Thesis - Photovoltaic power system

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PHOTOVOLTAICPOWERSYSTEMSubmittedbyCHNGSZEYUN(ZHUANGSHIYUN)N0605200SchoolofScienceandTechnologyAthesissubmittedtoSIMUniversityinpartialfulfillmentoftherequirementsforthedegreeofBachelorofEngineeringJuly2008 STATEMENTOFASSISTANCEPageii ACKNOWLEDGEMENTThisprojectwouldnothavebeenpossiblewithoutthecontributionfromafullwholelistofpeoplearoundme.Thus,Iwouldliketoshortlistfewofthosespecialones.First,Iwouldliketoexpressmymostsinceregratitudeandappreciationtomysupervisor,MrAyyanarappanChandranforhisvaluableguidanceandforsharingthe“cowandplane”story.Asimplestory,yetwithsignificantenlightenment…Next,ismyspecialsweetiefriend–Desireeaka“charbor”.Withoutallherencouragements,comfortingwords,encouragementsurprisegifts,“wangwang”therapyandpatienceinlisteningtomywoes,Imightnotevenbeabletopullthroughthistoughestanddowntimeofmylifeandthecompletionofthisthesisisdefinitelyimpossible.Thankyouforeverything.I’mreallysoblessedtohaveyoubymyside.AndIdonotforgettothankmywonderfulPVfamily.Especially,thankyou“tuzi”sanforvettingmythesisandsourcingofvaluableinformation;andWenxisanforallyourunderstanding,patienceandsupport.Butmostofall,thankyouforbeingsuchagreatbossthatanyonecaneverimagine.Pleaseacceptmymostsincereapologyforbeingsuchanannoying,repulsive,unreasonableandshort-temperShirlynduringthesetimesduetoallmypersonalstress.Lastly,tothemostimportantperson-Henry.WordsalonecannotexpresswhatIowehimforhisencouragementandwhosepatientloveenabledmetocompletethisproject.Thankyouforstayingbymysideandforthoseenergizingmassagethroughoutthesetimes.Sorry,tohavethneglectedyouandtohaveoverlook28April.Dearall,Ihadmadeit!Pageiii DISCLAIMERStandardsandcriteriaofinstallations,procedures,andapprovalguidelineshavebeenroutinelyauditedandreviewedbyEMAandSP.Assuch,criteriaandapprovalproceduresdiscussedisthvalidandcorrectasofsystemcommissioneddated24September2008.;nordotheseapprovalsexemptanyrequirementsofelectricutilitiesorlocaljurisdictionalauthoritiesasrequiredforPVsysteminstallations.Pageiv ABSTRACTThisthesispresentsatwofoldobjective.Theprincipleobjectiveaimstohighlightandsummarizetheactualdesign,planningandimplementationprocessesofan8.88kWpgrid-connectedPhotovoltaic(PV)powersystem(projectreferencehereinafteras“MEAP8.88kWp”).ThisthesisalsoreviewsthekeydesignparametersandoutlinedthecriteriaforinterconnectingaPVsystemwiththeutilitygrid.ThesecondobjectivepresentsdetaileddataanalysisoftheoperationalperformancedrawnfromtheinstalledMEAP8.88kWpPVSystem.Apartfromtheabovementionedobjectives,thethesisincludesacasestudythatreviewedperformancedataofapreviouslycompletedPVsysteminstallationproject(projectreferencehereinafteras“PVS492kWp),whichcomprisesoffourdifferentPVtechnologies–Monocrystalline,Polycrystalline,AmorphousandMonocrystallineglass-glass.Thethesisaimsatgaininganincreasedunderstandingoftheoperationalperformance,characterizationanddesignofphotovoltaicsystems.Inaddition,itisacrucialelementinthelearningcycleofdesign,installation,monitoring,andevaluation.Pagev TABLEOFCONTENTSPAGESTATEMENTOFASSISTANCE……………………..……………………….………iiDISCLAIMER………………………………….…….…………………….….…………iiiACKNOWLEDGEMENTS………………….………….…..…………….…….…………ivABSTRACT……………...………………….………….……………….……….………vLISTOFFIGURES………………………………………………………….….…………ixLISTOFTABLES…………………………………………………………..……………xiiCHAPTER1INTRODUCTION…………………………………………….…..…11.1IntroductiontoPhotovoltaic(PV)System………….……………11.2ScopeofWork……………………………..……………………31.3ThesisOverview……………………………..……………………51.4SystemOverview……………………………..……………………7CHAPTER2REVIEWOFLITERATURE…………………………..…..…..…92.1OverviewofPVTechnology………………………………....…..92.2TypesofPVTechnology…………………………..……..…..122.3PVElectricalPrinciples………………………..…..…..……142.4OverviewofPVsystem……………………………..…..…172.4.1TypesofPVsystem..…………………………..….……182.4.2PVPowerSystemComponents…………………..…..…..222.5OverviewofPVSystemDesignConsiderations…………....…....262.5.1KeySystemDesignParameters………..…..……262.5.2PerformanceParameters………………………...…...……372.6StandardsandRequirementsofUtilityInterconnection…..….v…38Pagevi TABLEOFCONTENTSCHAPTER3SYSTEMDESIGNCONSIDERATIONS………..………...……...…403.1SiteSurveyandEvaluation….……….…………….………….….413.2SystemdesignstrategyandMethodology………...……....……443.2.1PVArraySizingandLayoutConfiguration……………443.2.2ElectricalParameterdesign………….…………...............…483.2.3ElectricalParameterEvaluation…….….……………......…493.3StructureDesign…….……………....………….……..……….......513.4OverallPVSystemandElectricalDesign…….…….……….......523.5EstimatingSystemOutput…….…………..…….…….…………...55CHAPTER4SYSTEMINSTALLATIONANDCOMMISSIONING………….......594.1ProceedingofInstallation……………………...…………...……..594.2SystemTestingandCommissioning………...…………...……..…684.3ProblemEncountered………...…………...…………...……..……74CHAPTER5RESULTSANDFINDINGS………...…………...…………...................755.1ProjectReferenceI:MEAP8.88kWpPVsystem…….......………755.1.1Overallsystemperformance……...………...………............765.1.2EfficiencyofPVarray,InverterandOverallSystem….…795.1.3Shadingeffectanalysis…...………...………....……....…805.1.4DetermineofShadingDerateFactor…...………...……….825.1.5SystemavailabilityAnalysis…..…...………...……………..885.1.6EstimatingAnnualSystemOutput……...………...…………90Pagevii TABLEOFCONTENTSCHAPTER6CASESTUDY(DATAANALYSIS)...………...………..………....….…916.1ProjectReferenceII:PVS492kWpPVsystem...………...…….……916.2OverallPVS4PVSystemperformance...…………………....…….…94CHAPTER7CONCLUSIONS...………………………………………………….....…997.1FeasibilityReport...…...…………………...…………………...….…997.1.1EnvironmentandPollutionAbatementConsideration……..…997.1.2EconomicConsideration...………........................................…1027.2Conclusion..................................................................……………..…105REFERENCE............................................................................................……………….…108ACRONYMSANDABBREVIATIONS...............................................................…….......113LISTOFAPPENDICES...........................................................................……………..…114Pageviii LISTOFFIGURESPageFigure1-1GeographicalMapofSingapore1Figure1-2Grid-connectedPVpowerSystem2Figure1-3Scopeofwork4Figure1-4ProjectReferenceI:MEAP8.88kWpgrid-connectedsystem7Figure1-5Phasesandkeystepsinimplementingthegrid-connectedsystem8Figure2.1PrincipleofPVenergyconversion10Figure2.2Cross-sectionofaPVcell11Figure2.3CrystallinePVvaluechain11Figure2.4SeriesconnectionofPVmodulewithresultingvoltage-currentcharacteristic14Figure2-5ParallelconnectionofPVmodulewithresultingvoltage-currentcharacteristic15Figure2-6I-Vcurve16Figure2-7Overviewonthemanifoldapplicationareasofphotovoltaicsystems18Figure2-8Blockdiagramofstand-alonesystem19Figure2-9PowerflowdiagramofStand-alonesystem19Figure2-10BlockdiagramofGrid-connectedsystem20Figure2-11PowerflowdiagramofGrid-connectedsystem20Figure2-12BlockdiagramofGrid-connectedsystemwithbattery21Figure2-13PowerflowdiagramofGrid-connectedsystemwithbattery21Figure2-15StructureofPVmodule22Figure2-16Cell,ModuleandArray23Figure2-17Typicalgrid-connectedinverter24Figure2-18Blockdiagramoftypicalcircuittopologyofgrid-connectedinverter25Figure2-19SunPathDiagramforSingapore27Figure2-20PVarraymounting(installationreference)28Figure2-21Yearlysumofglobalirradiance.29Figure2-22Relationshipbetweensolarirradiance,insolationandpeaksunhours30Figure2-23EffectofSolarirradianceonmoduleperformance31Figure2-24Temperatureeffect(Voltage)32Figure2-25Temperatureeffect(current)32Figure2-26Effectofshadingonmoduleperformance34Figure2.27ProceduresofPVsysteminstallationandConnectiontoPowerGrid39Figure3-1Surroundingofintendedinstallationsite42Figure3-2:Differentviewofintendedinstallationlocation42Figure3-3Systemandcomponentlayoutplan43Pageix Figure3-4ConfigurationofARRAY146Figure3-5ConfigurationofARRAY246Figure3-6OverviewofARRAY1Configuration47Figure3-7MountingFrameofStructure151Figure3-8MountingFrameofStructure251Figure3-9Overviewofgroundmountedarraystructure51Figure3-10OneLineDiagram52Figure3-11ModuleArrangement53Figure3-12PVStringsconnectiontogrid-connectedinverter53Figure3-13Grid-ConnectedInverter.54Figure3-14DataloggerMonitoringsystem54Figure3-15Summaryofkeydesignparameters,factorsandestimatedvalue58Figure4-1Installationstages59Figure4-2:Sitepreparation61Figure4-3Structureinstallation63Figure4-4PVModuleInstallation64Figure4-5BOSinstallation66Figure4-6FinalAlignment67Figure4-7Start-upteststepsandprocedures68Figure4-8TestingproceduresofLOMT72Figure4-9aResultshowingACcurrentoutputofinverteras1.1A(switchON)73Figure4-9bResultshowingACcurrentoutputofinverteras0A(SwitchOFF)73Figure4-10Dailysystemoutput(Dec)74Figure4-11InverterPowerModule74Figure5-1Dailytotalandtrendsystemoutput(Oct’08toFeb’09)76Figure5-2DailySystemOutputkWh(OCT’08)76Figure5-3:DailySystemOutputkWh(NOV’08)76Figure5-4:DailySystemOutputkWh(DEC’08)77Figure5-5:DailySystemOutputkWh(JAN’09)77Figure5-6:DailySystemOutputkWh(FEB’09)77Figure5-7:MonthlyActualandEstimatedSystemOutput(OCT’08–FEB’09)78Figure5-8:ShadingonPVarray-15thFeb(mid-day)80Figure5-9:ComparisonofArrayOutput.81Figure5-10ComparisonofArrayOutput(Period:2PMto4PM)81Figure5-11ComparisonofEstimatedandfinalSystemOutput82Figure5-12ComparisonofShadingFactorvalue(0.60,0.70and0.75)83Pagex Figure5-13ComparisonofPRvalueon15thFEBsystemoutput.85Figure5-14PRofOCT’08toFEB’0988Comparisonofsystemoutputbetween2phaseand3phasemodeofinverterFigure5-1589operation.Figure5-16EstimatedAnnualSystemOutput90Figure6-1SystemA–MonocrystallinesiliconInstallation92Figure6-2SystemB–Monocrystallineglass-glassinstallation93Figure6-3SystemC–AmorphousSiliconInstallation93Figure6-4SystemD–PolycrystallineSiliconInstallation93Figure6-5OverallsystemperformanceComparisonChart94Figure6-6ComparisonofPRwithaverageirradiance95Figure6-7Systemsyieldsandmoduletemperature(between10amto4.30pm)96Comparisonofirradianceandtemperatureontypicalsunny,rainyandcloudyFigure6-897dayFigure7-1:comparisonofCO2emissionsfromdifferentfuelsources100Figure7-2:ElectricityconsumptionofSingapore(perPersoninMWh)102Figure7-3:Costofelectricitytariffagainstthefueloilprices103Figure7-4:Breakdownoftotalsystemcost103Figure7-5:MonthlySystemOutput(includingMarchandApril)106Pagexi LISTOFTABLESPageTable2-1:ComparisonofPVtechnologies13Table2-2:AveragemonthlyInsolationofSingapore30Table2-3:Effectsofshadingonmodulepower35Table2-4:DerateFactors36Table2-5:PerformanceParameters37Table3-1:OverviewofSystemDesignConsideration40Table3-2:ArraySizing–NumberofPVmodules45Table3-3BasicMethodologyinPVarrayconfiguration49Table3-4:DesignTable–TabulatedresultofPVARRAY1topology.50Table3-5:MonthlyaverageInsolation,MeanTemperatureandnumberofrainydaysof56SingaporeTable3-6Estimatedvalueofdaily,weeklyandyearlysystemOutput.57Table4-1:Start-uptestingandmeasurementsofPVsystem70Table5-1:MonthlySystemOutputStatisticforOCT’08toFEB’0977Table5-2:EfficienciesofPVarray,Inverterandoverallsystem(Basedonmonthly79maximumandminimumsystemoutputs)Table5-3:ResultsofEstimatedSystemoutputandPR(withnewestimatedshading83factors)Table5-4:Re-calculationofPVS4EstimatedsystemOutput86Table5-5:ComparisonofPRvaluestatisticsofperiodfrom1stto15thFEB87Table6-1SystemTypeandCapacityofinstallation92Table6-2Systems’outputandperformanceratioonsunny,rainyandcloudyday97respectively.Table7-1:Availabilityoffossilfuelsupply99Table7-2:EstimatedelectricUtilitybillsavingsandpaybackperiodcalculation104Pagexii CHAPTER1INTRODUCTIONInrecentyears,Singaporegovernmentiscommittedinitseffortstoholisticallypromoteandtakingtheleadbyacceleratingcapabilitydevelopmentinrenewableenergy.Ithasbeenmadetoputenergyefficiencyonthenationalagenda[1].Situatedat1.17°northoftheequator,Singaporereceivesaround11½hoursofdaylightand2morethan4peaksunhoursdaily,withanaverageannualsolarinsolationof1635kWh/m.ThesurfacewindsoverSingaporegenerallyfollowtheprevailingmonsoonflowwithmeansurfacewindspeedatnormallylessthan20km/h[2].Figure1-1:GeographicalMapofSingaporeDuetothesegeographicallimitationsandclimatologyofSingapore,manyrenewableenergysourceslikehydroelectricity,windandgeothermalenergyarenotaccessibleandfeasibleinSingapore,exceptPhotovoltaic(PV)energy.Page1 1.1IntroductiontoPhotovoltaic(PV)SystemUnlikedevelopingcountrieswhereelectricityisnotalwaysreadilyavailable,residentialandcommercialbuildingsinSingaporeareconnectedtothereliableutilitygrid.PoweroutageinSingaporeisrare,andshouldthishappen,timerequiredtorestoreelectricitysupplyoutagecausedbynetworkfaultislessthan3hours[3].Thus,implementinggrid-connectedPVpowersysteminurbanareaslikeSingaporeisofmorefeasibleandeconomicalascomparedtoothertypesofPVsystem.Figure1-2:Grid-connectedPVpowerSystemInterconnectingaPVsystemwiththeutilitygridwillrequireenteringintoaninterconnectionagreementsandattainingapprovalwithlocalutilityauthority.Forwhich,severalprocedures,technicalstandards,safetystandardsandrequirementsmustbecomplywiththerequirementsstipulatedintheSingaporestandardintheCodeofPracticeforElectricalInstallations(SingaporeStandardCP5:1998),publishedbySPRINGSingapore[4].Page2 1.2ScopeofWorkThescheduleofoverallscopeoftheprojectisasshowninGanttchartasattachedinAppendixA.Figure1-3indicatesthefivefundamentalphasesundertookinthescopeofwork.Figure1-3:Scopeofwork.Page3 1.3ThesisOverviewChapter2summarizesthebasicbackgroundstudyofPVtechnology,characteristicsofsystemcomponentsanddesignconsiderationsparametersthataffecttheoutputperformanceandefficiencyoftheoverallsystem.Inaddition,thischapteralsohighlightsthebasicrequirementsandstandardsforinterconnectingaPVsystemwiththeutilitygrid,inordertoattaintheapprovalfromrelevantlocalauthoritiesChapter3presentsthekeydesignconsiderationsandstepsundertakenindesigningtheimplemented8.88kWpgrid-connectedPVpowersystem.ThekeychallengeistodesignaPVsystemwithoptimumsystemperformance,whichmatchesthelocation,environment,applications,andlocalutilityrequirements.Chapter4summarizestheactivitylogoftheinstallationprogressoftheimplementedgrid-connectedPVsystem.ThislaterpartofthechapteralsohighlightsthemainproblemencounteredduringtheoperationphaseofthePVsystem.Chapter5presentsdetailedanalysisoftheoperationalperformanceresultsofPVsystemsdrawnfromProjectreferenceI:MEAP8.88kWpPVSystem.Focusingondataanalysisoftheoverallsystemperformanceovertime,systemavailabilityandshadingeffect.Chapter6includesacasestudyreportthatreviewedoperationalperformanceresultsofProjectReferenceII:PVS492kWpPVsystem.TheprimaryobjectiveaimstoproviderelativePage4 performanceanalysisofthedifferenttechnologiestobemeasuredside-by-sideandtostudythesuitabilityofdifferentPVpowersystemsunderthetropicalclimateconditions.Lastly,Chapter7presentsafeasibilitystudythatwasconductedtoevaluatetheeconomicalandenvironmentalconsiderationoftheimplemented8.88kWpgrid-connectedPVsystemwithasummaryofitsconclusions.Page5 1.4SystemOverviewProjectReferenceI:MEAP8.88kWpgrid-connectedsystem(asshowninFigure1-5below)wasdesignedandbuildincompliancewiththerequirementsbylocalutilityandrelatedauthoritiesofthSingapore.Itwasapprovedandofficiallycommissionedon24September2008.Thetotal2installedcapacityisof8.88kWpunderSTCandcoversanareaof66m.Figure1-4:ProjectReferenceI:MEAP8.88kWpgrid-connectedsystemPage6 Figure1-5summarizesthekeystepsthatwereundertakenatdifferentphasesinimplementingMEAP8.88kWpgrid-connectedsystem.Figure1-5:PhasesandkeystepsinimplementingtheMEAP8.88kWpgrid-connectedsystemPage7 CHAPTER2REVIEWOFLITERATURE2.1OverviewofPhotovoltaic(PV)TechnologyTheprefix“photo”means“producedbylight,”andthesuffix“voltaic”refersto“electricityproducedbyachemicalreaction”.Photovoltaictechnologyproducesdirectcurrent(DC)ofelectricitydirectlyfromtheelectronsfreedbytheinteractionofsunlightwithsemiconductormaterials,suchassilicon.AtypicalPVcellconsistsofap-njunctionformedfromdiodeandtransistors,whichformthebuildingblocksoftheentireworldofelectronics[4].Figure2.1and2.2illustratestheenergyconversionofthePVcell[4].(RefertoAppendixBforfurtherdetailsofPVcellphysics)Page8 Figure2-1:PrincipleofPVenergyconversionSemiconductorelementsusedinelectronicsareconstructedbyfusingtwoadjacentlydopedsiliconwaferelements.Dopingimpliesimpregnationofsiliconbypositiveandnegativeagents.Thepositiveagentscreateafreeelectronthatproducesso-calledN-typematerialandthelattercreatesa“hole”,orashortageofanelectron,whichproducesso-calledP-typematerial[6].Figure2.2presentsthecross-sectionofaPVcell.Page9 Figure2-2:Cross-sectionofaPVcellThecrystallinePVchainvalueconsistsofsixessentialcomponentswhichconstitutethevaluechain,asshowninFigure2.3.Figure2-3:CrystallinePVvaluechainPage10 2.2TypesofPVTechnologyThemostcommontypesofsiliconsemiconductormaterialusedformanufacturingPVcellsare:MonocrystallineSicells,PolycrystallineSiCellsAmorphousSicellsTable2-1summarizesandcomparesthecharacteristicofthesePVtechnologies[5].TypesofPVtechnologiesPVCellMonocrystallinePolycrystallineAmorphousmaterialsiliconsiliconsiliconPhysicaloutlookHatomGrainBoundaries(danglingbond)Structuresingle-crystallineRegionsofcrystallineNolong-rangeorderinsilicon(c-Si)hasansiliconareseparatedbythestructuralorderedcrystal“grainboundaries”wherearrangementofthestructure,witheachbondingisirregular.Theatoms,resultinginareasDescriptionatomideallylyingingrainboundariesreducewithinthematerialapre-ordainedthecellperformancebycontainingunsatisfiedpositionblockingcarrierflowsor“dangling”bondsPage11 EnergyConversion15-2214-187-10Efficiency(%)Cost/Wp(USD)3.5-43-3.71.5-2Size(mm)1575x826x461658x834x461129x934x46SolarRadiationMoredirectMoredirectDirectanddiffusePreferenceReliabilityHighHighLowWarrantyPeriod20~25Years20~25Years10~12YearsModuleperformanceinhighsurfaceLowMediumHightemperature(60ºC~70ºC)Temperature–0.45to-0.50%/ºC–0.45to-0.50%/ºC–0.20%/ºCCo-efficientTable2-1:ComparisonofPVtechnologiesPage12 2.3PVElectricalPrinciplesPVmodulesarethebuildingblocksofaPVpoweredsystem.Eachmodulehasaratedvoltageorcurrent,theycanalsobewiredtogethertoobtainadesiredsystemvoltage[7].SeriesConnectionWhenthePVmodulesareconnectedinseries(commonlyreferredasstring),thevoltageoutputisincreased,beinganadditionofthevoltagesfromeachPVmodulesinthestring;andwhilecurrentoutputremainsequivalenttothecurrentofaPVmodule.Figure2-4illustratestheseriesconnectionofPVmodulewithresultingvoltage-currentcharacteristic.Figure2.4:SeriesconnectionofPVmodulewithresultingvoltage-currentcharacteristicPage13 ParallelConnectionWhenthePVmodulesareconnectedinparallel,thecurrentoutputisincreased,beinganadditionofthecurrenteachPVmodules;andwhilevoltageoutputremainsequivalenttothevoltageofaPVmodule.Figure2-5illustratestheparallelconnectionofPVmodulewithresultingvoltage-currentcharacteristic.Figure2-5:ParallelconnectionofPVmodulewithresultingvoltage-currentcharacteristicPage14 SeriesandParallelConnectionTheelectricalconnectionofformingaPVarraycanbearrangedincombinationofseriesandparallelconnectionofthemodule.IndesigningaPVSystem,inordertoachieveappropriatevoltageandoutputfordifferentapplication,wiring(inparallelorseries)onboththemoduleandthearraylevelthendeterminestheoverallarrayvoltageandamperage.PVModuleElectricalPerformancePVmoduleelectricalperformanceischaracterizedbyitsopencircuitvoltage(Voc),shortcircuitcurrent(Isc),maximumpowervoltage(Vmp),andmaximumpowercurrent(Imp),andisgenerallyrepresentedbycurrentversusvoltage(I-V)curveasshowninFigure2-6.TheVocisthemaximumvoltageatzerocurrent,whileIscisthemaximumcurrentatzerovoltage.Themaximumpowerpointoccursatthekneeofthecharacteristiccurvewherethetwosegments(VmpandImp)meet.Figure2-6:I-VcurvePage15 2.4OverviewofPVsystemIngeneral,aPVpowersystemcomprisesofPVarray(madeupofPVmodules),DC-ACinverters,andBalanceofSystem(BOS)asshowninFigure2-7.Figure2-7:PVSystemcomponents[8]ThetangiblebenefitsofPVpowersysteminclude:Usabilityinremoteareas–wheregrid-connectionisnotavailableAbilitytogenerateelectricityduringpeakusagetimesOffsetsoffossilfueldepletionReductionofenvironmentaldegradationwithnoassociatedCO2emissionsReliabilityandlowmaintenance–longwarrantyperiodforPVmoduleandnomovingpartsVersatility—abletooperatewellinalmostanyclimateModularity–ableforfutureincrementinsystemsize/capacityPage16 2.4.1TypesofPVpowersystemPVpowersystemsareclassifiedaccordinglytotheiroperationrequirements,functionalandcomponentsconfiguration.Thetwoprincipleclassificationsare:Off-gridpowersupply:Supplypowerdirectlytoelectricalequipmentsorcomponents.Grid-connectedpowersystem:tofeedenergyintopublicutilitygrid.Figure2-8providesanoverviewonthemanifoldapplicationareasofthesetwoclassificationsofPVsystems.Figure2-7:OverviewonthemanifoldapplicationareasofphotovoltaicsystemsPage17 Off-gridsystemOff-gridpowersupply,alsoknownasstand-alonesystems(showninFigure2-8)areusuallyinstalledinremoteareaswhereutilitygridsarenotreadilyavailablefortelecommunicationsystem,andwater-pumpingsystem.Otherapplicationsalsoincludeparkingsignageandstreet-lightings[9].Thetypicalstand-alonesystemconsistsofaPVarray,abatteryconnectionandinverterasshowninFigure2-8.Figure2-8:Blockdiagramofstand-alonesystem[6]Figure2-9:PowerflowdiagramofStand-alonesystemPage18 Grid-connectedsystemThegrid-connectedsystemsaredesigntooperateinparallelwiththeutilitypowergridforcommercialandresidentialuse.Itisusuallyimplementedforoffsettingaverageannualenergyuseandthearraymaybemountedonaroofforaesthetic[10].Therearetwogeneraltypesofelectricaldesignsforgrid-connectedPVpowersystems:SystemsthatareinterconnectedwiththeutilitypowergridwithnobatterybackupcapabilityasshowninFigure2-10;andsystemsthatincorporateenergystorage(informofbattery)tokeep“criticalload”operatingduringpoweroutage,orforpoweringDCloadsand/ortomeetelectricitydemandduringnight,asshowninFigure2-12.Figure2-10:BlockdiagramofGrid-connectedsystem[6]Figure2-11:PowerflowdiagramofGrid-connectedsystemPage19 Figure2-12:BlockdiagramofGrid-connectedsystemwithbatteryFigure2-13:PowerflowdiagramofGrid-connectedsystemwithbatteryThepowersupplydrawnfromtheutilitygridwillbecorrespondinglyreducedbytheamountofpowergeneratedbythePVsystem.DuringperiodsoftimewhentheelectricalloadsaregreaterthanthesupplyfromthePVsystem,theremainingpowerwillbedrawnfromtheutilitygrid.Intermsofsystemdesigning,itisoftennotgovernedbythesizeoftheload,butbyotherconstraintssuchasareaavailabilityandthebudgetforsysteminstallation.Page20 2.4.2PVPowerSystemComponentsPVModulesandArrayAtypicalPVmodulecomprisesofelectricallyinterconnectedPVcells,embeddingmaterialsinanenvironmentallyprotectivelaminate,whichincludesafrontpaneloftemperedglass,EVA,back-film,junctionbox,electricalconnectingcablesandframe[11](asshowninFigure2-15).Figure2-15:StructureofPVmodulePage21 IndividualPVcellsareinterconnectedtoformthePVmodule.AnarrayisthebasiccomponentofaPVsystemwhichconsistsofseveralofPVmodules.Figure2-16:Cell,ModuleandArrayPage22 Grid-connectedInverterTheinverter,usedtoconvertphotovoltaicDCenergytoACenergy,isthekeytothesuccessfuloperationofthesystem,butitisalsothemostcomplexhardware[12].(RefertoAppendixCforbasicoperationofinverter)Figure2-17showsatypicalgrid-connectedinverter.Figure2-17:Typicalgrid-connectedinverter[12]Thebasicrequirementsofthegrid-connectedinverterare:OperateoverawiderangeofvoltagesandcurrentsRegulateoutputfrequencyandvoltageSynchronizeACpowerwithgoodpowerqualitytogridutilityAgrid-connectedinverterconvertstheDCpowerfromthePVarraytoACpowerthatisconformtoutilitypowerqualitystandards.Theinvertermusthaveallthenecessarycontrolstosafelyinteractwiththeutilitygrid[13].Figure2-18belowshowstheblockdiagramofatypicalcircuittopologyofgrid-connectedinverter.Page23 Figure2-18:Blockdiagramoftypicalcircuittopologyofgrid-connectedinverterPage24 2.5OverviewofPVSystemDesignConsiderationsPVsystemdesignessentiallyconsistsofelectronicandpowersystemsengineering,whichrequiresathoroughunderstandingofspecificationsforthevariousPVcomponentsandbasicknowledgeofvariousdesignparametersthataffecttheoutputperformanceandefficiencyoftheoverallsystem.2.5.1KeySystemDesignParametersThefollowingaremajoressentialstepsofkeydesignparametersthatmustbetakenintoconsiderationindesigningaPVsystem.Thekeydesignparametersinclude:TiltangleandorientationofthemoduleSolarInsolationCell/ModuleTemperatureShadingDerateFactorsPage25 TiltAngleandOrientationoftheModuleTheorientationofthemodulewithrespecttothedirectionoftheSundeterminestheintensityofthesunlightfallingonthemodulesurface.Thesun’spathsweepsadailyarcthatchangeseasonallythroughouttheyearandfollowsaprescribedsolarpositiondescribedbyanaltitudeangle(vertical)andazimuthangle(horizontal).Figure2-19showsthesunpathdiagramofSingapore.Figure2-19:SunPathDiagramforSingaporeTiltangleandazimuthanglearethetwomainparametersindeterminetheorientationofmodule.Tiltangleistheanglebetweentheplaneofthemoduleandthehorizontal.ForafixedPVarray,thetiltangleistheanglefromhorizontaloftheinclinationofthePVarray(0°=horizontal,90°=vertical)AzimuthistheangleclockwisefromtruenorthofthedirectionthatthePVarrayfaces.Thedefaultvalueisanazimuthangleof180°(south-facing)forlocationsinthenorthernhemisphere,and0°(north-facing)forlocationsinthesouthern[14].Page26 GivenSingapore’sgeographicallocationproximitytotheEquator,themodule’scompassorientationshouldbeinstalledfacingthenorthorsouthorientationtomaximizetheamountofsolarenergyreceived.Asfortiltangle,layingthemodulesflat(0°)willinfactmaximizeexposuretothesun.However,itissuggestedtomountthemodulesatanangleof10-15°topreventtheflat-mountedmodulesfromgettingdirtyduetotrappedrainwateranddust[15].Figure2-20:PVarraymounting(installationreference)Page27 SolarInsolationSolarinsolationisanamountofsolarenergyreceivedonasealevelsurfaceatapeakof21kWh/m.Itiscommonlyexpressedassolarirradiance(sunintensity)whenintegratedwithrespecttotime,inunitsofwattspersquaremeter(W/m²).IntermsofestimatingPVsystemenergyyield,itiscommonlymeasuredaskilowatthoursperyearperkilowattpeakrating(kWh/kWp/yr).Figure2-21showstheyearlysumofglobalirradiance.Figure2-21:Yearlysumofglobalirradiance[16]Whensolarinsolationdataisrepresentedonanaveragedailybasis,thevalueisexpressedaspeaksunhours(PSH),andcanbethoughtofasthenumberofequivalenthoursperdaythatsolar2irradiancelevelof1kW/m.PSHisthereferenceconditioncommonlyusedtoratethepeakelectricaloutputofphotovoltaicmodulesandarrays[17].Page28 Figure2-22showstherelationshipbetweensolarirradiance,insolationandPSH.(RefertoAppendixDforPVconversionfactortable)TheaveragemonthlyinsolationandaveragesolarirradianceofSingaporeareaslistedinTable22-2,indicatingthePSHofSingaporeisaround4.46hours,1621kWh/m/year,and21205kWh/kWp/yearandof185W/m[18][19].Figure2-22:Relationshipbetweensolarirradiance,insolationandpeaksunhours.AveragesolarInsolationMonthirradiance(kWh/m²/day)(W/m²)January4.25177.08February5.13213.75March5.03209.58April4.83201.25May4.53188.75June4.33180.41July4.25177.08August4.37182.08September4.49187.08October4.52188.33November4.02167.50December3.77157.08Average4.46185Table2-2:AveragemonthlyInsolationofSingaporePage29 IntermsofeffectonPVmoduleperformance,thecurrentoutputisdirectlyproportionaltotheintensityofsolarirradiance.Asirradiancedecreases,thearraycurrentwilldecreasenearlyindirectproportion,butthearraypowermaynotdecreaseinthesameproportion[20].AsillustratedinFigure2-23,astheirradiancedecrease,itresultsinlowercurrentoutputandpoweroutput;andvoltageonlydecreasesslightly.Figure2-23:EffectofSolarirradianceonmoduleperformancePage30 Cell/ModuletemperatureWhencelltemperaturerisesabovethestandardoperatingtemperatureof25ºC,moduleefficiencyandvoltagewilldecreaseaccordingly.Thethermalderatemustbetakenintoconsiderationbasedonthetemperature-coefficient.Onaverage,foreverydegreethatcelltemperatureincreaseabove25ºC,themodulevoltagewilldroppedby0.5%;andvice-versaifcelltemperaturedecreasebelow25ºC;whereas,theeffectivecurrentoutputincreaseswiththeincreaseoftemperature[21].Figure2-24and2.25illustratestheeffectoftemperatureonvoltageandcurrentrespectivelyFigure2-24:Temperatureeffect(Voltage)Figure2-25:Temperatureeffect(Current)Page31 Theoretically,theaveragetemperatureofthePVmodulecanbeestimatedwiththefollowingformula[21]:Tcell.eff=Ta.day+25°CWhereTcell.eff=Averagedailyeffectivecelltemperature°CTa.day=Daytimeaverageambienttemperature,°CBasedonSingaporeMeteorologicaldata,theaveragetemperatureofSingaporeisaround30ºC.Thus,themoduletemperatureisgenerallyexpectedtobearound50ºCto60ºC.Thetemperaturederatingfactorofmodulecanbecalculatedasfollows:ftemp=1–[γ×(Tcell.effy-Tstc)]Whereftemp=temperaturede-ratingfactorγ=powertemperatureco-efficientper1ºCdegreeCelsiusTcell.effy=Averagedailycelltemperature,in°C.Tstc=celltemperatureatstandardtestconditions,in°C.Page32 ShadingShadingofPVarraysisextremelydetrimentaltotheperformance.ThereductionofoutputduetoshadingvariesinmagnitudedependingontheelectricalcharacteristicofthetypeofPVtechnologiesandelectricalconfigurationofthearray.Crystallinesiliconmoduleoutputsaregenerallymoresusceptibletoshadingthanthin-filmmoduleoutputs,becausethethin-filmcellstructuretraversesthefulllengthofthemodulerequiringmoreshadingforthesameeffect.Intheeventthatasinglemoduleofaseriesstringispartiallyshaded,thecurrentoutputwillbereducedandthiswilldictatetheoperatingpointofthewholestring.Ifseveralmodulesareshaded,thestringvoltagemaybereducedtothepointwheretheopen-circuitvoltageofthatstringisbelowtheoperatingpointoftherestofthearray,andthenthatstringwillnotcontributetothearrayoutput[5][22].Figure2-26showtheeffectonshadingonmodulepower.Figure2-26:EffectofshadingonmoduleperformanceHowever,forPVinstallationsinurbanareas,itisunlikelytoavoidallshading,unlessmarkedlyinrestrictingthesizeofthearraywhichisinefficient.Page33 DerateFactorWhendesigningaPVsystem,theintendednetenergyoutputmustbecalculatedbytakingintoconsiderationlossesassociatedwiththetotallyintegratedsystem.Thelosses,knownasderatefactorswillhaveaprofoundeffectontheperformanceofthePVsystem[23].Table2-4below,summarizethelistofthedefaultcomponentderatefactors.DetailsofderatefactorcouldbefoundinAppendixE.FACTORSTYPICALVALUERANGEArrayorPVPanelVoltage0.980.97-0.995MismatchACCabling0.990.98to0.993DCCabling0.980.93–0.98Inverterselection0.930.88-0.96Dirtanddust0.9950.30-0.995DiodesandConnections0.980.80to1.05SystemAvailability0.980.00to0.995OverallatSTC0.84Temperature(at50ºC)0.8750.75–0.90Overall0.735Table2-4:DerateFactorsPage34 2.5.2PerformanceParametersTheuseofappropriateperformanceparametersfacilitatesthedataanalysisandcomparisonofPVsystemsthatmaydifferwithrespecttodesign,technology,orgeographiclocation.Themainperformanceparametersthatdefinetheoverallsystemperformancewithrespecttotheenergyproduction,solarresource,andoveralleffectofsystemlossesare[24]:Table2-5:PerformanceParametersTheseperformanceparametersarediscussedfortheirsuitabilityinprovidingdesiredinformationforPVsystemdesignandperformanceevaluation.RefertoAppendixFfordetailsoftheseperformanceparameters.Page35 2.6StandardsandProceduresofUtilityInterconnectionApprovalThispartofchapterisintendedtoprovidebasicinformationonthestandards,requirementsandtheprocessofimplementingthegrid-connectedPVsystem.Standardsandrequirementsoftheapprovalguidelineshavebeenroutinelyauditedandreviewedbylocalrelevantauthorities.Thelocalrelevantauthoritiesdiscussedinthisthesisinclude:BuildingandConstructionAuthority(BCA),EnergyMarketAuthority(EMA)andSPPowerGrid(SPPG)[4][15].RefertoAppendixGforfurtherdetailsofthesestandardsandrequirementsofthelocalrelevantauthorities.Ingeneral,duringdesigningandinstallationofaPVsystem,requirementsforapprovalincludecompliancewithacceptedindustrystandardsandmethodsdeployedininterconnectingPVsystemtotheutilitygrid[25].Figure2-27belowillustratesandsummarizestheprimaryproceduresofPVsystemimplementationandconnectiontoPowerGrid.Page36 Figure2.27–ProceduresofPVsysteminstallationandConnectiontoPowerGrid[15]Page37 CHAPTER3SYSTEMDESIGNCONSIDERATIONSThischapterisintendedtopresenttheessentialdesignconceptoftheimplemented8.88kWpgrid-connectedPVpowersystem.Thefollowingdesigncriteriaandplansaresolelyprovidedforthepurposeofthesisdiscussiononly.Theactualdesigncriteriaandcalculationsmayvarydependingonthegeographiclocation,costoflabor,andmaterials,whichcansignificantlyvaryfromoneprojecttoanother[26][27].Table3-1providesanoverviewofthestepsundertookindesigningtheinstalled8.88kWpgrid-connectedPVPowersystem.Table3-1:OverviewofSystemDesignConsiderationPage38 3.1SiteSurveyandEvaluationTheon-sitepreliminaryfieldworksetouttobethemostessentialandsignificantsteppriortodesigningthePVpowersystem.Initialsiteevaluationandinvestigationofsiteconditionsmustbethoroughtoobtainaccurateinformationanddetailsrequiredforcompletelydesignandplanningofinstallation.EnvironmentsurroundingFollowingpointswerehighlightedbythecompanymanagementpriorinplanningandbuildingofthePVpowersystem:Areaofinstallationshallnotexceedby33mx3mPreventionshouldbedonetoavoidanydamagesfromvehicles(proposedinstallationareaisnexttocarpark)Thefinalinstallation(namelytheheightofthesystem)mustnotblocktheviewofthebuildinglobbyentrance.Totalinstallationcostmustnotexceedgivenbudget.Besidestheabovelimitations,surroundingofintendedinstallationsiteisalsooneofthebiggestconstraints.Duringsitesurvey,itwasnotedthatthesurroundingtreesandbuildingwillcastshadingstotheinstallationareabetween2PMto4PM(asshowninFigure3-1below).Theseshadingwilladverselyaffectonthesystemperformance.Page39 Figure3-1:SurroundingofintendedinstallationsiteDuetothiseffect,thesignificantuncontrollablelossfactorsarethearrayorientationandshading.Withtheselimitationandrequirements,itismuchofexpectedthatthePVpowersystemwillnotbeabletoproduceitsoptimumresultasdesigned.Figure3-2presentsthedifferentviewoftheintendedinstallationsite.Figure3-2:DifferentviewofintendedinstallationlocationPage40 InitialcomponentsLayoutplanningTheplacementofthesystemcomponentsshouldbecarefullyplannedtoaccommodateaprofessionalandneatinstallation.AREAOFINSTALLATION230mX3m(90m)INVERTERLOCATIONEXISTINGTREESLOCATIONMAINDBANDSUBDBLOCATIONEXISTINGCARPARKLOCATIONPVARRAYLOCATIONFigure3-3:SystemandcomponentlayoutplanPage41 3.2SystemdesignstrategyandMethodologyWiththeabovepreliminaryfieldwork,thesystemdesignsetsouttobethefundamentalandcrucialpartofthePVpowersystem.Thisinvolvesinundertakingcomprehensivestudyoftheinformationgatheredformsiteassessment.Thekeychallengeistodesignasystemaccordingly,whichmatchestherequirements,location,environmentandapplications,andalsoinensuringtodesignthetopologicalconfigurationofPVarraysthatwillproduceanoptimumsystemperformance.3.2.1PVArraySizingandLayoutConfigurationPVArraySizingSincegrid-connectedPVsystemhavegrid-utilityasthemainsourceofpowersupply,systemsizingisoftennotgovernedbythesizeofpoweringloads,butonconsiderationssuchastheoffsettingaverageannualenergyuse,budget,andavailabilityofmountingareaforthesystem.Inordertoensureoptimumoperationatminimumcost,itisimportanttodeterminethecorrectsystemsize,intermsofbothpeakoutputandoverallannualoutput.ThePVarrayisconfiguredsothatmaximumratedpowercanbeprovidedtotheinverterduringmid-dayperiodsofhighestirradiance[28].ThesizingofarraywilldeterminethenumberofPVmodulesandselectionofinverter.Page42 LengthWidth(m)(m)TotalAvailableArea30.03.5AvailableArea(Toincludespaceallowance)28.03.0ModuleDimension(Basedon50cellsizemodule)1.70.8MaximumNumberofRow3MaximumNumberofColumn16TotalNo.ofPVModules48Table3-2:ArraySizing–NumberofPVmodulesUponcompletingtheprecedingsteps,thenextstepistoconfigurethetopologyofPVarrayinaccordanceformostappropriateusewiththe3-phasegrid-connectedinvertersystem’sinputrequirementsforpowerconversion.PVArrayLayoutConfigurationUpondeterminingtheallowednumberofPVmodulesfortheavailableareaofinstallation,thenextessentialstepisonthePVarrayconfiguration[29][30].Duringthesiteevaluation,itwasnotedthattreeshadingwilloccursduring2PMto4PMattheareaofinstallation.Assuch,itisessentialtodesignalayoutconfigurationofPVarraythatwillminimizetheimpactofover-shadingderate.TheintendedconfigurationoftwoPVarray,ARRAY1andARRAY2areasillustratedinFigure3-4and3-5respectively.Page43 ARRAY1waschosenforthefinalPVarraytopologywiththefollowingadvantagesoverARRAY2:Lossesareisolatedtothestringinwhichtheyoccur,ratherthanaffectingthewholearray.DCCablelossesduetoARRAY2aremuchhigherduetothelongerdistancecablingtotheinverterpoint.Excessivelongwirerunswillresultinlossofpowerandlowersystemefficiency.Page44 ThefinalPVarrayconfigurationisasshowninFigure3-6.Page45 3.2.2ElectricalParameterdesignTheselectionsofcomponentsaremainlybasedonthereliability,designapproach,engineeringsupportoffered,thepreferentialpricingandcomplianceoftechnicalspecifications.TechnicalspecificationsofselectedPVmoduleandinvertercouldbefoundinAppendixH.Ingeneral,theselectionoftheinverterfortheinstallationwilldependon:TheestimatedsystemoutputofthearrayandsystemToaccruedforfutureupgrade/increasinginPVsystemcapacity.Thematchingoftheallowableinverterstringconfigurationswiththesizeofthearrayandthesizeoftheindividualmoduleswithinthatarray.Safetyfeaturesandtechnologysuchasislandprotection,galvanicisolationbetweentheDC-inputandtheACoutput,frequencysynchronizationrequiredforgridconnectivity.Page46 3.2.3ElectricalParameterevaluationThenextstepistoevaluateandensurethedesignedPVarray’selectricalperformanceparameterisinaccordancetothe3phasegrid-connectedinvertersystem’sinputrequirements.TheexcursionofoutputvoltageproducedbyPVstringsisdeterminedbyVmp,orthecombinedseriesPVstringmaximumpeakvoltagewhenmeasuredinanopen-circuitcondition[33][34].ThebasicmethodologyinPVarrayconfigurationisasfollow:OpenCircuitVoltage(Voc):Thetotalopencircuitvoltage(Voc)ofeachseries-stringmustbelessthanthemaximumallowableinputvoltageoftheinverter.*Incold-region,itmustbenotedthatVocincreasebyapproximately0.5%per°Cwithtemperaturedecrease.Maximumpowervoltage(Vmp):Thevoltageatmaximumpower(Vmp)oftheseries-stringisequaltoorgreaterthanthegridvoltage;andwithintheMPPrangeofinverter.Asthemoduletemperatureincreases,Vmpdecreasesbyapproximately0.5%per°C.TheminimumVmpandmaximumVocoftheseries-stringmustbewithintheoperatingvoltagewindowoftheinverter.Maximumpowercurrent(Imp):Theparallel-stringsoutputcurrent(Imp)islessthantheinverter'sDCinputcurrentlimit.Table3-3:BasicMethodologyinPVarrayconfigurationPage47 Table3-5showstabulatedestimatedresultbasedonthePVARRAY1topology.ThedesigntablehelpstoensurethattheelectricalparameterofthedesignedPVarrayisinaccordancetothetechnicalspecificationofgrid-connectedinverter.ModulesperString:16inseriesResultingParameterInverterLimitsNumberofParallelString:3SingleStringTotalSingleConditionParameterOutputOutputMinMaxModule(16modulesin(3Stringsinseries)Parallel)Maximumpower24.4V390.4V390.4V100V550Vvoltage(Vmp)OpenCircuit30.6V489.6V489.6V100V550VVoltage(Voc)25ºC,Maximumpower27.58A7.58A22.74A3x15A1000W/mcurrent(Imp)ShortCircuit8.13A8.13A24.39A3x15ACurrent(Isc)MaximumPower184.95W2959.23W8,877.6W8,100W11,700W(Pmax)Maximumpower20.7V331.6V331.6V100V550Vvoltage(Vmp)OpenCircuit26.9V430.8V430.8V100V550VVoltage(Voc)60ºC,Maximumpower27.7A7.7A23.2A3x15A1000W/mcurrent(Imp)ShortCircuit8.3A8.3A24.9A3x15ACurrent(Isc)MaximumPower160.3W2553.3W7,693W8,100W11,700W(Pmax)Table3-4:DesignTable–TabulatedresultofPVARRAY1topology.Page48 3.3StructureDesignAsdiscussedinChapter2.5.1,themodule’scompassorientation(tiltangle)isnotacriticalfactor.Mountingthemodulesatanangleof10-15°helpspreventtheflat-mountedmodulesfromgettingdirtyduetotrappedrainwateranddust.Inaddition,intermsofshowcasepurpose,thisprovidesabetterviewofthesysteminstallation.Thegroundmountedarraystructureusespairsofaluminumprofilebeamthatisbolteddirectlytogrounddepthof2masfootings.Themountingframeconsistsoftwoparallelchannelbarstoformasimplerackwithtiltangleof10°(asshowninFigure3-7)andcrosssupportsareboltedtothemoduleframetoincreaselateralstructuresupport(asshowninFigure3-8).Figure3-9showstheoverviewofthegroundmountedarraystructure.Page49 3.4OverallPVSystemandElectricalDesignFigure3-10:OneLineDiagramDetailedelectricaldiagramofPVsystemcouldbefoundinAppendixI.PVArrayThePVarrayismadeupof48polycrystallinePVmodules,withD.C.powerratingat185Wpeach.ThePVmodulesarearrangedinto3parallelstrings(labeledas:ArrayR1,ArrayY1andArrayB1)andeachstringconsistsof16modulesarrangedinseries.Theoutputofindividualstringsisconnectedtothepowermodulesofthe10kW3-phasegrid-connectedinverter.Figure3-11and3-12illustratedthemodulesarrangementsandstringconnectiontogrid-connectedinverterrespectively.Page50 Figure3-11:ModuleArrangementFigure3-12:PVStringsconnectiontogrid-connectedinverterPage51 Grid-ConnectedInverterThegrid-connectedinverterconsistsof3powermodules,whichcanconvertupto3.5kWACindividually,totalingpowerratingof10kWACwithoutputvoltageof230VACthree-phase,50Hz.Theinverterisenclosedinanoutdoorcabinetwhichincludesdataloggermonitoringcontrolsystem,externalDCandACcircuitbreakers(asshowninFigure3-13below).DataLoggerMonitoringSystemPerformancedataaregatheredviathedataloggermonitoringsystemat15minuteintervalandcanstoreupto6weeksofdata.Theperformancedataaredownloadedbymeansofwirelesscommunicationsystematregularintervals.Themonitoringsystemprovidesalogofoperationperformanceparameters,suchasvoltageandcurrentofPVarrayoutputandinverteroutput.Page52 3.5EstimatingSystemOutputTheoverallperformanceofgrid-connectedPVsystemisbasedonthesize(peakpowerrating)ofthePVarray,withassociatedreductionsinperformanceatactualoperatingconditions.Ingeneral,theestimatingofaveragesystemOutputofthePVarraycanbecalculatedbythefollowingformula:Earray=Pstc×fman×ftemp×foverall×NWhereEarray=AveragesystemOutputofthePVarray(kWh)Pstc=RatedoutputpowerofthemoduleunderSTC(Wp)fman=DerateFactorformanufacturingtolerance(withreferencetotechnicalspecificationofPVmodule)ftemp=DerateFactorfortemperaturefoverall=DerateFactorforothersystemlossesN=TotalnumberofPVmodulesinthearrayTherefore,theestimatedaveragesystemOutputofthe8.88kWpgrid-connectedPVsystem(whichexcludesderatingduetoshading)is:Earray=185Wp×0.97×0.875×0.84×48=6.330kWPage53 Forestimatingthedailysystemyield,PeakSunHours(PSH)willbeappliedtotheabovecalculation.Table3-6presentstheMonthlyMeteorologicaldataofaverageInsolation,MeanTemperatureandnumberofrainydaysofSingapore[18].MONTHJANFEBMARAPRMAYJUNJULAUGSEPTOCTNOVDECAVGInsolation,4.35.15.04.64.54.34.24.44.54.54.03.84.4kWh/m²/dayMeanMax.29.931.031.431.731.631.230.830.931.131.431.230.431.1Temperature,°CMeanMin.24.024.924.525.525.424.924.724.625.024.524.324.224.7Temperature,°CNumberof12.510.413.414.614.413.114.213.514.616.220.219.414.7RainyDaysTable3-5:MonthlydataofaverageInsolation,MeanTemperatureandnumberofrainydaysofSingaporeBasedontheabovemetrologicaldata,theaveragePSHisof4.4hours.Estimateddailysystemyieldisof:Earray×PSH=6.330kW×4.4=27.85kWh/kWp/dayPage54 Table3-7belowsummarizestheabovecalculationsofestimateddaily,weeklyandyearlysystemyield.InstalledEstimatedSystemEstimatedSystemEstimatedSystemCapacity*Output(Daily)Output(Weekly)Output(Yearly)8.88kWp27.85kWh/kWp/day194.95kWh/kWp/wk10,065kWh/kWp/yrInstalledCapacityvalueisbasedonthePVmoduleMaximumPowerRating(Pmax)EstimatedDailySystemOutputvalueisbasedonaveragePeaksunhoursof4.4hoursandEarraycalculation.EstimatedWeeklySystemOutputvalueisbasedonaveragePeaksunhoursof4.4hoursandEarraycalculationoveraperiodof7days.EstimatedWeeklySystemOutputvalueisbasedonaveragePeaksunhoursof4.4hoursandEarraycalculationoveraperiodof365days.TheaboveestimatedsystemOutputvalueDOESNOTincludesderatingduetoshading.Itisestimatedthattheshadingderatefactorwillbeinrangeof0.65to0.75.(thisshallbediscussedinChapter6.1)Table3-6:Estimatedvalueofdaily,weeklyandyearlysystemOutputFigure3-15summarizesthekeydesignparameters,factorsandvalueinestimatingthesystemoutput.Page55 TiltangleDerateandInsolationFactororientationofthemodule(Losses)ArrayorPVPanelVoltageMismatch:0.98Dirtanddust:Insolation0.995(PeakSunnorth-southHours):4.46ACCabling:0.99orientationDiodesandConnections:0.98DCCabling:0.9910-15°(Topreventsolarirradiancesoilingdueto(PVsystemSystemtrappedwater)Yield):1205kWh/Availability:0.98kWp/YearInverter:0.93MEAPGRID-CONNECTEDPVSYSTEMKEYDESIGNPARAMETERSAverageModuleTemperature:50°CShadingderatefactor:XX(Tobeconfirmatdataanalysisstage)Cell/ModuleTemperatureShadingFigure3-15:Summaryofkeydesignparameters,factorsandestimatedvaluePage56 CHAPTER4SYSTEMINSTALLATIONANDCOMMISSIONINGThisChapterisintendedtopresenttheengineeractivitylogoftheinstallationprocess.Itaimstoaidsexplanationandprovideclearerviewoftheinstallationprocesswithillustratedphotosoftheactualinstallationstepsthatwereundertookinthefieldwork.ActualinstallationofthePVpowersystemwasbeingcarriedoutbyexperiencedSystemIntegrator,withtime-to-timeanticipationandunderstudyinvolved.4.1ProceedingsofInstallationThefollowinginstallationprocesswithillustratedphotosoftheactualinstallationstepsareprovidedforthisthesisdiscussiononly.Theinstallationphasecomprisesofthefollowingstages:Figure4-1:InstallationstagesPage57 Stage1:SitePreparationthDate:4August2008,SunnySitepreparationforplacementofgroundmountedstructure’sfootings.AsanymisalignmentwillaffectthesafetyandaestheticsofthePVsystem,precisemeasurementsandalignmentsofplacementofstructurefootingsmustbeundertaken.Woodenpolesweretemporarydeployedforplacementmarkingofthestructurefootings.Bumperswereinstalledtopreventanycontactsofvehicles.BumperWoodenPolesTrencheswerebeingdugasaccordinglytotheplacementofthewoodenpoles.*(Continued)*Page58 *(Continued)*Distancebetweeneachtrench:17cm(centre-to-centre)Distancebetweenside-wallandtrench:6cm17cm6cmCylinder-areaofaround6.5cm(diameter)by60cm(height)forimplantingstructurefootingstoground.*Seeproblemencounteredinchapter4.3*6.5cmTotalnumberoftrench:16Stage1:Completedon10thAugust2008Figure4-2:SitepreparationPage59 Stage2:StructureInstallationthDate:11August2008,RainyUponcompletingthesitepreparation,thenextstepwastoinstalltheprefabricatedverticalstructurefootings.Structurefootings,whichactasthesystemstructurefoundationssupport,mustbeinstalledspecificallyaspermeasurementstoavoidanymisalignmentandload-bearingfailure.Thestructurefootingsarebuiltfrom2.5’diameterreinforcedconcretecastinasaunatube.Metalpolesweretemporarydeployedtosupportandstabilizedthestructurefooting.MetalPole*(Continued)*Page60 *(Continued)*Toinspectthestabilityandlevelplacementofeachstructurefootings.Inclinometerlevelwasusedtoensurelevelplacementofstructureandgroundfoundation.Structureinstallationwasunabletocompleteasperscheduleduetorainyweather.Timedelayed:oneweek.thStage2:Completedon19August2008Figure4-3:StructureinstallationPage61 Stage3:PVModuleInstallationthDate:20August2008,CloudyBeforecommencementofPVmoduleinstallation,structurewasexaminedagaintoensureitsstabilityandalignment.Themountingframeconsistsoftwoparallelchannelbarstoformasimplerackwithtiltangleof10°andcrosssupportsareboltedtothemoduleframetoincreaselateralstructuresupport.Modulesareinterconnectedaccordingtothesystemlayout(parallelorseriesconnection)toformthedesignedarraysize.Essentialcareandpreciseexamineofarraywastakentoensurethearraywasmountedsecurelyandspecificallyintheirplannedposition.Visuallyinspectionofarrayforcrackedmodules,damagedjunctionboxes,andloosewire.thStage3:Completedon22August2008Figure4-4:PVModuleInstallationPage62 Stage4:BOSInstallationrdDate:23August2008,sunnyINVERTERInteriorviewoftheMastervoltInverterinterior.TheinverterconvertstheDCPowerpowerinto230VAC,50Hz.Modulex3Detailedinstallationsandwiringofinverterareinaccordancetomanufacturers’specificationsandprocedures.Top(markedyellow):SystemDatalogger–forsystemdatasetting.Bottomleft(markedorange):DCswitch–forisolationonDCoutputfromPVarray.Bottomright(markedBlue):ACswitch–forisolationonACoutputfrominverter.(refertoAppendixJforelectricalwiringdiagram)PVIsolator45cmclearanceareaForoptimalandsafeoperation,ensurethereisadequateclearancearoundtheinverter.*(Continued)*Page63 *(Continued)*Viewofsub-DB(withACswitchtoinverter–forisolationoninvertertoutilitygrid)Connectionoftheinvertertotheutilitygridwasconductedbylicensedengineers.DetailedmarkingandlabelingweredoneasperEMArequirements.OtherBOSincludes:Thewiringsystemsincludedisconnectsforthedcandacsidesoftheinverter,ground-faultprotection,andover-currentprotectionforthePVmodules.thStage4:Completedon29August2008Figure4-5:BOSinstallationPage64 Stage5:FinalAlignmentthDate:30August2008,cloudyAdditionalstructurefootingswereaddedtotheinitialdesigntostrengthentheoverallstructure.(**seeChapter4.X,problemencountered)AdditionalstructurefootingsToensureallPVmodulesareattachedsecurelytothemountingbrackets.TomakefinalalignmentofPVmodules.CompletionoftheMEAP8.88kWpPVsystemon3rdSeptember08.Figure4-6:FinalAlignmentDetailedinstallationscheduleisasperstatedinFigure4-7.Page65 Figure4-7:DetailedInstallationSchedulePage66 4.2SystemTestingandCommissioningStart-upTestingUponcompletionofinstallation,thenextessentialstepistoensureallconnectivityofindividualsystemcomponentswasmethodicallyandvisuallychecked.PriortointerconnectingthePVsystemtothegrid-utility,thestart-uptestingofthePVarraywasperformedoncloudlessmidday(idealcondition)toensurethesystemisfunctioningwellasexpected.Figure4-6presentsthestart-upteststepsandprocedures.Figure4-7:Start-upteststepsandproceduresPage68 PriortoactualcommissioningdateofPVsystem,LicensedElectricalWorker(LEW)shallconfirmthecomplianceofsystemwithregardstopowerqualityandsubmittoSPPowerGrid(SPPG).FurtherdetailsofthelistedrequirementsbySPPGcouldbefoundinAppendixK.WheredeemednecessarybySPPG,SPPGmaycarryoutmeasurementstoverifythecompliancereportsubmittedThetestresultsofabovementionedrequirementscouldbefoundinAppendixL.Page69 CommissioningOnactualcommissioningdateofthePVsystem,theparameters(aslistedinTable4-1below)werebeingmeasuredandcheckedabouttheelectricperformanceandensurethatthevalueswerewithintheacceptablerangeusingcalibratedsensorsandmeters[35].Table4-1:Start-uptestingandmeasurementsofPVsystemPage70 T.V:TheoreticalValue,M.V:MeasuredValueNote1-Peaksunfactor:MeasuredIrradianceValue21000W/mNote2-Temperaturefactor:o(100-[(T-25C)temperaturecoefficientofthePVmodule])module100Note3-PVArrayEstimatedPower:BasedonactualenvironmentalfactorsNominalPowerPeaksunfactorTIemperaturefactornverterefficiencycablelosses88800.8180.890.960.955895.9Note4–Factorvaluemustbewithin90%orhigherofWattsAC-estimatedrecordedinPVArrayEstimatedPower.Ifitislessthan90%,thePVsystemiseitherdirty,miswired,fusesareblown,orthemodulesorinverterarenotoperatingproperly,systemwillnotbeapprovedwithfactorvaluebelow90%[36][37][38].Page71 Inaddition,“LossofMainTest”(LOMT)wasconductedbySystemIntegratedaspartoftherequirementinattainingapproval.TheLOMTistoverifycorrectoperationoftheinverteronanti-islandingprotection,whichisthemaintechnicalconcernforutilities‘islanding’[39].Figure4-7presentsthetestingproceduresofLOMT.Figure4-8:TestingproceduresofLOMTPage72 Figure4-8aand4-8billustratetheresultsontheLOMTwithACutilityswitchonandoffrespectively.Figure4-9a:ResultshowingACcurrentoutputofinverteras1.1A(switchON)Figure4-9b:ResultshowingACcurrentoutputofinverteras0A(SwitchOFF)Page73 4.3ProblemencounteredEachPVPowersystemimplementationpresentsuniquechallenges,requiringspecialintegrationthatmaynothavebeenencounteredbefore.Thissectionshallhighlightthemajorchallengefaceduringtheoperationphase,wheretheinverterfailureoccurs.kWhDailySystemOutputkWh(DEC'08)3025MAX:2016.02151050cccccccccccccccc1‐De3‐De5‐De7‐De9‐De‐De3‐De‐De‐De‐De‐De‐De‐De‐De‐De‐De111151719212325272931Figure4-10:Dailysystemoutput(Dec)Figure4-11:InverterPowerModuleFigure4-9plotsthedailysystemoutputofDecember.Itisclearlyshownthatsystemththgeneratesnooutputduringtheperiodof5–16December08,whichwasduetotheinverterfailurewithnotbeingdetected.Thetotalsystemoutputremainsrelativelylowththfortheperiodof17Dec08to10Jan09duetotheunavailabilityofthereplacementmodule.Thus,thesystemwaslefttooperatewithtwopowerinvertermodules,whichresultinanunbalancesystem.Thefailureisduetothebreakdownofoneoftheinverterpowermodule’sphasedetectorcircuit,whichisusedtoensuresynchronizationofthe3phases(protectionfeatures)–manufacturer’sexplanation.Thishighlightstheneedforreliablecomponentsandapromptdiligenceresponsetoanysystemfailures.Page74 CHAPTER5RESULTSANDFINDINGSThisChapterpresentsdataanalysisoftheoperationalperformanceresultsofProjectReferenceI:MEAP8.88kWpgrid-connectedPVsystem.5.1ProjectReferenceI:MEAP8.88kWpPVsystemThissectionwillproviderepresentativeperformanceresultsofProjectReferenceI:MEAP8.88kWpPVsystem.Theapproachinthissectionistodiscussandelaborateaboutthesystemperformancebasedonin-fieldmonitoringdataofvaluesoverperiodofOctober’08toFebruary’09.Thedataanalysisfocustodiscussonthefollowingtopics:5.1.1OverviewofSystemperformance;5.1.2EfficiencyofPVarray,InverterandOverallSystem5.1.3ShadingeffectAnalysis5.1.4Determineofshadingderatefactor5.1.5Systemavailability5.1.6EstimatingAnnualSystemOutputPage75 5.1.1OverviewsystemperformanceFigure5-1plotsthedailysystemoutputandthetrendovertheperiodfromOctober’08toFebruary’09.Sincecommissioning,thesystemproduced2106.84kWhofACenergyandtotalsystemyieldof237.26kWh/kWp(basedontotalsystemDCnameplateratingof8.88kWp).ThedailysystemoutputwithindicationofmaximumandminimumoutputofindividualmonthsareshowninFigure5-2to5-6respectivelyPage76 ThestatisticdataforperiodfromOctober’08toFebruary’09aresummarizedinTable5-1.ThesystemproducedanaveragedailyACenergyoutputof14.01kWhandaveragethsystemyieldof1.57kWh/kWp.Thehighestsystemoutputrecordedof26.31kWhon15February’09.RefertoAppendixMfordetaileddailysystemoutput.MonthlySystemOutputStatisticsforOCT'08TOFEB'09SumofAvgOutputMaxOutputMinOutputStdMonthOutput(kWh)(kWh)(kWh)(kWh)DeviationOCT'08544.4817.5626.116.645.78NOV'08433.8214.4623.714.324.91DEC'08197.946.3916.0205.85JAN'09462.2514.9125.125.385.07FEB'09468.3516.7326.317.744.75Table5-1:MonthlySystemOutputStatisticforOCT’08toFEB’09Page77 kWhMONTHLYSYSTEMOUTPUT(OCT'08~FEB'09)1000250090080020007006000.6315005000.520.540.5940010003000.2320050010000October'08November'08December'08January'09February'09MonthlyOutputEstimatedMonthlyOutput(noshading)ACTUALAccumulative_OutputFigure5-7:MonthlyActualandEstimatedSystemOutput(OCT’08–FEB’09)Figure5-7presentstheestimatedandactualmonthlysystemoutputwithPerformanceRatio(PR)valuesasindicated.AsdiscussedinChapter2.5.2,PRisdefinedasActualsystemoutput(kWh)overEstimatedsystemoutput(kWh).Itisclearlyshownthattheestimatedsystemoutputhasasignificantdifferenceovertheactualsystemoutput,whichinturnresultsinlowPRvalues(between0.23to0.63)-anindicativeofverypoorsystemperformance.TheprimaryfactorthatresultedinsuchlowPRvaluewasduetoinaccuratecomputationoftheEstimatedsystemoutput–whichshadingderatefactorwasexcludedduringcomputationofestimatedsystemoutput.Inordertohaveanaccurateassessmentandbettermonitoringofsystemperformance,itisthereforeessentialtodeterminethevalueofshadingderatefactorofthePVsystem,andre-calculationoftheEstimatedsystemoutput.FurtherdetailsshallbediscussedinChapter5.1.3.Page78 5.1.2EfficiencyofPVarray,InverterandOverallSystemThePerformancefactors(PVarrayefficiency,inverterefficiency,andPVsystemefficiency)ofthePVsystemaretabulatedasshowninTable5-2below.(DetailsoftheseperformancefactorswereasdiscussedinChapter2.5.2)Calculationsoftheseefficienciesweredonebasedonrecordeddatafromeachmonth’smaximumandminimumsystemoutput.TheaveragesystemefficiencyofotherinternationalPVgrid-connectedsysteminstallationsisof8.58%[40].Usingthisasabenchmark,resultshadshownthatonlyefficienciesofthemonthlymaximumsystemoutput(nottakingintoconsiderationofDEC’08)areclosetothisvalue.OCT'08NOV'08DEC'08JAN'09FEB'09MaxMinMaxMinMaxMinMaxMinMaxMin3Oct23Oct29Nov10Nov1Dec21Jan1Jan15Feb26FebPVArrayDC27.617.0425.134.5316.8826.55.4927.98.1Power(kWh)PVArrayDC110.428.02100.4717.9867.35106.122.0111.432.5Power(kW)InverterAC26.116.6423.644.2616.0225.15.426.37.7Power(kWh)InverterAC104.426.4394.5216.9163.78100.421.5105.231.6Power(kW)PVarray13.64%3.48%12.42%2.24%8.34%13.11%2.71%13.78%4.02%efficiency(%)Inverter94.5%94.3%94.0%94.0%94.9%94.6%98.1%94.4%95.1%efficiency(%)System8.9%2.2%8.1%1.4%5.5%8.6%1.9%9.0%2.7%efficiency(%)Table5-2:EfficienciesofPVarray,Inverterandoverallsystem(Basedonmonthlymaximumandminimumsystemoutputs)Page79 5.1.3ShadingEffectAnalysisAsdiscussedinChapter2.3.1,shadingofPVarraysisextremelydetrimentaltothesystemperformance.ThischapterisintendedtodiscussontheshadingeffectonthePVsystemperformance.ShadingEffectAnalysisShadingoccursduringthemid-daybetween2PMto4PMandthemaximumrecordedpercentageofshadedareaisofapproximately25%ofArray.Figure5-8and5-9illustratedtheamountofshadingsonthePVarraysandtheresultedarrayoutputsrespectively.ItcanbeclearlyseenthatArray1ismoreheavilyshaded,whichresultedinasignificantdecreaseinthearrayoutputwithcomparisontoArray2and3.thFigure5-8:ShadingonPVarray-15Feb(mid-day)Page80 Figure5-10comparestheoutputofarraysbetweentimeperiodsfrom2PMto4PM.Duringthistimeperiod,thepercentagedifferenceofthearrayoutputbetweenArray1toArray2and3areof41%and53%respectively.Page81 5.1.4DetermineofShadingDerateFactorDuringtheinitialstageofestimatingsystemoutput,thecomputationresultof27.85kWpdoesnotincludetheshadingderatefactor–asitwasdifficulttodeterminetheactualshadingeffecttothePVsystemandaccurateshadingderatefactor.Thishasresultedinasignificantdifferencebetweentheestimatedandfinalsystemoutput(asshowninFigure5-11),andverylowPRvalues.MONTHLYSYSTEMOUTPUT(OCT'08~FEB'09)100050009004500800400070035006003000500250040020003001500SYSTEMOUTPUT(kWh)200100010050000October'08November'08December'08January'09February'09MonthlyOutputEstimatedMonthlyOutput(noshading)ActualAccumulative_OutputEstimatedAccumulativeOutput(noshading)Figure5-11:ComparisonofEstimatedandfinalSystemOutput.Inordertohaveanaccurateassessmentofcomponentsandmonitoringofsystemperformance,itisthereforeessentialtodeterminetheaccuratevalueofshadingderatefactorofthePVsystem.Arangeofshadingderatefactors(0.65,0.70and0.75)areestimatedtoidentifyandre-calculateofmoreaccurateEstimatedsystemoutput.TheresultedPRvaluewiththesuggestedshadingderatefactorareasshowninFigure5-12andTable5-3.Page82 COMPARISONOFSHADINGFACTORVALUE(O.75,0.70,0.65and0.60)7001.20.840.310.716000.690.900.330.7610.740.780.970.350.800.820.845000.900.84000.63000.42000.210000October'08November'08December'08January'09February'09ACTUALMonthlyOutputEstimatedMonthlyOutput(withshading0.65)EstimatedMonthlyOutput(withshading0.70)EstimatedMonthlyOutput(withshading0.75)Figure5-12:ComparisonofShadingFactorvalue(0.60,0.70and0.75)SHADINGFACTOR0.75SHADINGFACTOR0.70SHADINGFACTOR0.65EstimatedEstimatedEstimatedMONTHPRPRPRSystemOutputSystemOutputSystemOutputOCT647.510.84604.350.90561.180.97NOV626.630.69584.850.74543.080.80DEC647.510.31604.350.33561.180.35JAN647.510.71604.350.76561.180.82FEB584.850.78545.860.84506.870.90Table5-3:ResultsofEstimatedSystemoutputandPR(withnewestimatedshadingfactors)Basedontheresearch,theaveragePRvalueofotherinternationalPVgrid-connectedsystemsisgenerallyof0.725to0.75[40][41].Takingthisvalueasbenchmarking,andcomparisonofresultsfromTable5-3,itissuggestedtoletshadingderatefactortobe0.75.Furtherverificationsaredonetoensurehigheraccuracyoftheshadingderatefactorvalue.Page83 Twoverificationsstepsweredonetoensurethechosenshadingderatefactorisofrealisticandhigheraccuracy.1.TocomputenewEstimatedsystemoutputwiththechosenderatefactorof0.75.FollowingwithdataanalysisofPRvaluesbasedonactualsystemoutputofFebruary’09.ResultsofPRvaluesaretargetedtobein-linewiththeaveragePRvalueofotherinternationalPVgrid-connectedsystemsof0.725to0.75.2.TomakecomparisonofthePRvaluesbetweenresultsfromverificationstep1withperformancedatafromcasestudyreport-PVS492kWpPVsystem(SystemD–Polycrystalline).TakingconsiderationthatPVS4SystemDisnotaffectedbyanyshadingeffect(i.e.shadingderatefactorofzero),PRvaluesofPVS4SystemDaresetasbenchmarkinverificationstep2.(DetailsofcasestudyPROJECTREFERENCEII:PVS492kWpPVsystemshallbediscussedinChapter6)Page84 VerificationStep1:Tore-calculatenewEstimatedsystemoutputwithchosenderatefactorof0.75:EstimatedSystemoutput=Earray×PSH=Pstc×fman×ftemp×foverall×fshading×N×PSH=20.89kWh(RefertoChapter3.5forparametersvalueanddefinition).BasedonactualsystemoutputofFEB’09,PRvalueswerecomputedwithabovenewEstimatedSystemOutputof20.98kWh.Figure5-13indicatethenewdailyPRwithaveragevalueof0.8.ResultshadshownthatthenewaveragePRvalueisclosetothebenchmarkvalueof0.75.301.401.261.20)251.101.071.021.031.011.021.041.000.96200.920.93h(FEB'090.880.870.800.790.800.720.75150.690.670.670.660.670.610.600.580.53100.410.390.400.3750.20DailyEnergyYieldkW00.00bbbbbbbbbbbbbbbbbbbbbbbbbbbbeeeeeeeeeeeeeeeeeeeeeeeeeeee-F-F-F-F-F-F-F-F-F-F-F-F-F-F-F-F-F-F-F-F-F-F-F-F-F-F-F-F12345678901234567890123456781111111111222222222DailyEnergyYield(kWh)EstimatedSystemYield-Daily(kWh)(withshadingfactor0.75)Figure5-13:February’09PRvalues(BasedonnewEstimatedSystemOutput)Page85 VerificationStep2:Theavailabilityofon-sitemeteorologicaldataandinstallationsitefreefromshadingofPVS4PVSystemD(Polycrystalline)enablesnormalizedperformanceindicatorsPRtobecalculated.Thus,PRofPVS4SystemDisusedasabenchmarkingagainstMEAPinstallation.However,inordertoachieveamoreaccuratePRcomparison,itisnecessarytore-calculatetheestimatedsystemOutputofPVS4withreferencetotheparametersofMEAP(asshowninTable5-4below).SystemSize47.28kWpDerateFactorformanufacturingtolerance,fman0.97DerateFactorfortemperature,ftemp0.875DerateFactorforothersystemlosses,foverall0.84PSH4.4EstimatedSystemOutput(Reference)148.31kWhTable5-4:Re-calculationofPVS4EstimatedsystemOutputNext,istoanalysisandmakecomparisonoftheresultedPRvalueofPVS4SystemDandPRvalues(withderatefactorof0.65,0.70and0.75)ofMEAPPVsystemoverthestthperiodfrom1to15ofFEB.ThecomputedPRvaluesofMEAPPVSystemareasshowninTable5-5.Page86 PVS4PVMEAPPVSystemsystemPRPRPRPRPRPR(noShading)(S.F:0.6)(S.F:0.65)(S.F.:0.70)(S.F.:0.75)Average0.601.000.920.860.801.03Max0.941.571.451.351.261.39Min0.280.460.430.400.370.74RefDate:15Feb0.941.571.451.351.261.28stthTable5-5:ComparisonofPRvaluestatisticsofperiodfrom1to15FEB1.80MEAP1.60PTM1.40-23.2%-13.7%-5.6%1.4%o1.2026.1%1.000.80PerformanceRati0.600.400.200.00PR(noShading)PR(0.6)PR(0.65)PR(0.70)PR(0.75)thFigure5-13:ComparisonofPRvalueon15FEBsystemoutput.Inaddition,furtherdetailedanalysiswithpercentageofdifferenceinPRvaluethcomparisonisdonebasedonsystemoutputof15FEBasshowninFigure5-13.Theresultshadshownshadingderatefactorof0.75hastheclosestPRvalueofPVS4withdifferenceof1.4%.Withtheabovetwoverificationstepsandanalysisdone,theresultshadverifiedthatthesuggestedshadingderatefactorof0.75isofmostrealisticandaccuratevalue.Page87 5.1.4SYSTEMAVAILABILITYFigure5-14belowclearlyindicatesthatDEC’08resultthelowestPRvalueascomparedthtotheothermonth.Thisisduetotheinverterfailurewithnotbeingdetectedduring5toth16December08.Thefailureisduetothebreakdownofoneofthepowermodulesoftheinverter.(DetailsofInverterfailurearediscussedinChapter4.3)MONTHLYSYSTEMOUTPUT(OCT'08~FEB'09)kWh60025000.635000.540.5920000.52400150030010000.2320050010000October'08November'08December'08January'09February'09MonthlyOutputACTUALAccumulative_OutputFigure5-14:PRofOCT’08toFEB’09Inaddition,duetotheunavailabilityofthereplacementpowermoduleoftheinverter,thethPVsystemwaslefttooperateinthe2-phaseoperationmodefrom17December08toth10January09.Figure5-15comparesthesystemoutputbetweentheperiodof2-phaseand3-phaseoperationmodeofinverter.Duringperiod1(2-phaseinverteroperation),thesystemproduces244.59kWhofACenergy.Thisresultinasignificantdecreaseinsystemoutputof75%ascomparedtonormal3-phasemodeoperationoverthesameperioddurationPage88 (period2and3),andthisequatetoanenergylossof3.3%overtheyear.Thishighlightstheimportanceforreliablecomponentsandapromptdetectiontofailures.ComparisonbetweenPeriods50045040035030075.6%75.2%250200150SystemOutput(kWh)100500Period1and2Period1and3Period1:17Dec08~10Jan09Period2:07Oct08~31Oct08Period3:01Feb09~25Feb08**Period1:2-phaseoperationmode**Period2and3:Normal3phaseoperationmodeFigure5-15:Comparisonofsystemoutputbetween2phaseand3phasemodeofinverteroperation.Page89 5.1.5EstimatingAnnualSystemOutputESTIMATEDANNUALSYSTEMOUTPUT(kWh)70012000h60010000500800040060003004000200MonthlySystemOutput(kWh2000100AccumulativeSystemOutput(kW00OCT'08NOV'08DEC'08JAN'09FEB'09MAR'09APR'09MAY'0JUN'09JUL'09AUG'09SEPT'0ACTUALSYSTEMOUTPUT(kWh)EstimatedMonthlyOutput(withshading0.75)Accumulative_Output(basedonshading0.75)Accumulative_Output(withnoshading)Figure5-16:EstimatedAnnualSystemOutputFigure5-16plotstheestimatedmonthlysystemOutputoveraperiodof12months(includingactualOutputfromOct’08toFeb’09).ThenewestimatedannualsystemOutputisof7,624kWhofACenergy,or859kWh/kWp(basedonnameplateratingof8.88kWp).Thisequatesatotalsystemlossof46.5%fromD.C.nameplateratingof8.88kWp.Ingeneral,thePVsystemisperforminglesswellthanexpectedwithaveragesystemefficiencyof6.37%.ThisisofalowervalueascomparedtootherinternationalPVsystemsof8.58%.Page90 CHAPTER6CASESTUDY(DATAANALYSIS)ThischapterpresentsacasestudyreportthatreviewedoperationalperformanceresultsofProjectReferenceII:PVS492kWpPVsystem.Theprimaryobjectiveaimstoproviderelativeperformanceanalysisofthedifferenttechnologiestobemeasuredside-by-sideandtostudythesuitabilityofdifferentPVpowersystemsunderthetropicalclimateconditions.Withconcernoftheaccuracyofirradiancemeasurements,powervaluesfrominvertersandmanufacturers’ratedpeakpowerofmodules,itisimportanttonotethattheanalysisresultsandfindingspresentedinthethesisaresitedependantandarenotbiastoanyexistingtechnology.However,whilstabsolutevaluesmayvary,theconclusionsaboutthesystemperformanceofthedifferenttechnologieswillstillholdtrue6.1ProjectReferenceI:PVS492kWpPVsystemThissectionwillproviderepresentativeperformanceresultsofProjectReferenceII:PVS492kWpPVsystemwhichcomprisesof4differentPVtechnologiesinstallations-Page91 Monocrystalline,Monocrystallineglass-glass,AmorphousandPolycrystalline.ThesystemtypeandcapacityoftheinstallationsarelistedasinTable5-6.IndividualsystemoverviewandperformanceanalysiscouldbefoundinAppendixN.InstalledTargetSystemExpectedSYSTEMTYPEOFPVTECHNOLOGYCapacity*Output**SystemOutput(kWp)(kWp)(kWh)***AMonocrystalline272530,000BMonocrystallineglass-glass11.641012,000CAmorphous6.085.887,056DPolycrystalline47.2844.553,400Total9285.38102,456*InstalledCapacity:SystemcapacitybasedonSTCrated.**TargetSystemOutput:EstimatedminimumSystemoutputbasedonmanufacturerPmax***ExpectedSystemYield:Expectedtotalannualsystemoutputbasedon1,200kWh/kWp/yr(Basedonsimulationprogram)Table6-1:SystemTypeandCapacityofinstallationPage92 Figure6-2:SystemB–Monocrystallineglass-glassinstallationPage93 6.2OVERALLPVS4PVSYSTEMPERFORMANCE1.401.20o1.00tiaR0.80ance0.60rformPe0.40SystemASystemBSystemCSystemDMax:1.08Max:0.84Max:1.28Max:1.060.20Min:0.86Min:0.45Min:1.01Min:0.650.00JanFebMarAprMayJunJulAugSepOctNovDecSystemA(Mono)SystemB(Mono-Glass)SystemC(Amorphous)SystemD(Poly)Figure6-5:OverallsystemperformanceComparisonChartOvertheentireyear,thesystemyieldisof1217kWh/kWpwithoverallhighPRof1.01.However,withcomparisontotheaveragePRvalue(0.75)ofotherinternationalPVsysteminstallations,theoverallPRof1.01istoohightoberealistic[42].Oneofthereasonsmightbeduetotheunderestimationofreferenceyieldof1200kWh/kWp/yearbysimulationprogram.Page94 ModuleTemperature45070400603505030040250Wh/kWp20030Temperature15020SystemASystemB100SystemCSystemDModuleTemperature10500010:0010:3011:0011:3012:0012:3013:0013:3014:0014:3015:0015:3016:0016:30Figure6-7:Systemsyieldsandmoduletemperature(between10amto4.30pm)Asdiscussedinchapter2.5.1,crystallinesiliconPVcells,ingeneraldeclineinefficiencyby0.50%/°Candmostamorphouscellsdeclineby0.15-0.25%/°C.Figure6-8presentsresultsconsistentwiththeabovefindings.Onatypicalsunnyday(between12noonto2PM),itisseenthatSystemCoutperformtherestofthesystems,withconsistentsystemyields.Amorphoussilicon(SystemC)relativelyoutperformstheotherPVtechnologies(particularlyMonocrystallineandPolycrystalline)athighinsolationsbecauseitislesssusceptibletothehighertemperatures[44][45].Itisalsonotedthatasthemoduletemperaturerisesabove50°C,SystemAhasagreaterdeclineinsystemyieldwithcomparisontoSystemD.ThiscouldbeduetothehighersensitivityofMonocrystallinesiliconcomparedtopolycrystalline.Page95 SolarIrradianceTemperatureisproportionallyrelatedwithirradiancelevel–i.e.higherirradianceisassociatedwithhightemperatures.Figure6-9andTable6-2presentsthecomparisonofirradiancewithtemperature;andthesystems’outputandPRinaccordancetosunny,rainyandcloudydayrespectively.Figure6-8:Comparisonofirradianceandtemperatureontypicalsunny,rainyandcloudyday6/17/20086/29/20086/2/2008(SUNNY)(RAINY)(SLIGHLYCLOUDY)kWh/dayPRkWh/dayPRkWh/dayPRSystemA132.981.6238.720.4778.820.96SystemB40.931.2811.840.3721.390.67SystemC33.721.779.520.5018.050.95SystemD206.631.4267.790.46143.080.98Table6-2:Systems’outputandperformanceratioonsunny,rainyandcloudydayrespectivelyLowirradiancelevelsarefoundwhenconditionsareduringrainydaysandoccurduringdawnanddusk.Undersuchconditions,thelightreceivedisprimarilydiffuse.Thegoodlowirradiance2performanceofSystemCresultsinhigherreturnsofenergybetween0and400Wm.SystemA2andDproducebettersystemyieldsatmediumirradiance,between400and800Wm,wheretheyarenothamperedbyovercastconditionsandhightemperatures[45].Page96 CHAPTER7CONCLUSIONS7.1FeasibilityReport7.1.1EnvironmentandPollutionAbatementConsiderationWiththeincreaseofelectricityconsumption,itisinevitablethatenergycostswillsurpasshistoricalcostescalationsandresultinseriousdeficienciesoffossilfuelssources.Theentireglobalcrudeoilreservesareestimatedtolastabout30to80years[46].TheavailabilityoffossilfuelsupplyisasshowninTable6-1.FossilFuelPetroleumUraniumNatualGasCoalRunsoutin39.9years64.2years61years227years(DateofEstimate)(2001)(1999)(2001)(2001)150Extractible1,0463.95984trillioncubicvolumebillionbarrelsmilliontonsbilliontonsmetersTable7-1:Availabilityoffossilfuelsupply[46]Page97 Thissubstantialincreaseintheuseofthisnon-renewablefossilfuelsupplyisaprincipalfactor2oftherapidincreaseinglobalgreenhousegasemission.AnaverageintensityofCOemissionsfromcoalbasedthermalpowerplantis0.98kg/kWhforgenerationofoneunitofelectricityAt2present,40%oftheworld’sCOemissionscomefromcoal-burningpowerplants[47].2TheamountofCOemissionsassociatedwiththeproductionofelectricityfromtherenewablefuelsisminisculeincomparisontofossil-fuel.Incontrast,PVpowersysteminturnifimplementedwillsubstantiallyminimizetheairpollutionindex,carbondioxideandmitigateadverseeffectsontheecologyandglobalwarming[48].Figure7-1presentsthecomparisonofCO2emissionsfromdifferentfuelsources.Figure7-1:comparisonofCO2emissionsfromdifferentfuelsources[47]Page98 TheCO2emissionsmitigatedduetothepowergenerationcanbeestimatedasfollows:ECO2mitigated=AvgCO2emission×Earray×NWhereECO2mitigated=CO2emissionsmitigatedduetothepowergeneration,KGAvgCO2emission=AverageintensityofCO2emissions,0.98KG/kWhEarray=EnergygeneratedbyPVsystem,(kWh/year)N=LifespanofPVsystem(years)Byimplementingan8.88kWpPVgrid-connectedpowersystemwithanestimatedlifespanof30years,theCO2emissionsmitigatedisestimatedtobe:ECO2mitigated=0.98KG×7,624kWh/year×30=224,146KG(224tons)Forone8.88kWpPVpowersystemwithestimatedlifespanof30years,thetotalamountofCO2emissionsmitigatedintotheatmosphereisestimatedtobe224tons,anddoesnotdissipateanyenormousamountofheatenergyintotheenvironment.Page99 7.1.2EconomicConsiderationWiththeadvancementoftechnologiesandextensivedemands,theelectricityconsumptionhadincreasedgreatlyovertheyears,andisthereforeinevitablethatenergycostswillsurpasshistoricalcostescalations[49].Figure7-2showstheelectricityconsumptionofSingapore(perpersoninMWh)fromyear1986to2007.Itisestimatedthatwithinthenextdecade,thecostofnon-renewableenergywillincreasedbyapproximately4to5percentbyproducers[50].Inconjunctionwithgeneralinflationrateof3percent,theaveragecostoverthenextdecadeisexpectedtoriseatarateofaround7percenteachyear.Figure7-2:ElectricityconsumptionofSingapore(perPersoninMWh)[51]OneofthekeybenefitsofPVpowersystemsistooffsetelectricutilitybillresultingfromtheenergythatthePVsystemproduces.Atcurrent,therateoftheelectricitytariffarereviewedquarterlybySPPower,andadjustedinlinewiththechangesofthecostofelectricityandfueloilprices.Diagram7-3presentsthelatestcostofelectricitytariffagainstthefueloilprices.Page100 Figure7-3:Costofelectricitytariffagainstthefueloilprices[52]ThetotalcostoftheinstalledPVsystemisapproximately$98,000(basicgrid-connectedsystem).Figure7-4presentsthebreakdownofthetotalsysteminstallationcost.Figure7-4:BreakdownoftotalsystemcostPage101 Theestimatedelectricutilitybillsavingsandpaybackperiodoftheimplemented8.88kWpgrid-connectedsystemispresentedinTable6-2below.**TotalBasicSystemCost:AroundElectricityTariff$98,000EstimatedAnnualPeriod$0.2507/kWh0.3045/kWh0.2293/kWhsystemoutputAnnual$1,911.34$2,321.51$1,748.187624kWh/yr(withshading)Electric30yearsUtility(Basedonsystem$57,340.10$69,645.24$52,445.50Billlife-span)SavingAnnual$2,548.37$3,095.24$2,330.8310,165kWh/yr(withnoshading)30years(Basedonsystem$76,451.10$92,857.20$69,924.90life-span)7624kWh/yr51years42years56years(withshading)PaybackPeriod10,165kWh/yr38years31years42years(withnoshading)Table7-2:EstimatedelectricUtilitybillsavingsandpaybackperiodcalculationForan8.88kWpPVsystem(withnoshadingeffect),theestimatedpaybackperiodisof31years–basedonsystemlifespanof30year.Toconclude,thereasoncitedfortheslowdevelopmentprogressofrenewableenergyinSingaporeisduetoitshighinvestmentwithlongperiodsoffinancialpaybackPage102 7.2ConclusionTheMEAPgrid-connectedPVsystemwasdesignedandbuildsincompliancewiththerequirementsbyapprovalauthoritiesofSingapore.Thetotalinstalledcapacityisof8.88kWp2thunderSTCandcoversanareaof66m.Itwasofficiallycommissionedon24September2008.Thisthesishadsummarizestheactualdesign,buildingandimplementationprocessesoftheinstalledPVsystem.Inaddition,thisthesisalsohighlightthebasicbackgroundstudyofPVtechnology,keydesignconsiderationsparametersandoutlinedthecriteriaforinterconnectingaPVsystemwiththeutilitygrid.Thisthesishaslaidparticularemphasisontheanalysisofoperationalperformanceoftheinstalled8.88kWpgrid-connectedPVsystem.ItillustratesthedetailedperformanceresultsofthesystemwithsuitablegraphsandpresentstheevaluationdatawithnormalizedperformanceparameterssuchasPR,energyyieldsandefficiencies.Analysisandobservationsmadeinthisthesisledtothefollowingconclusions:Overallconclusion:-ShadingofPVarraysisextremelydetrimentaltothesystemperformance.ResultshaveshownthatthepercentageofshadedareaonPVarraywillnotresultindecreaseofarrayoutputproportionally-significantlygreaterthanthereductioninilluminatedarea.-Forbetterassessmentofsystemcomponentsandmonitoringofsystemperformance,determinetheaccuratevalueofshadingderatefactorandre-determineofestimatedPage103 -Systemcomponentfailurethatwasundetectedforaperiodoftimewillcontributeinasignificantannualsystemyieldlossof3.3%.Thishighlightstheimportanceforreliablecomponentsandapromptdetectiontofailures.OverallSystemPerformance:-Thenewestimatedannualsystemyieldisof7,624kWhofACenergy.Thisequatesatotalsystemlossof46.5%fromD.C.nameplateratingof8.88kWp.-BasedonperformancedataofperiodbetweenOCTtoFEB,thePVsystemisperforminglesswellthanexpectedwithaveragesystemefficiencyof6.37%.-Asidederatingduetopartialshadingandinverterfailure,otherfactorssuchaslowerirradianceandrainyseasonoverperiodofNovembertoJanuary(monsoonseason)alsocontributetothelesswellperformanceofthesystem.BasedonlatestperformancedataofMarchandApril,acleartendencyofhighersystemoutputwasevidentasshowninFigure7-5.Figure7-5:MonthlySystemOutput(includingMarchandApril)Page104 EcologyandEconomicconsideration:-Forone8.88kWpPVpowersystemwithestimatedlifespanof30years,thetotalamountofCO2emissionsmitigatedintotheatmosphereisestimatedtobe224tons.-Thethreemainelementsdeterminetheeconomicsofagrid-connectedPVsystemare:thenetinstallationcost,annualsystemyield,andpaybackperiod.-Withanestimatedpaybackperiodof31years,itisseemnotfeasibleforimplementingPVpowersysteminSingaporeatthismoment.ThehighinvestmentwithlongpaybackperiodisconsideredprimaryfactorwhichcitedfortheslowdevelopmentprogressofrenewableenergyinSingapore.Thus.,ecologicaladvantagesshouldbetakenasthemainconsiderationatthispointoftimeInaddition,thecasestudypresentedinthisthesissummarizestherelativeperformanceanalysisofthedifferenttechnologiestobemeasuredside-by-side(aspresentedinAppendixN)andhadstudythesuitabilityofdifferentPVpowersystemsunderthetropicalclimateconditions.AnimportantfindingofthiscasestudyshowsthatamorphoussiliconrelativelyoutperformstheotherPVtechnologiesintropicalclimateconditionsofhighirradiancewithlowseasonalvariationbecauseitislesssusceptibletothehighertemperatures.Toconclude,inviewofconstantandinevitablefossilfuel-basedenergycostescalationandavailabilityofupcomingenergyrebateprograms,PVpowerwillbecomeanimportantcontenderinresidential,commercialandindustrialinstallationsinthecomingcentury.Byanyobjectivemeasure,thethesishasmetitsinitialgoalsandobjectives.Page105 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INDEXOFAPPENDICESAppendixA:ProjectGanttchartAppendixB:PVCellPhysicsAppendixC:BasicOperationofInverterAppendixD:PVConversionFactorTableAppendixE:DetailsofDerateFactorAppendixF:DetailsofPerformanceParameterAppendixG:StandardsandRequirementsforgrid-interconnectionG1:BuildingandConstructionAuthority(BCA)G2:EnergyMarketAuthority(EMA)G3:SPPowerGrid(SPPG)AppendixH:TechnicalspecificationofselectedPVmoduleandinverter.H1:PVModulespecificationH2:InverterspecificationAppendixI:ElectricalSchematicDiagramofPVsystemPage112 AppendixJ:ElectricalWiringofInverterAppendixK:RequirementsbySPPG(Informationtobesubmittedforapproval)AppendixL:TestResultsforcompliancetoSPPGApprovalAppendixM:DailySystemOutputAppendixN:IndividualsystemoverviewandperformanceanalysisN1:SystemA–MonocrystallineSiliconN2:SystemB–MonocrystallineGlass-to-glassN3:SystemC–AmorphousSiliconN4:SystemD–PolycrystallineSiliconPage113