pv technologies series and parallel config · step 2.a) multiply daily consumption with losses (as...
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Off-gridPVtechnologies Irradia2on
Seriesandparallelconfig
Cablecalc.
Chargecontroller
DCDisconnect
Voltdrop
InverterVoltageCalcula2ons
Ba=eriesPr
Moun2ngStructures
Systemsizingwhenstorageisincluded
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Step1-Calculateconsump<on
Step1.b)DailyConsump<oninWhStep1.a)PowerRequirementinW
• LeadAcidSystemLossesvarybetween±22to30%• Li-ionSystemLossesvarybetween±18to22%• hMp://www.baMerysizingcalculator.com
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Step2-BaMerySizing
Inverters
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5
2
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Inverter
Chargecontroller
Cabling
System(BaMeries+connec<ons)
Step 2.a) Multiply daily consumption with losses (as a factor) = 3152Wh x 1,27 = 4003Wh Daily Storage required
Step 2.b) Divide Daily storage by DC voltage = 4003Wh / 48V = 83Ah of Average Daily Ah needed
Step 2.c) Adjust to depth of discharge = 83Ah / 0,5 = 166Ah Sub Total of storage required
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BaMerySizing–LeadAcid
Thisvaluerepresents27%Losses
The“48V”valueisfoundinthedatasheetStep1.ashowedusweneed414WofPower.Atleastan800Wto1000Winverterwouldbe
required.Forthiscalc.itisassumedthecustomerwouldwanttoincreasehissystemover<me.FromthedatasheetPageB1,wewillseethe5000Winverterusesa48VbaMery/baMerybank.
Use0,5for50%D.o.D,0,4for40%D.o.Dandsoon.....
Step 2.d) Make provision for rainy days =166Ah x 2 days = 332Ah Total Storage required
The battery bank needs to be 48V 332Ah according to our calculations.
Step 2.e) Select battery to match both 48V and 332Ah as close as possible.
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BaMerySizing–LeadAcid
Thisvalueisjustaguessandwouldvarybasedonthenumberofrainydaysforthatarea
12VoltBaMery200Ah4baMeriesinseriesto
reach48V200Ah2stringsin
paralleltoreach
400A
h
BaMerySizing–LeadAcid
• Step2.f)ChecktoensurethatthechosenbaMerycanhandletherateofdischarge(c-ra<ng)
=400Ah@C20=400AhataCapacityof20hrs=400Ah/20hrs=20A
ThechosenbaMerycanhandlearateof20Aforaperiodof20hoursandthenitwillbecompletelydischarged.
WedonotwanttodischargethebaMerycompletelyandideallyshouldsizeaccordingtolessthanhalfofthenumberofhourswheretheD.o.Disintendedtobe50%
Power =VoltagexCurrent =48Vx20A =960W 960WiswhatthebaMerybankcanhandleinPOWERdischargerate
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Dischargerate
FromStep2f.–ThebaMerybankcanhandle960W.Atmaxwewillonlydischargeat414W
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Conductorcurrentcarryingcalcula<on
5000WInverterI = __PV
TV
400Ah48VoltBaMeryBank
Stepscon<nuedStep 3.a) Calculate Power required to charge batteries
Power = Volts x Amps - Where: Volts = The battery’s absorption voltage Amps = Maximum Current the battery bank can handle
This information will be found in your inverter datasheet or charge controller datasheet or charge controller rating – Depending on what is being used to charge the batteries.
The rate of charge from the charge controller and AC charger has to be balanced with rate at which the battery can accept charge. See the next slide. . . . .
BaMerybankchargerate
• BaMerybankchargerate
• =20%ofC20• =20%oftheCapacityofthebaMeryat20hrs• =20%of400Ah• =80A
400Ah48VoltBaMeryBank
From Page B5 we can see the battery can handle a maximum charge rate of 20% at C20.
Thisisourmaximumchargerateaswellasthecurrentvaluerequiredforourcalcula<on
Choosemethodofcharge
• ACCharger• Chargecontroller• Othermeansofcharging
BaMerybankchargeVoltage
• Power(WaMs) =Volts x I(Amps)• =57,6Vx80Amps
Thevoltagevaluealsocomesfromthedatasheet.PageB5
• Power(WaMs) =Volts x I(Amps)• =57,6V x 80Amps• =4608WaMs
This 4608 Watt value is the absolute maximum power required for the battery bank.
Module/PanelSelec<on
• Step 3.b) Select modules to match – Power Requirement, – Roof space – Ease of handling – And stock availability
From page B2 the 60 Cell 260W module is selected
• Objec<ve:Calculatethemodule’ssummerandwintervoltages
• SummerVoltageisthelowestpossiblevoltageatthehighesttemperature
• WinterVoltageisthehighestpossiblevoltageatthelowesttemperature
Tempco-efficientcalcula<ons
Winter Summer
ModuleVoltagesareHigh
Temperaturesarelow
ModuleVoltagesareLow
Temperaturesarehigh
ModuleTempcoefficientcalc
• Weneedtoknowwhattheminimumandmaximumvoltagesforthemoduleisgoingtobe.ForthisstepweusefactorsfromtheSANS10142-1-2standard.
• Summervoltagefactorof0,75• Wintervoltagefactorof1,15
• SummerMinVoltage
• 30,9Vx0,75• 23VmpMin
• WinterMaxVoltage
• 30,9Vx1,15• =36VmpMax
• -0,45%/℃260W60cell
• Effoftemp=30,9Vmpx0,45%/℃
• =0,139V
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Temperatureco-efficientcalcs
23Vmp
80℃25℃-15℃STC
Mul<plyco-efficientfactor
30,9Vmp
36Vmp
MaximumVoltage(VDC-max)=VmpMax_STC(SolarPV)x1.15=VmpMin_STC*0.75
Mul<plyco-efficientfactor
• MicrocarevsVictronrecommendedchart
• Pleasecheckothermanufacturerspecifica<ons
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Step4-SelectChargeController
Stepscon<nued
Step 4.a) Module layout and design is done according to charge controller power, voltage and current limitations. (Group Exercise)