Performance evaluation of hybrid PVthermal waterai

RenewableEnergy31(2006)2460–2474PerformanceevaluationofhybridPV/thermalwater/airheatingsystem:AparametricstudyArvindTiwari
,M.S.SodhaCentreforEnergyStudies,IndianInstituteofTechnologyDelhi,HauzKhas,NewDelhi-110016,IndiaReceived18May2005;accepted6December2005Availableonline7February2006AbstractInthispaper,athermalmodelofanintegratedphotovoltaicandthermalsolar(IPVTS)water/airheatingsystemhasbeendeveloped.AnanalyticalexpressionforthetemperatureofsolarcellandwaterandanoverallthermalefficiencyofIPVTSsystemhavebeenderivedasafunctionofclimaticanddesignparameters.NumericalcomputationshavebeencarriedoutforcompositeclimateofNewDelhiforparametricstudies.Fourconfigurations,namely(a)unglazedwithtedlar(UGT),(b)glazedwithtedlar(GT),(c)unglazedwithouttedlar(UGWT)and(d)glazedwithouttedlar(GWT)havebeenconsidered.ComparisonoftheIPVTSsystemwithwaterandairheaterhasalsobeencarriedout.ItisfoundthatthecharacteristicdailyefficiencyofIPVTSsystemwithwaterishigherthanwithairforallconfigurationsexceptGWT.ItisalsoobservedthatanoverallthermalefficiencyofIPVTSsystemforsummerandwinterconditionsisabout65%and77%,respectively.r2006ElsevierLtd.Allrightsreserved.Keywords:HybridPV/thermal;Solarenergy;Water/airheater1.IntroductionThemainreasonsforreductionofelectricalefficiencyofthephotovoltaic(PV)modulearepackingfactor(PF),ohmiclossesbetweentwoconsecutivesolarcellsandtheincreaseinthetemperatureofthePVmoduleduetosolarradiation.TheoverallelectricalefficiencyofthePVmodulecanbeincreasedeitherbyincreasingthePForreducingthetemperatureofthePVmodulebyusingthethermalenergyassociatedwithPVmodule[1,2]orbyboth.ARTICLEINPRESS:10.1016/j.renene.2005.12.002
Correspondingauthor.Tel.:[phone].E-mailaddress:[e-mail](A.Tiwari).ARTICLEINPRESSNomenclatureAarea,m2bbreadth,mCspecificheat,J/kgKFRflowratefactor,nounithheattransfercoefficient,W/m2Khp1penaltyfactor,nounithp2penaltyfactor,nounitI(t)incidentsolarintensity,W/m2Kthermalconductivity,W/mKLlength,mMmass,kg_Qurateofusefulenergytransfer,Wttime,sTtemperature,1CUbanoverallheattransfercoefficientfrombottomtoambient,W/m2KULanoverallheattransfercoefficientfromsolarcelltoambientthroughtopandbacksurfaceofinsulation,W/m2KUtanoverallheattransfercoefficientfromsolarcelltoambientthroughglasscover,W/m2KUTconductiveheattransfercoefficientfromsolarcelltowaterthroughtedlar,W/m2KUtTanoverallheattransfercoefficientfromglasstotedlarthroughsolarcell,W/m2KUtwanoverallheattransfercoefficientfromglasstowaterthroughsolarcellandtedlar,W/m2KSubscriptsoglasstoambientaambientbsbacksurfaceoftedlarcsolarcelleffeffectiveffluidfiinletfluidGglassiinsulationrreferencewwaterTtedlarththermalA.Tiwari,M.S.Sodha/RenewableEnergy31(2006)2460–24742461TheutilizationofthermalenergycanbeachievedbyflowingeitherthewaterorairbelowPVmodule[1–4].TherateofthermalenergyavailablewithPVmodulewasestimatedbyJonesandUnderwood[5]bydevelopinganon-steady-statethermalmodelforPVsystem(BP585)byconsideringtheeffectofheatcapacityofthePVmodule.Infieldetal.[6]haveanalyzedasystemthatconsistsofthePVmoduleanddoubleglasswall.TheyhaveconcludedthatthetemperatureofthePVmodulecanbereducedbyflowingairbetweenthePVmoduleanddoubleglasswall.TheavailableextractedthermalenergyfromPVmodulecanbeusedeitherforspaceheatingorcropdrying.Forthewaterheating,twotypesofcombi-panel(hybridPV/T)havebeenconsidered,namely(i)Thetube-in-plateconfiguration,[1,2,7,8,13]and(ii)Theparallelplateconfiguration[4,7].ThetransientbehaviorofahybridPV/Tforbothwaterandairascarriersofthermalenergyforcogenerationoftheelectricityandthehotair/waterforparallelplateconfigurationwasstudiedindetailbyPrakash[4].HeconcludedthattheoverallefficiencyofthePV/Tsystemissignificantlyincreasedforbothwaterandairheater.However,hecouldnotcomparetheperformanceofthehybridPV/Twaterandairheaters.TheincreaseoftheoverallefficiencyofthehybridPV/Tsystemreducesenergypaybacktime(EPBT),whichofcourseaffectsthetechno-economicanalysisofthehybridPV/Tsystem.Inthispaper,thermalmodelsofintegratedphotovoltaicandthermalsystem(IPVTS)developedbyTiwariandSodha[8]havebeenconsideredforparametricstudiesandforcomparisonofthehybridPV/Twaterandairheaters.Theparallelplateconfigurationofwaterandaircollectorhasbeenconsideredforcomparison.2.ConfigurationofthePV/TwaterheatingsystemAschematicdiagramofahybridIPVTS,unglazedwithtedlar(UGT)isshowninFig.1.Thestoragetankofcapacity45kgisconnectedwiththePVmodulewithaneffectiveareaof0.64m2(0.54m
1.2m)throughinsulatedpipes.AwaterpumpwithcontrollerisprovidedbetweenthePV/Tsystemandthestoragetanktocirculatethewater.ThefollowingconfigurationsforIPVTShavebeenconsideredforthepresentstudy:(a)theunglazedwithtedlar(UGT),(b)theglazedwithtedlar(GT),Fig.2,(c)theunglazedwithouttedlar(UGWT)and(d)theglazedwithouttedlar(GWT).ARTICLEINPRESSGreeklettersaabsorptivitybpackingfactorZefficiencyttransmittivityA.Tiwari,M.S.Sodha/RenewableEnergy31(2006)2460–24742462HerethetedlarisaninsulatingmaterialusedbelowthesolarcellsofthePVmoduletogivestrengthtothePVmodule.Thethermalcircuitdia