Pumps on groundwater

Transcription

1 Proceeding European Geothermal Congre 7 Unterhaching, Germany, 3 May-1 June 7 Influence of Ground-ource Heat Pump on groundater Jordi Guimerà 1, Felip Ortuño, Eduardo Ruiz 1, Anne Delo 1 and Alfredo Pérez-Paricio 1 Enviro Spain S.L., Paeig de Rubí, 9-31, Valldoreix, Barcelona, Spain. correponding author: jordi.guimera@enviro.biz Catalan Water Agency, Provença, 4, 836 Barcelona, Spain Keyord: Ground-ource heat pump, thermal impact, heat tranport, geothermal energy, numerical model ABSTRACT Differently to the deep, high enthalpy geothermal reource exploitation, the idepread ue of lo grade, hallo geothermal ytem for heating and/or cooling ha not come along ith a proportional development of conceptual and numerical undertanding of the impact of thee ytem on groundater. Environmental agencie requirement often neglect the particularity of the hydrogeological ytem and conequently, advere ituation uch a increae of temperature of ater may occur in aquifer but alo in the heat pump extraction ell themelve. Thi latter hould be of particular concern yet reduce the long-term efficiency of thee ytem. A tate-of-the-art on the exiting regulation at different countrie here groundater geothermal ytem are implemented i briefly preented, putting pecial attention on ome of the key regulated iue that concern the reource. The paper preent a to-phae methodological approach, folloed to fulfil the Catalan Water Agency requirement. Firt, analytical expreion are propoed and the direct equation are olved to obtain a preliminary aement of the thermal impact. Second, e imulate explicitly the impact of groundater heat pump ith numerical method that can take the particularitie of the aquifer into account. Code that can handle the coupled heat and flo problem are preferred, but in fact, mot code that olve for groundater flo and olute tranport can be ued in the methodology. The methodology i applied to a tudy cae here interference ith groundater ell and underground contruction like concrete all and tunnel are analyzed. In general term, the tudy ho the feaibility of the ytem and that the thermal plume i motly controlled by the amount of ater involved and the difference in temperature beteen thee ater. 1. INTRODUCTION AND FRAMEWORK Today major environmental challenge i global arming. Society and government had received the meage that the cientific community ha proclaimed all through the lat year that an improvement of energy efficiency and a reponible energy uage reduce green-houe ga (GHG) emiion that contribute to climate change and everal key action are focued on thi. Within thi context, heating, cooling or air conditioning of houe and facilitie repreent one of the major percentage in the total energy conumption. Among the everal conventional ytem for thee purpoe, the mot idely extended ytem are baed on the utilization of foil 1 compound uch a carbon, ga oil or natural ga- hich increae the GHG emiion. An alternative to conventional ytem that permit improving energy efficiency in climate control, are the o called geothermal heat pump or ground-ource heat pump. Ground-ource heat pump ytem (GSHP) are one of the ne energy technologie that ha hon rapid increae orldide in uage over the pat year. Thee ytem offer ubtantial benefit to conumer and utilitie in energy aving. Additionally, a frameork of grant i available ithin many countrie to individual, organiation and companie ihing to intall GSHP technology, ince geothermal energy i conidered a reneable energy ource. Thi paper i not devoted to proclaim the energy efficiency and effectivene of the ytem; ince there are a lot of publication focued on thi (Pratch 199, Pratch 199 or Lienau et al. among many other), but particularly it ill be centred on the influence of GSHP on groundater, pecifically in thoe ytem in hich thermal exchange i produced in groundater. When uing a Groundater Heat Pump (GWHP) ytem, alo named open loop, for heating, and epecially for cooling, ater i injected back into the aquifer at different temperature from the original one. Thee difference in ater temperature can produce abnormal effect in the aquifer temperature. In fact, temperature at different aquifer at ome European citie here an intenive ue of groundater for thee purpoe exit, ha increae beyond 5 ºC, having preently little notion on the environmental impact produced on the reource, and conequently, on the aociated ecoytem. Frequently, regulator requirement do not take, neither the particularitie of the GWHP, nor the hydrogeological ytem into account, thu lacking of a robut regulation etablihed orldide. Hence, the little knoledge on the influence of GWHP in term of thermal, biological or chemical impact on the aquifer do not foter regulation in protected area or vulnerable aquifer. GSHP ytem had been implemented in many countrie along the lat decade, epecially in the EEUU, Canada, Japan and ome of the northern European countrie, but it implementation i incipient or relatively ne in many other countrie. Thi i the cae of Catalonia in Spain, here high energy demand building, uch a for example hotel are focuing their interet in thi technology. With the aim of protecting the groundater reource, the Catalan Water Agency (CWA) by mean of it Hydraulic Public Domain Department require to any potential uage of groundater for building climate control a thermal and hydrogeological tudy of feaibility of the ytem. With thi end, ENVIROS ha etablihed a to-phae tudy to fulfil the requirement of the CWA. Thi methodology

2 ha been applied to ome cae of tudy, one of hich ill be hon in the preented paper. Simultaneouly, ENVIROS ha been committed by the agency to perform an elaboration of a good practice guideline concerning climate control uing groundater to be folloed by contructor, architect, engineering and environmental conultant. The guide ill addre to the folloing objective: (1) to revie the tate of ater agencie regulation orldide; () to ae if the actual tudie devoted to etimate the impact on groundater and infratructure have enough technical rigor (3) to evaluate the effectivene of imple analytical approache to be applied for an eay etimation of thermal impact; (4) to compare analytical olution ith thoe produced by mean of numerical approache; and (5) to compare the olution produced by ome of the mot conventional groundater flo and tranport numerical code and to tet their applicability to ae thermal impact. Thi project i till on-going and only ome of the above mentioned iue ill be briefly dicued along thi paper.. BRIEF STATE-OF-THE-ART ON REGULATION OF GWHP SYSTEMS Depite the high development and efficiency of the geothermal heat pump and it implementation orldide, only ome etate of EEUU, Seden or France have a relatively unambiguou legal frameork ithin Some other countrie uch u Sitzerland or Autria are preently developing it on regulation and ome other uch u Greece, Romania or Germany are focuing their effort in term of regulation on cloed loop ytem in hich thermal exchange doe not involve groundater. In general term, regulation on GWHP ytem contraint a erie of key iue of concern for the reource. Thee are mainly: (1) the difference in temperature beteen extracted and injected ater or thermal range ( t), () additive utiliation, (3) typology of the involved aquifer and (4) protected area to open loop ytem. The thermal range ( t) repreent the difference beteen the temperature of injected and extracted ithdraal. Some guideline and recommendation are given regarding t. While ome countrie, a for example Canada or Autria, regulate and recommend 5ºC for t other like France or Germany regulate 11 and.5 ºC repectively. On the other hand, a country ith a ell etablihed regulation frameork, a Seden, doe not have any contraint on the t produced to groundater. Additive are forbidden in Canada, Seden, Sitzerland and Holland, hile in ome countrie, uch a France or Denmark, can be ued preenting feaibility tudie. Thermo-hydraulic hort circuiting beteen different aquifer i not alloed for mot of the regulation found, and uually, the ytem concentrate on the ort quality aquifer in citie,. At many location, area here a drinking ater ell or mineral ater companie exit, implementation of open loop ytem i trictly forbidden. Additionally, other particular cae uch Japan here ater extraction i aociated to land ubidence alo forbid open loop ytem, thu having a knock-on effect on a major implementation and development of cloed loop technologie. Other regulation coincide ith natural park (a for example in France) or contaminated area (Seden or EEUU). At countrie here no regulation i currently in force, uch a for example UK, Denmark, Holland or Spain each particular cae i treated pecifically and a hydro-geothermal tudy of aquifer vulnerability and impact on the reource i often required by the regulating agencie. 3. METHODOLOGY APPLIED TO ASSESS THERMAL IMPACT Until the guideline ill be finihed or any robut regulation ill exit, CWA requirement can be fulfilled by organiation and companie ihing to intall GWHP ytem by mean of hydro -and thermo- geological tudie to be checked and approved by their correponding technician. ENVIROS had been committed in the lat year by everal companie, uually hotel chain and other large building here open loop can have better energy aving and full cot of implementation than cloed loop. Among the tak performed throughout thee project can be found: the feaibility of the propoed ytem; the dimenion of injection and extraction ell and their optimal location to avoid thermal and hydraulic interference and the aement of the thermal impact expected to fit CWA requirement. With thi end, a to-phae approach methodology baed on both analytical expreion and numerical modelling technique had been ell etablihed to reach the previou objective. The tarting phae of the tudy i devoted to a preliminary aement of the feaibility of the ytem; in term of both accomplih and fulfil ater and energy- demand and to analytically etimate if the heat plume could be diipated donard. A econd numerical approach phae i devoted to tune location; to fix a more exactly ater and energy demand throughout operating time; and to more accurately etimate expected impact on ingular feature. Thi paper ill deal ith to topic ithin the overall tandard project: ho to etimate the expected impact ith both analytical olution and numerical technique. 3.1 Preliminary evaluation of the expected impact by uing analytical expreion Major development of technologie and conceptualiation i purely aociated to cloed loop ytem ince thee are the more implemented everyhere. Conequently, cientific literature ha groth in parallel to development, and hile there are an important amount of paper focued on cloed loop ytem, only a fe can be found concerning GWHP. Some example on cloed loop geothermal impact can be found at Diao et al. (4); Fujii et al. (5) or Gehlin et al. (3). Thi fact could be explained by the intrinic characteritic of the ytem that require an aociated hidrogeologic tudy for the deign (and impact) and a frequently extenive bureaucratic and adminitrative documentation to be preented at the correponding regulating agency (Bernton, ; Rafferty, 3). Heat tranport had been tackled in term of media characteriation (Anderon, 5) and heat -or cold- torage (Chevalier, 1999; Dyer and Ecktein, 1987) but only fe article tackle thermal impact of thee ytem. An

3 example on thi lat i Ferguon and Woodbury (6), here importance on deign of open loop ytem i put evidence in a hydraulic ytem here 4 different GWHP ytem interfere beteen them, affecting their operating ratio. Prior to the decription of analytical expreion to ae thermal impact it i neceary to decribe ho the heat can be tranported in aquifer. With thi end, the next ubection hortly decribe controlling procee and parameter. Energy (heat) tranport in aquifer Energy i tranported in the ater-olid matrix ytem by groundater flo, and by thermal conduction from higher to loer temperature through both the fluid and olid. A the true, not average, velocity field i uually too complex to be meaured in real ytem, an additional tranport mechanim approximating the effect of mixing of different temperature of groundater moving both fater and loer than the average velocity, (v) i hypotheized. Thi mechanim i called energy diperion, and tend to approximate, the decription of thee mixing proce. In thi ay, the energy tranport balance equation follo the expreion: T ρ " c" = ( ( λ + Dρ c ) T ) ( qρ c T ) ( qrtr ) (3.1) t here ρ i the aquifer denity (Kg m -3 ); c i the aquifer pecific heat (J Kg -1 K -1 ); ρ i ater denity (Kg m -3 ); c the fluid pecific heat (J Kg -1 K -1 ); T i the temperature (ºK); t i time (); λ i the aquifer (bulk) thermal conductivity (J -1 m -1 K -1 ); D i the diperion (m -1 ); q i the Darcy flux (m 3 /); q R i an injected/extracted flo rate (m 3 /); and T R i the injected/extracted temperature of the injected/extracted fluid (ºK). The time derivative (left-hand ide of equation 3.1) expree the total change in energy tored in both the olid matrix and fluid per unit total volume. On the right hand ide, the firt term can be undertood a divided into to; the term involving bulk thermal conductivity (λ) expree heat conduction contribution to local tored energy; and the term involving the diperivity tenor (D) approximately expree the contribution of irregular flo and mixing, hich are not accounted for by average energy advection. The term involving q expree contribution to locally tored energy from average-uniform floing fluid (average energy advection). The term involving q R account for the energy added by a fluid ource ith temperature, T R. Additional ink/ource term can be added to thi expreion to account for energy production in the fluid and olid, repectively, due for example to chemical (endothermic) reaction. Aquifer calorific capacity can be expreed a the um of pecific heat from both ater and oil (G. de Marily, 1986): ( φρ c ) + (( φ ) ρ c ) ρ" c"= 1 (3.) here ρ i the olid denity (Kg m -3 ); c i the olid pecific heat (J Kg -1 K -1 ); and φ i poroity. ( φλ ) + (( φ ) ) λ = 1 (3.3) λ S here λ and λ S repreent thermal conductivitie for both ater and olid (J -1 m -1 K -1 ) repectively. Subtituting equation 3. and 3.3 into equation 3.1 reult in: φ1+ ρ ( 1 φ) ρ λ D = α q + ρ c ρ c ( 1 φ) ρ c R = 1+ φ c c T λ = q T t α + c φ ρ (3.4) ( q T ) ( q T ) R R (3.5) (3.6) D [L T -1 ] repreent the diipation coefficient and R [-] i the retardation coefficient. Walton (1979) lit a erie of analytical olution available to perform the olute and energy tranport equation in an aquifer. Among thee equation and ith the end of a preliminarily aement of the thermal impact of a ytem, different analytical approximation can be elected for thee purpoe: (1) heat tranport in a emi-infinite 1D column and () radial heat tranport from an injection ell. Heat tranport in a emi-infinite 1D Thi expreion tate that in a emi-infinite 1D column, ith a boundary condition of contant heat flux at x=, equivalent to a heat injection, the hortet pathay in a dipole tet ill follo the folloing initial and boundary condition: t, x >, T = t >, x =, [ T T ] t >, x >, T = T v = D x (3.7) The olution of Gerhon and Nir (1969) (alo detailed in Bear; 197) follo: T ( x, t) 1 Rx vt 1 vx Rx + vt Rx + vt = erfc + exp erfc 1 + T RDt D RDt RD 4 4 v v t vx ( Rx + vt) + (3.8) exp πrd D 4RDt here T(x,t) [T] i the temperature at a ditance x from the boundary domain and at a time t; T [T] i the precribed temperature -thermal range ( t) of the ytem-; x [L] i the obervation ditance; v [L T -1 ] i the average velocity (Darcy velocity time the poroity) and erfc i the complementary error function. A tandard temperature olution for a emi-infinite media for a given thermal range in a GWHP ytem can be hoed in Figure 1. Thi olution follo a igmoid. Thermal conductivity of the aquifer can be expreed a the um of ater and olid thermal conductivitie folloing the expreion: 3

4 Temperature (ºK) Time (day) Figure 1: Standard energy tranport 1D olution for a emi-infinite media and a thermal range ( t=5ºk). radial heat tranport from an injection ell Another ueful analytical equation that can be potentially utilied to ae thermal impact i the olution expreed on Gelhar and Collin (1971). The expreion i a modification of the conventional radial flo equation for a fully penetrating injection ell in a confined aquifer. Fluid i injected at a rate of Q tot, ith a temperature of T*, into an aquifer initially at a temperature of T. Radial flo propagation from the injected ell follo the expreion: T T 1 r = erfc * T T 4 α L 3 here: φρc QTOT AT = γ πφbρ r * 1 ( AT t) * ( r ) * 3 λ * 4 ( r ) + ( r ) AT 1 (3.9) (3.1) = (3.11) and here the ret of the term had been defined in previou equation. The above energy olution may be obtained from the olute olution by retarding the velocity of tranport to repreent energy torage in the olid grain of the aquifer material in the torage term of the analytical olution. normalied temperature (T-Tº)/(T*-Tº) radial ditance [m] Figure : Standard analytical olution for radial energy tranport (modified from Gelhar and Collin, ) for different time tep (18, 9, 45 and 5) here 1 time tep repreent 41. Thee olution become ort cae cenario that not contemplate all the exiting feature and ingularitie of the aquifer. In the cae of the firt one approach, ince the equation i one-dimenional, no temperature loe ithin other geological material in the vicinity of the aquifer (top, bottom and laterally), or atmophere are conidered, and a heat injection remain contant, the etimated impact olution repreent the highet and ort limit for the olution. Furthermore, the olution produce valuable information on the heat behaviour, a can aport an etimation for the teady tate of the heat plume in aquifer natural condition. Concerning the econd analytical expreion, no diipation on top and bottom layer of the aquifer i taken into account and alo repreent a conervative approximation. On the other hand, analytical olution repreent potent tool for benchmarking of the olution that numerical code compute, playing an important role on the teting and validation of the reliability of the numerical technique. 3. Aement of the expected impact by uing numerical technique Analytical expreion can not permit to repreent all the real exiting heterogeneitie in aquifer. For thoe cae that preliminary firt- evaluation doe not clearly dicard the implementation of thi technology, a numerical conceptualiation ill allo tuning ell location and fixing ater florate and aociated temperature to fulfil energy demand through operating time. Thu, benefit in the ytem deign are clearly a key point. Another key point to take into account, lie in that numerical model ill permit to include ithin it dicretiation, key infratructure potentially to be affected, other exiting GSHP ytem or drinking ell, a ell a, the heat plume diipation itelf, conequently, aeing in a more accurate manner the thermal impact of the geothermal ytem. Numerical model to be preferred applied are thoe olving the coupled flo and energy equation, but in fact, mot code that permit olving groundater flo and olute tranport can be ued, applying an eay analogy beteen ome of the key parameter of the olute and energy tranport. In the next ection, a cae of tudy here ENVIROS had applied the preented methodology i briefly decribed. Only thoe iue concerning numerical modelling ill be decribed, ince prior information a devoted to conceptualization of the problem and ite characteriation tak. 4. ASSESSMENT OF THE THERMAL IMPACT IN A CASE OF STUDY The cae of tudy i located in l Hopitalet del Llobregat, a nearet village in the outheat part of the Barcelona city. Concerning the hydrogeology, the area i located ithin the Llobregat alluvial multilayer aquifer, hich correpond to the Delta area of the Llobregat River (Figure 3). Syntheizing, thi multilayer aquifer i formed by to and and gravel quaternary aquifer eparated by an aquitard (clay and ilt material ith a lo hydraulic conductivity) placed over a marl hot material (Agència, 4). The thickne of the uperficial aquifer range from 1 to

5 meter, and in general term it behaviour matche ith an unconfined aquifer. It exploitation ha decreae through the lat year, ince it quality ha a parallel decreae due to ome contamination epiode, a ell a it i affected by alt ater intruion. The principal -deep- aquifer ha thicknee ranging from 4 to meter and a confined behaviour. It i exploited for drinking ater purpoe and play an important role on the ater management context of the Barcelona area, and conequently of the Catalonian region. 5 m Figure 4: Well point in the vicinity of the hotel. The figure ho a configuration of 3 dipole (extraction/injection ell) and ome of the exiting monitoring point. Figure 3: Simplified geological frameork of the tudied area (Agència, 4). Within above hydrogeological context a hotel chain ihing to have preence in thi particular area, tarted bureaucratic and adminitrative documentation at CWA ith the end of implementing an open loop geothermal ytem for cooling pace, baically. If the propoed GWHP ytem i feaible, thi ill be placed in the uperficial aquifer, a a firt requirement of the CWA. Meh refinement around ell point had been performed in order to avoid any numerical problem due to high thermal and hydraulic gradient. With the end to give advice and helping implementer in the GWHP deign tak, a ell a to atify CWA requirement, ENVIROS a committed by the company to perform ome part of the overall project. Prior tak devoted to geological, hydrogeological and geotechnical characterization ill not be object of thi paper that ill focued their effort on the decription of the econd numerical modelling phae undertaken to ae thermal impact and feaibility of the GWHP technology. A great number of borehole (Figure 4) ere available from the characterization phae. Hoever, borehole diameter differed beteen them, and not all permitted to produce expected ater demand. Conequently they ere not being introduced in the model to optimizing meh ize. The elected domain repreent an area of 15x15 meter in the vicinity of the hotel plot and can be dicretied in a finite element meh (FEM) here computation ill be finally done. The model repreent thi domain by mean of a quai-3d finite element meh (a plan vie of the FEM i hoed in Figure 5). Figure 5: Dicretiation of the area. The figure ho a plan vie of the finite element meh ithin the domain (up) and a detail of the meh refinement in the vicinity of the hotel (don). The domain a elected in uch a ay that boundary condition to be applied did not affect reult. In thi ay, lateral (E and W) boundarie ere precribed a no flux boundarie, ince flux had a clearly S-N component, here 5

6 the north coincided ith the don gradient direction. In order to repect thi flo direction, N and S boundarie Three-dimenionality a modelled by mean of 1D finite element in order to repreent heat diipation through the atmophere and through the underlying aquitard. D model are not uitable to repreent thee heat tranport realitie, and conequently ub-etimate heat diipation in the third dimenion, converting quai-3d or fully 3D model into the mot rigorou approach. m3 / month 7, 6, 5, 4, 3,, 1, January February Mar April May June July Augut September October November December 4, 36, 3, 4, 18, 1, 6, accumulate m3 Folloing thi, top and bottom ere alo elected a no flux boundary condition, a top coincide ith topography and no flux though the underlying aquifer a aumed. Concerning energy tranport boundary condition, ater entering S boundary entered in the ytem at 15 ºC, hile the injected ater in the ell injection a done at 3 ºC. Additionally, heat can be diipated through the atmophere and aquifer. The ytem a uppoed initially at a temperature of 15ºC and the correponding head level at each node according the exiting piezometer field ere fixed. Figure 6: Water demand through a year. The left axi ho needed florate to fulfil energy demand, and the right axi ho the accumulating demand along the year. Modelling reult hoed that at the higher extracted volume (July and Augut) the hydraulic affection on the vicinity a not negligible. In term of dradon (ell influence perimeter) the affected area ome centimetrearie to 5 meter (Figure 7), hile in the ell extraction area exceeded 1 meter. In pite of, the ytem did not affect any of the ingular feature coniderably. In order to perform the computation, a FE numerical code a elected. A mention, a conventional code that olve groundater flo and olute tranport can be ued, applying an eay analogy beteen ome of the key parameter of the olute and energy tranport. TRANSIN code (Medina et al., 1996) a elected for the modelling of the coupled tranient flo and tranport equation. Time dicretiation a elected in order to avoid numerical problem aociated to Courant and Peclet number. Alo, the total imulation time a elected in uch a ay that the ytem arie a teady heat tranport tate. Finally, year of imulation ere computed. Energy demand and conequently ater demand- i one of the key point in the overall deign of a ytem. A tight collaboration and feedback beteen climate engineer and hydrogeologit mut exit and i extremely neceary in order to ucce. Thermal range to be applicable to groundater can be combined ith different florate of the extraction ell in order to atify the energy demand, but it i indipenable to have in mind the available reource and the donard impact. Numerical imulation (modelling cenario) play an important role to optimize the ytem. In the cae of tudy, ater demand (Figure 6) ere conidered the controlling factor, a the accumulating florate expected to be in a year raied to.4 hm 3, thu leading to important impact. The model alo conidered nearet infratructure and ell to be potentially affected. After a calibration phae of the main controlling parameter, a erie of modelling cenario ere elected to check different ell configuration, volume and thermal range. Figure 7: Hydraulic impact of the ytem. The figure ho the dradon in the area after 18 day of imulation (value in meter). Concerning thermal plume, the affected area clearly exceeded 5 meter (ome fe degree). Extraction ell ere alo affected putting in evidence that efficiency of the ytem a compromied by the preented configuration. Not only the effectivene and efficiency of the ytem a putted in evidence ith the expected energy demand but alo CWA requirement in term of expected impact ere urpaed. 6

7 Only the thermal impact of GWHP a tackled and other plauible impact, uch u biological groing or chemical impact are till area of little knoledge. The methodology a applied to a tudy cae here interference ith groundater ell and underground contruction like concrete all and tunnel ere analyzed. The numerical model ha hon that can be a potent tool to approach thermal impact and deigning a GWHP ytem and tet it efficiency. REFERENCES Agència 4: Agència Catalana de l Aigua (4) Programa de getió del aqüífer de la cubeta de Sant Andreu, Vall Baixa i Delta del Llobregat. Memòria i document d actualització fin deembre del 4 del model del aqüífer. Generalitat de Catalunya, Departament de Medi Ambient. Anderon, M. P. (5) Heat a a Ground Water Tracer. Ground Water, 43 (6), Figure 8: Thermal impact of the ytem. Steady heat plume in the aquifer achieved at 1 year of imulation (value in ºC). The thermal range produced to groundater i 15 ºC. Additionally, a enitivity analye on the mot relevant parameter a made ith particular emphai on the abtraction/injection ater yield and their correponding temperature difference. The analyi hoed that the impact in groundater, in term of temperature plume, ere relatively inenitive to the thermal propertie of the rock, and to ome of the mot relevant for olute tranport uch a diperivity, hile the mentioned temperature difference and florate involved ere deemed crucial in the propagation of the perturbation. 5. CONCLUSIONS A brief tate-of-the-art on the exiting regulation at different countrie here groundater geothermal ytem are implemented i preented. A hon, much can be done in term of regulation and recommendation. The paper ha centred effort on thermal impact of open loop ytem in groundater but alo cloed loop can affect on the reource. The paper ha preented a to-phae approach methodology to ae thermal impact baed on both analytical and numerical approache. Analytical expreion can be ueful tool to preliminary ae the thermal impact in aquifer but they uually become ort cae cenario becaue do not contemplate all the exiting feature and ingularitie of the aquifer. Furthermore, they can produce valuable information to reject a propoed ytem. On the other hand, numerical model can match environmental agencie requirement, a ell a deign demand of implementer, yet can tet the long-term efficiency of thee ytem. Code that can handle the coupled heat and flo problem are preferred to model heat tranport, but alo code that olve groundater flo and olute tranport can be ued uing a imple analogy beteen olute and energy parameter. Bear,J. (197) Dynamic of Fluid in Porou Media. American Elevier, Ne York, N-Y, 764. Bernton, T. () Heat ource technology, economy and environment. International Journal of Refrigeration 5, Chevalier, S.; Banton, O. (1999) Modelling of heat tranfer ith the random alk method. Part 1. Application to thermal energy torage in porou aquifer. Journal of Hydrology, De Marily, G. (1986) Quantitave Hydrogeology: Groundater hydrogeology for Engineer. Orlando, Florida, Academic Pre, 44. Diao, N. ; Li, Q.; Fang, Z. (4) Heat tranfer in ground heat exchanger ith groundater advection. International Journal of Thermal Science 43, Dyer T. E.; Ecktein Y. (1987) Finite-element imulation of lo-temperature heat-pump-coupled, aquifer thermal energy torage. Journal of Hydrology, 95, Ferguon, G.; Woodbury, A. D. (6) Oberved thermal pollution and pot-development imulation of lotemperature geothermal ytem in Winnipeg, Canada. Hydrogeology Journal 14, Fujii, H.; Itoi, R.; Fujii J.; Uchida Y. (5) Optimizing the deign of large-cale ground-coupled heat pump ytem ú ing groundater and heat tranport modelling. Geothermic. 34, Gehlin, S.E.A.; Helltröm, G. (3) Influence on thermal repone tet by groundater flo in vertical fracture in hard rock. Reneable Energy 8, Gelhar and Collin (1971) General Analyi of longitudinal diperion in nonuniform. Water Reource Re. V.7, nº6, Gerhon, N. and Nir, A. (1969) Effect of boundary condition of model on tracer ditribution in flo through porou media. Water Reource Re. 5, Lienau P. J., Boyd T. L. and Roger R. L. () Groundource heat pump cae tudie and utility program. Geo-Heat Center. Oregon Intitute of Technology. Prepared for the U.S. Department of Energy: 7

8 Geothermal Diviion. Grant No. C April Medina, A., Galarza, G., and J. Carrera. (1996). TRANSIN III: Fortran code for olving the coupled non-linear flo and tranport invere problem. ETSE CCPB, UPC. El Berrocal Project, Topical Report 17. ENRESA. Pratch, L. Geothermal Heat Pump Benefit the Conumer, Utility, and Nation. Geo-Heat Center Quarterly Bulletin, Vol. 14, No. 1, 1-6, 199. Pratch, L. (OH-41) (199) Geothermal Heat Pump Annual Fuel Conumption & Energy Saving. Columbu, OH. Rafferty, K. (3) Ground ater iue in geothermal heat pump ytem. Ground Water, 41 (4)