A DEMONSTRATION GEOTHERMAL PROJECT IN BEIJING - MULTIPLE UTILIZATION OF GEOTHERMAL ENERGY

Transcription

1 GEOHERMAL RAINING PROGRAMME Repot 2002 Okutofnun, Genávegu 9, Numbe 19 IS-108 Reykjavík, Iceland A DEMONSRAION GEOHERMAL PROJEC IN BEIJING - MULIPLE UILIZAION OF GEOHERMAL ENERGY Yin Heng Geological Suvey echnical Intitute of Beijing Jia No. 2, Lihuiqiao Chaoyang Ditict, Beijing P. R. CHINA Hago1976@yahoo.com.cn ABSRAC hi epot decibe a demontation poject fo diect ue of geothemal enegy in Beijing. he object of the poject i to find a uitable way to optimie utilization of geothemal enegy in Beijing with a wate tempeatue ange of 45-88/C. Geothemal wate, 71/C wam and with a flow ate of 140 m 3 /h, come fom the o-called Shae-6 well, and i ued fo ditict heating and a wimming pool. Seveal diffeent teminal ytem ae dicued in thi pape. A heat pump i ued a a eeve fo peak load duing the heating peiod. It i alo ued fo cooling in umme with hallow goundwate a a cold eouce. Cacaded ue and automatic contol ytem contibute to lowe enegy conumption which, in tun, enable moe extenive ue of the geothemal enegy. he ue of a heat pump futhe extend the field and capacity of geothemal utilization. he envionmental advantageou effect of geothemal enegy ae ignificant. 1. INRODUCION Beijing i the capital city of People Republic of China. he total population of Beijing i 14 million; of that, moe than 7 million people live in the cente of the city and need heating in the winte. he enegy fo pace heating came motly fom coal a few yea ago; at leat 2.8 million ton tandad coal wee equied pe yea. Hence, the envionment wa heavily polluted by emiion fom buning coal. hi ha caued much concen in ecent yea. Govenment and public both want to change the ituation. Now, it i fobidden to contuct new coal boile fo heating and the ue of clean and enewable enegy i encouaged intead. hi will lead to a big impovement in the enegy ecto. Geothemal enegy i a clean and enewable fom of enegy, which ha been widely ued aound the wold in the lat centuy fo electicity geneation, pace heating, pa, geen houe etc. Beijing i ituated on top of a lage and deep edimentay bain with eveal (-10) geothemal field. he hot wate ange in tempeatue fom 45 to 88/C, and ha been exploited fom uface ping and geothemal well vaying in depth fom 1000 to 3500 m. he yealy poduction of geothemal wate i about 10 million m 3, 10% of the etimated potential capacity, pimaily ued fo aquacultue, eceation and bathing etc. Geothemal 395

2 Yin Heng 396 Repot 19 wate ued fo pace heating only tated a few yea ago. Due to the geat benefit to the envionment and ignificant effot towad a bette economy, geothemal heating ytem have been developing apidly. With apid development, a high technical level, efficiency and economic ytem ae tongly demanded, a well a a eaonable impact management ytem. hi popoed poject i a demontation poject with the pupoe of invetigating geothemal utilization in ditict heating and cooling with the aid of a heat pump. he plan i to ue geothemal hot wate fom Shae-6 well a a heat eouce and fou hallow wate well a cooling ouce. All the building ued in thi demontation poject belong to the the Geological echnical Intitute of Beijing. hey ae thee old eidential building (12,000 m 2 ) built in 1975; one office building (3,800 m 2 ) efitted in 2000; one old apatment building (5,900 m 2 ) built in 1970; a new hotel and pot mueum (4,000 m 2 ) an indoo wimming pool (pace aea, 2000 m 2 ); and a new etauant (1500 m 2 ), a hown in Figue 1. Noth Yad SPW Hotel SPW Pump Sation Retauant DN100 DN150 DN100 DN200 Li-ang Road Office Building Synthei Natatoium GPW SRW SRW Wate eament Room Reidental Building 2 Reidental Building 3 Reidental Building 1 SPW: Shallow Poduction Well SRW: Shallow Reinjection Well GPW: Geothemal Poduction Well GRW: Geothemal Reinjection well GRW FIGURE 1: Ditibution map; the thee ditict compoed of eveal building ae hown and location of well with net-pipe connected to the pump tation 2. GEOHERMAL FIELD AND SHARE-6 WELL he geothemal well in thi poject i well Shae-6, which wa dilled duing the winte of 1999/2000 to a depth of 2418 m. It i located at No. 2 Jia, Liuhuiqiao and belong to the Shehe geothemal field (Zhu et al., 2001). Liuhuiqiao i an aea located in the nothen pat of Beijing, in cloe poximity to the ite of the futue Olympic aea. When well Shae-6 wa finihed, the wellhead peue wa 2.7 ba. Initial ateian flow ate wa about 120 m 3 /h; the maximum pumped dichage capacity i believed to be moe than 140 m 3 /h. But fo the whole popoed aea only 45 m 3 /h geothemal wate ae needed. In othe wod, the capacity of Shae-6 i highe than the demand of the poject. he main pupoe of the poject i to ue the geothemal enegy a economically a poible fo the mot optimal heating ytem. he plan i to ell the emaining geothemal eouce to the neighbouing eidential ditict, o connect to anothe much bigge geothemal ditict heating ytem, the Beiyuan Gaden geothemal ditict heating poject with a 400,000 m 2 pace heating aea in the fit phae and 800,000 m 2 in the econd phae.

3 Repot Yin Heng At the beginning of 2002, a einjection well wa uccefully finihed, 1000 m outhwet of well Shae-6. hi winte, , it will be connected to the peent ytem fo einjection expeiment. But the head peue of thi well i alo elatively high. heefoe, high einjection peue and equipment i needed. Caeful monitoing hould be taken, in ode to get detail infomation about the einjection capacity and to etimate the ate of caling and cooion. Some wate ample wee taken fom well Shae-6. he concluion of geochemical analyi i that thee ae no ilica, calcite o magneium depoit aociated with utilization of thi well. And thee i no diolved oxygen component in thi wate, but hydogen ulphide (H 2 S). Becaue of the fat eaction between diolved oxygen and hydogen ulphide, they ae not peent in the wate at the ame time. Hence, coppe pipe and component in contact with the wate hould be avoided in the ytem. It i ecommended to ue a cloed-loop ytem. If the high ion content of the geothemal wate get into contact with the atmophee it may oxidize to ion hydoxide, cauing the wate to tun a bownih colou. 3. DIREC USE OF GEOHERMAL WAER 3.1 Space heating and cooling Due to the elatively low tempeatue of the geothemal wate, it ue fo ditict heating had not developed much in Beijing befoe the end of the lat centuy. In ecent yea, technical inulation of building ha been ignificantly impoved and vaiou teminal equipment with high heat tanfe efficiency have been taken into ue. Hence, hot geothemal wate i conideed uitable fo pace heating ytem, in ome cae aociated with othe enegy upplie. he pupoe of thi poject i to find the bet way of utilizing geothemal wate in ditict heating ytem. Both in diect and indiect geothemal heating ytem, taditionally geothemal wate ha been dichaged to dain even at tempeatue above 45/C a it wa deemed unuitable fo heating. Iceland and ome othe Euopean countie have employed heat pump to boot the wate tempeatue by uing abobed heat fom the wate geothemal wate fo moe than ten yea. Reult indicate that it i an efficient and economical way of uing geothemal eouce. An impotant benefit of intalling a heat pump i that it can be ued fo cooling duing the umme. Moe dicuion about uing a heat pump aociated with a geothemal ditict heating ytem will be peented in thi pape Weathe condition he load on heating ytem i cloely elated to the influence of the outdoo climate. he main facto influencing the load ae the ai tempeatue, wind peed and ola adiation. Othe mino influence ae due to teep cold wave and pecipitation, etc. he pupoe of the analyi i to examine the dynamic chaacteitic of weathe on heat demand. he thee main facto ae analyed. en yea of climate data, fom Septembe 1991 to Septembe 2000, wee obtained fom the Meteoological Bueau of Beijing. Obevation on highet, aveage and lowet ai tempeatue, wind peed and unhine adiation wee made at daily inteval. Aveage yea indicato can be etablihed baed on the ten yea of weathe data. In Figue 2 uch aveage yea ae hown, along with two tandad deviation confidence inteval fo outdoo ai tempeatue. he outdoo tempeatue of 9/C and 33/C wee choen a the heating and cooling deign tempeatue, epectively. hee value wee choen baed on the ASHRAE fundamental fom hey give the limit unde which the actual outdoo tempeatue hould not be expected to fall fo moe than 1% of the limit hou of the yea (Figue 3). Unfotunately, the weathe data collected i only ufficient fo a tatic tudy, but not fo the pupoe of evaluation by a dynamic model. Moe detailed data in inteval of not moe than 2 hou, hould be obtained fo a dynamic model imulation.

4 Yin Heng 398 Repot empeatue C Outdoo tempeatue ( C) Day No. FIGURE 2: Daily aveage, maximum and minimum outdoo ai tempeatue in Beijing Day No. FIGURE 3: Outdoo ai tempeatue duation cuve Accoding to the Chinee Building Code, the indoo tempeatue of houing mut lie between 16 and 18/C duing the heating peiod in winte and between 23 and 24/C duing the cooling peiod in umme. hat mean 18 and 24/C wee conideed acceptable duing cold peiod and heat wave, epectively, i.e. when the outdoo tempeatue exceed the deign tempeatue (-9 o 33/C) fo hot peiod of time Geneal deign and load aement A hown in Figue 1, the building (29,200 m 2 pace aea) ae divided into thee ditict. he building ae chaacteied by diffeent type of inulation and heating method and, fo the pupoe of the analyi, building of imila chaacte ae gouped togethe. Ditict A include the thee old building in the outh yad which ue old ingle-pipe adiato heating ytem. Ditict B i anothe aea with old building, in the noth yad, which alo ue an old ingle-pipe adiato heating ytem. Ditict C i the bigget, and include five ubunit, i.e. a new hotel, a ynthei cente, an office building, a natatoium and a etauant. New ai fan coil unit ytem ae ued hee with diffeent type and intallation denity, of diffeent heating and cooling load capacity value. hee ae two tank ued fo ditibution and collection of upply and etun wate, epectively. heefoe, each ditict (A to C) mut be analyed epaately when imulating the themal ytem. Figue 4 how the ytem diagam of the whole poject. hee ae fou heat exchange ued fo the thee diffeent ditict. he ciculation wate i heated via heat exchange 1, with 13/C diffeence between the upply and etun tempeatue. he upply tempeatue can each 65/C, uitable fo the old adiato ytem in ditict A. Simultaneouly the geothemal wate i cooled down fom 71/C to 59/C and flow into heat exchange 2. Due to the lowe geothemal tempeatue in heat exchange 2, the outlet (upply) tempeatue i lowe, only 53/C. But ditict B i mall compaed with the othe. he equied heat output may be eached by high ciculation flow ate with lowe tempeatue dop. he etun wate fom the ciculation i about 43/C. he geothemal wate cool down to 52/C and then goe futhe to heat exchange 3. A mentioned befoe, Ditict C include five ubunit; two tank ae ued to ditibute and collect the ciculation wate. he outlet wate tempeatue fom heat exchange 3 i about 50/C and the etun wate fom the collection tank i 40/C. he enegy deficit of Ditict C can be complemented by the heat pump, with imila upply and etun tempeatue. he geothemal wate tempeatue goe down to 42/C and patly goe to heat exchange 4 whee it i cooled down to 15/C, and anothe pat goe to the

5 Repot Yin Heng ANK Ditict A HEA EX(1) 71C 65C GEOHERMAL WELL 59C HEA EX(2) 52C 53C Ditict B 42C 52C 43C HEA EX(3) 50C 40C Ditict C o hotel o ynthei o office o natatoium o etauant O SWIMMING POOL HEA EX(4) 12C O REINJECION 15C 6C HEA PUMP1 Fom hotel Fom ynthei Fom office Fom nataoium Fom etauant HEA PUMP2 FIGURE 4: Sytem diagam of the poject wimming pool. he geothemal wate afte heat exchange 4 i mixed with the et of the 42/C wate, and then dained o injected into the einjection well. Pat of the geothemal wate i tanfeed to a cloed loop between heat exchange 4 and the two heat pump unit. On the heat pump ide, the outlet and inlet tempeatue of the heat exchange ae 12 and 6/C, epectively. Baed on the pecification of Chinee building contuction and the petinent weathe data, the pecific heat load of building in Beijing i defined a follow: Reidential building: 50 W/m 2 ; Public building: 70 W/m 2 ; Natatoium: 125 W/m 2. And pecific cooling capacitie ae Public building: 90 W/m 2 ; Natatoium: 160 W/m 2. he deign tempeatue elative to deign load capacitie ae Heating deign tempeatue: Outdoo tempeatue a0-9/c; Indoo tempeatue i0 18/C. Cooling deign tempeatue: Outdoo tempeatue a0 33/C; Indoo tempeatue i0 24/C. he maximum enegy load capacity of the whole aea, both in winte and umme wa calculated with the eult lited in able 1.

6 Yin Heng 400 Repot 19 ABLE 1: Maximum heating and cooling load Ditict Aea Heating load Cooling load (m 2 ) (kw) (kw) A 12, B 5, C_1 2, C_2 4, C_3 3, C_4 2, C_5 1, C - total 13,400 1,069 1,379 otal 30,100 1,964 1,379 Real-time enegy demand depend on weathe condition, tempeatue, wind, and o on. Hee we can imply conide the ai tempeatue to etimate the enegy demand. he heat tanfe fom houe to the outdoo uounding (heat lot), o fom the outdoo uounding (heat gain), i a linea faction of outdoo tempeatue: k) (1) whee k anfe coefficient of building [kw//c]; Diffeence between indoo and outdoo tempeatue [/C]. Aume the indoo tempeatue a contant. i only a function of outdoo tempeatue. Compaed with the efeence condition alo called deign condition, k can be omitted: t i a (2) o i ao o, t i i a ao o (3) whee a, i and 0 ae given a efeence paamete, but diffeent in heating and cooling phae. he enegy conumption wee evaluated in the following two diagam in the fom of duation cuve (Figue 5 and 6). Fo the cooling load duation of Ditict C (Figue 6), value ae baed on aveage outdoo tempeatue. he nomal heating peiod in Beijing i fom 15 Novembe to 15 Mach, a total of 120 day. But accoding to weathe analye (Figue 2), in the coldet 120 day the highet outdoo tempeatue i only about 6/C. If we extend the heating peiod to 150 day, it will be 10/C and moe uitable fo cutome than the conventional method. Accumulating the enegy demand fo one winte, it i etimated that kwh o 96 kwh/m 2 will be needed. he cooling aea doe not include ditict A and B. Ditict cooling opeate when the outdoo tempeatue i highe than 24/C. Accoding to weathe analye (Figue 2), it i about 80 day fom 10 June to 30 Augut. Accumulating the enegy demand fo one umme, it i etimated that kwh o 48.5 kwh/m 2 will be needed. In the following chapte, moe detail of enegy pefomance in the ytem will be dicued. Some model and imulation will be et up fo analyi.

7 Repot Yin Heng Heat load demand (kw) Cooling load demand (kw) Day No. FIGURE 5: Maximum heating load duation Day No. FIGURE 6: Cooling load duation of Ditict C baed on aveage outdoo tempeatue Old adiato ytem In ditict A and B, the old heating ytem wa deigned to ue hot wate coming fom a coal boile tation. Supply and etun wate tempeatue wee 90 and 70/C, epectively. It i clea that the ytem cannot maintain the indoo tempeatue above 18/C afte the ytem ha been changed to ue the geothemal eouce with a upply tempeatue which i not above 70/C. he ditibution ytem wa upplying fit the adiato at the top floo, and ubequently all the adiato on each floo down to the lat one connected to the etun pipe. hi wa a ingle pipe ytem fom top to bottom with a gadually falling tempeatue. Hence, the ize of adiato on each floo i diffeent, inceaing fom top to bottom. It i not eay to change the whole ytem becaue of all the inhabitant living in thoe building. A a olution, we can inceae the numbe of adiato. Fit we have to know the atio of each floo a hown in Figue 7 (A). 5 RADIAOR 5 RADIAOR 4 RADIAOR 5 5F 4 RADIAOR 5 5F 3 RADIAOR 4 4F 3 RADIAOR 4 4F 2 RADIAOR 3 3F 2 RADIAOR 3 3F 1 RADIAOR 2 2F 1 RADIAOR 2 2F 1 1F 1 1F (A) (B) FIGURE 7: (A) Radiato aangement diagam of old building of Ditict A uing the ingle-pipe ytem; (B) Radiato aangement uing double-pipe ytem

8 402 Yin Heng Repot ) ( ) ( ) ( ) ( ) ( C C C C C u P u p u P u P u P ν ν ν ν ν m na k Fit we will dicu Ditict A, which ha five floo. hen uing the ame method, it i eay to calculate Ditict B with fou floo, and o on. he aea of each floo i the ame. Ignoing the diffeence between diffeent floo, top and bottom floo having diffeent heat demand than intemediate floo, the heat load of each floo can be aumed the ame, i.e (4) he heat balance of each adiato, and the elationhip of each adiato can be decibed by the following equation: (5) and (6) in which C p i the pecific heat capacity of wate and < u i the flow ate of a ingle unit. Combine thee equation and the eult ae hown in able 2: ABLE 2: Inlet and outlet tempeatue (/C) of each floo adiato of Ditict A Sytem Supply temp. Retun temp. 5 th floo 4 th floo 3 d floo 2 nd floo 1 t floo Old New he heat tanfeed fom the teminal adiato to the uounding ai i given by the following equation (Kalon, 1982): (7) whee k he oveall heat tanfe coefficient of adiato; n Numbe of adiato; A Suface aea of each adiato; ) m Logaithmic mean tempeatue diffeence fo a adiato.

9 Repot Yin Heng Hee, the heat tanfe coefficient of the adiato, k, i mainly detemined by thei natual heat convection behaviou inide the building. he empiically coelated equation between k and ) m can be expeed in the fom k α β m (8) in which " and $ ae empiical contant depending on the type of adiato. Fo the fou-pole cat ion adiato, " i 0.25 and $ i he logaithmic mean tempeatue i defined a: m (9) i ln i In a low-tempeatue heating ytem, the tanfeed heat fom adiato to the ame aea oom hould be equal to the high-tempeatue heating ytem. It mean: o kono A mo 1 (10) k n A n n n If we compae the two ytem uing the diffeent value of the fifth floo, we can find the elationhip of the neceay numbe of adiato (auming that all adiato ae the ame ize): mn n n n o5 (11) hi mean that in the new ytem, we have to add 60% of the oiginal numbe of adiato on the fifth floo, in ode to achieve the ame heat tanfe to the oom, i.e. to maintain the indoo tempeatue i above 18/C. Futhemoe, uing the data in able 2, we can calculate the elationhip of the numbe of adiato on the fifth floo to the numbe of adiato on the othe floo: n n n n5 ; n n n n5 ; n n n n5 ; n n n n5 (12) Uing thee equation it i eay to find out how many adiato mut be added on each floo, if the numbe of unit on the top floo i available. he eitance in the ytem will inceae due to the inceae in the numbe of adiato. Hence, it i ecommended to ue a bigge ciculation pump to keep the flow ate, < u, contant. able 3 give the eult fo Ditict B calculated with the ame method. ABLE 3: Inlet and outlet tempeatue ( C) of each floo adiato of Ditict B Sytem Supply Retun 4 th floo 3 d floo 2 nd floo 1 t floo temp. temp Old New he numbe of adiato ae: and n n n o4 (13) n n n n4 ; n n n n4 ; n n n n4 (14)

10 Yin Heng 404 Repot 19 Figue 8 how the conveion facto numbe of adiato needed if we change the ytem fom high-tempeatue (coal boile) heating ytem to a low-tempeatue (geothemal) heating ytem, with upply and etun tempeatue of 65 and 52/C, epectively. Anothe poibility i to change the ingle-pipe ytem to a double-pipe one a hown in Figue 7 (B). hi i bette than a ingle-pipe ytem. Relative numbe of adiato No. of floo FIGURE 8: he facto of added adiato coeponding to the floo Simulation of the ciculation In thi ubection, the imulation of the heating ciculation and the pefeence fo ytem type will be dicued. Due to the cooive action and caling poblem that might occu with ue of geothemal wate, heat exchange ae ued to avoid ciculating the geothemal fluid diectly though the ditict heating ytem. hi i called Indiect Geothemal Ditict Heating Sytem (IGDHS) (Dai, 1996). Plate heat exchange (PHE) ae ued becaue they have high heat tanfe coefficient. he imple model i illutated in Figue 9. Some neceay aumption ae made in thi themal imulation and analyi. he whole ditict heating aea can be egad a a big adiato; he wate heat lo duing tanfe in the pipe and heat lo in the heat exchange ae ignoed; the efficiency of the heat exchange i aumed 100%; he whole ditict heating ytem i themotatic; he heat lo due to ventilation and heat gain fom the un adiation, etc. ae ignoed, all the influence can be epeented by integation of the heat load capacity of the building. Following the aumption lited above, fou enegy conevation equation decibing fou heat tanfe ytem can be devied. hey ae a follow: 1) he enegy loe fom building to the outdoo atmophee. A mentioned befoe, the enegy,, equied to maintain the indoo tempeatue, i, i a function of outdoo tempeatue accoding FIGURE 9: Sketch of a imple ytem

11 Repot Yin Heng to the following equation: i a 1 i ao A whee i, ao and 0 Refeence condition paamete; A otal otal given aea of the building needing heating. o otal (15) (2) he heat tanfeed fom the teminal adiato to thei uounding ai (indoo ai) i given by the following equation (Kalon, 1982): 2 k na m (16) Fan coil unit ued in ditict C can alo be conideed a kind of adiato with pecific empiical contant " and $. (3) he heat tanfe fom the ciculating wate though the adiato o the heat gain of ciculating wate fom the heat exchange ytem can be eaily calculated though available upply and etun tempeatue ( and ). he elevant equation i given by 3 F C c p ( ) (17) (4) he heat tanfeed fom the geothemal wate to the ciculating wate though the plant heat exchange (Dai and Liang, 2000) can be expeed by 4 C p ( )( S 1) g g c ( ) c S 1 F F ka g ka 1+ F C p F F g g F c F c (18) whee S i given by S e kaf 1 1 C p Fg Fc (19) whee k A Oveall heat tanfe coefficient; otal aea of the heat exchange. he tempeatue diffeence coection facto, F, i a function of the heat exchange aangement and the numbe of plate. In the cae encounteed, S can be calculated uing the pefomance condition. Accoding to the peviou aumption (20) hee ae the eential equation of the ytem baed on pefomance condition. When the outdoo tempeatue change, the heat demand change. In othe wod, it i neceay to change the contollable paamete to achieve the change and o on. he ytem can uccefully maintain the indoo

12 Yin Heng 406 Repot 19 tempeatue a well a aving enegy. In the fome model, thee tempeatue eno wee intalled to meaue the outdoo, indoo and dained geothemal wate tempeatue. Fequency convete contol the ciculation pump and the geothemal wate boote pump; in othe wod, the flow-ate of ciculation wate and geothemal wate ae vaiable. If the outdoo tempeatue a deceae inceae Deceae F c and d both inceae Deceae F g and d both deceae If d i lowe than the et point inceae F g If i i lowe than the et point inceae F c If i i highe than the et point deceae F c he ditict heating etun wate tempeatue fom a building i detemined by the pefomance of the building adiato ytem. It i like a heat exchange tanfeing heat fom the ditict heating wate to the indoo ai. Accoding to Valdimaon, (1993) the elative heat duty of a adiato can be witten a: 1 o m mo n o ln ( ) o i o ln i ( ) o io io n (21) Hee, the value of paamete n i equal to (1+$). he index o efe to the efeence condition; they ae deign paamete fo a cetain building. Fo example, in Ditict A of thi poject, the new efeence condition afte inceaing the numbe of adiato i o 65/C; o 52/C io 18/C ao -9/C Combining Equation 15 and 21, we can find the elationhip between a and without adjuting the flow ate, a hown in Figue 10. Fc m 3 /h t a FIGURE 10: he elationhip between outdoo tempeatue and ciculation flow ate he enegy balance theoy equation at each ide of the heat exchange ae: F C ( g p g ) F C c p ( ) (22) Combine Equation 17, 18 and 22. In ode to keep d contant, F g hould change it elationhip to F c. In a contol ytem, the common method i that hown in Figue 11, uing PID contol.

13 Repot Yin Heng L1 HEA EX(1) ia Vg Mg HEA EX(1) Ditict A ia a HEA EX(2) Ditic B ib HEA EX(3) Ditic C Vg ia ib HEA EX(4) Vg ia HEA EX(1) FIGURE 11: Schematic diagam of the popoed contol ytem 4. HE CONROL SYSEM he eential of automatic contol ae Maintain the indoo tempeatue of each ditict; Povide optimum opeation and enegy aving; Monito and ecod opeating data of the ytem. he chematic diagam in Figue 11 how the automatic contol popoed fo the ytem. Seveal eno and contol device ae intalled. he function and peentation of them ae lited in able 5. All eno and contol equipment ae connected to five pogammable logic contolle (PLC). All pump ae contolled by uitable vaiable fequency peed dive convete and connected to the PLC. A net cable connect the PLC and a PC. Included with evey PLC i the following equipment: A CPU (Cental Poceing Unit); EEPROM fo pogam toage. he memoy keep it content even duing powe failue; A bae whee the input/output cad ae mounted. Input and output cad in vaying numbe and a field-bu contolle ae included with each PLC; An opeating panel. he panel i mounted in the ame cubicle a the PLC. A bu-mateing cable connect the PLC though a R232 potocol fo communication with the PC contol pogam. he pogammable contolle ae pe-pogammed and deliveed mounted in a cubicle, togethe with teminal block and aociated equipment. Bief logical contol i dicued a follow: Geothemal well unit. Fit, geothemal wate will pa though the de-aeato tank. Wate level eno L t will contol the peed of geothemal wate pump F g and contol valve V g to maintain a contant wate level. V g i, ued in cae of ateian flow fom the well, i moe than the demand. When the well, unde cetain low-demand condition, povide enough wate by ateian flow, the pump will not un. If demand i moe than the ateian flow, then V g i full-open and F g i ued to maintain the contant wate level.

14 Yin Heng 408 Repot 19 ABLE 5: Paamete of contol ytem PLC-1 PLC-2 PLC-3 PLC-4 PLC-5 g L g L t F g V g Geothemal wate tempeatue Geothemal wate level De-aeato tank wate level Vaiable fequency of geothemal well pump Contol valve of geothemal wate d1 Outlet tempeatue of Heat Exchange 3 F Vaiable fequency of boote pump V d1 Fit contol valve of dain wate a Ai tempeatue ia Indoo tempeatue of ditict A F a Vaiable fequency of ciculation A ib Indoo tempeatue of ditict B F b Vaiable fequency of ciculation B ic Indoo tempeatue of ditict C F c Vaiable fequency of ditict C V d2 Second contol valve of dain wate c Retun wate tempeatue of ditict C V h Contol valve on heat pump outlet h1 Heat pump ciculated wate inlet tempeatue F h Vaiable fequency of ciculation pump in heat pump unit d2 Outlet tempeatue of Heat Exchange 4 P 1 Peue of ciculation wate Vaiable fequency of upply pump F c Ciculation unit. Combining outdoo and indoo tempeatue of each ditict, adjut the ciculation pump fequency to maintain the indoo tempeatue a a contant. On the ide of the geothemal wate, thee ae two cae. a) Fit if the heat load i low enough that it can be obtained only fom enegy extacted fom geothemal wate. Ue the outlet wate tempeatue d1 of the heat exchange to adjut the gade of contol valve V d1 aociated with totally open V d2, to enue d1 i not highe than 40/C. b) On the othe hand, when the heat load inceae in colde weathe, the heat pump i needed. he etun tempeatue of ciculation C i the et point to contol the tat o top of the heat pump. Futhe, the tatu of the heat pump contol the ciculation pump between the heat pump and heat exchange 4. Combine valve V d1 and V d2 to adjut the flow ate into heat exchange 4. Uually, PLC ha facilitie to monito the tatu of the main poce paamete. In the event of a netwok failue individual PLC will function independently. Softwae combining the function of monitoing, opeating, ecoding and o on i ued a a Men-Machine Inteface fo the contol ytem. hi contol ytem (CS) include gaphical diplay fo the pump tation and well tation opeation, event and alam lit and epot. he ytem monito and toe all poceed data to an SL elational databae fo tending and analye of data ove time. he ue of a SL databae enable ue of the ytem to acce the poceed data fo eay numeical analyi of data with compehenive data epoting poibilitie and enable them to optimie the oveall pefomance of the ytem. he CS gathe data fom the PLC. Fom the CS ytem, PID loop contolle et point and manual output and tuning can be pefomed. Stating and topping of pump, including well pump, and adjuting the thottling of contol valve, etc. can be pefomed by the ytem.

15 Repot Yin Heng 5. HEA PUMP FOR COOLING IN SUMMER Anothe impotant advantage of uing a heat pump i the poibility of cooling in umme. In thi poject, Ditict C need cooling duing umme. Figue 12 how the ytem ued fo that. he upply wate fom the heat pump to building i 6/C and the etun wate i about 12/C. hi ciculation wate pae the evapoato of the heat pump. Goundwate i pumped up fom the hallow poduction well at 15/C. Afte being heated by the condene of the heat pump, it i pumped back to the einjection well at 25/C. Heat fom the building(cooling) Powe of Heat Pump Heat eleae into gound Ditict C Pump Evapoato Expanion valve Heat pump unit Condene FIGURE 12: Heat pump fo cooling ytem Injection well Poduction well he baic component of a tandad heat pump ae an electic moto-diven compeo, a eveing valve, an expanion device, and two heat exchange. Refigeant ente the compeo hell a a lowtempeatue, low-peue ga. It pae aound the moto and i heated befoe enteing the intake of the compeion chambe. he compeion poce elevate both the peue and tempeatue of the efigeant ga. hi ga ente the eveing valve and i outed to the heat exchange in contact with the goundwate. Since the ga i at a high tempeatue, the goundwate can be ued to emove heat fom the efigeant in the heat exchange. Removal of heat eult in the cooling and condening of the efigeant. Peue lo i uually mall in the condene; theefoe, the efigeant exit the condene a a liquid with a tempeatue lightly above that of the envionment. he liquid then expeience a dop in peue aco the etiction in the expanion device (Rybach and Hopkik, 1995). hi caue a apid deceae in tempeatue. he tempeatue of the etun wate i much wame than the efigeant enteing the indoo heat exchange. heefoe, the liquid i evapoated, and in the poce, heat i emoved fom the building ai in the evapoato. hu, we have the deied cooling effect. he evapoated ga i then paed though the eveing valve befoe etuning to the compeo. hee ae eveal eno intalled on the heat pump fo meauing the tempeatue and peue of each inlet and outlet and phae of the efigeant. All the opeating infomation i ent to a PLC in the heat pump. Uually thee ae two et point of etun wate a ignal of the heat pump tating and topping. Fo example, in thi cae, it i et at 6 and 8/C; if the etun wate tempeatue i lowe that 6/C, the heat pump top, and tat again when the tempeatue i highe than 8/C. All the opeation ae automatically contolled by the PLC.

16 Yin Heng 410 Repot SWIMMING POOL DESIGN he hitoy of geothemal wate ue fo bathing and wimming in China can be dated back 3000 yea. In thi poject, a wimming pool will be contucted a pat of the eceation cente. It i planned to ue geothemal wate a the heat eouce. A heat exchange i employed to heat the wimming pool ciculation wate. Appopiate municipal net wate will be added fo egula eplacement of pool wate. wo additional mall pond will ue the geothemal wate diectly and maintain the tempeatue a little highe than in the wimming pool, about 40/C. Due to the pecial chemical chaacteitic of geothemal wate, a well a it high tempeatue, the ytem need a pecific deign diffeent fom conventional wimming pool. In the following, apect of geothemal wimming pool deign and poceing equipment will be dicued, a well a ome apect of common wimming pool. 6.1 Baic condition he wimming pool i located in the fit floo of the eceation cente building. Due to limited aea, it cannot be deigned like legal competition pool, with one of the thee egulation length, i.e. 25, (33.3), and 50 m. he length of the pool i 23 m, the maximum acceptable length in the eceation cente. he pool i 13 m wide and the uface aea i thu 299 m 2. he depth of the pool i 0.8 m in the hallowe end of the pool and 2 m in the deepe end, divided into pogeively thee deepe tep. he total volume of the pool appoximate 525 m 3. Figue 13 how a co-ection of the deigned pool and baic equipment. Inlet Geothemal wate Outlet Heat exchange ank Filte Filte Filte Feh wate Pump Pump Pump Dain Peliminay eeach and deign involve: FIGURE 13: he wimming pool ytem Deign of the pipe ytem fo the bain; Deign of the filtation ytem fo the wate; Deciion on the powe needed to wam up the wate and keep it wam; Choice of equipment, ize of equipment etc.; A daft of the wimming pool ytem; Point of view on enegy aving and economical iue.

17 Repot echnical outline he pipe ytem fo the wimming pool 411 Yin Heng he wate ouce of the wimming pool i municipal tap wate. Geothemal wate heat the ciculation wate though a heat exchange to maintain the pool tempeatue at 28/C. he inflow pipe fo the pool ae put in the hallowe end and connected to even ditibution pout on the wall. Outflow pipe ae put in the deepe end and connected to even ditibution dain outlet on the wall. In addition, the wate flow though 12 oveflow dain ditibuted evenly aound the peiphey of the pool. hi wate ditibution ytem i becoming vey common in pool and i conideed to give bette ciculation and blending a well a poviding fo moe efficient cleaning of the pool wate. hi oveflow ytem ha been vey ucceful, a much of the impuitie which get into the pool float on the top of wate, uch a body fat and hai (Ramewo, 1995). he mateial mot often ued fo the piping i polyvinyl chloide, but polypopane o polyethylene i a bette choice, a thee ae moe heat eitant (Svavaon, 1990). Junction and connection ae uually butt welded togethe with equipment deigned fo that pupoe. It i neceay to peue-tet all the pipe befoe final connection with at leat 0.3 MPa fo 30 minute Cleaning equiement and capacity of the wimming pool he maximum deign capacity of thi pool i 80 guet at a time. he aveage aea fo each peon i about 3.7 m 2. he quantity of pool wate flowing though the filtation equipment hould be at leat 2.0 m 3 /peon h 2 (Pekin, 1988). Hence, 160 m 3 /h of wate need to pa though the filte duing peak hou. hi mean that in jut ove 4 hou, all the wate in the pool ha gone once though the filtation equipment. It i common to ue only cloed and filte to clean pool wate. he filtation equipment conit of a wate tank of platic fibe, painted teel o tainle teel. Sand of a cetain gain ize i put in the tank, a and i a vey good natual filte. A wate ditibuto i in the tank ove the and o that all the and take equal pat in the filtation of the wate. he wate i pumped at a cetain peed though the and and the impuitie ae left in the and. he ining quality depend on the peed of the wate and inceae if the flow i low. Peue gauge on the inflow and outflow pipe mut be monitoed. When the peue dop ove the and ha eached a cetain figue, the flow though the ytem i eveed to clean the and. he ining wate mut be led into an open citen, befoe letting it into the ewe ytem o that the ining efficiency can be evaluated. he evee flow ining i contolled manually with faucet. It i poible to inceae the cleaning of pool wate by adding alum to the wate befoe it ente the cleaning equipment Enegy equiement fo heating wimming pool A mentioned befoe, the wimming pool i an indoo one. he condition of the pool ae elatively table. he indoo tempeatue i mainly maintained by the ai condition fan. he peequiite needed to calculate the equied enegy to keep a pool wam ae the following: Wate tempeatue 27/C; Outide tempeatue (indoo ai tempeatue) 20/C; Wate fom the geothemal well 70/C; Wate fom the heating ytem 42/C; Cold wate 15/C; Wind peed (due to ventilation and people moving) 1.0 m/; Ai humidity 80%.

18 Yin Heng 412 Repot 19 Heat lo fom the pool i mainly due to the following: Convection; Evapoation; Radiation; Conduction. A geneal equation i ued to calculate heat lo due to convection [W/m 2 ] (Halldóon, 1975); whee h c K+1.88 V 2 [W/m 2 A/C]; K ( w - a ) [W/m 2 A/C]; w Wate tempeatue [/C]; a Ai tempeatue [/C]; Wind peed at 2 m height [m/]. V 2 q c h c ( W - a ) (23) he equation fo the heat tanfe coefficient h c i named afte Rimha Doncenko. he value of the peequiite ae ued to calculate, q c equal to Heat lo due to evapoation. Evapoation occu becaue of diffeent patial peue of the wate team at the pool uface and in the ai ove it. Fo wate to evapoate, cetain enegy ha to exit, i.e. evapoation heat. o calculate the heat lo [W/m 2 ], the following equation fom Rimha Doncenko i ued whee e w Patial peue of team at uface [mba]; e a Patial peue of team in ai [mba]. q e (1.56 K V 2 ) (e w - e a ) (24) he humidity peue of the ai, e a, i about 5 mba, when the humidity i 80% and tempeatue i about 20/C. e w i the humidity peue of team at the wate uface. It can be aumed that in the maginal laye on the pool uface, the tempeatue i the ame a in the wate; the humidity in thi maginal laye i 100%, i.e. atuation peue i obtained. At thi tempeatue the atuation peue i 4250 Pa, i.e. e a, i equal to 42.5 mba. So q e i equal to Becaue thi pool i an indoo one, the heat lo fom adiation and conduction ae negligible. hey ae mall in compaion to heat loe fom convection and evapoation. he total enegy demand [W] of the pool can thu be calculated a: whee S i an additional value of heat lo [cal/am 2 ] given by he calculated heat load of the pool i thu 138 kw. (q c + q e + )A pool (25) S 10% (q c + q e ) (26) In thi cae, heat upplied to the wimming pool i exchanged between the geothemal wate fom the ditict heating ytem (42/C) and the ciculation wate (25/C). Aume that 138 kw enegy i needed to maintain the pool wate above 28/C, that 20 m 3 /h feh wate (15/C) will be added into the ciculation, and the efficiency of the heat exchange i about 90%; then, about 25 m 3 /h geothemal tail wate i equied. he ciculation flow ate i 160 m 3 /h and 17 m 3 /h feh wate will be added to it. hat mean 20 m 3 /h wate in the wimming pool will dain though the oveflow lane.

19 Repot Yin Heng he wimming pool need to be filled in the beginning, afte epai, and when the pool ha been dained fo pecial cleaning. he pool take about 520 m 3 of wate and filling take about 6 hou. About 87 m 3 /h feh wate (15/C) i needed and mut be heated to 28/C. o heat that amount of wate 1315kW ae needed. Geothemal wate fom the ditict heating ytem i not abundant anymoe, o an appopiate quantity of geothemal wate hould be added fom the geothemal well. 7. ENVIRONMENAL ASPECS o utain development, moe and intene attention hould be paid to the envionmental apect aociated with the utilization of a geothemal eouce. Fit, the envionmental cot of geothemal utilization i aeed and econdly the envionmental benefit gained. he common impact of low-tempeatue geothemal ytem ae: Well dilling and ytem opeation noie. hi i the mot common complaint in a cowded city like Beijing. Dilling noie i fo a hot time only, but neceay potection hould be taken by avoiding uing old intument which would make noie quite highe than elevant tandad. Sytem opeation noie, like pump and maintenance noie, ae long tem. he pump tation hould have good iolation o be contucted undegound. Low-noie equipment and intument hould be conideed in advance when deigning the ytem. Wate liquid dipoal. If the geothemal wate i diectly dipoed of into the ewage ytem it will lead to chemical and themal pollution. hi impact i a majo concen, due to it potential dange to the local envionment. Reinjection i the bet olution fo the poblem. he main envionmental benefit ae the local benefit in ai quality, due to educed buning of foil fuel. able 5 how the main emiion fom ome altenative of heating media in the popoed aea of thi poject, compaed to geothemal. ABLE 5: Main emiion fom ome altenative to geothemal utilization (M/y) Coal boile Ga boile Geothemal + heat pump CO CO SO NO X N 2 O NMVOC S PM tot In the above table, it i aumed that 73% of the electicity fo heat pump come fom coal fied powe and the emiion fom thoe powe plant ae included. he table how only the main ubtance of the emiion fom a natual ga boile and coal-fied powe plant. Many chemical ae emitted fom ga boile and the powe plant, both oganic and inoganic. Natual ga boile ae, fom an envionmental point of view a conideably bette altenative than a coal boile. he envionmentally bet altenative i geothemal uage with electical heat pump fo peak powe. hi will by fa give the leat cabon dioxide emiion and chemical pollution compaable o le than mixed ga/geothemal heating.

20 Yin Heng 414 Repot 19 ACKNOWLEDGEMENS I would like to expe my gatitude to the United Nation Univeity fo giving me the oppotunity to paticipate in the Geothemal aining Pogamme. Epecially to D. Ingva B. Fidleifon, diecto of the UNU, to M. Lúdvík S. Geogon, deputy diecto, and to M. Gudún Bjanadótti fo he aitance and kind help duing the pat ix month. My pecial thank go to my upevio, holeiku Jóhanneon and Páll Valdimaon, fo giving me patient and efficient guidance and fo haing thei knowledge and expeience, which made thi epot poible. Special thank to the lectue in the intoductoy and pecialied pat of the coue, both fom Okutofnun and othe companie o intitute. Deepet thank to all othe taff membe at Okutofnun fo thei valuable teaching and help. Finally, I am geatly indebted to my intitute and D. Zhao Ping, fo ecommending me to attend the pecial taining. Wamet wihe to them, I believe I will happily wok with them and ue the knowledge I leaned in the geothemal development of China. REFERENCES Dai C., 1996: hemal analyi of indiect geothemal ditict heating ytem. Geothemic, 26-3, Dai C., and Liang J., 2000: Diect and indiect low tempeatue geothemal ditict heating ytem. Poceeding of the Wold Geothemal Conge 2000, Kyuhu - ohoku, Japan, Halldóon, G., 1975: Heating and cleaning of wate in wimming pool. Sigudu hoodden Conulting Enginee, epot S (in Icelandic), 63 pp. Kalon, h., 1982: Geothemal ditict heating. he Iceland expeience. UNU G..P., Iceland, epot 4, 116 pp. Pekin, P.H., 1988: Swimming pool. Elevie Applied Science Ltd., London, 359 pp. Ramewo, M., 1995: Deign of a dye and a wimming pool uing geothemal wate. Repot 7 in: Geothemal aining in Iceland UNU G..P., Rybach, L., and Hopkik, R.J., 1995: Shallow and deep boehole heat exchange achievement and popect. Poceeding of Wold Geothemal Conge 1995, Floence, Italy, 3, Svavaon, G., 1990: Deigning wimming pool. Univeity of Iceland, B.Sc. thei (in Icelandic), 52 pp. Valdimaon, P., 1993: Modelling of geothemal ditict heating ytem. Univeity of Iceland, Ph.D. thei, 315 pp. Zhu, B., Xing, H., Lou, H., and Xie, D., 2001: Application of heat pump in geothemal ditict heating of Beijing. Poceeding of China Geothemal Ditict Heating Sympoium, Fuzhou