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bifiPVWorkshop–September10th,2018:Denver,Colorado
BifacialCommercialInstallationswithImprovedBifacialGains
bifiPVWorkshop–September10th,2018:Denver,Colorado
Outline
• WhoisPrismSolarTechnologies?• Quickoptimizationmethod• Whatistheissuefacingtheoptimizationofbifacialsystems?
• BifacialCommercialWhiteRoofs• BifacialCarportSystems• Conclusions
bifiPVWorkshop–September10th,2018:Denver,Colorado
PrismSolarTechnologiesInc.
• PrismSolarTechnologieswasfoundedin2005.• Researchingbifacialandholographic/bifacialtechnologyandapplicationssince2006(Hitachicells);sixawardedpatentsinbifacialtechnologyandapplications.
• Commerciallysellingbifacialmodulessince2012.
bifiPVWorkshop–September10th,2018:Denver,Colorado
DesignOptimizationWithModelBGE’(%) = (0.317/deg*(θ)+12.145/m*(h)+0.1414/%*(α)) * (BR’[%]/95%) *(Azimuth Correction Factor(%)) * (Inter-row Correction Factor(%)) * (1-η(%))
θ = Module Tilt Angle (deg) h = Module Minimum Height/Elevation (m) α = Ground Albedo/Reflectance BR’ = Bifacial Ratio, or Bifaciality of the Module η = Rear Obstruction Factor (%)
Total Bifacial System Energy Yield [%] = Monofacial*(BGE’(%) + 100%)
Azimuth Correction Factor =0.0000822*(φ^2)-0.0005129*(φ)+0.9988
φ=Azimuthdeviationfromsouthinnorthernlatitude(deg.) Inter-row Correction Factor =(-0.0467*(t)+1.42)*100%;max=100%,min=86%
t=TimeusedforDec21stShadowLengthCalculationsforinter-rowspacingdetermination;between9amand12pm.PrismSolarModelReference:J.E.Castillo-AguilellaandP.S.Hauser,"Bifacialphotovoltaic module best-fit annual energy yield model with azimuthalcorrection," 2016 IEEE 43rd Photovoltaic Specialists Conference (PVSC),Portland,OR,2016,pp.3109-3112.doi:10.1109/PVSC.2016.7750238
AgoodmatchhasbeenfoundbetweenthePrismSolarannualbest-fitmodelandtheannualresultswith PVSyst 6.70 for the high bifacial gainsregionsofinterestofthispresentation.
**Use your preferred model toestimate bifacial gains for yourdesign**
bifiPVWorkshop–September10th,2018:Denver,Colorado
OptimizingtheBifacialGain:Issue
MaximizingthebifacialgainbeyondcertainvaluescansignificantlyincreasethecostofthebifacialsystemBifacialgainsreachsaturationpointsatcertainheightsandtilts.Thisisespeciallytrueinareaconstrainedinstallationsites.
Maximumbifacialgainsleadtocostincreasesthatarenotcompensatedbythepeakachievablebifacialgain.Lawofdiminishingreturns
bifiPVWorkshop–September10th,2018:Denver,Colorado
ExamplesofBifacialInstallationsinLiterature
TableSource:Sun,Xingshu,Khan,MohammadRyyan,Deline,Chris,andAlam,MuhammadAshraful.Optimizationandperformanceofbifacialsolarmodules:Aglobalperspective.UnitedStates:N.p.,2018.Web.doi:10.1016/j.apenergy.2017.12.041.
bifiPVWorkshop–September10th,2018:Denver,Colorado
BifacialCommercialWhiteRoofCommercialRooftopAndBifacialModules:• Higheralbedo• Highertiltacceptable• Increasedmoduleheight(advantageinsnowyregions)• Optimizers/Microinverter[*](Otherbuildingcodebenefits)DetrimentalSystemConsequences:• Areaconstrained,lowersystemGCRduetohighertilt• Lackofwinddeflector&atthehighermoduletiltand
heights,rackingcostscanbecomeprohibitive.• Optimizingthebifacialgainleadstolessmodulesinstalled
[*]: Riley, D. et al. 2018 Performance of Bifacial PV Modules with MLPE vs. String Inverters, WCPEC-7, Waikoloa, HI.
bifiPVWorkshop–September10th,2018:Denver,Colorado
BifacialOptimizedRackingExamples
Additionalbracingforextraheightandsnowloads
Uprightrackingelementscanbereducedinquantity,reducingthesystemcosts,increasingtheRearObstructionFactorforthebifacialmodule.Alternative,thecross-railscanbestrengthenedtoreducethenumberofuprights,butthisalsoincreasesthesystemcost. Rearobstructionfactorsof4%
to5%arerelativelyeasytoobtainwithcarefuluprightplacement,buttryingtoachieve0%to2.5%mightbecostprohibitivefromarackingperspective.
bifiPVWorkshop–September10th,2018:Denver,Colorado
WhiteRoofsBifacialRecommendations• Min.TiltAngle=10degrees;Max.TiltAngle=30degrees• Min.ModuleElevation=0.3m;Max.ModuleElevation=0.5m,
or0.6mforsnowregions• Min.InitialRoofAlbedo=75%(Albedodecreaseswithtime)• Min.Inter-rowspacing=11am• Min.recommendedrearObstructionFactor=3%• Max.recommendedrearObstructionFactor=8%
Usingallthesevaluesattheworstcondition,andusingthePrismSolarbifacialmodel,thisstillyieldsa~14%BifacialGainwitha90%Bifacialitymodule.
Thebifacialgainwouldbedirectlyreducedifthemodulebifacialityisreduced.
bifiPVWorkshop–September10th,2018:Denver,Colorado
154.3kWBifacialUpstateNYInstallation
bifiPVWorkshop–September10th,2018:Denver,Colorado
Component Model Rating(W) QTY Specifications/Manufacturer’sWebsite:Module Bi60-368BSTC 290WDC 532 http://www.prismsolar.com/pdf/bi60specs.pdfOptimizer P730 730WDC 266 http://www.solaredge.com/sites/default/files/se-P5-series-
commercial-add-on-power-optimizer-datasheet-na.pdfInverter SE33.3KUS 33,300WAC 5 http://www.solaredge.com/sites/default/files/se-three-phase-us-
inverter-datasheet.pdfRacking SunrailBifacial - - http://opsun.com/mounting-solutions/flat-roof/bifacial-pv-
racking/
020406080100120140160180200220240260280300320
0
25000
50000
75000
100000
125000
150000
175000
3/22/20176:00
3/22/201710:48
3/22/201715:36
3/22/201720:24
3/23/20171:12
3/23/20176:00
3/23/201710:48
3/23/201715:36
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AVGM
oduleAC
produ
ction(W
)
System
Produ
ction(W
)
SystemandAverageModuleProduction(InverterLimited)
15minSystemProduction(W)
15minAVGSystemProduction/module(W)
Clientsupplieddatasystem:Basedonthemodulesandinverters,thesystemhasaDC/ACratioof0.927Inter-rowspacing11am,Albedoof+75%,systemtiltof30degrees,Azimuth=10degreesfromsouth,andRearObstructionFactorof~5%.Oncetheoptimizerscapped,themoduleswereproducing12.7%to21.45%overSTC.UsingthePrismSolarModel+PVSystforthefrontyieldsayearlyoutputof1633.5kWhac/kWdc.ThePVSystbifacialmodelV6.70yields1657kWhac/kWdc.
154.3kWBifacialUpstateNYInstallation
bifiPVWorkshop–September10th,2018:Denver,Colorado
154.3kWBifacialUpstateNYInstallation
Clippingwas
Observed
bifiPVWorkshop–September10th,2018:Denver,Colorado
Themedianannualproduction,usinga12-monthaveragingwindowis1633.9kWhac/kWdc.MedianPR=1.025
154.3kWBifacialUpstateNYInstallationThesystemwasturnedonafewmonthsbeforetheirradiancesystem/PRsystemwasputinplace.ThehighestPerformanceRatio(PR)coincideswithlowestdailykWh/kW,andvice-versa.
98.4478.50
57.64
117.02
152.33 149.73 159.11179.85 179.96 175.48 166.53
135.70
94.5566.56
96.7284.98
138.55 144.61169.90 174.41 175.97
0
60
120
180
N-16 D-16 J-17 F-17 M-17 A-17 M-17 J-17 J-17 A-17 S-17 O-17 N-17 D-17 J-18 F-18 M-18 A-18 M-18 J-18 J-18
Mon
thlyACEn
ergy
Gen
erated
[kWh/kW
] MonthlyEnergyProduction[kWh/kW]
0.6
0.8
1
1.2
1.4
1.6
0
1
2
3
4
5
6
7
8
9
10
2/22/173/8/173/22/174/5/174/19/175/3/175/17/175/31/176/14/176/28/177/12/177/26/178/9/178/23/179/6/179/20/1710/4/1710/18/1711/1/1711/15/1711/29/1712/13/1712/27/171/10/181/24/182/7/182/21/183/7/183/21/184/4/184/18/185/2/185/16/185/30/186/13/186/27/187/11/187/25/18
Performan
ceRatio(P
R)
DailyEne
rgyProd
uctio
n[kWh/kW
]
DailyEnergyProductionforthe154.3kWBifacialSystem(532Modules)DailySystemProduction(kWh/kW)PerformanceRatio(Bi60-290W)14per.Mov.Avg.(PerformanceRatio(Bi60-290W))
bifiPVWorkshop–September10th,2018:Denver,Colorado
CommercialRooftop• Bifacialrooftopandcarport
systeminQuebec,Canada.• 30Degreemoduletilt• Elevation=0.42m• EstimatedBifacialGain=+20%• OwnerdatasinceJuly2018
bifiPVWorkshop–September10th,2018:Denver,Colorado
BifacialCarportsCarportAndBifacialModules:• Highercarportmodule/systemheight• East/WestConfigurations• UsuallynotGCRconstrained• Aligningthemoduleslongedgeswiththestructurepurlins,reducesthe
RearObstructionFactor.
DetrimentalSystemConsequences:• Rackingcostsincreasewithcarportheightandtiltanglesover+10degrees• GroundReflectance/Albedoinmostcasesbetween8%(FreshAsphalt)
-20%,rarelyexceeds40%.• Increasingtheheightortiltangleexcessively,canreducethecarport
shadingeffectforthevehiclesunderthestructure.
bifiPVWorkshop–September10th,2018:Denver,Colorado
BifacialCarportsRecommendations
• Min.TiltAngle=7degrees;Max.TiltAngle=20degrees• Min.ModuleElevationRatio=0.3• Max.ModuleElevationRatio=0.6• Max.recommendedrearObstructionFactor=10%
Usingallthesevaluesattheminimum/worstcondition,Albedo=10%,andusingthePrismSolarbifacialmodel,thisstillyieldsan~6%BifacialGainwitha90%Bifacialitymodule.Thisincreasesto~10%foranEast/Westinstallation.
Thebifacialgainwouldbedirectlyreducedifthemodulebifacialityisreduced.
bifiPVWorkshop–September10th,2018:Denver,Colorado
BifacialCarportExample
Carportsystemdesignedinsuchamannertominimizetherearobstructionfactor,modulealignedwithpurlins,andthemajorstructureelementsareplacedintheplaceswheremodulesmeet.
bifiPVWorkshop–September10th,2018:Denver,Colorado
BifacialCarportExample
• ElevationRatio=~0.5• +600kWBifacialcarportsysteminQuebec,Canada.
• MostlyE/Waligned• DatasinceJuly2018
bifiPVWorkshop–September10th,2018:Denver,Colorado
9.72kW(36modules)DC/ACratio=1.28(capsMay-Aug)BifacialRatio=90%Azimuth=EastFacingHeightRatio=0.5Tilt=7degreesAlbedo/SR=40%EstimatedBifacialGain:21.4%Ownerprovideddata
BifacialCarport–TucsonAZ(2Yeardata)
Theaveragemeasuredannualenergyproductionforthe2yearperiodwas1817.9kWhac/kWdc
TheaveragedGainmeasuredforthe2yearperiodwas19.6%,justunderthepredicted21.4%.
bifiPVWorkshop–September10th,2018:Denver,Colorado
Conclusions• Significantbifacialgain’sareobtainableinvariousrealworldapplications
• MaximizingBGEgenerallydoesnotmakefinancialsense
• Financialoptimizationisthekey• Allthesitevariablesmustbeconsideredwhendesigningthesystem.Thisincludescostofelectricity
bifiPVWorkshop–September10th,2018:Denver,Colorado
ThankYou
Additionalquestions:[email protected]@prismsolar.com