Bifacial PV System Performance - NREL

1 Bifacial PV System Performance : Separating Fact from Fiction Chris Deline, Silvana Ayala Pel ez, Bill Marion, Bill Sekulic, Michael Woodhouse, and Josh Stein (Sandia National Labs). PVSC-46, Chicago, IL 2019. nrel /PR-5K00-74090. Bifacial PV in the news nrel | 2. Status of Bifacial Installations 2019. nrel | 3. R. Kopecek, Photonics North 2019, May 22nd Quebec Historic & projected PV market Different cell technology Bifacial cell in world market SHJ. PERC. Al-BSF. ITRPV 2018, PV Celltech Conference March 10-11th 2019 Penang Malaysia nrel | 4. PERC cell technology easily Bifacial Reduced screen-print metallization . Module bifaciality = =. (p-PERC) (n-PERT) (Si Heterojunction). Thorsten Dullweber et al. PERC+: industrial PERC solar cells with rear Al grid enabling bifaciality and reduced Al paste consumption, Prog. Photovolt: Res. Appl. (2015) nrel || 5. Monofacial vs Bifacial module manuf. cost Monofacial PERC PERC+ n-PERT SHJ Bifacial Calculated Minimum Sustainable Price R&D, Sales, Administrative Module Assembly BOM Materials Stringing and tabbing consumables Other Cell direct costs Cell Metallization April 2019 Wafer pricing Additional details given in: (1) M Woodhouse, B Smith, A Ramdas, and R Margolis Economic Factors of Production Affecting Current and Future Crystalline Silicon Photovoltaic Module Manufacturing Costs and Sustainable Pricing , In preparation.

2 (2) A Faes, C Ballif, M Despeisse, et al, Metallization and interconnection for high efficiency Bifacial silicon heterojunction solar cells and modules , Photovoltaics International, 3, 1 12 (2018) (3) A Louwen, W van Sark, R Schropp, and A Faaij, A Cost Roadmap for silicon heterojunction solar cells , Solar Energy Materials and Solar Cells, 147, 295 314 ( 2016 ) nrel | 6. Bifacial Performance Modeling Photo credit: Prism Solar Bifacial total irradiance = + ) ( ) ( . Gfront Grear * _ . 0 . Module bifaciality _ = nrel | 8. 0 . Modeling Rear Irradiance Grear = Gdiffuse,r + Greflected,r + Gbeam,r nrel | 9. Modeling Rear Irradiance Grear = Gdiffuse,r + Greflected,r + Gbeam,r nrel | 10. What Bifacial gain can be expected? Bifacial energy gain BGE. = / 1. = ?? nrel | 11. Surface Albedo has a big effect Rear irradiance, single module at STC. (1kWm-2 frontside). 500. White EPDM. 400. Grear Wm-2. Built-up roof 300. 200. Soil Concrete 100. Asphalt 0. 0 1. Ground reflectance (R).

3 NASA Earth Observations, R. Kopecek and J. Libal, Bifacial Photovoltaics: Technology, applications and economics, IET publishing, 2019 nrel | 12. System GRear experiences self-shading 150. 120. Single row Grear (Wm-2). 90 Front row 60 Interior row Grear: -50%. 30. 0. 0 5 10 15 20. Modules per row nrel | 13. C. Deline et al., Assessment of Bifacial Photovoltaic Module Power Rating Methodologies Inside and Out, J. Photovoltaics 7, 2017. Photo credit: Bifacial Performance Models Bifacial_Radiance Model for Rear Irradiance Complicated geometries possible, including racking and terrain. Radiance uses backward ray-trace to evaluate the irradiance (W/m2) at the modules Open-source software freely available at nrel | 15. Bifacial_Radiance Model for Rear Irradiance Measured 300 View Factor Radiance 250. h = Grear [Wm-2]. 200. 150. 100. h = 50. 0. 50 150 250 350 450 550. Back Sensor Position (mm). Open-source software freely available at Field validation shows good agreement with close-mount rooftop mockup S.

4 Ayala Pelaez, C. Deline, S. MacAlpine, B. Marion, J. Stein, R. Kostuk, "Comparison of Bifacial solar irradiance model predictions with field validation" IEEE Journal of Photovoltaics, 2019, vol 9 no. 1, pp. 82-88. View Factor Model for Rear Irradiance PVSyst Simple Fast Common basic computationally Behind geometry inexpensive SAM, Pvsyst, and others nrel | 17. View Factor Model for Rear Irradiance Grear is summed over 180 field-of-view: 180 . Grear = , + ;. =1 . 1. = cos 1 cos ;. 2. = ( ). = , , ;. Irradiance sources: sky, ground (shaded or unshaded). B. Marion et al., A Practical Irradiance Model for Bifacial PV Modules, 2017. B. Marion, Numerical method for angle-of-incidence correction factors for diffuse radiation incident photovoltaic modules, 2017 nrel | 18. nrel SAM Model 14 1-axis tracking model comparison 13. 12. GRear \ GFront [%]. Bifacial_Radiance 11. 10 PVSyst 9 SAM. albedo 8. Ground Coverage Ratio SAM N. DiOrio, C. Deline, Bifacial simulation in SAM , presented at 5th BifiPV in Denver, CO 2018.

5 S. Ayala Pelaez, C. Deline, S. MacAlpine, B. Marion, J. Stein, R. Kostuk, "Comparison of Bifacial solar irradiance model predictions with field validation". IEEE Journal of Photovoltaics, 2019, vol 9 no. 1, pp. 82-88. nrel | 19. Bifacial trackers, 75 kW. 5 Bifacial technologies Bifacial System configuration 20 modules ( kW) / row 4 PERC, 1 SHJ Bifacial strings 3 PERC monofacial strings Module electronics / monitoring String kWhDC monitoring Front, rear POA irradiance nrel | 21. Bifacial System configuration 20 modules ( kW) / row 4 PERC, 1 SHJ Bifacial strings 3 PERC monofacial strings Module electronics / monitoring String kWhDC monitoring Front, rear POA irradiance nrel | 22. Bifacial System configuration 20 modules ( kW) / row 4 PERC, 1 SHJ Bifacial strings 3 PERC monofacial strings Module electronics / monitoring String kWhDC monitoring Front, rear POA irradiance nrel | 23. Bifacial System configuration 20 modules ( kW) / row 4 PERC, 1 SHJ Bifacial strings 3 PERC monofacial strings Module electronics / monitoring String kWhDC monitoring Front, rear POA irradiance nrel | 24.

6 Bifacial System configuration 20 modules ( kW) / row 4 PERC, 1 SHJ Bifacial strings 3 PERC monofacial strings Module electronics / monitoring String kWhDC monitoring Front, rear POA irradiance nrel | 25. Bifacial System configuration 20 modules ( kW) / row 4 PERC, 1 SHJ Bifacial strings 3 PERC monofacial strings Module electronics / monitoring String kWhDC monitoring Front, rear POA irradiance = Front POA. = Rear POA nrel | 26. Initial field results Bifacial trackers . BGE = 1.. Bifacial Bifacial gain: 15% gain: 5%. nrel | 27. Initial field results Bifacial trackers . BGE = 1.. Bifacial Bifacial gain: 15% gain: 5%. nrel | 28. Initial field results Bifacial trackers . BGE = 1. More diffuse = . higher BGE. nrel | 29. Initial field results Bifacial trackers . Annual power BGE = 1.. histogram 50% energy production nrel | 30. Modeled vs Measured kWDC Power Monofacial Bifacial *SAM using 15-minute measured DNI, DHI, albedo from SRRL BMS. Andreas, A.; Stoffel, T.

7 ; (1981). nrel Solar Radiation Research Laboratory (SRRL): Baseline Measurement System (BMS); Golden, Colorado (Data); nrel Report No. DA-5500-56488. Bifacial systems assume 5% shading loss, 5% mismatch loss, 0% transmission factor nrel | 31. Bifacial modeling sensitivity BGE =.. 1.. 11%. PERC Bifacial gain 4-8% 9%. 3 sensitivity Ground PERC Si-HJT. cases: albedo Bifi Bifi 8%. Field test High case results to date Average case 6%. Low case Si-HJT Bifacial gain 4%. *SAM using 15-minute measured DNI, DHI, albedo from SRRL BMS. Andreas, A.; Stoffel, T.; (1981). nrel Solar Radiation Research Laboratory (SRRL): Baseline Measurement System (BMS); Golden, Colorado (Data); nrel Report No. DA-5500-56488. Bifacial systems assume 5% shading loss, 5% mismatch loss, 0% transmission factor nrel | 32. Market Analysis LCOE Analysis for Monofacial and Bifacial PV Systems Bifacial vs Monofacial LCOE at various US sites 6% Nominal Discount Rate. Single Owner and Unlevered Pro Forma with 30% ITC.

8 $45 Monofacial LCOE Bifacial LCOE. Seattle, WA $ $ LCOE (2019 USD/MWh). $40. Kansas City, MO. $35. $30 Miami, FL. Daggett, CA. $25. 1,200 1,450 1,700 1,950 2,200 2,450. Site kWh/kW annual Pre-Tariff situation illustration based on R. Fu, D. Feldman, R. Margolis, M. Woodhouse, K. Ardani, Solar Photovoltaic System Cost Benchmark: Q1 2017 . nrel /TP-6A20-68925, 2017 And Solar Energy Industries Association. US Solar Market Insight: 2018 Year in Review. Washington, DC March. 2019. nrel | 34. Assumptions: 100MW System , DC-AC ratio, GCR. LCOE Analysis for Monofacial and Bifacial PV Systems Bifacial vs Monofacial LCOE at various US sites PRE-TARIFF Situation LCOE - Miami, FL. 6% Nominal Discount Rate. Single Owner and Unlevered Pro Forma with 30% ITC. $ Bifacial PERC. Monofacial LCOE Bifacial LCOE $ Low case $ $45. LCOE (2019 USD/MWh). Seattle, WA $ $ +4% BGE. LCOE (2019 USD/MWh). +1 /w $ Bifacial $40. Avg. case $ +6% BGE. Kansas City, MO. $35. $ Monofacial -1 /w reference Miami, FL $ $ High case $30.

9 +8% BGE. Daggett, CA $ $25 2,180 2,200 2,220 2,240 2,260 2,280. 1,200 1,450 1,700 1,950 2,200 2,450 Site kWh/kW annual Site kWh/kW annual Pre-Tariff situation illustration based on R. Fu, D. Feldman, R. Margolis, M. Woodhouse, K. Ardani, Solar Photovoltaic System Cost Benchmark: Q1 2017 . nrel /TP-6A20-68925, 2017 And Solar Energy Industries Association. US Solar Market Insight: 2018 Year in Review. Washington, DC March. 2019. nrel | 35. Assumptions: 100MW System , DC-AC ratio, GCR. LCOE Analysis for Monofacial and Bifacial PV Systems POST-TARIFF Bifacial vs Monofacial LCOE at various US sites POST-TARIFF LCOE - Miami, FL. 6% Nominal Discount Rate. Single Owner and Unlevered Pro Forma with 30% ITC. $ Monofacial LCOE PERC Bifacial SHJ Bifacial Monofacial $ $ $ reference $45. LCOE (2019 USD/MWh). $ LCOE (2019 USD/MWh). Seattle, WA. $ $40. Bifacial SHJ. $ $35 Kansas City, MO Bifacial PERC. $ $ $30 Miami, FL. Daggett, CA $ $25 2,210 2,220 2,230 2,240 2,250 2,260 2,270 2,280 2,290.

10 1,200 1,450 1,700 1,950 2,200 2,450 Site kWh/kW annual Site kWh/kW annual (monofacial). Post-Tariff illustration: -5 /W Bifacial based on R. Fu, D. Feldman, R. Margolis, M. Woodhouse, K. Ardani, Solar Photovoltaic System Cost Benchmark: Q1 2017 . nrel /TP-6A20-68925, 2017 And Solar Energy Industries Association. US Solar Market Insight: 2018 Year in Review. Washington, DC March. 2019. nrel | 36. Assumptions: 100MW System , DC-AC ratio, GCR. Conclusions: Bifacial PV is becoming mainstream with GW's of installed projects Energy gain depends on the site configuration and surface albedo. Models like SAM, PVSyst and Bifacial_Radiance can assist with System design and power estimation. 1-axis tracker validation is underway at nrel , showing good initial match with model, and energy gain of 6% and 9% annually for PERC and Si-HJT. LCOE of Bifacial systems is competitive with monofacial systems now, even with initial cost adder of 5-6 /W. Post-tariff, Bifacial is a clear winner.