handbook of photovoltaics-1-status,trends,challeng

1Status,Trends,ChallengesandtheBrightFutureofSolarElectricityfromPhotovoltaicsStevenS.Hegedus1andAntonioLuque21InstituteofEnergyConversion,UniversityofDelaware,Newark,Delaware,USA,2UniversidadPolitecnicadeMadrid,Madrid,Spain1.1THEBIGPICTURECongratulations!Youarereadingabookaboutatechnologythathaschangedthewaywethinkaboutenergy.Solarelectricity,alsoknownasphotovoltaics(PV),hasshownsincethe1970sthatthehumanracecangetasubstantialportionofitselectricalpowerwithoutburningfossilfuels(coal,oilornaturalgas)orcreatingnuclearfissionreactions.Photovoltaicshelpsusavoidmostofthethreatsassociatedwithourpresenttechniquesofelectricityproductionandalsohasmanyotherbenefits.Photovoltaicshasshownthatitcangenerateelectricityforthehumanraceforawiderangeofapplications,scales,climates,andgeographiclocations.Photovoltaicscanbringelectricitytoaruralhomemakerwholives100kilometersand100yearsawayfromthenearestelectricgridconnectioninhercountry,thusallowingherfamilytohaveclean,electriclightsinsteadofkerosenelamps,tolistentoaradio,andtorunasewingmachineforadditionalincome.Or,photovoltaicscanprovideelectricitytoremotetransmitterstationsinthemountainsallowingbettercommunicationwithoutbuildingaroadtodeliverdieselfuelforitsgenerator.ItcanhelpamajorelectricutilityinLosAngeles,Tokyo,orMadridtomeetitspeakloadonhotsummerafternoonswhenairconditionersareworkingfulltime.Itallowshomesandbusinessesanewlevelofguaranteedenergyavailabilityandsecurity,andphotovoltaicshasbeenpoweringsatellitesorbitingtheEarthorflyingtoMarsforover30years.Photovoltaicsisanempoweringtechnologythatallowsustodototallynewthings,aswellas,dooldthingsbetter.ItallowsustolookatwholenewmodesofsupplyingHandbookofPhotovoltaicScienceandEngineering.EditedbyA.LuqueandS.Hegedus2003JohnWiley&Sons,LtdISBN:0-471-49196-9CopyrightedMaterialCopyright©2003JohnWiley&SonsRetrievedfrom:(inouterspace).Italsoallowsustodowhatwealreadydo(generateelectricity,whichisdistributedoverthetransmissiongrid)buttodoitinasustainable,pollution-free,equitablefashion.Whyisphotovoltaicsequitable?Becausenearlyeveryonehasaccesstosunlight!Electricityisthemostversatileformofenergywehave.Itiswhatallowscitizensofthedevelopedcountriestohavenearlyuniversallightingondemand,refrigeration,hygiene,interiorclimatecontrolintheirhomes,businessesandschools,andwidespreadaccesstovariouselectronicandelectromagneticmedia.Accesstoandconsumptionofelectricityiscloselycorrelatedwithqualityoflife.Figure1.1showstheHumanDevel-opmentIndex(HDI)forover60countries,whichincludesover90%oftheEarth’spopulation,versustheannualpercapitaelectricityuse(adaptedfromref1).TheHDIiscompiledbytheUNandcalculatedonthebasisoflifeexpectancy,educationalachieve-ment,andpercapitaGrossDomesticProduct.Toimprovethequalityoflifeinmanycountries,asmeasuredbytheirHDI,willrequireincreasingtheirelectricityconsumptionbyfactorsof10ormore,fromafewhundredtoafewthousandkilowatt-hrs(kWh)peryear.Howwillwedoit?Ourchoicesaretocontinueapplyingtheanswersofthelastcenturysuchasburningmorefossilfuels(andreleasingmegatonsofCO2,SO2,andNO2)orbuildingmorenuclearplants(despitehavingnomethodofsafelydispos-ingofthehigh-levelradioactivewaste)ortoapplythenewmillennium’sanswerofrenewable,sustainable,nonpolluting,widelyavailablecleanenergylikephotovoltaicsandwind.(Windpresentlygeneratesoverathousandtimesmoreelectricitythanpho-tovoltaicsbutitisverysite-specific,whereasphotovoltaicsisgenerallyapplicabletomostlocations.)00.20.40.60.810200040006000800010000120001400016000Annualpercapitaelectricityuse[kWh]CanadaUSAAustraliaJapanFranceGermanyUKSpainS.KoreaChileMexicoRussiaSaudiArabiaS.AfricaEthiopaCongo(Kinshasa)PakistanIndiaIraqChinaPolandEgyptNether.UkraineHumandevelopmentindexFigure1.1Humandevelopmentindex(HDI)vs.percapitakWusage[1]CopyrightedMaterialCopyright©2003JohnWiley&SonsRetrievedfrom:(DC)electricalpowermea-suredinWatts(W)orkiloWatts(kW)fromsemiconductorswhentheyareilluminatedbyphotons.Aslongaslightisshiningonthesolarcell(thenamefortheindividualPVelement),itgenerateselectricalpower.Whenthelightstops,theelectricitystops.Solarcellsneverneedrecharginglikeabattery.SomehavebeenincontinuousoutdooroperationonEarthorinspaceforover30years.Table1.1listssomeoftheadvantagesanddisadvantagesofphotovoltaics.Note,thattheyincludebothtechnicalandnontechnicalissues.Often,theadvantagesanddisad-vantagesofphotovoltaicsarealmostcompletelyoppositeofconventionalfossil-fuelpowerplants.Forexample,fossil-fuelplantshavedisadvantagesof:awiderangeofenviron-mentallyhazardousemissions,partswhichwearout,steadilyincreasingfuelcosts,theyarenotmodular(deployableinsmallincrements),andtheysufferlowpublicopinion(noonewantsacoalburningpowerplantintheirneighborhood).Photovoltaicssuffersnoneoftheseproblems.ThetwocommontraitsarethatbothPVandfossilfueledpowerplantsareveryreliablebutlacktheadvantageofstorage.Noticethatseveralofthed