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英文资料ENERGYFROMTHESUNTHESUNHASPRODUCEDENERGYFORBILLIONSOFYEARSSOLARENERGYISTHESOLARRADIATIONTHATREACHESTHEEARTHSOLARENERGYCANBECONVERTEDDIRECTLYORINDIRECTLYINTOOTHERFORMSOFENERGY,SUCHASHEATANDELECTRICITYTHEMAJORDRAWBACKSPROBLEMS,ORISSUESTOOVERCOMEOFSOLARENERGYARE1THEINTERMITTENTANDVARIABLEMANNERINWHICHITARRIVESATTHEEARTHSSURFACEAND,2THELARGEAREAREQUIREDTOCOLLECTITATAUSEFULRATESOLARENERGYISUSEDFORHEATINGWATERFORDOMESTICUSE,SPACEHEATINGOFBUILDINGS,DRYINGAGRICULTURALPRODUCTS,ANDGENERATINGELECTRICALENERGYINTHE1830S,THEBRITISHASTRONOMERJOHNHERSCHELUSEDASOLARCOLLECTORBOXTOCOOKFOODDURINGANEXPEDITIONTOAFRICANOW,PEOPLEARETRYINGTOUSETHESUNSENERGYFORLOTSOFTHINGSELECTRICUTILITIESARETRYINGPHOTOVOLTAICS,APROCESSBYWHICHSOLARENERGYISCONVERTEDDIRECTLYTOELECTRICITYELECTRICITYCANBEPRODUCEDDIRECTLYFROMSOLARENERGYUSINGPHOTOVOLTAICDEVICESORINDIRECTLYFROMSTEAMGENERATORSUSINGSOLARTHERMALCOLLECTORSTOHEATAWORKINGFLUIDOUTOFTHE14KNOWNSOLARELECTRICGENERATINGUNITSOPERATINGINTHEUSATTHEENDOF2004,10OFTHESEAREINCALIFORNIA,AND4INARIZONANOSTATISTICSAREBEINGCOLLECTEDONSOLARPLANTSTHATPRODUCELESSTHAN1MEGAWATTOFELECTRICITY,SOTHEREMAYBESMALLERSOLARPLANTSINANUMBEROFOTHERSTATESPHOTOVOLTAICENERGYPHOTOVOLTAICENERGYISTHECONVERSIONOFSUNLIGHTINTOELECTRICITYTHROUGHAPHOTOVOLTAICPVSCELL,COMMONLYCALLEDASOLARCELLAPHOTOVOLTAICCELLISANONMECHANICALDEVICEUSUALLYMADEFROMSILICONALLOYSSUNLIGHTISCOMPOSEDOFPHOTONS,ORPARTICLESOFSOLARENERGYTHESEPHOTONSCONTAINVARIOUSAMOUNTSOFENERGYCORRESPONDINGTOTHEDIFFERENTWAVELENGTHSOFTHESOLARSPECTRUMWHENPHOTONSSTRIKEAPHOTOVOLTAICCELL,THEYMAYBEREFLECTED,PASSRIGHTTHROUGH,ORBEABSORBEDONLYTHEABSORBEDPHOTONSPROVIDEENERGYTOGENERATEELECTRICITYWHENENOUGHSUNLIGHTENERGYISABSORBEDBYTHEMATERIALASEMICONDUCTOR,ELECTRONSAREDISLODGEDFROMTHEMATERIALSATOMSSPECIALTREATMENTOFTHEMATERIALSURFACEDURINGMANUFACTURINGMAKESTHEFRONTSURFACEOFTHECELLMORERECEPTIVETOFREEELECTRONS,SOTHEELECTRONSNATURALLYMIGRATETOTHESURFACEWHENTHEELECTRONSLEAVETHEIRPOSITION,HOLESAREFORMEDWHENMANYELECTRONS,EACHCARRYINGANEGATIVECHARGE,TRAVELTOWARDTHEFRONTSURFACEOFTHECELL,THERESULTINGIMBALANCEOFCHARGEBETWEENTHECELLSFRONTANDBACKSURFACESCREATESAVOLTAGEPOTENTIALLIKETHENEGATIVEANDPOSITIVETERMINALSOFABATTERYWHENTHETWOSURFACESARECONNECTEDTHROUGHANEXTERNALLOAD,ELECTRICITYFLOWSTHEPHOTOVOLTAICCELLISTHEBASICBUILDINGBLOCKOFAPVSYSTEMINDIVIDUALCELLSCANVARYINSIZEFROMABOUT1CM1/2INCHTOABOUT10CM4INCHESACROSSHOWEVER,ONECELLONLYPRODUCES1OR2WATTS,WHICHISNTENOUGHPOWERFORMOSTAPPLICATIONSTOINCREASEPOWEROUTPUT,CELLSAREELECTRICALLYCONNECTEDINTOAPACKAGEDWEATHERTIGHTMODULEMODULESCANBEFURTHERCONNECTEDTOFORMANARRAYTHETERMARRAYREFERSTOTHEENTIREGENERATINGPLANT,WHETHERITISMADEUPOFONEORSEVERALTHOUSANDMODULESASMANYMODULESASNEEDEDCANBECONNECTEDTOFORMTHEARRAYSIZEPOWEROUTPUTNEEDEDTHEPERFORMANCEOFAPHOTOVOLTAICARRAYISDEPENDENTUPONSUNLIGHTCLIMATECONDITIONSEG,CLOUDS,FOGHAVEASIGNIFICANTEFFECTONTHEAMOUNTOFSOLARENERGYRECEIVEDBYAPVARRAYAND,INTURN,ITSPERFORMANCEMOSTCURRENTTECHNOLOGYPHOTOVOLTAICMODULESAREABOUT10PERCENTEFFICIENTINCONVERTINGSUNLIGHTWITHFURTHERRESEARCHBEINGCONDUCTEDTORAISETHISEFFICIENCYTO20PERCENTTHEPVCELLWASDISCOVEREDIN1954BYBELLTELEPHONERESEARCHERSEXAMININGTHESENSITIVITYOFAPROPERLYPREPAREDSILICONWAFERTOSUNLIGHTBEGINNINGINTHELATE1950S,PVSWEREUSEDTOPOWERUSSPACESATELLITESTHESUCCESSOFPVSINSPACEGENERATEDCOMMERCIALAPPLICATIONSFORPVTECHNOLOGYTHESIMPLESTPHOTOVOLTAICSYSTEMSPOWERMANYOFTHESMALLCALCULATORSANDWRISTWATCHESUSEDEVERYDAYMORECOMPLICATEDSYSTEMSPROVIDEELECTRICITYTOPUMPWATER,POWERCOMMUNICATIONSEQUIPMENT,ANDEVENPROVIDEELECTRICITYTOOURHOMESPHOTOVOLTAICCONVERSIONISUSEFULFORSEVERALREASONSCONVERSIONFROMSUNLIGHTTOELECTRICITYISDIRECT,SOTHATBULKYMECHANICALGENERATORSYSTEMSAREUNNECESSARYTHEMODULARCHARACTERISTICOFPHOTOVOLTAICENERGYALLOWSARRAYSTOBEINSTALLEDQUICKLYANDINANYSIZEREQUIREDORALLOWEDALSO,THEENVIRONMENTALIMPACTOFAPHOTOVOLTAICSYSTEMISMINIMAL,REQUIRINGNOWATERFORSYSTEMCOOLINGANDGENERATINGNOBYPRODUCTSPHOTOVOLTAICCELLS,LIKEBATTERIES,GENERATEDIRECTCURRENTDCWHICHISGENERALLYUSEDFORSMALLLOADSELECTRONICEQUIPMENTWHENDCFROMPHOTOVOLTAICCELLSISUSEDFORCOMMERCIALAPPLICATIONSORSOLDTOELECTRICUTILITIESUSINGTHEELECTRICGRID,ITMUSTBECONVERTEDTOALTERNATINGCURRENTACUSINGINVERTERS,SOLIDSTATEDEVICESTHATCONVERTDCPOWERTOACHISTORICALLY,PVSHAVEBEENUSEDATREMOTESITESTOPROVIDEELECTRICITYHOWEVER,AMARKETFORDISTRIBUTEDGENERATIONFROMPVSMAYBEDEVELOPINGWITHTHEUNBUNDLINGOFTRANSMISSIONANDDISTRIBUTIONCOSTSDUETOELECTRICDEREGULATIONTHESITINGOFNUMEROUSSMALLSCALEGENERATORSINELECTRICDISTRIBUTIONFEEDERSCOULDIMPROVETHEECONOMICSANDRELIABILITYOFTHEDISTRIBUTIONSYSTEMSOLARTHERMALHEATTHEMAJORAPPLICATIONSOFSOLARTHERMALENERGYATPRESENTAREHEATINGSWIMMINGPOOLS,HEATINGWATERFORDOMESTICUSE,ANDSPACEHEATINGOFBUILDINGSFORTHESEPURPOSES,THEGENERALPRACTICEISTOUSEFLATPLATESOLARENERGYCOLLECTORSWITHAFIXEDORIENTATIONPOSITIONWHERESPACEHEATINGISTHEMAINCONSIDERATION,THEHIGHESTEFFICIENCYWITHAFIXEDFLATPLATECOLLECTORISOBTAINEDIFITFACESAPPROXIMATELYSOUTHANDSLOPESATANANGLETOTHEHORIZONEQUALTOTHELATITUDEPLUSABOUT15DEGREESSOLARCOLLECTORSFALLINTOTWOGENERALCATEGORIESNONCONCENTRATINGANDCONCENTRATINGINTHENONCONC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