Bifacial PV System Mismatch Loss Estimation & Parameterization

Christopher Deline, Silvana Ayala Pelaez, Sara MacAlpine, Carlos Olalla

Research output: NRELPresentation


Non-uniform irradiance on the rear-side of bifacial PV systems can cause additional mismatch loss which may not be appropriately captured in PV energy production estimates and software. We have evaluated several rooftop mounted systems over high albedo reflective roofs. Mismatch losses of up to 2% annual loss for very close-mounted (0.15 m) rooftop systems were found, but losses for high ground-clearance rooftop systems were lower (<0.5%). A simplified empirical relationship was found that links the spatial variation of irradiance (specifically the mean absolute difference of irradiance) to the resulting mismatch loss factor, with a R2 fit better than 0.985. This approximate relationship has been validated by experiments on mismatched PV modules, and provides a basis for fast estimation of bifacial mismatch loss factors for use in hourly PV performance simulations such as PVSyst or SAM.
Original languageAmerican English
Number of pages33
StatePublished - 2019

Publication series

NamePresented at the 36th European PV Solar Energy Conference and Exhibition (EU PVSEC), 9-13 September 2019, Marseille, France

Bibliographical note

Originally published September 2019. Revised in December 2019.

NREL Publication Number

  • NREL/PR-5K00-74885


  • bifacial PV system
  • irradiance distribution
  • photovoltaic
  • power output
  • PV
  • solar


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