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ChemicaltreatmentofcrystallinesiliconsolarcellsasamethodofrecoveringpuresiliconfromphotovoltaicmodulesRenewableEnergyPhotovoltaictechnologyisusedworldwidetoprovidereliableandcost-effectiveelectricityforindustrial,commercial,residentialandcommunityapplications.TheaveragelifetimeofPVmodulescanbeexpectedtobemorethan25years.ThedisposalofPVsystemswillbecomeaprobleminviewofthecontinuallyincreasingproductionofPVmodules.Thesecanberecycledforaboutthesamecostastheirdisposal.Photovoltaicmodulesincrystallinesiliconsolarcellsaremadefromthefollowingelements,inorderofmass:glass,aluminiumframe,EVAcopolymertransparenthermetisinglayer,photovoltaiccells,installationbox,Tedlar®protectivefoilandassemblybolts.Fromaneconomicpointofview,takingintoaccountthepriceandsupplylevel,puresilicon,whichcanberecycledfromPVcells,isthemostvaluableconstructionmaterialused.Recoveringpuresiliconfromdamagedorend-of-lifePVmodulescanleadtoeconomicandenvironmentalbenefits.Becauseofthehighqualityrequirementfortherecoveredsilicon,chemicalprocessingisthemostimportantstageoftherecyclingprocess.Thechemicaltreatmentconditionsneedtobepreciselyadjustedinordertoachievetherequiredpurityleveloftherecoveredsilicon.ForPVsystemsbasedoncrystallinesilicon,aseriesofetchingprocesseswascarriedoutasfollows:etchingofelectricconnectors,anti-reflectivecoatingandn-pjunction.Thechemistryofetchingsolutionswasindividuallyadjustedforthedifferentsiliconcelltypes.Effortsweremadetoformulateauniversalcompositionfortheetchingsolution.Theprincipaltaskatthispointwastooptimisetheetchingtemperature,timeandalkaliconcentrationinsuchawaythatonlyasmuchsiliconwasremovedasnecessary.Engineering,institutions,andthepublicinterest:EvaluatingproductqualityintheKenyansolarphotovoltaicsindustryEnergyPolicySolarsalesinKenyaareamongthehighestpercapitaamongdevelopingcountries.WhilethiscommercialsuccessmakestheKenyamarketagloballeader,productqualityproblemshavebeenapersistentconcern.Inthispaper,wereportperformancetestresultsfrom2004to2005forfivebrandsofamorphoussilicon(a-Si)photovoltaic(PV)modulessoldintheKenyamarket.Threeofthefivebrandsperformedwell,buttwoperformedwellbelowtheiradvertisedlevels.Theseresultssupportpreviousworkindicatingthathigh-qualitya-SiPVmodulesareagoodeconomicvalue.Thepresenceofthelowperformingbrands,however,confirmsaneedformarketinstitutionsthatensurethequalityofallproductssoldinthemarket.Priorworkfrom1999indicatedasimilarqualitypatternamongbrands.Thisconfirmsthepersistentnatureoftheproblem,andtheneedforvigilant,long-termapproachestoqualityassuranceforsolarmarketsinKenyaandelsewhere.Followingthereleaseofour2004/2005testresultsinKenya,theKenyaBureauofStandardsmovedtoimplementandenforceperformancestandardsforbothamorphousandcrystallinesiliconPVmodules.ThisappearstorepresentapositivesteptowardstheinstitutionalizationofqualityassuranceforproductsintheKenyasolarmarket.ElectricalperformanceresultsfromphysicalstresstestingofcommercialPVmodulestotheIEC61215testsequenceSolarEnergyMaterialsandSolarCellsThispaperpresentsstatisticalanalysisofthebehaviouroftheelectricalperformanceofcommercialcrystallinesiliconphotovoltaic(PV)modulestestedintheSolarTestInstallationoftheEuropeanCommission'sJointResearchCentrefrom1990upto2006totheIECStandard61215anditsdirectpredecessorCECSpecification503.Astrongcorrelationbetweendifferenttestresultswasnotobserved,indicatingthatthestandardisasetofdifferent,generallyindependentstressfactors.TheresultsconfirmtheappropriatenessofthetestingschemetorevealdifferentmoduledesignproblemsrelatedrathertotheproductionqualitycontrolthanmaterialweaknessincommercialPVmodules.EfficiencymodelforphotovoltaicmodulesanddemonstrationofitsapplicationtoenergyyieldestimationAnewmethodhasbeenproposed[W.Durisch,K.H.Lam,J.Close,Behaviourofacopperindiumgalliumdiselenidemoduleunderrealoperatingconditions,in:ProceedingsoftheWorldRenewableEnergyCongressVII,PergamonPress,Oxford,Elsevier,Amsterdam,2002,ISBN0-08-044079-7]forthecalculationoftheannualyieldofphotovoltaic(PV)modulesatselectedsites,usingsite-specificmeteorologicaldata.Theseyieldsareindispensableforcalculatingtheexpectedcostofelectricitygenerationfordifferentmodules,thusallowingthetypeofmoduletobeselectedwiththehighestyield-to-costratioforaspecificinstallationsite.Theefficiencymodeldevelopedandusedforcalculatingtheyieldstakesthreeindependentvariablesintoaccount:celltemperature,solarirradianceandrelativeairmass.Openparametersofthemodelforaselectedmoduleareobtainedfromcurrent/voltage(I/V)characteristics,measuredoutdoorsatPaulScherrerInstitute'stestfacilityunderrealoperatingconditions.Fromthemodel,cellandmoduleefficienciescanbecalculatedunderallrelevantoperatingconditions.Yieldcalculationswereperformedforfivecommercialmodules(BPSolarBP585F,KyoceraLA361K54S,Uni-SolarUPM-US-30,SiemensCISST40andWuerthWS11003)forasunnysiteinJordan(AlQawairah)forwhichreliablemeasuredmeteorologicaldataareavailable.Theserepresentmono-crystalline,poly-crystallineandamorphoussiliconaswellaswithcopper–indium-diselenide,CuInSe2PVmodules.Theannualyieldforthesemoduleswi