UNIT III - SOLAR PV AND THERMAL SYSTEMS.pdf

SOLAR PV AND THERMAL SYSTEMS

1. UNIT III -SOLAR PV AND THERMAL SYSTEMS
SolarRadiation,RadiationMeasurement,SolarThermalPowerPlant,CentralReceiver
PowerPlants,SolarPonds-ThermalEnergystoragesystemwithPCM-SolarPhotovoltaic
systems:BasicPrincipleofSPVconversion–TypesofPVSystems-TypesofSolarCells,
Photovoltaiccellconcepts:Cell,module,array,PVModuleI-VCharacteristics,Efficiency&
QualityoftheCell,seriesandparallelconnections,maximumpowerpointtracking,
Applications

2. Introduction
Thebasicprinciplebehindbothsolarpanel–solarphotovoltaic(PV)andsolarthermal–is
thesame.Theyabsorbrawenergyfromthesunanduseittocreateusableenergy.Insolar
PVsystemsthisisthroughthecreationofelectricity,whereasthermalsystemsareused
directlyforheatingwaterorair.
Solarthermalpowerplantscollectandconcentratesunlighttoproducethehigh
temperatureheatneededtogenerateelectricity.Thermalenergystorage(TES)isa
technologythatstocksthermalenergybyheatingorcoolingastoragemediumsothatthe
storedenergycanbeusedatalatertimeforheatingandcoolingapplicationsandpower
generation
AphotovoltaicmoduleconsistsofmultiplePVcellsconnectedinseriestoprovideahigher
voltageoutput.AphotovoltaicarrayisasystemcomposedofmultiplePVmodules.They
canbeconnectedinoneormoreseriescircuits,whichareconnectedtoacombinerboxto
provideasingledirect-currentoutput.

3. Solar Radiation
Solarradiation,oftencalledthesolarresource,isageneraltermfortheelectromagnetic
radiationemittedbythesun.Thesunemitselectromagneticradiationsasablackbody
havingasurfacetemperatureofabout6000K.Thisisbecauseofthenuclearreaction
runninginit,wherethesunisconvertinghydrogenintohelium.Theradiusofthesun
amountsto1.39×109m.Thetotalradiationpowerreceivedfromthesunonaunitarea
perpendiculartothesunraysatthemeanearthsundistance,termedanastronomicalunit,
iscalledthesolarconstant(SC),where1astronomicalunit=1AU=1.496×1011m
Likeablackbodyradiation,thesun‘sradiationcoversawidespectrumofwavelengthsfrom
deepultraviolettofarinfrared.Thepowerspectraldistributionofthesunlightisshownin
Fig.1.TheverticalaxisrepresentsthespectralirradianceI(λ)whilethehorizontalaxis
representsthewavelengthinmm.TheirradianceI(λ)isequaltotheincidentsolar
power/m2/δλ=[W/m2/mm],whereδλistherespectivewavelengthrangeinμm

4. Thespectralirradiancedecreasesbecauseofthepresenceofairintheatmosphere.Theair
moleculesscatterandabsorbthesolarradiation.TherearemultipleabsorptionbandsforO2,
H2O,andCO2.Itisimportanttonoticethatthesolarirradianceresemblestheblackbody
radiationat~6000Krepresentedbythedashedline
Asthesolarradiationpassesthroughthe
atmosphere,itgetsabsorbed,scattered,
reflected,ortransmitted.Alltheseprocesses
resultinreductionoftheenergyfluxdensity.
Actually,thesolarfluxdensityisreducedby
about30%comparedtoextraterrestrial
radiationfluxonasunnydayandisreduced
byasmuchas90%onacloudyday.The
followingmainlossesshouldbenoted:
•absorbedbyparticlesandmoleculesinthe
atmosphere-10-30%
•reflectedandscatteredbacktospace-2-
11%
•scatteredtoearth(directradiation
becomesdiffuse)-5-26%

5. •Asaresult,thedirectradiationreachingtheearthsurface(oradeviceinstalledonthe
earthsurface)neverexceeds83%oftheoriginalextraterrestrialenergyflux.This
radiationthatcomesdirectlyfromthesolardiskisdefinedasbeamradiation.
•Thescatteredandreflectedradiationthatissenttotheearthsurfacefromalldirections
(reflectedfromotherbodies,molecules,particles,droplets,etc.)isdefinedasdiffuse
radiation.Thesumofthebeamanddiffusecomponentsisdefinedastotal(orglobal)
radiation.Thebeamradiationcanbeconcentrated,whilethediffuseradiation,inmany
cases,cannotbeconcentrated.
•Short-waveradiation,inthewavelengthrangefrom0.3to3μm,comesdirectlyfromthe
sun.Itincludesbothbeamanddiffusecomponents.
•Long-waveradiation,withwavelength3μmorlonger,originatesfromthesourcesat
near-ambienttemperatures-atmosphere,earthsurface,lightcollectors,otherbodies.
•Thesolarradiationreachingtheearthishighlyvariableanddependsonthestateofthe
atmosphereataspecificlocality.Twoatmosphericprocessescansignificantlyaffectthe
incidentirradiation:scatteringandabsorption

6. Scatteringiscausedbyinteractionoftheradiationwithmolecules,wateranddustparticles
intheair.Theamountoflightscattereddependsonthenumberofparticlesinthe
atmosphere,particlesizeandthetotalairmasstheradiationcomesthrough.
Absorptionoccursuponinteractionoftheradiationwithcertainmolecules,suchasozone
(absorptionofshort-waveradiation-ultraviolet),watervapour,andcarbondioxide
(absorptionoflongwaveradiation-infrared).Duetotheseprocesses,outofthewhole
spectrumofsolarradiation,onlyasmallportionreachestheearthsurface.Thusmostofx-
raysandothershort-waveradiationisabsorbedbyatmosphericcomponentsinthe
ionosphere,ultravioletisabsorbedbyozoneandnot-soabundantlong-waveradiationis
absorbedbyCO2.Asaresult,themainwavelengthrangetobeconsideredforsolar
applicationsisfrom0.29to2.5μm

9. Inthecircuit,itcanbeseenthattheblackbodyabsorbs
theradiationfallingfromthelensandaperfectblack
bodycompletelyabsorbsanyradiationfallingonit,sothe
radiationfallingintothetubegetsabsorbedbytheblack
objectentirely.Oncetheradiationgetsabsorbedthe
atomsinthebodygetsexcitedbecauseoftheincreasing
temperatureoftheentirebody.Thistemperature
increasewillalsobeexperiencedbythethermocouple
junction‗A‘.
Now with junction ‗A‘ of the thermocouple at high temperature and junction ‗B‘ at low
temperature, a current flow takes place in its loop.(Thermocouple action) This current in
the loop will also flow through the galvanometer which is in series and thereby causing a
deviation in it. This deviation is proportional to current, which in turn is proportional to
temperature difference at junctions.
Thedeviationinthegalvanometercanbereducedbyadjustingtherheostattochangethecurrentinthe
Metalconductor.Nowbyadjustingtherheostatuntilthegalvanometerdeviationbecomescompletelyvoid.
Oncethishappenswecanobtainvoltageandcurrentreadingsfromthemetersanddoasimplecalculationto
determinetheheatabsorbedbytheblackbody.Thiscalculatedvaluecanbeusedtodeterminetheradiation,
asheatgeneratedbytheblackbodyisdirectlyproportionaltotheradiation

12. Solarpond:Thesolarenergycomingfromthesunisfirstlyabsorbedbythesolarpond.Solar
pondisareservoirofwaterwheresun‘sraysdirectlyfocusbyusingsolarenergycollectors.
Afterthat,solarenergyincreasestheinternalenergyandraisesthetemperatureofsolar
pond.Thefluidinthesolarpondmaybedirectlyusedastheworkingfluidifitstemperature
reachesuptoevaporatingtemperatureorotherwayistouseasecondaryfluidknownas
workingfluid.Thefluidfromthesolarpondgoesintocyclicprocess.
Thedetailedoperationofsolarpondisas
follows.
Solarpond,alsocalledsolarsaltpondisan
artificiallydesignedpond,filledwithsalty
water,maintainingadefiniteconcentration
gradient.Itcombinessolarenergyradiation
andsensibleheatstorage,andassuch,itis
utilisedforcollectingandstoringsolarenergy.
Asolarpondreducestheconvectiveand
evaporativeheatlossesbyreversingthe
temperaturegradientwiththehelpofnon-
uniformverticalconcentrationofsalts

13. Theverticalconfigurationof―saltgradientsolarpondnormallyconsistsofthefollowing
threezones:
1.―Surface(homogeneous)convectivezone(SCZ)-Itisadjacenttothesurfaceandserves
asabufferzonebetweenenvironmentalfluctuationsatthesurfaceandconductiveheat
transportfromthelayerbelow.Itisabout10to20cmthickwithalowuniform
concentrationatnearlytheambientairtemperature.
2.―Lowerconnectivezone(LCZ)-Itisatthebottomofthepondandthisisthelayerwith
highestsaltconcentration,wherehightemperaturesarebuiltup.
3.―Concentration/Intermediategradientzone(CGZ)-Thiszonekeepsthetwoconvective
zones(SCZandLCZ)apartandgivesthesolarponditsuniquethermalperformance.It
providesexcellentinsulationforthestoragelayer,whiletransmittingthesolarradiation.To
maintainasolarpondinthisnonequilibriumstationarystateitisnecessarytoreplacethe
amountofsaltthatistransportedbymoleculardiffusionfromtheLCZtoSCZ.Thismeans
thatsaltmustbeaddedtotheLCZ,andfreshwatertotheSCGwhilstbrineisremoved.The
brinecanberecycled,dividedintowaterandsalt(bysolardistillation)andreturnedtothe
pond.

15. Solarenergyisacompletelyfree
sourceofenergyanditisfoundin
abundance.Thoughthesunis90
millionmilesfromtheearth,it
takeslessthan10minutesforlight
totravelfromthatmuchof
distance.
Limitations of Solar Ponds:
1. Sunny climate is required
2. Need for large land area.
3. Availability of salt.
4. Availability of water.

18. Evacuated-TubeCollector
Thisisatypeofavacuum
collector.Itsabsorberstripis
placedinanevacuatedand
pressureproofglasstube.The
heattransferfluidflowsdirectly
theabsorberintoaU-tubeorin
atube-in-tubesystem.Theheat
pipecollectorintegratesa
specialfluid,whichevaporates
evenatlowtemperatures,thus
thesteamrises
intheindividualheatpipesandwarmsupthefluidinthemainpipe,generatingheat.
Thermodynamicpanelsarealsobasedonsucharefrigerantfluidbutareexploitingtheheatin
theambientair,and,therefore,areonlysuitableforhotwater.
Thetechnologyisveryreliableasithasanestimatedlifespanof25years.Thevacuumthat
surroundstheoutsideofthetubesgreatlyreducestheriskofheatloss,thereforeefficiencyis
greaterthanitiswithflat-platecollectors

20. PowerTowerReceiver
Inthiscollector,thereceiverislocatedatthe
topofthetower.Ithasalargenumberof
independently-movingflatmirrors(heliostats)
spreadoveralargeareaofgroundtofocusthe
reflectedsolarradiationsonthereceiver.The
heliostatsareinstalledallaroundthecentral
tower.Eachheliostatisrotatedintotwo
directionssoastotrackthesun.Thesolar
radiationsreflectedfromheliostatsare
absorbedbythereceivermountedonatower
ofabout500mheight.
Thetowersupportsabundleofverticaltubescontainingtheworkingfluid.Theworkingfluid
intheabsorberreceiverisconvertedintothehigh-temperaturesteamofabout600oC–
700oC.Thissteamissuppliedtoaconventionalsteampowerplantcoupledtoanelectric
generatortogenerateelectricpower.

22. FresnelLensConcentratingCollector
•Inthiscollector,aFresnellenswhichconsistsoffine,lineargroovesonthesurfaceof
refractingmaterialofopticalqualityononesideandflatontheothersideisused.
•TheangleofeachgrooveissodesignedthattheopticalbehaviouroftheFresnellensis
similartothatofacommonlens.
•Thesolarradiationswhichfallnormallytothelensarerefractedbythelensandarefocused
onalinewheretheabsorbertube(receiver)isplacedtoabsorbsolarradiations
WorkingFluid:Itisthefluidusedinthecyclic
operation.Weusesomeotherfluidasaworkingfluid
becausesometimessolarenergyisnotcapableto
evaporatethewater.Weuseworkingfluidwhichgains
energyfromthesolarpondandevaporateeasilyor
havingevaporationtemperaturelessascompareto
water.
Generally,brineorsomeorganicfluidsareusedasthe
workingfluid.Afterevaporationworkingfluidgoes
throughcyclicoperationsinturbineandthenthrough
condenseritgoesagainintotheevaporatorboiler.The
cycleiscontinuouslyrepeated

23. EvaporatorBoiler:Inthisdevice,workingfluidiskeptandgainslatentheatofvaporisationfrom
thesun‘sradiationsorbysolarpond.Workingfluidiscirculatingthroughoutthecycleby
evaporatingboiler.
TurbineandGenerator:Turbineandgeneratorsaretheessentialpartofthepowergeneration
system.Workingfluidgoesthroughthecyclicoperationandrunstheturbinewhichisconnected
tothegenerator.Generatorgenerateselectricitywhichistransferredtotherequiredlocation.
Condenserandcoolingtower:Afterturbine,theworkingfluidgoesintothecondenserand
coolingtowercondensestheworkingfluidandsendsbacktotheevaporatorboilerwiththehelp
ofpump.
Workingofsolarpowerplant
Theworkingisverysimplealmostsimilartoanythermalpowerplant.Solarpowerplantalsoworks
onRankinecycleandBraytoncycleaspertherequirements.Withthehelpofconstruction,wecan
easilypredictthecycleofoperationandworking.Workingfluidgainslatentheatofvaporisation
fromthedirectsolarradiationsorbymeansofsolarpondsintheevaporatorboilingandconverts
itintovapourform.Afterthatitrunstheturbinewhichisconnectedtothegenerator.Thenthe
turbineworkingfluidgoesintothecondenserandlosesheatandagainsendsbacktothe
evaporatorboilerwiththehelpofpump.Thiswholecyclerepeatscontinuouslyuntilthesun
remainsintheskyandradiationfallsontheearthsurface.

26. Heliostatfield:Theheliostatfieldcomprisesalargeheliostat,structure,and
control/tracking.Theheliostattypicallyutilizesamirror,whichcanbeoriented
throughoutthedaytoredirectsunlight
alongafixedaxistowardastationarytargetorreceiver.Thereflectingelementof
aheliostatistypicallyathin,back(second)surface,low-ironglassmirror.This
heliostatiscomposedofseveralmirrormodulepanelsratherthanasinglelarge
mirror.Thethinglassmirrorsaresupportedbyasubstratebackingtoforma
slightlyconcavemirrorsurface
Individualpanelsonthe
heliostatarealsocanted
towardapointonthereceiver.
Theheliostatfocallengthis
approximatelyequaltothe
distancefromthereceiverto
the farthestheliostat.
Subsequent―tuning‖ofthe
closermirrorsispossible

27. •Storage:CentraltowerbasedsystemstypicallyuseMoltensalt,hotconcretestorage,phase
changematerials,saturatedsteamorpressurizedairasstoragemedia.
oNitratesaltmixturescanbeusedasbothaheattransferfluidandastoragemediumat
temperaturesofupto565°C.However,mostmixturescurrentlybeingconsideredfreezeat
temperaturesaround140to220°Candthusmustbeheatedwhenthesystemisshutdown.
Theyhaveagoodstoragepotentialbecauseoftheirhighvolumetricheatcapacity.
oLiquidsodiumcanalsobeusedasbothaheattransferfluidandstoragemedium,witha
maximumoperatingtemperatureof600°C.Becausesodiumisliquidatthistemperature,
itsvapourpressureislow.However,itsolidifiesat98°Ctherebyrequiringheatingon
shutdown.Thecostofsodium-basedsystemsishigherthanthenitratesaltsystems.
oForhigh-temperatureapplicationssuchasBraytoncycles,itisproposedtouseairorhelium
astheheattransferfluid.Operatingtemperaturesofaround850°Cat12atmpressureare
beingproposed.Althoughthecostofthesegaseswouldbelow,theycannotbeusedfor
storageandrequireverylargediameterpipingtotransportthemthroughthesystem.

30. Itiseasytopicturethisprocessbyconsideringthemeltingofanicecube.Youcanheatthe
icecubebyexposingittoambientroomtemperatureconditions,byheatingitwithahair
dryer,orbyblastingitwithablowtorch,butnomatterhowmuchheatfluxissuppliedtoit,
thaticecubewillnotincreaseintemperatureuntilthemeltingprocessiscomplete.The
latentheatabsorbedduringthemeltingprocessisreferredtoasthelatentheatoffusionthe
changeinphasefromaliquidtoagas.Incontrasttolatentheat,whichdoesnotincreasethe
temperatureofamaterial,sensibleheatisthatheatwhichdoesresultinachangein
temperaturewithinthematerial.
Astandardcontinuousheatingprocessmaybeginwithasubcooledsolid,whichisheatedto
themeltingpointthroughsensibleheating.Astheheatingprocesscontinuesthesolid
transitionstoaliquidthroughthelatentofheatfusion,andsensibleheatthenincreasesits
temperaturetotheboilingpoint.Oncetheboilingpointisreached,theliquidtransitionstoa
vapourthroughthelatentheatofvaporizationuntilthephasechangeprocessiscomplete.
Anyadditionalheatingisnowintheformofsensibleheatwhichactstosuperheatthevapour
Theamountofenergyabsorptionorreleaseduringthemelting-solidificationcycleisgovernedbythevalueof
thatmaterial‘slatentheatoffusion.ThelatentheatoffusioniscommonlyexpressedinunitsofJ/gorkJ/kg.
Thustheprocessisamass-basedprocess.Theamountofenergyabsorbedbythematerialduringmelting
dependssolelyonthemassofmaterialpresentinthedesign.

31. Advantages of PCMs

32. Application of PCM in Concentrating Solar Power Plants
Intheseplants,sunlightisreflectedandconcentratedusingmirrorsandthenusedtoheata
carrierfluid.AnexampleofparabolictroughtechnologyisshowninFig.Inthisimage,the
thermalreceiverissupportedabovetheconcentratingmirrors.Thereceiverisablackpipe
encasedinavacuumtubetoreduceconvectivelosses
Ahightemperature,highpressureheattransferfluid(HTF)circulatesthroughthereceiver
pipes.Dependingonthedesignofthesystem,theHTFfluidmayserveastheheatsourceinan
evaporator,creatingsteamwhichpowersastreamturbinewhichdrivesagenerator,ortheHTF
maydirectlyvaporizeasitpassesthroughthesolarfieldandthenpassstraightthroughthe
turbinewithoutanintermediateheatexchanger(knownasDirect
SteamGeneration—DSG).
Ineitherdesign,duringperiodsofhigh
insolation,itispossibletoabsorbmore
solarthermalenergyintotheHTFthanis
necessarytopowertheturbine.This
excesssolarthermalenergycanbe
storedusingsensibleorlatentheatin
storagetanksasshowninFig

33. Theaveragecostof
installationof
rooftopPVsystem
withoutsubsidyis
aroundRs60,000–
70,000afteravailing
30percentsubsidy,
peoplejusthaveto
payRs42,000–
49,000forinstallinga
rooftopPVsystem.

34. Solar Photovoltaic systems: Basic Principle of SPV conversion
Aphotovoltaic(PV)cellisanenergyharvestingtechnologythatconvertssolarenergyinto
usefulelectricity(DC)throughaprocesscalledthephotovoltaiceffect.Itismadeupof
semiconductormaterialssuchassilicon,galliumarsenideandcadmiumtelluride,etc.These
cellsvaryinsizerangingfromabout0.5inchesto4inches.TherearedifferenttypesofPVcells
whichallusesemiconductorstointeractwithincomingphotonsfromtheSuninorderto
generateanelectriccurrent

41. SolarGridTiedSystemwithoutBatterybackup
ThesearemostcommontypeofPVsystems.Theyarealsoknownason-grid,grid-tied,gridintertied,
orgrid-directsystems.Theygeneratesolarelectricityandrouteittotheloadsandtothegrid,
offsettingsomeofelectricityusage.SystemcomponentscomprisesofthePVarrayandinverter.Grid
connectedsystemissimilartoregularelectricpoweredsystemexceptthatsomeorallofthe
electricitycomesfromthesun.Thedrawbackofthesebatterylesssystemsisthattheyprovideno
outageprotectionwhentheutilitygridfails,thesesystemscannotoperate.
•grid-tied-system
•Increaseddesignflexibilitybecausethesystemdoesnothavetopowerallofthehome‘sloads
•Itislessexpensivecomparedtostand-aloneorgrid-tiedwithbatterybackupsystems
•Itrequirestheleastamountofmaintenance
•Ifthesystemproducesmorethantheloadsneed,thentheextraenergyisexchangedwiththe
grid
•Grid-directsystemshaveahigherefficiencybecausebatteriesarenotpartofthesystem
•Highervoltagemeanssmallerwiresize
•Electricitycostsarefixedforthelifeofyoursystem
•Thereisnopowertothehomewhenthegridgoesdown
•Paperworkrequirementsforinterconnection,incentives,andrebates

42. Hybridsystem
Hybridsystemtriesto
combinemultiplesources
ofpowertomaximize
availabilityofpower.Itmay
sourceenergyfromsun,
windordieselgenerator
andbackitupwithbattery.

43. NoorComplexisthe
world's largest
concentratedsolar
power(CSP)plant,
locatedinthe
Sahara
Desert.Theproject
hasa580-megawatt
capacity.

44. graphshowsthecurrent-voltage(I-V)characteristicsofa
typicalsiliconPVcelloperatingundernormalconditions.The
powerdeliveredbyasolarcellistheproductofcurrentand
voltage(I×V).Ifthemultiplicationisdone,pointforpoint,
forallvoltagesfromshort-circuittoopen-circuitconditions,
thepowercurveaboveisobtainedforagivenradiationlevel
Withthesolarcellopen-circuited,thatisnotconnectedtoany
load,thecurrentwillbeatitsminimum(zero)andthevoltage
acrossthecellisatitsmaximum,knownasthesolarcellsopen
circuitvoltage,orVoc.Attheotherextreme,whenthesolarcell
isshortcircuited,thatisthepositiveandnegativeleads
connectedtogether,thevoltageacrossthecellisatitsminimum
(zero)butthecurrentflowingoutofthecellreachesits
maximum,knownasthesolarcellsshortcircuitcurrent,orIsc.
ThespanofthesolarcellI-Vcharacteristicscurverangesfromthe
shortcircuitcurrent(Isc)atzerooutputvolts,tozerocurrentat
thefullopencircuitvoltage(Voc).Inotherwords,themaximum
voltageavailablefromacellisatopencircuit,andthemaximum
currentatclosedcircuit.neitherofthesetwoconditions
generatesanyelectricalpower,buttheremustbeapoint
somewhereinbetweenwerethesolarcellgeneratesmaximum
power
Thereisoneparticularcombinationof
currentandvoltageforwhichthepower
reachesitsmaximumvalue,atImpandVmp,
Wherethecellgeneratesmaximumelectrical
powerandthisisshownatthetoprightarea
oftherectangle.Thisisthe―maximum
powerpointorMPP.Thereforetheideal
operationofaphotovoltaiccell(orpanel)is
definedtobeatthemaximumpower
point

45. Photovoltaic I-V
characteristicscurves
provide the
informationneeded
forustoconfigurea
solar
powerarraysothatit
canoperateasclose
aspossibletoits
maximumpeakpower
point.Thepeakpower
pointismeasuredas
thePVmodule
producesitsmaximum
amountofpower
whenexposedtosolar
radiationequivalentto
1000wattspersquare
metre,1000W/m2
or1kW/m2

48. •Efficiencycanalsobeincreasedthroughconcentratedphotovoltaics.Thismethodinvolves
concentratingtheSun'senergythroughvariousmethodstoincreasetheintensityofenergyhitting
thesolarcell

49. parallelwiringisabetteroptionformanyelectricalapplicationsbecauseitallowsforcontinuousoperationofthe
panelsthatarenotmalfunctioning.But,itisnotalwaysthebestchoiceforallapplications.Whendesigningyour
solarsystem,yourinstallermightdecidethatserieswiringisbettersuitedforyourapplicationorhemightchoosea
hybridapproachbyserieswiringsomepanelsandparallelwiringothers

53. •MPPTsolarchargecontrollerisnecessaryforanysolarpowersystemsneedtoextractmaximum
powerfromPVmodule;itforcesPVmoduletooperateatvoltageclosetomaximumpowerpointto
drawmaximumavailablepower.
•MPPTsolarchargecontrollerallowsuserstousePVmodulewithahighervoltageoutputthanoperating
voltageofbatterysystem.ifPVmodulehastobeplacedfarawayfromchargecontrollerandbattery,its
wiresizemustbeverylargetoreducevoltagedrop.WithaMPPTsolarchargecontroller,userscanwire
PVmodulefor24or48V(dependingonchargecontrollerandPVmodules)andbringpowerinto12or
24Vbatterysystem.ThismeansitreducesthewiresizeneededwhileretainingfulloutputofPVmodule