太阳能光伏系统效率的影响因素研究

AplaceforPV,TrackedPVandCPVLahmeyerInternationalGmbH1APlaceforPV,Tracked-PVandCPVAComparativeStudyoftheEnergyProductionfromtheThreeTechnologiesAccordingtotheAvailableSolarResources2ndInternationalWorkshoponConcentratingPhotovoltaicPowerPlants9-10March2009,Darmstadt,GermanyDavidLecoufle,FabianKuhnRenewableEnergyDivisionLahmeyerInternationalGmbH,FriedbergerStrasse173,[e-mail],tel:[phone]AbstractThechoicestogenerateelectricityusingsolarenergyareincreasingfromoneyeartotheother.Today,amongstthemaintechnologies,fixedcrystallinePhotovoltaic(PV),trackedcrystallinePVandmorerecentlyConcentratorPhotovoltaic(CPV)arejusttonameafewalternatives.ACPVsystemoffersamuchhigherefficiencythanconventionalPV,buthasthedisadvantagethatitonlyusesthedirectfractionofthesunirradiation.Consequently,thehighertheDirectNormalIrradiation(DNI),themoreprofitableaCPVsystembecomes.Butwhereisthelimit,andhowdoesitcomparetoconventionaltrackedPVsystems?Thispapercomparestherelativeenergyyieldofthethreesystemsinseveralregionsoftheworldwhilepointingouttheadvantagesofeachinordertotryandtoidentifyanappropriateinterfacebetweenthem.Thisinterfaceisinnowayregardedasanabsolutelimitbutcanhelpchoosingatechnologyforasite,orviceversa.Additionally,otherpointsofcomparisonsuchastherelativeenergyoutputperhectareareconsideredaswellasanoutlookforthecomingyears.IntroductionThispaperuseseightexemplarylocationsfromEurope,AfricaandtheMiddleEastwithdifferentGlobalHorizontalIrradiation(GHI),diffuseirradiationratioandthereforedifferentDirectNormalIrradiation(DNI).Thisapproachwaschoseninordertounderstandtherelationshipbetweenthesefactorsandtheoutputenergyfordifferenttechnologies.Theconsiderationsandresultsshowninthispaperaremerelyregardingtechnicalandenergyefficiencymatters.Anyeconomicalmatterwasexplicitlynotconsidered.Allassumptionsandresultsshowninthispaperareapproximationsanddonothavethepurposetobeusedforplanningordecisionmaking:theyshallservetogiveanideaabouttheperformanceofthedifferenttechnologiesaccordingtotheresources.Figure1showstheirradiationconditionsconsideredandforindicationalsothenamesoftownswithapproximatecorrespondingcharacteristics1.Discussionoftheaccuracyofthedataforeachtownisnotpartofthispaper.TheGHIvaluesconsideredforthestudyrangefromabout1,000kWh/m².ato2,300kWh/m².aandbothintegralpartsoftheGHI,theDirectHorizontalandtheDiffuseIrradiation,areshown.TheDNIontheotherhandisapartoftheGlobalNormalIrradiation(GNI)andisalsorepresentedhere.1Source:PVGISAplaceforPV,TrackedPVandCPVLahmeyerInternationalGmbH205001,0001,5002,0002,5003,0003,500FrankfurtLyonBarcelonaSevillaLagosDubaiN'DjamenaWindhoekIrradiation[kWh/m².a]DiffuseIrradiationDirectHorizontalIrradiationDNIGHIFigure1:RangeofSolarIrradiationconsideredforthestudy2Table1:AssumptionsconsideredforthestudyPVTrackedPVCPVTechnologyFlatplatePolycrystallineFlatplateMonocrystallineFresnellensesIII-VTrippleJunctioncellsStandardTestConditions(STC)1000W/m²,25°Ccelltemperature850W/m²,25°CambienttemperatureSTCmoduleefficiency*13.5%14.5%25%STCpowerofa1m²module135W145W212WModulepowerona“typical”summerday115W120W250WMountingSystemfixedatlatitudetiltdualaxistrackingdualaxistrackingModulesurfacefor1MW7,400m²6,900m²4,700m²Terrainsurfacefor1MW2.5ha4.5ha2.4haTypicalannualPerformanceRatio*77%79%97%*theSTCmoduleefficiencyandtheperformanceratioforCPVinthistableareinreferencetoDNIForeachoneoftheseeightlocations,briefsimulationsoftheenergyproductionwerecarriedoutforthreetechnologies:polycrystallinemodulesinstalledatafixedtiltcorrespondingtothesitelatitude,monocrystallinemodulesinstalledondual-axistrackingsystems(bothcrystallinemodulesarealsoreferredtoas“conventionalPV”or2Source:PVGISAplaceforPV,TrackedPVandCPVLahmeyerInternationalGmbH3“flatplatePV”),andCPVmoduleslikewisemountedondual-axistrackingsystems.TheassumptionstakenonthetechnologiesforthepurposeofthisstudyaresummarizedintheTable1.Theperformanceratiostatedinthetabletakesintoaccountthelossesinthesystemswithregardstomodulelossesorgainsduetodeviationfromlaboratoryconditions(mainlythetemperaturecellandtheirradiationlevels)andnon-modulelosses(mainlyinvertersandcables).Thesevaluesarebasedonaveragesobtainedfromfieldexperience3.TheperformanceratioforaCPVsystemismuchhigherthanforconventionalflatplatePVmainlyduetothefactthatthestandardtestconditionscanbeachievedandevensurpassedinthefield.STCforCPVrepresent“realconditions”wherethecellsarealreadyat40-60°C,andtheDNIwith850W/m²is“sub-optimal”sinceitcanreachhighervaluesonthefield.EspeciallythedifferenceincelltemperatureforconventionalPVbetweenlaboratoryandfieldconditionscaneasilybring10-15%performancedropofthesystem.Asaconsequence,aCPVmodulecanachieveapowerof120%ofitsnominalpoweronatypicalhotsummerday,whereasaPVmodulecanhardlyreach80-85%ofitsnominalpowerthatday.Thiscanbeseeninthetable:althoughthenominalpoweroftheCPVmoduleisnottwicethepowerofaflatplatePV,itsrealpoweronacleardaysiseasilymorethandoublethatofthePV.SimulationsTheconventionalflatplatetechnologyandtheCPVconsideredforthisstudyhavedifferentgainsandlos