太阳能光伏讲义Lecture note 8

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1、PHOTOVOLTAICTECHNOLOGYShuntresistanceDefine:rSH=RSH/RCHnormalizedshuntresistance·ThenFFSH~FFO[1-1/rSH]OrmoreaccuratelybyFFSH~FFO[1-(Voc+0.7)*FFo/(Voc*rSH)]validforrSH>0.4WhereFFSHistheFFwithRSHpresent(noRS)andFF0istheFFwithRS=0andRSHinfinite·InthepresenceofbothRsandRSHtheFFcanstillbeestimate

2、dusingtheaboveequationforFFSH,butreplacingFF0withFFS.L87EffectofParasiticResistances:IVequation·ConsideringbothRsandRSHtheIVequationbecomes:CellPropertiesandDesignEfficiencyandCost·Theenergyconversionefficiency,ή,ofasolarcellisdefinedas:maximumpoweroutputofacell/inputfromthesun,typical1kW/m2

3、η=PM/Pin·Singlec-Siworldrecordis25%(Aug08)·Industrycellefficienciesaretypicallylowerandintherangeof12-17%.Manylaboratorytechniquesarenotsuitedtoindustrialproduction(tooexpensive,tooslow…).Typicallylowerefficiencyindicateslowerproductioncosts.·simplifiedmethodtocalculatethecostofelectricity:C

4、OE=[Cm+Cb(1+i)FCR]/(ηS)+0.016COE=costofelectricityinUS$/kW-hCm=PVmodulecostperunitareaCb=balanceofsystemcost(batteries,inverters,controlsystem,etc.)perunitareai=indirectcapitalcostfactorFCR=fixedchargerateS=annualincidentenergyή=systemefficiency–modules,includinglossesduetoheating,wiringandm

5、ismatch0.016=powerconditioning,operatingandmaintenancecost(US$/kW-h)L87Factoraffectingefficiencyopticallossessourcesofopticallossinasolarcell:1.shadingbytopcontact;2.surfacereflection;3.Reflectionformrearcontact.Waystoreducetheselosses:1.Minimisedthetopcontactcoverage.2.Reducesurfacereflecti

6、onbyusing“antireflectioncoatings”.“Quarterwavelength”ARCisideal(thicknessd1andrefractiveindexn1suchthat:d1=λ0/4n1.)ARCisdesignedforawavelengthλ0=0.6μm(i.e.closetothepeakofthesolarspectrum).theopticalpathdifferencebetweenthesebeamsduetotheARCintroducesa180phasedifferenceforλ=λ0.Thiseffectwill

7、reducethereflectionparticularlyforwavelengthsclosetothedesiredwavelengthλ0.L87IftherefractiveindexoftheARCsatisfiesthefollowingrelation:η1=√(ηoη2)reflectionatλ0willbezero!1.Surfacetexturingofthesiliconcelltominimizereflection.Iftheroughenedsurfaceh