Performance Degradation of Grid-Tied Photovoltaic

PerformanceDegradationofGrid-TiedPhotovoltaicModulesinaDesertClimaticConditionbyAdamAlfredSuleskeAThesisPresentedinPartialFulfillmentoftheRequirementsfortheDegreeMasterofScienceinTechnologyApprovedNovember2010byTheGraduateSupervisoryCommittee:GovindasamyTamizhMani,ChairBradleyRogersNarcisoMaciaARIZONASTATEUNIVERSITYDecember2010iABSTRACTPhotovoltaic(PV)modulesappeartohavethreeclassificationsoffailure:Infantmortality,normal-lifefailure,andend-of-lifefailure.Littleisknownoftheend-of-lifefailuresexperiencedbyPVmodulesduetotheirinherentlongevity.AcceleratedLifeTesting(ALT)hasbeenatthecruxofthislifespanprediction;however,withoutnaturallyfailingmodulesanaccurateaccelerationfactorcannotbedeterminedforuseinALT.Byobservingmodulesthathavebeenagedinthefield,acomparisoncanbemadewithmodulesundergoingacceleratedtesting.Inthisstudyaninvestigationonabout1900aged(10-17years)grid-tiedPVmodulesinstalledinthedesertclimaticconditionofArizonawasundertaken.Theinvestigationwascomprisedofachecksheetthatdocumentedanyvisualdefectsandtheirseverity,infrared(IR)scanning,andcurrent-voltage(I-V)curvemeasurements.Afterdatawascollectedonmodules,ananalysiswasperformedtoclassifythefailuremodesandtodeterminetheannualperformancedegradationrates.iiDEDICATIONIwouldliketodedicatethisworktomygrandmother,GloriaPleasant.Withoutherconstantloveandsupportthiswouldnothavebeenpossible.iiiACKNOWLEDGMENTSIwouldfirstliketothankDr.GovindasamyTamizh-ManiforhisguidanceinmytimestudyingatArizonaStateUniversity.Iwillforeverbegratefulforhisguidanceandforgivingmetheopportunitytoworkonaprojectofsuchimportance.IwouldalsoliketothankDr.BradleyB.RogersandDr.NarcisoF.Maciafortheirinterestandcarefulreadingofthiswork.IwouldalsoliketothankArizonaPublicServiceandthegreatpeopleattheAPSSolarTestingandResearchfacility.Theirpatienceandhelpwasinvaluable—itwaswonderfulworkingwithyou.ImustalsogivegreatthankstoLynetteSalikatAPSSTAR.Ifitwerenotforherhelponallofthose117Fdays,thiswouldneverhavebeenpossible—Iamforeverindebted.Finally,Imustthankmyfamilyandmysweetheart,Sue.EverytimeIfalloffthehorse,youhelpmebackup.ivTABLEOFCONTENTSPageLISTOFTABLES.........................................................................................viiLISTOFFIGURES......................................................................................viiiCHAPTER1INTRODUCTION.....................................................................11.1Background.......................................................................11.2StatementofProblem........................................................11.3Scope.................................................................................3CHAPTER2LITERATUREREVIEW...........................................................42.1ReliabilityandLifetimePrediction.....................................42.2WhyitisNecessarytoStudyReliability............................42.3ReliabilityModeling............................................................52.4PhotovoltaicDegradation..................................................52.4.1PhotovoltaicUsefulLife.............................................72.4.2CatastrophicFailure..................................................72.5Analysis.............................................................................82.5.1PhotovoltaicFailureModes.......................................82.5.2CausesofPhotovoltaicFailure..................................92.5.3InfraredScanning......................................................92.5.4DangersFromFailingModules..................................92.6ModuleConstruction........................................................102.6.1GlassSuperstrate....................................................11vPage2.6.2EncapsulatingMaterial................................................112.6.3Backsheet....................................................................11CHAPTER3METHODOLOGY..................................................................133.1BuildingaFailureModeDatabase..................................133.1.1ScopeofMethodology.............................................143.2VisualInspection.............................................................153.3InfraredScan...................................................................153.4I-VCurveTracing............................................................163.4.1DataNormalization...................................................17CHAPTER4RESULTSANDDISCUSSION............................................214.1ModelsandManufacturers..............................................214.2VisualInspection.............................................................224.3InfraredScanning............................................................264.4OverallPowerDegradation.............................................294.5AnnualPowerDegradation.............................................32CHAPTER5CONCLUSIONSANDRECOMMENDATIONS....................375.1Conclusions.....................................................................375