Bifacial PV System Mismatch Loss Estimation and Parameterization: Preprint

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

Research output: Contribution to conferencePaper


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 scenarios including horizontal single-axis tracking (HSAT) and 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 HSAT systems and 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 pages8
StatePublished - 2019
Event2019 European PV Solar Energy Conference (EU PVSEC) - Marseille, France
Duration: 9 Sep 201913 Sep 2019


Conference2019 European PV Solar Energy Conference (EU PVSEC)
CityMarseille, France

NREL Publication Number

  • NREL/CP-5K00-73541


  • bifacial photovoltaics
  • PV systems


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