Payback Period Estimation of Ground-Source and Air-Source Multi Heat Pumps in Korea Based on Yearly Running Cost Simulation

Transcription

1 Purdue nverty Purdue e-pub Internatonal Refrgeraton and Ar ondtonng onference Scool of Mecancal Engneerng 00 Payback Perod Etmaton of Ground-Source and Ar-Source Mult Heat Pump n Korea Baed on Yearly Runnng ot Smulaton Noma Park G Electronc Seung-Hyun Jung G Electronc Hee-Woong Park G Electronc Hwan-Jong o G Electronc Smon n G Electronc See next page for addtonal autor Follow t and addtonal work at: ttp://doc.lb.purdue.edu/racc Park, Noma; Jung, Seung-Hyun; Park, Hee-Woong; o, Hwan-Jong; n, Smon; and Jung, Hoon, "Payback Perod Etmaton of Ground-Source and Ar-Source Mult Heat Pump n Korea Baed on Yearly Runnng ot Smulaton" (00). Internatonal Refrgeraton and Ar ondtonng onference. Paper 46. ttp://doc.lb.purdue.edu/racc/46 document a been made avalable troug Purdue e-pub, a ervce of te Purdue nverty brare. Pleae contact epub@purdue.edu for addtonal nformaton. omplete proceedng may be acqured n prnt and on D-ROM drectly from te Ray W. Herrck aboratore at ttp://engneerng.purdue.edu/ Herrck/Event/orderlt.tml

2 Autor Noma Park, Seung-Hyun Jung, Hee-Woong Park, Hwan-Jong o, Smon n, and Hoon Jung artcle avalable at Purdue e-pub: ttp://doc.lb.purdue.edu/racc/46

3 496, Page Payback Perod Etmaton of Ground-Source and Ar-Source Mult Heat Pump n Korea Baed on Yearly Runnng ot Smulaton Noma PARK *, Seung-Hyun JNG, Hee-Woong PARK, Hwan-Jong HOI, Smon HIN, and Hoon JNG G Electronc Inc., orporate Ar ondtonng R&D aboratory 37-3, Gaan-Dong, Geumceon-Gu, Seoul, 53-80, Korea Pone: , e-mal: noma.park@lge.com, dave.jung@lge.com, eewoong.park@lge.com, wanjong.co@lge.com, mon.cn@lge.com Korea Electrc Power Reearc Inttute, Munj-Ro 65, Yuung-Gu, Daejeon, , Korea Pone: , e-mal: oony77@kepr.re.kr * orrepondng Autor ABSRA In t tudy, we compute yearly runnng cot of ar- and ground-ource mult eat pump for pace coolng, floor eatng, and dometc ot water. From computed yearly runnng cot, payback perod wa computed wen tey replace te ga-fred boler and ar-condtoner combnaton. oward accurate runnng cot mulaton, we develop an n-oue mulaton code tat ntegrate eat pump performance, realtc floor eatng, pace coolng by ndoor unt, and ot water torage tank. Annual runnng cot computed by ntegratng nput power conumpton by te compreor and pump baed on detaled ourly outdoor temperature data of Seoul and dometc ot water uage pattern. It own tat te annual runnng cot of ground- and ar-ource eat pump are, repectvely, 0~45%, and 56% of tat of boler and ar condtoner, and tat te payback perod are from 3.0 to 5 year dependng on te progreve electrcty tax, ubdy level for te ntallaton cot, and dcarge water temperature control metod.. INRODION Heat pump are condered a promng alternatve to ga/ol-fred boler n te ene tat tey do not ue fol fuel, and tat tey are gly effcent and tu emt le O tan boler. It epecally true to a number of E countre, were eat pump already take non-neglgble porton n te local eatng market tank to ubtantal ncentve and ubde. However, eat pump are not yet accepted a redental eatng oluton n Korea due to unacceptably g ntal cot and te progreve tax n te electrcty cot. In addton, for te cae of ground ource eat pump (denoted a GSHP erenafter), boreole contructon cot nurmountably g to overwelm all oter economc mert of GSHP (Fgure ). Very recently, tee urdle are beng removed by te government draftng energy polce favorable to eat pump. e mot mportant cange te ubde and exempton of te progreve tax n electrcty bll for product ung renewable energy, wc te cae wt GSHP. Now te prce of electrcty per kw comparable to tat of ga o tat te runnng cot competton wt boler become mply te matter of OP. However, nce ar-ource eat pump (denoted a ASHP) are not regarded a renewable energy product, ASHP ould prove t own compettvene wtout ubdy purely baed on t low energy conumpton and relatvely low ntal cot a compared to GSHP. Internatonal Refrgeraton and Ar ondtonng onference at Purdue, July -5, 00

4 496, Page Fgure : Intal cot (product ntallaton) comparon between boler ar condtoner and mult eat pump n Korea. Here, cot are n S dollar. e man objectve of te preent tudy are ) to elucdate te economc vablty of GSHP and ASHP by takng te above mentoned envronmental cange nto conderaton, ) to fnd te optmal control logc to maxmze energy avng, and 3) to fnd ngt nto approprate amount of ubdy for eat pump and reaonable electrcty tarff ytem. o t end one need an accurate annual mulaton tool for te realtc etmaton of energy conumpton and dynamc repone of eat pump to urroundng. oward accurate runnng cot mulaton, we develop an n-oue mulaton code tat ntegrate eat pump cycle, realtc floor eatng, pace coolng/eatng by n-door unt (ID), ot water torage tank. For eat pump cycle mulaton, compreor and eat excanger are modeled by regreon ft of expermental data. In order to calculate ntantaneou room temperature, mplfed model for eac zone wt ID combned wt analytc oluton of eat equaton on te urface of floor wt ot water flowng underneat. One-dmenonal water/termal torage tank model developed to account for te tratfcaton effect. paper organzed a follow: In ecton, we decrbe te man caractertc of ASHP and GSHP condered n t tudy. Governng equaton, numercal metod, floor eatng mulaton metod, outdoor temperature and ot water uage pattern are gven n Secton 3. Smulaton reult and runnng cot etmaton performed n Secton 4, and te ummary and concluon are gven n Secton 5.. MI HEA PMPS GSHP condered n t tudy an all-n-one type mult nverter eat pump wt ngle outdoor unt tat contan tree water-refrgerant eat excanger (HEX), wc are for ground water, floor eatng, and dometc ot water, repectvely. It adopt 5p nverter compreor, woe nomnal coolng and eatng capacte are 4.5 kw and 6 kw, repectvely. See able for more detal on te pecfcaton of GSHP. e cematc of GSHP operaton cene depcted n Fgure. A own n Fgure, ndoor unt (ID) are ued for pace coolng, and floor eatng condered ntead of eatng by ID nce te floor eatng cloe to tradtonal Ondol eatng and, tu, te mot preferred eatng opton n Korea. e nomnal dometc ot water (DHW) capacty 5kW and DHW at pecfed temperature aceved by te mxng valve. e ze of te antary tank 00 lter, wc large enoug to cover averaged daly ot water demand. Internatonal Refrgeraton and Ar ondtonng onference at Purdue, July -5, 00

5 496, Page 3 able : Specfcaton of GSHP and ASHP Fgure : Scematc on man functonalty of ground ource eat pump. A own n able, te pecfcaton of ASHP bacally mlar to GSHP except tat t adopt fn-tube HEX ntead of ground HEX, and tat ASHP a plt-type one tat a ID called ydro-kt avng water-refrgerant for floor eatng and DHW (Fgure 3). Internatonal Refrgeraton and Ar ondtonng onference at Purdue, July -5, 00

6 496, Page 4 Fgure 3: A mplfed model for runnng cot mulaton of ASHP 3. YEARY RNNING OS SIMAION In t ecton, yearly runnng cot mulaton metodology ummarzed ncludng ytem confguraton, governng equaton, dcretzaton metod, outdoor temperature, floor eatng mulaton, and antary tank mulaton. 3. Sytem confguraton and governng equaton A own n Fgure 3 for ASHP ytem, we conder a mplfed model oue wt 0m () by 0m (D) by.7m (H) ze, and a 0.5m dameter, 00 lter antary tank. We alo conder te ame ntallaton cene for GSHP. In order to mplfy te mulaton only one ID and ngle zone condered. However, t approac can be ealy expanded to mult-zone mulaton. e man purpoe of t mulaton to run eat pump to mantan ettng ndoor and antary tank temperature a actual eatng/coolng ytem doe, and to meaure correpondng energy conumpton. Indoor and antary tank temperature are aumed to obey te followng lumped and one-dmenonal energy equaton dd md p, ar = Q floor QID d Aoue( d od ), dt () S S S ρ w p, w AS u = qp ( z) kas ( ), S S od t z z () Were d, S, and OD are, repectvely, temperature of ndoor, antary tank and outdoor. Q floor, Q ID, and q p (z) denote eat capacty gven by floor eatng, ID coolng and nternal HEX of antary tank, repectvely, were z denote coordnate drecton of tank egt. md = ρarvoue te wegt of ndoor ar, A oue te urface area of te oue, A S te cro ectonal area of antary tank, and te permeter of te antary tank. d and S, repectvely, are eat lo coeffcent of oue and antary tank. Snce lo coeffcent play te crucal role n te determnaton of termal load, a evdent from equaton () and (), te energy conumpton gly dependent upon te coce of tee value. omputatonal parameter ncludng lo coeffcent and operatonal condton of HP are ummarzed n able. Internatonal Refrgeraton and Ar ondtonng onference at Purdue, July -5, 00

7 496, Page 5 able : ondton for yearly runnng cot mulaton Snce energy conumpton by DHW take relatvely mall porton n te total energy conumpton, equaton () can be replaced by a lumped one lke equaton () wtout caung gnfcant error. However, one-dmenonal ytem preferred to accurately ee te effect of tratfcaton on te energy conumpton. For te patal dcretzaton of (), trd-order upwnd dfference and econd order central dfference are adopted for convecton and dffuon term, repectvely. A pecal care ould be gven to te boundary condton of equaton (), nce te nlet and outlet mxng a gnfcant mpact on te temperature dtrbuton. We followed te defnton of mxng parameter derved by Nelol et al. (998) for boundary condton. Snce nverter compreor adopted coolng and eatng capacte are ubject to cange accordng to coolng and termal load. e control logc for cangng capacte wll be explaned later. In order to compute requred power nput for gven eat capacty and outdoor/ndoor condton, one can numercally mulate eat pump baed on model on compreor, evaporator, condener and expanon devce (ee, e.g. Zao et al., 003). However, uc a detaled numercal mulaton not approprate for te preent annual runnng cot mulaton due to gnfcant computatonal overead. Intead, for a gven nverter coolng load and external condton, power nput or coeffcent of performance (OP) for ASHP gven by te followng regreon ft: OPcoolng c0 c d cod c3 = Q, (3) ID Fgure 4: Heatng OP of ASHP at varou condton: (a) jont PDF between expermental data and econd order regreon ft; (b) OP at varou outdoor and water temperature condton at nomnal eat capacty. Internatonal Refrgeraton and Ar ondtonng onference at Purdue, July -5, 00

8 496, Page 6 were c 0 ~ c 3 are determned by te error mnmzaton wt repect to expermental data at varou condton n te leat-quare ene. Smlarly, OP for floor eatng gven by OP = Q Q Q Q, (4) eatng 0 w w 3 od 4 od 5 ID 6 ID 7 w od 8 w ID 9 od ID were coeffcent 0 ~ 9 are agan determned from te leat-quare ft of expermental data. For te cae of eatng, econd order regreon condered a frt order regreon owed non-neglgble catter wt expermental data. Fgure 4 ow eatng OP gven by equaton (4) and expermental data. A own by Fgure 4(b), OP trongly dependent upon outdoor temperature and water temperature, nce tey ave trong correlaton wt evaporatng and condenng temperature, repectvely. OP of DHW take te ame form a equaton (4) wt dfferent coeffcent. For GSHP, OP ndrectly nfluenced by outdoor temperature, but governed by water temperature of ground HEX. u, te outdoor temperature od n te regreon ft (3) and (4) replaced te ground HEX water temperature. For te temporal ntegraton of () and (), 4 t order Runge-Kutta metod appled at fxed tme tep Δ t = 60 ec = mn, and te ntegraton carred out for a year, or for = 55,600 tme tep. Once we know eatng capacty, for example, and correpondng OP te energy conumpton durng a pecfed perod readly computed by t Q ( ~ ) = eatng E eatng t t dt. (5) t OP eatng Energy conumpton by coolng and DHW can be computed n te ame way. 3. Outdoor temperature, daly ot water conumpton, and ground HEX temperature For te runnng cot mulaton decrbed n te prevou ecton, one need outdoor temperature data and daly ot water conumpton amount and detaled uage pattern. For outdoor temperature, we adopt publed data for weater data at Seoul (Km and Km, 003), gven by te followng ere form: ( d, ) = 3 n= 0 nd An ( )co 365 nd Bn ( )n. 365 (6) Snce t data gven at eac our for a complete year, lnear nterpolaton ued to obtan mnute-by-mnute data. A complete ourly plot of equaton (6) gven n Fgure 5. For daly ot water uage pattern, we adopt a tandard JRA data for DHW (Yokoyama et al., 00) a own n Fgure 6. ange of daly DHW uage modeled by multplyng contant factor to te pattern own n Fgure 6. In t tudy, 70 lter of daly ot water conumpton aumed trougout a year. On te oter and, te effcency of GSHP drectly nfluenced by te ol temperature, wc te functon of boreole dept and outdoor temperature (Kauda and Arcenbac, 965): ol ( z, t) = mean amp exp z 365α 0.5 co t t 365 ft z 365α 0.5, (7) were mean te mean urface temperature (average ar temperature), amp te ampltude of urface temperature, and ft te day of te year of te mnmum urface temperature. ey are gven by equaton (6), te outdoor temperature data. α te termal dffuvty of te ol. In t tudy, we aume te type vertcal boreole woe dept 00m. en, local ground HEX temperature GH determned by te conductve and convectve eat tranfer wt ol. e termal retance of ol can be calculated ung te lnear ource teory or cylndrcal ource teory, wle tat nde te boreole more complcated due to te ntegrated retance of flud convecton, and te conducton troug ppe and grout (u et al., 009). In te preent tudy, we mply aume a fxed total Internatonal Refrgeraton and Ar ondtonng onference at Purdue, July -5, 00

9 496, Page 7 termal retance R = 05m. K/ W, from expermental data from u et al. (009), o tat eat tranfer per dept gven by q ( GH ol )/ R(W / m) blank lne below te ttle. =. enter te manucrpt ttle wt font ze of 4-pont bolded wt a Fgure 5: A complete ourly plot of modeled outdoor temperature at Seoul (Km and Km, 003). Fgure 6: daly dometc ot water uage pattern Internatonal Refrgeraton and Ar ondtonng onference at Purdue, July -5, 00

10 496, Page 8 Fgure 7: emperature dtrbuton of floor baed on analytc oluton and ppe-by-ppe eat balance 3.3 Floor eatng mulaton In order to accurately mulate floor eatng, we propoe a new ppe-by-ppe metod. A own n Fgure 7 (b), eat tranferred to te room by a ppe equvalent to eat lo by te temperature decreae acro ppe: 4 4 ( ) σεa( ) = m ( ) δ Q, (8) = n c A,, amb, amb p, w were, and denote averaged urface temperature of te floor egment wt area, A under conderaton and t negbor, repectvely, and and are correpondng water temperature flowng nde te ppe. Here, σ te Stefan-Boltzmann contant, ε = 0. 8 te emvty of radaton. By uccevely applyng equaton (8) to eac floor egment, one can determne te entre urface temperature dtrbuton, total eat tranferred to te room, and return water temperature. n, c = k Nu / te natural eat tranfer coeffcent determned by (urcll and u 975) / Ra Nu = /6 8/ 7, (9) [ (0.49/ Pr) ] were Ra te Rayleg number, and = A/ te caractertc lengt, and te permeter of te area egment. In order to olve equaton (8), we need correlaton between te floor urface temperature and te water temperature nde ppe. o t end, we ue te analytc oluton of te followng eat equaton = A ( x, z) =, f 3 ( ) A( ), x z δ, (0) Internatonal Refrgeraton and Ar ondtonng onference at Purdue, July -5, 00

11 496, Page 9 Internatonal Refrgeraton and Ar ondtonng onference at Purdue, July -5, 00 were and are convectve eat tranfer coeffcent for upper and lower de of floor materal (Fgure 7(a)),, and 3 are room temperature, bottom wall temperature, and water temperature nde te ppe. δ te dameter of te ppe and te termal conductvty of floor materal uc a cement mortar. e analytc oluton of equaton (0) take te followng form (Holopanen et al., 007): ( ) ( ) ( ) ( ) ( ) { } Γ = = 3 co / exp ) ( ) ( / exp / / ) / ( / ), ( x z g g z z z z d z x () were ( ) ( ) ( ) ( ). 4 exp 4 exp 4 exp ) (,, ) ( ) ( ln 3 = = = Γ = = d d d d d g d g g δ () Here, d, d and are geometrcal parameter defned n Fgure 7(a). In t tudy, tee parameter are gven a follow: cm d 5 =, cm d 5 =, cm 0 =, and K m W = / 0.4. e bottom wall temperature aumed to be 8 o, and eat tranfer coeffcent are teratvely determned untl tey matc computed value by equaton (8) and (9). Fgure 8 ow reult from floor eatng mulaton, or overall eat tranfer coeffcent, floor eatng capacty, water return temperature, and averaged urface temperature a functon of nlet water temperature. Here, 8 o of ndoor temperature and 0 PM (lter per mnute) of water ma flow rate aumed. A own n te fgure, overall eat tranfer coeffcent are n te range of 6 ~ 8 W/m K, wc are n good agreement wt prevou reult (Karadag 009). e amount of eat ejected from 00m urface, a own n fgure 8, le tan 0 kw for water temperature up to 70 o. fact gve a valuable ngt nto eat pump operaton tat current eat pump woe nomnal capacty are 6kW would run under partal load condton, and tat tere uffcent room for multaneou operaton for DHW. Fgure 8: floor eatng mulaton reult: (a) eat tranfer coeffcent & floor eatng capacty; (b) Return water temperature and averaged urface temperature at varou water nlet temperature for a 00m oue.

12 496, Page 0 It tell anoter tory on te optmal water dcarge temperature. Snce, we are dealng wt a low energy oue wt d = 0.4W / m K, termal load to mantan 5 o ndoor temperature at -5 o outdoor temperature only Q = d Aoue( d od ) = 0.4 ( ) 40 = 4.93kW. erefore, from fgure 8, t appear tat water temperature doe not ave to exceed 50 o to cover te maxmum termal load. mple tat for low energy oue, g water temperature no longer requred, and t fact epecally favorable to eat pump wt R40A woe maxmum condenng temperature lower tan 55 o. 3.4 Dcarge water temperature control e man objectve of eatng and coolng to mantan dered ndoor temperature wt mnmal devaton or fluctuaton. o t end, eat pump wt fxed rotaton frequency uually turn on and off compreor frequently. Werea eat pump adoptng nverter accompl t objectve by cangng te rotaton frequency of te compreor accordng to gven load. From equaton (), t obvou tat dered eat pump capacty Q deal = A ( ), amb (3) d oue wt wc ndoor temperature reman uncanged once t reace ettng value. However, mpong Q deal a target mpractcal nce te exact value of lo coeffcent ard to know and cangng accordng to external weater condton. In practce, o called weater compenated control often adopted to aceve energy avng, wc cange target dcarge temperature to be precrbed on correpondng to outdoor temperature. However, tere no guarantee tat precrbed target temperature rgt one to matc termal load. Here, we propoe a dynamc dcarge water temperature control metod purely baed on termo off tme, or tme requred to rae ndoor temperature up to termotat ettng temperature. e man dea to rae (reduce) dcarge temperature wen meaured termo-off tme too long (ort) a compared to dered termo-off tme. metod appear ound n te ene tat ll-degned ar condtonng devce wt exceve capacty reult n frequent termo-off, and vce vera. e logcal expreon for t control ummarzed a follow: f termo off > target,max et, new = f termooff < target,mn et, new = f no termo off untl fal et, et et new d, d, o = 5, (4) were target,mn and target,max are, repectvely, mnmal and maxmum allowable target termo-off tme. e lat condton te falafe condton to prevent no termo-off due to unexpected decreae of outdoor temperature, wc proven to be neceary. e temperature ncrement d and d are gven by d d = mnd = mnd max max,, ta rget,max ta rget,mn ta rget,max ta rget,mn termooff termooff d d max max,, (5) were a rater arbtrary value d = max 0o et a te lmtaton of te ncrement to enure mld varaton of temperature. e man advantage of te current control tat t completely black box approac, wc doe not need any oter nformaton tan termo-off tme. u, t applcable to any eatng and coolng ytem compatble wt dcarge ar/water temperature varaton. e mpact of te propoed control metod on te energy effcency wll be nvetgated n te followng ecton. Internatonal Refrgeraton and Ar ondtonng onference at Purdue, July -5, 00

13 496, Page able 3: Summary of annual mulaton 4. SIMAION RESS AND PAYBAK PERIOD ESIMAION Summary of mulaton decrbed n te prevou ecton gven n able 3, were annual energy conumpton, overall OP, electrcty cot and O emon are compared for varou oluton. 4. Boler ar condtoner combnaton For te mulaton of boler ar condtoner combnaton (denoted a conventonal ytem erenafter), developed code for eat pump are modfed to ave OP of 0.9 for water eatng at all water temperature up to 70 o, and reduce te ze of antary tank to be 0 lter o tat t can be ncluded nde te boler jut a current condenng boler. omputed energy conumpton by boler ar condtoner and annual energy cot agree well wt averaged redental energy eatng/coolng conumpton (~0,000 kw/year) and correpondng annual eatng plu coolng cot (~,000$) for 00m oue n Korea. enance te relablty of preent numercal mulaton. 4. Ground ource eat pump A ndcated n able 3, 50% ubdy for te ntallaton cot condered for GSHP, wle no ubdy aumed for ASHP. For electrcty cot, bacally current 6-level progreve tarff by KEPO (Korea Electrc Power orporaton; ee and An 006) condered. In addton to t, fxed rate cot (0.07 $/kw) alo condered for GSHP nce t gly probable to get progreve tax exempton n te near future for te cae of GSHP. It own tat overall OP a g a 5.3 for GSHP, wc defned a annual energy output over energy conumpton. u, annual energy conumpton by GSHP only 7% of tat by te conventonal ytem, reultng n 60% and 80% reducton n annual energy cot wt and wtout progreve tax n electrcty. nder t condton, payback perod of GSHP, wen t replace conventonal ytem, are only 3. and 4. year, repectvely. mple tat GSHP tll gly compettve wtout progreve tax exempton. A own n Fgure 9(b), epecally low runnng cot requred n wnter nce, unlke ASHP, te evaporatng temperature le entve to outdoor temperature. u, montly energy bll doe not exceed 70 $ even wt current electrcty tarff ytem. A wll be own, uc gnfcant reducton of te runnng cot prmarly due to dynamc water temperature control. Internatonal Refrgeraton and Ar ondtonng onference at Purdue, July -5, 00

14 496, Page Fgure 9: Reult from annual mulaton. (a) Intantaneou temperature evoluton on January 4 from ASHP and GSHP, (b) montly energy bll wt varou oluton Fgure 0: Payback perod etmaton of GSHP mult (w/ and w/o progreve tax and ubdy) wt repect to boler ar condtoner. Fnally, n order to ee te effect of ubdy level, we computed payback agan wt no ubdy et al. to get 5. year and.3 year wt and wtout progreve tarff (Fgure 0). erefore, t can be concluded tat te level of ubdy te mot mportant factor to determne vablty of GSHP. 4.3 Ar ource eat pump Snce no ubdy or ncentve can be expected for ASHP a mentoned earler, n order for ASHP to be compettve, t runnng cot ould be ubtantally le tan tat of te conventonal ytem. So far, t a not been te cae n Korea manly due to progreve electrcty tarff unfavorable to eat pump. In order to reproduce t tuaton, we performed ASHP mulaton wt fxed dcarge water temperature for eatng at 5 o, and reult are ummarzed n able 3. A own, a reaonable overall OP of 3.38 obtaned and tu, annual energy conumpton only 8% of te conventonal ytem. Nevertele, annual runnng cot of ASHP over 80% of tat of te conventonal ytem to end up wt almot 0 year of payback. erefore, ASHP n te margnal zone n te ene tat a lgt degradaton of OP would mean no payback at all. A nce way of gettng out of t zone to ntroduce dynamc temperature control, a ummarzed n able 3. By adoptng dynamc water temperature control, overall OP ncreaed to be 4.5. nder t condton, te annual energy conumpton and energy cot, repectvely, are 3% and 54% of te conventonal ytem. Now, correpondng payback perod 4. year. A own n Fgure 9(b), montly runnng cot of ASHP at leat 0% ceaper tan te conventonal ytem for all mont. It urprng to ee a mple cange n te water temperature control logc can gnfcant enancement of ASHP feablty. Internatonal Refrgeraton and Ar ondtonng onference at Purdue, July -5, 00

15 496, Page 3 Fgure : Varaton n te floor eatng water temperature wt A(G)SHP durng (a) a day (Jan. 4) and (b) year. For (b), daly average plotted. 4.4 e effect of dynamc dcarge water temperature control Fgure 9(a) ow ntantaneou temperature evoluton from bot GSHP and ASHP on January, 4 wt dynamc water temperature control. It own tat bot ndoor and antary tank mantan ettng temperature wt mall varaton. For floor eatng, t een tat total 30 termo-off event occurred durng a day, wc correpond to 48 mnute average termo-off tme. mean tat te current dynamc control wt 45 mnute target termo-off tme (ee table ) uccefully workng. Here target,mn and target,max are et 30 and 60 mnute, repectvely. e correpondng ntantaneou water temperature varaton own n Fgure (a). nlke fxed temperature control at 5 o, dynamc ceme cange water temperature from 44 o to 5 o. It alo own tat te temperature varaton rougly correpond to tat of outdoor temperature own n Fgure 9(a). Intended or not, termo-off tme baed control metod alo a nce weater compenated control wtout enng outdoor temperature. feature clearly own by daly mean water dcarge temperature for a year a own n Fgure (b). One can ee tat daly mean water dcarge temperature vare from 30 o to 46 o, and a perfect compenaton to te outdoor temperature own n Fgure 5(a). erefore, t no wonder tat dynamc control metod enance OP by more tan 0% a compared to fxed water temperature metod f we recall tat OP gly entve to dcarge water temperature a own n Fgure 4(b). 6. ONSIONS In t tudy, we propoed metodology for computng yearly runnng cot of ar- and ground-ource mult eat pump and performed annual mulaton to etmate economcal compettvene of eat pump n Korea. ondered one are mult eat pump for pace coolng, floor eatng, and dometc ot water, wc are condered a te replacement of te ga-fred boler and ar-condtoner combnaton, or te conventonal eatng/coolng ytem n Korea. oward accurate runnng cot mulaton, we developed an n-oue mulaton code tat ntegrate eat pump performance, realtc floor eatng, pace coolng by ndoor unt, and ot water torage tank. Annual runnng cot wa computed by ntegratng nput power conumpton by te compreor and pump baed on detaled ourly outdoor temperature data of Seoul and dometc ot water uage pattern. For floor eatng mulaton, we propoed a ppe-by-ppe metod combned wt analytc oluton of eat equaton n order to fnd te relatonp between water temperature and ma flow rate nde ppe and eat releaed by floor urface of gven area. We alo propoed dynamc dcarge water temperature control algortm for floor eatng baed purely on target termotat-off tme. It own tat te annual runnng cot of ground- and ar-ource eat pump are, repectvely, 0~45%, and 56% of tat of boler and ar condtoner, and tat te payback perod are from 3.0 to 5 year dependng on te progreve electrcty tax, ubdy level for te ntallaton cot, and dcarge water temperature control metod. Internatonal Refrgeraton and Ar ondtonng onference at Purdue, July -5, 00

16 496, Page 4 For ground-ource eat pump, te level of ubdy for te ntallaton cot play detrmental role n avng realtc payback. Werea, te mpact of progreve tax n te electrcty tarff on te payback relatvely mall. On te oter and, t agan own tat te runnng cot avng by conventonal ar-ource eat pump over ga-fred boler mall under current electrcty tarff. However, wen a dynamc water dcarge temperature control metod employed, over 0% ncreae of OP expected and te correpondng payback perod ortened to be 4. year, wc gly appealng to end uer wo are to be new oue redent. Promng a t may eem, te preent tudy purely numercal one baed on eat pump performance from laboratory data. e confrmaton of te preent concluon by feld tet at reference te te topc of our ubequent reearc. REFERENES urcll, S. W., and u, H. H. S., 975, orrelatng equaton for lamnar and turbulent free convecton from a vertcal plate, Int. J. Heat Ma ranfer, vol. 8: pp Holopanen, R., uomaala, P., Pppo, J., 007, neven grddng of termal nodal network n floor eatng mulaton, Energy and Buldng, vol. 39: p Karadag, R., 009, e nvetgaton of relaton between radatve and convectve eat tranfer coeffcent at te celng n a cooled celng room, Energy converon and management, vol. 50: p -5. Kauda,., and Arcenbac, P.R., 965, Eart emperature and ermal Dffuvty at Selected Staton n te nted State, ASHRAE ranacton, vol. 7, Part. Km, S. and Km, Y., 003, Development of Standard weater data correlaton of Seoul, Journal of Ar-condtonng and Refrgeraton, vol. 9, no. 4: p ee, B. and An, H., 006, Electrcty ndutry retructurng revted: te cae of Korea, Energy Polcy, vol. 34: p 5-6. u J., Zang X., Gao J., and Yang J., 009, Evaluaton of eat excange rate of GHE n geotermal eat pump ytem, Renewable Energy, vol. 34: p Nelol, J. E. B., Balakrnan, A. R., Srnvaa Murty, S., 998, ranent analy of energy torage n a termally tratfed water tank, Int. J Ener. Re., vol. : p Yokoyama, R., Waku,., Kamakar, J., akemura, K., 00, Performance analy of a O eat pump water eatng ytem under a daly cange n a tandardzed demand, Energy, vol. 35: pp Zao, P.., Dng, G.., Zang,.., Zao,., 003, Smulaton of a geotermal eat pump wt non-azeotropc mxture, Appled ermal Engneerng 3: p AKNOWEDGEMEN work wa upported by Ar ondtonng Reearc and Development aboratory n G Electronc Inc. Internatonal Refrgeraton and Ar ondtonng onference at Purdue, July -5, 00