Cascade Uses of Geothermal Energy in Sabalan - Iran

Transcription

1 Poceedings Wold Geothemal Congess 2010 Bali, Indonesia, Ail 2010 Cascade Uses of Geothemal Enegy in Sabalan - Ian Saeid Jalilinasabady, Ryuichi Itoi, Hikai Fujii, oshiaki anaka Faculty of Engineeing, Kyushu Univesity, No. 418 West Building 2, 744 Motooka, Nishi-ku , Jaan. jalili@kyudai.j Keywods: Geothemal diect uses, distict heating, swimming ool, sabalan, Matlab ABSRAC he Sabalan geothemal aea in nothwest of Ian is otentially an imotant lace fo touism in Ian. Afte ealizing the lans fo building the fist geothemal electic owe lant in this egion and develoing swimming ools, using the geothemal wate available in this aea, hoefully it will be moe attactive fo touists and also ovide good sanitation facilities fo the local eole. Accoding to calculations descibed in the ae, Gheynajeh hot sing has been found to be suitable as a heat souce fo a swimming ool, both with egad to the equied temeatue and flow ate. he ae also descibes the design of a distict heating system fo Moeil village. he heat load fo one samle building was calculated. Comaison of mass flow fo a geothemal and fuel-fied system was done, and the influence of adiato size on indoo temeatue was analyzed based on a steady-state model. In addition to this, a distict heating netwok was designed and calculations done fo it. he simulation esults ae easonable and ovide a good stating oint fo a eal oject. 1. INRODUCION Ian has the second lagest gas esevois in the wold and also big oil esevois; additionally it has high otential fo enewable enegy like geothemal, sola, wind, biomass, etc. In 1975, a contact between the Ministy of Enegy of Ian (MOEI and Ente Nazionale e L Enegy Electica of Italy (ENEL, fo geothemal exloation in the noth of Ian (Azebaijan and Damavand egions was signed. Accoding to the final ENEL eots, ioities should be given to the Sabalan, Damavand, Khoy-Maku and Sahand egions. Afte the establishment of the Electic Powe Reseach Cente (EPRC and SUNA (the Renewable Enegy Oganization of Ian, and afte moe investigations, the Sabalan egion was ecommended fo the fist exloation dilling and electical geneation fom geothemal enegy in Ian. Hoefully, diect use of geothemal enegy will also be established in this aea. Meshkin Shah is a city in NW-Ian with a oulation of 164,000. Sabalan Mountain is located southeast of Meshkin Shah, 4811 m high and at 25 km distance fom the city. Meshkin Shah geothemal osect lies in the Moil valley on the westen sloes of Mt. Sabalan, aoximately 16 km southeast of the Meshkin Shah city. Mt. Sabalan was eviously exloed fo geothemal esouces in 1978, with geological, geochemical and geohysical suveys caied out (Fotouhi, Renewed inteest in the aea esulted in futhe geohysical, geochemical and geological suveys being caied out in he aea includes thee geothemal fields located in the nothen, easten and southen ats of the Sabalan cental volcano, and a numbe of geothemal osects ae associated with these (Sahabi et al., he Meshkin Shah osect has been identified as the best of these osects. In this ae, two altenatives fo diect use of geothemal in the Sabalan geothemal aea will be discussed, a swimming ool and a distict heating system fo the Moeil village. hese systems ae to be oeated in connection with a geothemal owe lant fo electicity geneation that hoefully will be established soon in this aea. 2. SWIMMING POOL IN HE SABALAN GEOHERMAL AREA, MESHKIN SHAHR Swimming has been one of the favoite sots in Ian fo many yeas. Also, based on eligion and cultual backgound, swimming is vey imotant fom the oint of sanitation. Public baths have existed in most ats of Ian fo many yeas. Coal, wood, oil, etc. ae used fo heating the wate. In almost all aeas whee hot sings ae found, the geothemal wate is used fo ools fo bathing, mainly because of theaeutic effects but also fo elaxation. In esent time, esecially in the Meshkin Shah and Saein cities (NW-Ian, thee ae many swimming ools using geothemal wate diectly. In this at of the ae the design of a swimming ool fo the Moeil village by using geothemal wate as a heat souce will be discussed. 2.1 Methodology and Design he size of a swimming ool is one of the imotant items fo design of the ool; it is a basic facto fo detemining the ool s sevice, wate value, selection of equiment etc. Hee swimming ools ae being built fo students who ae leaning to swim, eole who swim fo sot and thei elaxation, and fo touists. he swimming aea of a ool should be based on 3.5 m 2 e swimme. Fo oe swimming, a lane at least 2.0 m wide and 5.0 m long is equied. he designe feels that in a ool which is intended only fo swimming, and not fo diving and wate olo, the maximum deth of wate need not to exceed about 1.5 m. Fo the teaching at of a swimming ool, the amateu swimming association ecommends a minimum length of 12.0 m and a minimum width of 7.0 m. he deth geneally vaies fom 0.8 m to 1.0 m. he maximum deth should not exceed 1.2 m (Pekins, Futhe, it is assumed that the maximum numbe of swimmes in the ool at the same time will be 60. hus, the equied suface aea is 210 m 2, which is the minimum equiement accoding to standads. he ool shall have two ats, one at of the size m with the deth 1 m in the shallow end and 1.8 m in the dee end. he second at is to be a teaching ool of the size m with the deth 0.75 m in the shallow end and 0.90 m in the dee end of the ool. hus the total wate volume of the ool needs to be m 3 and the total ool aea is calculated as m 2. 1

2 2.1.1 Schematic Diagam of the Swimming Pool Figue 1 shows a schematic diagam of the swimming ool. he method adoted fo distibuting the uified wate to the ool and the withdawal of the contaminated wate is of the utmost imotance in maintaining the whole of the wate in the ool at the equied standad of uity and temeatue if the wate is heated. calculated. Figue 2 shows the wate distibution system, ie diametes and wate flow in each ie section in the ool s floo. A balancing tank is equied to even out vaiations in the quantity of wate leaving and enteing the ool. A easonable basis fo calculation of the size of the balancing tank is the following: lites e swimme fo the estimated maximum numbe of customes; 2. uantity of wate equied to back-wash one filte; 3. o the total of 1 and 2 add 10% to cove oveflow fom the ool due to wave action. he total of 1, 2 and 3 gives the net caacity of the balancing tank (Pekins, Wate Ciculation in the Pool he tunove eiod is one of the most imotant factos in oeation of the swimming ool. It is the time it takes to ciculate all the wate in the ool though all the outlets and inlets and all ciculation lanes. It changes with the ool loading and mostly deends on the tye of ool. Fo the teaching at of the ool, the tunove eiod is defined as 1.5 hous and fo the othe at of the ool 4 hous accoding to standads (Pekins, Fo maintenance of wate quality, at least 2 m 3 of oely teated wate should be etuned to the ool each day fo each bathe. Figue 2: Oveview of the ieline layout Pessue Do Based on the maximum flow ate calculated fom the tunove time equal to 44.9 l/s and essue do in the wate ciculation system, ciculation ums can be selected. One way of calculating the essue do in the ielines is using Equation 1 (Olson, 1973, assuming an aoiate value fo the oughness facto: Figue 1: A schematic view of the swimming ool he Piing System of the Swimming Pool Wate conveyance, wate teatment, and in fact the entie swimming ool technology equies ies and iing system comonents in lage numbes. he selection of mateials lays an imotant ole fo the wate quality of the entie oeation and its sevice life. hemal wate has cuative oeties, but it can also be vey aggessive. All ies made of olyoylene (PP o olyethylene (PVC have assed the tests, so the ie mateial chosen is PVC and PP which can esist the above conditions. Befoe conceting of the floo, ies with lage diamete must be ut in the bottom. It will ovide good facility fo the ies so they can be connected and acked late. Also, if thee ae oblems with the ies duing oeation, they can be solved without any destuction of the walls o floo of the ool. he wate distibution system in the swimming ool is accomlished with the iing system. Consideing the ool s volume and tunove eiod, the mass flow ate though each inlet nozzle in the floo of the ool was 2 2 ρv fl P. (1 2 D Whee P is essue do (kpa, k is oughness facto, ρ is density of fluid (kg/m 3, v is velocity of fluid (m/s, L and D ae the length and diamete of ie esectively (m and finally f 1/ (2logD/2k able 1 shows essue do fo the heat exchange and sand filte. hese have not been calculated, but have been selected accoding to exeimental and ecommended values though the manufactues, consultants and consumes. able 1. Pessue Do in the Whole System. No. Pessue do in diffeent ats of the system Pessue do (kpa 1 Heat exchange 15 2 Sand filte 50 3 Diffeent elevation of um and ool 20 4 Pessue do in the wate lane 25 5 otal essue do in the whole system Heat Loss Fom the Pool Heat loss fom outdoo ools is mainly due to convection, evaoation, adiation, conduction and ain (Svavasson, he main heat losses fom the swimming ool occu by convection and evaoation. he obtained esults fom ealie eseach and analyses show that heat losses due to the othe thee factos (adiation, conduction, ain can be

3 estimated to be equal to 10% of total heat loss due to convection and evaoation. Heat loss due to conduction is small, because of good insulation in the ool building mateials. Heat loss by means of ain and adiation is also not vey big. In the following calculation, 10% of total heat loss by convection and evaoation will be assumed fo these thee mentioned factos. Heat loss due to convection: Heat loss due to convection deends stongly on the ai temeatue aound the ool and the wind seed. Equation 2 shows that heat loss though convection will incease with highe wind seed and lowe outside temeatue: whee q C h (2 c ( w a qc is the amount of heat loss by convection (W/m 2, w is wate temeatue in the ool ( C, temeatue in the ool's aound ( C and c a is ai h is the convection heat tansfe coefficient (W/m 2 C which is vey deendent on wind seed. he elationshi between heat tansfe coefficient and wind seed is shown in equation 3 that is named Rimsha- Doncenko fomula: h c 4.19( k v (3 Whee v is wind seed at 2 mete height fom the gound suface (m/s and k is the emiical coefficient (W/m 2 C as shown in equation 4. k ( w (4 0 a Heat loss due to evaoation: Heat loss due to evaoation takes lace when thee is diffeent atial essue of wate vaou at the ool s suface and in the ai ove the ool. his will cause evaoation of wate at the ool suface, and this equies enegy that is taken fom the wate. his kind of heat loss in the ool can be calculated with Equation 6 fom Rimsha Doncenko (Svavasson, 1990: q E 2 (1.56k v.( e e (5 Whee qe is the amount of heat loss by evaoation (W/m 2, ew is the atial essue of steam at suface (mba and ea is the atial essue of steam in the ai ove ool (mba Results and Discussion Both inut and calculated aametes ae shown in able 2. he final esult is that the total heat loss fom the ool is 711 kw. W a able 2. Inut and Calculated Paametes to Calculate the Requied Heat fo the Swimming Pool. Ai temeatue known factos - design conditions Paamete Value Unit a -5 C Wind seed v 5 m/s Humidity (max H 60 % Amount of equied wate fo ciculated in the system m l/s Secific heat caacity of wate c 4.18 kj/kg C emeatue of ool's cold wate befoe heated by heat exchange 1 27 C emeatue of inlet geothemal wate at heat exchange 3 75 C emeatue of outlet geothemal wate at heat exchange 4 35 C Pool's aea A 413 m 2 Calculated values Amount of equied heat fo the ool i 711 kw Amount of geothemal wate as a heat souce m l/s emeatue of ool's heated wate by heat exchange C Coefficient deends on temeatue diffeence k 9.25 W/m 2. C Heat tansfe coefficient Convectional heat loss Patial essue of steam at wate suface Patial essue of steam in the ai ove ool Amount of heat loss by convection otal heat loss fom the swimming ool h C 18.7 W/m 2. C q C 598 W/m 2 e W 35.7 mba e a 2.41 mba q E 968 w/m 2 q 1723 w/m 2 3

4 Enegy Requiement fo Heating the Pool he total heat loss fom the swimming ool has been calculated and the same quantity of heat must be added to the wate sulied to the ool. his is done though a heat exchange that tansfes heat fom geothemal wate to fesh wate that is used as ool wate, o: q q i (7 whee q i is equied quantity of heat fo the ool (W/m 2. Equation 8 (wak, 1988 is used fo calculation of the amount of geothemal wate needed as a heat souce and the temeatue of ool's heated wate by heat exchange. he esults ae 4.25 kg/s and 30.7 C esectively. Equation 8 is known as the enegy balance equation in the steady-flow condition: m c m c ( (8 i 1 1( whee m1 is the amount of wate equied fo ciculated in the system (kg/s, m2 is the amount of geothemal wate as a heat souce (kg/s, c is secific heat caacity of wate (J/kg C, 1 is the temeatue of ool's cold wate befoe heated by heat exchange ( C, 2 is the temeatue of ool's heated wate by heat exchange ( C, 3 is the temeatue of inlet geothemal wate at heat exchange ( C, 4 is the temeatue of outlet geothemal wate at heat exchange ( C and i is the amount of equied heat fo the ool (W. he esults ae m l/s and C. able 2 shows all inut and calculated aametes in the calculation of the equied heat fo the ool, the geothemal wate s flow ate, ool wate temeatue afte heat exchange and the total heat loss fom the swimming ool. 3. DISRIC HEAING FOR MOEIL VILLAGE Moeil village is the neaest esidential lace to Sabalan geothemal field. Accoding to the weathe conditions in this aea, sace heating fo Moeil is an imotant oject. Pesently, oil is used fo sace heating. In this at of the ae, a distict heating system fo Moeil will be discussed. 3.1 Methodology Analysis of the outdoo temeatue in the aea being suveyed is the fist ste fo distict heating system design and simulation. Figue 3 shows the duation cuve of outdoo temeatue in the moeil village fom May 2000 to Ail he maximum and minimum temeatues ae about 30 C and - 22 C in July and Januay, esectively. he annual aveage temeatue is about 7 C Heat ansfe in Buildings In ode to calculate the heat load in buildings, the elationshi between the building and its suoundings must be defined. Heat tansfe is a tansient flow of themal enegy fom one system to anothe due to temeatue diffeence between two systems. hee ae thee kinds of heat tansfe including conduction, convection and adiation. In most cases, heat tansfe is dominated by conduction and convection. 4 Figue 3: Duation cuve of outdoo temeatue Heat tansfe calculation Accoding to fouie s law and consideing the comosite wall made of diffeent layes and numbe of mateials, using fim themal esistances of the fluid, the heat tansfe fom the building to the envionment can be calculated accoding to the following fomula: q UA (9 c ( i o Whee i and o ae the inside and outside design temeatue esectively. And the oveall heat tansfe coefficient of the wall is defined as follows: U 1 (10 R Whee, R is the total themal esistance of heat tansfe. Convection heat tansfe Newton's law of cooling in the following equation is the geneal equation fo heat tansfe by convection: q h A( (11 h. w o Whee h is the convection heat tansfe coefficient (W/m 2 C and its value deends on the comlexity of the system, A is the heat tansfe suface aea (m 2, w is wall suface temeatue ( C and o is the ai temeatue ( C. Radiation heat tansfe Heat tansfe by conduction and convection equie a medium fo existence, this activity by adiation can take lace in vacuum, and it is an electomagnetic adiation. he net heat exchange by adiation between two objects is given by the following equation: q 4 4 σ A F ε ( ( Whee q is the ate of heat tansfe by adiation (W, σ is Stefan-Boltzman constant (5.669*10-8 W/m 2.K 4, A1, A2 ae the aea of suface 1 and suface 2 (m 2, F 1 2 is the facto that indicates the faction of enegy between two objects, ε is the common emissivity of the objects and

5 1, 2 ae the temeatue of suface 1 and suface 2 esectively ( C Building Calculations hee ae two kinds of common buildings in the Meshkin Shah city. In the old at of city, the buildings have at least two stoies but without any heat insulation. In the new at of city, the buildings ae with fou o five stoies and with good heat stoage caacity. Building heating systems in the Moeil village ae not standad in view of its stuctue and enegy stoage, so new buildings close to Moeil village that ae exected to be built following the building of the fist geothemal electic owe lant will be discussed. A samle building with fou stoies is shown in Figue 4. he efeence outdoo temeatue is -5 C and indoo temeatue is 20 C. It has single glass windows and wooden doos. temeeatue ( C, c is mateial s secific heat (kj/kg. C and ρ is the mateial s density (kg/m 3. Equation 15 gives a simlified one, used fo actical calculations: o i Ro R1 R2 R3 R4 Ri 1 (15 Building aametes 1 heat tansfe coefficient: Heat tansfe coefficient is a constant descibing the heat tansfe between the building and its envionment due to conduction, convection and adiation heat loss, the calculation accoding to the following fomula: U tatal U A U A... ( Atatal Whee U n is heat tansfe coefficient of diffeent comonents constituting building suoundings (walls, windows, ceilings and floos, (W/ Cm 2, A n is each comonent suface aea (m 2 and A total is the total suface aea of the building (m 2. he heat tansfe coefficient is calculated unde no insulation. Afte detemining each suoundings heat tansfe coefficient, the total buildings heat tansfe coefficient can be easily detemined using Equation 13, it is shown in the able 3. able 3. Building s total heat tansfe coefficient. Suface U (W/m 2. C A (m 2 U*A (W/ C Roof Floo extenal walls Windows otal U 2408,6 / 990,4 2,43 (W/m 2 C total 2 Building hemal Mass (C: hemal mass is the ability of building to stoage heat. It is the second aamete needed fo simulation. hee is a temeatue gadient though the wall layes, with the lowest temeatue at the laye adjacent to the outside. So the concet of efficient themal mass is defined by which at of the wall that can stoe heat fo the indoo temeatue of 20. Figue 5 shows the heat tansfe though comosite walls. he theoetical equation fo calculations is given in Equation 14 (Valdimasson, 1993: E s s ( x 0 c ( x ρ( x dx ( i 0 c ( x ρ( x dx 0 0 (14 A whee E is wall s themal enegy (J, A is wall s aeas (m 2, S is wall s thickness (m, x is mateial s mean temeatue ( C, i is the indoo temeatue ( C, o is the outdoo Figue 4: Selected samle building s lan and details Fom able 3, Equation 15 can be solved giving the following (figue 6: ο ο ο i 20 C, o 5 C, W, C ο ο C, C, ο C, ο C 5 o i Figue 5: Heat tansfe though comosite walls hen the mean temeatue of each laye is found subtacted fom the outdoo temeatue and then multilied by that mateial s themal caacity and density to get the walls themal caacity. able 4 summaizes the calculations of the themal mass of the building. 5

6 Pie heat loss In the distict heating system thee is heat loss though the ie between uming station and the buildings to be heated. his value of heat loss can be calculated by using distict heating ie tansmission effectiveness aamete. Accoding to Valdimasson (2001 the tansmission effectiveness τ is defined as follows: U s g mc τ e (20 1 g he efeence value of the τ can be concluded fom the efeence flow conditions: Figue 6: emeatue gadient though walls Radiatos Fo heat tansfe fom the heating system to the heated lace heat exchange is used, that is known adiato. Accoding to Anon (1977, the elative heat load of a adiato can be witten as: (4/ 3 s0 i0 (4/ 3 0 m s i0. (16 0 m0 s 0 s i 0 ln i ln whee / o is the atio of the actual heat outut fom the adiato to the heat outut at design conditions, s is wate suly temeatue ( C, is wate etun temeatue ( C and i is the oom temeatue ( C. he logaithmic temeatue diffeence ( is defined as: m fo adiatos ( s i ( i ( s m (17 s i s i In ln( able 4. Building s hemal Mass. Suface C (kj/ C Roof Floo Extenal Walls Intenal Walls otal i Building heat loss Heat loss though the building can be calculated with equation 18: loss k ( o (18 l i Whee k l is building heat loss, which is a constant facto. Relative heat loss can be obtained as: loss loss0 i o io oo i (19 Paametes U s o g m o C τ o e (21 1 o g U and C is assumed to be constant all ove the system. Combining the equation 20 and 21, the tansmission effectiveness can be obtained: mm o m τ τ (22 Combining the equations 20 and 22, the suly temeatue to the house can be calculated: s g ( 1 g g + ( 1 g mo m o + τ τ (23 If the distict heating netwok ciculates wate, the etun wate temeatue at the uming station is obtained fom equation 24: 2 g + ( g g + ( g mo m o τ τ (24 Building enegy stoage When the heating of building is tuned of the building does not cool down immediately. he building has heat caacity and it stoes enegy. he building enegy stoage model is: di net ( su loss ( mc ( s kl ( i o (25 dt C C C All time deivatives equal to zeo in steady state model, in dynamic modelling these aametes ae effective Steady State Aoach When steady state condition, assume to be established in the distict heating system, thee is not heat to be stoed in the buildings. Retun temeatue can be calculated accoding to Naa (2000: 4 / 3 s i 0 0 ln s 0 i0. 0 s0 0 s i ln i i o io oo (26 can be calculated with iteation fom equation 26 Accoding to Valdimasson (2003 fastest convegence is obtained, when inside logaithm is calculated: z, n 1 ( s i e i (

7 Whee z is: z s so, n o io. i oo o 3/ 4. ln so o io io (28 When outside temeatue data is given, i is assumed to be constant and suly temeatue is known,, n+ 1 can be found iteatively fom the equation 27. In the steady state model, the heat loss fom buildings is the same as the heat load suly: su loss (29 mc ( s l i o k ( (30 Mass flow is obtained diectly fom equation 30. kl ( i o m (31 C ( s io Facto k l can be calculated fom the efeence conditions moc ( so o kl (32 oo he mass flow duation cuve is shown in Figue 8. hee ae 22 days e yea with highe mass flow than assumed available. he system will not be able to suly the equied heat duing those 22 days, if such limitation is imosed. An economical analysis is due hee to find the best value of such limit, consideing cost of lack of heat vesus the investment fo additional wells. Figue 9 shows the elationshi between etun temeatue and mass flow. Fom this cuve it can be seen that when mass flow inceases, the etun temeatue also becomes highe. his means that most of the mass flow in the system has highe etun temeatue, as shown in able 4. his is because when thee is moe heat equiement in the building (lowe outdoo temeatue, hot wate ciculation though the adiatos will be inceased (highe mass flow, and the temeatue diffeence between the suly and etun temeatue will be smalle. Figue 10 shows the wate temeatue in the distict heating netwok. he wate temeatue at um station ( 1, suly temeatue to consumes ( s, etun temeatue fom consume and etun temeatue to um station ( 2. emeatue diffeence between and 2 shows heat loss though the ie line. Refeence values and constants All efeence values ae maked with subscit o. Common efeence values fo geothemal distict heating netwok ae: Suly wate temeatue s0 80 C; Retun wate temeatue 0 40 C; Room temeatue 20 C. he efeence values used fo fossil fied netwok ae: Suly wate temeatue fo imay netwok s0 90 C; Retun wate temeatue fo imay netwok 0 70 C; Room temeatue i0 20 C. he efeence outside temeatue deends on climate. he efeence value fo moeil village oo 5 C was used hee in both the geothemal and the fossil fied systems. Gound temeatue was assumed to be constant 5 C. he efeence mass flow of wate is elated to the size of netwok to be studied. Hee it was selected to be 0.32 kg/s. he secific heat caacity of wate assumed to be constant and deendence of temeatue was neglected. he secific heat caacity ( C was assumed equal to (kj/kg. C. Figue 7: Duation cuve of suly, etun and outdoo temeatue 3.3 Results and Discussions he steady state model was ogammed with MALAB. he weathe data was used. In this section, some Figues ae lotted and discussed. Figue 7 shows the duation cuve fo outdoo temeatue o, etun temeatue and suly temeatue s duing one yea (e half an hou. It is necessay to mention that all calculations wee done in the Matlab ogam. Outdoo temeatues of moe than 15 C wee assumed to be 15 C as no heat is equied unde these conditions. In this figue, the Y-axis is evesed. Figue 8: Duation cuve of mass flow 7

8 Figue 9: Retun temeatue as a function of mass flow Figue 11: Pie tansmission effectiveness as a function of elative mass flow Figue 10: Diffeent temeatue in the netwok Figue 11 shows the ie tansmission effectiveness τ, as a function of elative mass flow (m/mmax. Figue 12 finally shows the elationshi between outdoo temeatue and mass flow fo tyical geothemal and fossil fuel fied systems. A tyical geothemal system is taken to have 80/35 C design temeatues fo suly and etun, wheeas a tyical fuel fied system has 90/65 C as design temeatues. he geothemal system will equie lage adiatos, in ode to obtain these design temeatue. his investment is justified by less mass flow equied fom the wells. Else moe wells will have to be dilled and the yealy utilization time of these additional wells will be low. It is inteesting to notice that when heat equiement is low, mass flow is low, so temeatue dos in both the suly and etun hot wate will be high. Some citical temeatues ae given in able 4. Figue 12: systems Comaison of mass flow fo two heating Netwok otimization Otimization involves finding the system aametes in such a way, that a edefined cost function has a minimum. Scheme of netwok is shown in Figue 13. Figue 13: Scheme of netwok 8

9 Nodal essue he essue at the nodes is detemined by the element essue loss. If a taget essue loss e unit length is defined, a taget nodal essue is also defined. he voltage law of Kichhoff laces estictions on this, because the essue loss along any closed ath has to sum u to zeo, and makes it theefoe imossible to obtain taget essue loss in all the elements. A loo fee netwok has a unique solution fo the nodal essue. If the nodal essue is consideed an indeendent vaiable, the essue loss e unit length can be calculated fo all elements (Valdimasson In this ae, we focus on the netwok with a total ie length of 3.82 km and seving 28 buildings. So-called h/l diagams ae esented hee to show the netwok efomance. On these diagams, the nodal head is lotted as a function of the distance fom the inlet oint, measued accoding to a selected tee set. hus one ie in each loo, the link, is not eesented with coect length. he h/l diagam fo the existing netwok is shown on Figue 14. he link ies ae shown gey on the figue. he netwok shown is the suly netwok with a total ie length of 3.82 km. he etun netwok has simila toology, but oosite flow diection, and is not teated in this ae. able 5. Maximum and Minimum Values fo Pessue and emeatue Dos. Paametes Max. (node 36 Min. (node 14 Peak value Pessue (m emeatue ( C CONCLUSIONS he main conclusions deived fom this wok ae summaized as follows: he swimming ool is designed accoding to the most common standads egading the equied dimensions and sanitay equiment. he suface aea of the ool is designed as m 2 and to kee the ool wate temeatue at 27 C at -5 C outdoo temeatue, a heating caacity of 711 kw is needed. he atesian hot wate sing available in the Sabalan geothemal aea, Gheynajeh with a flow ate of 7 l/s, at temeatue of 83 C, can be used as a eat souce fo a swimming ool. Accoding to the calculations efomed in the oject, 4.25 l/s of 75 C hot wate ae equied fo this uose. A steady-state model fo both a geothemal distict heating system and a fuel-fied system has been develoed and the elationshi between outdoo temeatue and mass flow in both of them comaed. In the geothemal heating system, the mass flow is lowe and the adiatos lage, so it is both ossible and favouable fom an economical oint of view. he heating has a sha eak load, so limitation of the maximum flow may be cost-effective comaed to dilling additional geothemal wells with low utilization time. A simulation model is a oweful tool fo studying and analyzing distict heating systems. Maximum mass flow and adiato sizes ae imotant aametes affecting the indoo temeatue of distict heating systems. he maximum mass flow can be contolled by a contol valve. Figue 14: Pessue do in the netwok Figue 15 shows the temeatue do e node of netwok. Fom able 5 it can be seen that the esults ae easonable. In the long un, it can be economically advantageous to ay moe attention to insulation of buildings and thei enegy stoage ability in Ian. his is based on esent condition of buildings and enegy costs in the county. ACKNOWLEDGEMENS he fist autho would like to exess his gatitude to unugt ogam in Iceland fo thei suot duing his wok on this eseach. Comments and advices fom Pofesso Páll Valdimasson and D Ani Ragnesson ae geatfully aeciated. Figue 15: emeatue do in the netwok REFERENCES Anon: DIN 4703 eil 3. Vameleistung von Raumheizköe (in Geman. Beuth Velag, Belin, Gemany, (1977. Fotouhi, M.: Geothemal develoment in Sabalan, Ian. Poceedings, Wold Geothemal Congess, Floence, Italy, 1, (1995, Naa, M.: Distict heating modeling, Reot, Univesity of Iceland, (2000, 47. 9

10 Olson, R.M.: Essentials of engineeing fluid mechanics. Intext Educational Publishes, New Yok, (1973, 637. Pekins, P.H.: Swimming ool. Elsevie Alied Science Ltd., London, (1988, 359. Sahabi, F., Khoshlessan, M.R., and Banett, P.R.: Geothemal exloation of Mt. Sabalan, NW Ian, Geothemal Resouces Council, ansactions, 23, (1999, Svavasson, G.: Designing swimming ools. Univesity of Iceland, B.Sc. thesis (in Icelandic, (1990, 52. Valdimasson, P.: Modeling of geothemal distict heating systems. Univesity of Iceland, PhD thesis, (1993, 144. Valdimasson, P.: Pie netwok diamete otimisation by gah theoy. Wate Softwae Systems: heoy and alications, Univesity of Iceland, 1, (2001, 13. Valdimasson, P.: Distict heating systems: Fundamentals and alication. Poceedings, 6 th National Heating Ventilating Ai-Conditioning and Sanitay Congess and Exhibition, ukey, (2003. Wak, K.: hemodynamics, McGaw-Hill Book Comany, New Yok, (1988, 954. able 4. Maximum and Minimum Paametes in the Geothemal Distict Heating System. o Paametes 1 2 s m s ( C ( C ( C ( C ( C ( C (kw ( C ( C Maximum Minimum Minimum Maximum