Lecture Note of Photovaltaic TechnologyWord格式文档下载.docx
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1hroftutorial
CommonTest20%
Lab10%
MiniAssignment15%
Tutorial10%
Exam45%
Cousecontents
∙Energydemandandglobalclimatechanges,
∙Propertiesofsunlight,
∙semiconductorproperties,
∙p-njunctions,
∙solarcelloperation,
∙solarcelldesign
∙solarmoduledesign
∙moduleinterconnection
∙PVsystems
Energydemandandglobalclimatechanges
TheGreenhouseeffect
Ø
IncreasinglevelsofCO2inEarth’satmosphere
(primarilyfromburningoffossilfuels).
280ppmbefore1860,355ppmtoday.
OtherGreenhousegasesarealsoincreasing
duetohumanactivity(methane).Ozone(near
theEarth’ssurface),nitrousoxides,andCFC.
CouldpotentiallyincreasetheEarth’saverage
temperatureby2-3°
Coverthenext100years.
Potentiallydisastrousformanyeco-systems
(e.g.corals,lowlyingislands,riverdeltas)
Riseinsealevel….Lostofseacoastareas,populationaffected
http:
//ukinjapan.fco.gov.uk/en/newsroom/?
view=Speech&
id=15027013
lostoffreshwatersupply
lostoffertilelands
Majorcontributortogreenhousegas:
burningoffossilfuelforelectricity
generationandtransport
Conclusion:
societyprogress>
increaseglobalclimatechanges>
instabilityetc
Solutions:
1)reduceourpollutionbyusingalternativeenergysources
thatareeco-friendlyandsustainableeghydro,wind,
geothermal,tidal,solar….
2)changeinlifestyle
3)investandinventenergysavingappliancesandmachines
ChallengesfacebyRE:
cost/kWhgeneration,geographicaldependence,intermittentsupply
andchangingclimatecausesREsuppliesunpredictable.
Windpower
Vertical–axiswindturbine(VAWT)
Advantages:
•harnesswindfromalldirectionpositionofrotorstays
•excellentpowerinslowwinds.
•windresourceisn’tcriticalsocanbeinstalledclosertobuildings
Disadvantages:
•notasefficientastheHAWTinhighwinds.
•requirebigspaceforguywirestokeepthemstable.
OthertypesofVAWT
Horizontal-axiswindturbine(HAWT)
Hydropower
Tidalpower
Biomass
Energycrops:
Woodycrops,agriculturalcrops
Wastes:
woodresidues,animalwastes,municipalsolidwaste,landfillgas…
Geothermal
•Heatfromgeothermalreservoirs(collectionofhotwater)providestheforcesthatspintheelectricalgenerators
•Twomajortypeofreservoirs-drysteam&
hotwaterreservoirs
HotspotTheories-YellowstoneNationalPark
Fuelcell
Solarenergy
AnnualamountofsolarincidentonEarth:
equivalenttoX160energystoredinprovenreservesoffossilfuel
equivalenttoX5,000Earthconsumptionoffossil,nuclearandhydro
power
Thermal
l
PV
Solarthermal
•Directconversionofsolarheattospaceheating,waterheating
•SolarCooking
•Electricitygenerationviaheatturbine
egsolartower,solarpond
Solarcollector&
solarcooker
Solartroughandsolartower
Photovoltaics
•Evolvefromspacetechnology
•Rapidadvancementthroughthesemiconductortechnology
•aboutalittleover20¢
perkilowatthour.
Energyfromsolarcellαincidentlight
αsurfacearea
•Efficiencyatpresent:
13-15%
∙Solarmodule(manysolarcellsconnectedtofirmamodule)
•Manysizeofsolarmadulesavailable,typically50W,75Wor80W
•Makeupofmanysolarcellsconnectedtogetherinseries
•Modulescanbeadduptomeettheneedsoftheusers
∙PVapplicabletoareaswithplentyofsunlightandwindy(ideal)
∙TypesofPVsystems:
Standalone,hybridandgridconnection.
PHOTOVOLTAICTECHNOLOGY
LESSON2
•Processthatconvertsunlighttoelectricity
•DevicethatcarryoutthisprocessiscalledPVcells/modules
•Notedirectheatingisnotphotovoltaicprocessegsolarcollector,solarcooker,solarpond
Particle/wavedualityoflight
•Lightbehavesasbothawaveandaparticle
•E=hf=hc/λ(E=energy,h=Planck’sconstant,c=velocityoflight)
Particlesproperties:
blackbodyRadiation
•Blackbody-idealabsorberandemitterofelectromagneticradiation.Thehottertheblackbody–themoreradiationitemits,andthepeakofthespectrummovestohigherenergy(lowerwavelength).
•Plank’sformula
•K–Boltzmann’sconstant(1.38x10-23J/K)
•ξ-Energydensityinintervalftof+df[Js/m3]
•Intensityemittedintoahemisphere
•I=intensity(W/m2)
•s-Stefan–Boltzmann’sconstant(5.67x10-8W/m2K4)
•radiationdistributionsfromperfectblackbodiesatdifferenttemperatures.Poweremittedperunitareaoftheblackbodyperunitwavelengthat6000K,4500K,3000K.
SunanditsRadiation
•Sun’senergyisderivedbythefusionofH.ThisformsHeandlargeamountsofenergy.
•TotaloutputoftheSun=4x1026W
•Powerreachingearth=1.78x1017W
•IntensityoutsideEarth’satmosphere=1367W/m2
6000Kblackbody
AM0
AM1.5
SolarRadiationattheEarth’ssurface
•Atmosphereattenuatessunlight-scatteringandadsorption.
•ThemaximumradiationreachestheEarth’ssurfacewhenthesunisdirectlyoverheadandtheskyisclear
•Theintensitydecreasesasthepathlengthoflightthroughtheatmosphereincreases.
•Describedusingtheconceptof:
•AirMass=1/cos(Æ
)whereÆ
istheanglebetweensunlightandthevertical(zenith).ExpressionlosesaccuracywhenÆ
>
75°
duetocurvatureoftheEarth.
AirMass(AM)
•AM1.5isoftenusedasastandardreferencespectrum(1000W/m2).
•Justoutsidetheatmosphereisdefinedas:
AirMasszero:
AM0(1367W/m2)
AM=1/cosθ
DirectandDiffuseRadiation
•Theatmosphereattenuatessunlightby~30%dueto:
•Rayleighscatteringbyairmolecules(verystrongatshortwavelengthsdueto1/l4dependence).
•Scatteringbyaerosolsanddustparticles.
•AbsorptionbygasessuchasO2,ozone,H2O&
CO2(reducestheintensityofthesunlight).
•Effect1and2giverisetobluesky,sunset,diffuselight.
•Thetotalradiationhastwocomponents:
directanddiffuse
•i.e.AMglobal=AMdirect+AMdiffuse
•Forexamplewhenthesunisdirectlyoverhead(AM1.0),thediffusecomponentisabout10%ofthetotal(orglobal)AM1.0spectrum.
•ThispercentageincreaseswithincreasingAMorwhenskiesarenotclear.
•Underclearskyconditions,thediffuseradiationistypically“moreblue”.
•Onacloudydaythenthespectrumis100%diffuse,andthediffuseintensityisabout20%ofthemaximumpossible.
LESSON3
•IncreasinglevelsofCO2inEarth’satmosphere(primarilyfromburningoffossilfuels).
•280ppmbefore1860,355ppmtoday.
•OtherGreenhousegasesarealsoincreasingduetohumanactivity(methane).Ozone(neartheEarth’ssurface),nitrousoxides,andCFC.
•CouldpotentiallyincreasetheEarth’saveragetemperatureby2-3°
•Potentiallydisastrousformanyeco-systems(e.g.corals,lowlyingislands,riverdeltas).
ApparentmotionoftheSun
•TheEarthorbitsthesunwithitsaxisofrotationinclinedatanangleofб=23.45°
tothenormaltotheplaneoftheorbit.
•ThismeansthattheSun’sapparentmotionacrosstheskyvariesthroughouttheyear(seasons)
DirectandDiffuseInsolationData
•Ifdataisavailablegivingthedirectanddiffusecomponentsonahorizontalplane,thecorrespondinginsolationonatiltedsurfaceatananglebtothehorizontalcanbecalculated.
•Wecanassumethediffusecomponentisindependentofthetiltangle(validforb<
45°
).
Sβ=Ssin(α+β)/sin(α)
Dec=23.45sin[(d-81)X360/365]
α=90–θ–dec[southhemisphere]
α=90–θ+dec[northhemisphere]
∙S-directcomponentonthetiltedsurface
∙S-directcomponentonthehorizontalplane
∙a-solarnoontimealtitudeofthesun
•Dec:
declinationofthesun
(TheattitudeatwhichtheSunisdirectlyoverhead),
•θ=latitude.
•d=daynumber
Solarpanel
Ifdirectanddiffusecomponentsarenotavailableandonlytheglobalinsolationonaplaneisknown:
•Thenyouneedtoknowthenumberof“sunny”and“cloudy”dayspermonth.
(i)intensityfor“sunny:
days
•I–intensityofdirectcomponentincidentonaplaneperpendiculartothesun’srays.
Diffusecomponent=10%ofI
Totalintensity=110%I
(ii)intensityfor“cloudy”days
•AssumealllightisdiffuseI=20%I
SolarRadiationinSingapore
RadiationinSingaporeinthemonthofJanuary
Singaporeinsolation
●Singaporereceives<
2/3ofthesolarradiation
●Meandailysunshinehoursfordifferentmonthsoftheyearvaryfrom33%to55%ofthemaximumpossible
●February,MarchandJulywith6.2hoursofbrightsunshine(highest)
●NovemberandDecemberwith4.5and4.4hours,respectively(lowest)
●AveragemaxsolarradiationisinFebruary(484.4