Lecture Note of Photovaltaic Technology.docx

Lecture Note of Photovaltaic Technology.docx

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LectureNoteofPhotovaltaicTechnology

PHOTOVOLTAICTECHNOLOGY

PHOTOVOLTAICTECHNOLOGY

LESSON1

ReferenceTextbooks

（1）“AppliedPhotovoltaics”

byS.R.Wenham,M.A.Green,M.E.WattandRCorkish.

（2）“PracticalPhotovoltaics–electricityfromsolarcells”

byRichardJ.Komp

（3）“EnergySystemsandsustainabiliy-Powerfora

substainablefuture”

byGBoyle,BEverettandJRamage

（4）“RenewableEnergy-Powerforasustainablefuture”

byGBoyle

（5）“Solarcells,materials,manufactureandoperation”

byTomMarkvartandLuisCastaner

（6）“Thephysicsofsolarcells”byJennyNelson

（7）“Semiconductorsforsolarcells”byHansJoachimMoller

Courseoutline

2hrsoflecture

2hrsoflabandminiassignmentwithpresentation

1hroftutorial

CommonTest20%

Lab10%

MiniAssignment15%

Tutorial10%

Exam45%

Cousecontents

∙Energydemandandglobalclimatechanges,

∙Propertiesofsunlight,

∙semiconductorproperties,

∙p-njunctions,

∙solarcelloperation,

∙solarcelldesign

∙solarmoduledesign

∙moduleinterconnection

∙PVsystems

Energydemandandglobalclimatechanges

TheGreenhouseeffect

ØIncreasinglevelsofCO2inEarth’satmosphere

（primarilyfromburningoffossilfuels）.

Ø280ppmbefore1860,355ppmtoday.

ØOtherGreenhousegasesarealsoincreasing

duetohumanactivity（methane）.Ozone（near

theEarth’ssurface）,nitrousoxides,andCFC.

ØCouldpotentiallyincreasetheEarth’saverage

temperatureby2-3°Coverthenext100years.

ØPotentiallydisastrousformanyeco-systems

（e.g.corals,lowlyingislands,riverdeltas）

ØRiseinsealevel….Lostofseacoastareas,populationaffected

http:

//ukinjapan.fco.gov.uk/en/newsroom/?

view=Speech&id=15027013

Ølostoffreshwatersupply

Ølostoffertilelands

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

ØThermal

l

ØPV

Ø

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

Photovoltaics

•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）whereÆistheanglebetweensunlightandthevertical（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.

PHOTOVOLTAICTECHNOLOGY

LESSON3

TheGreenhouseeffect

•IncreasinglevelsofCO2inEarth’satmosphere（primarilyfromburningoffossilfuels）.

•280ppmbefore1860,355ppmtoday.

•OtherGreenhousegasesarealsoincreasingduetohumanactivity（methane）.Ozone（neartheEarth’ssurface）,nitrousoxides,andCFC.

•CouldpotentiallyincreasetheEarth’saveragetemperatureby2-3°Coverthenext100years.

•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