Estimating and Parameterizing Mismatch Power Loss in Bifacial Photovoltaic Systems

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

Research output: Contribution to journalArticlepeer-review

41 Scopus Citations


Nonuniform irradiance on the rear side of bifacial photovoltaic (PV) systems can cause additional mismatch loss, which may not be appropriately captured in PV energy production estimates and software. We evaluated several scenarios including horizontal single-axis tracking (HSAT) over natural ground-cover and rooftop-mounted systems over high albedo reflective roofs. We found mismatch losses of up to 1.5% annual loss for very close-mounted (0.15 m) rooftop systems, 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 an R2 better than.99. This approximate relationship was experimentally validated on mismatched PV modules, and it provides a basis for rapidly estimating bifacial mismatch loss factors for use in hourly PV performance simulations such as PVSyst or SAM. Additional parameters investigated include (a) climate dependence and module orientation, which were not found to have a strong impact on bifacial mismatch losses and (b) PV module fill factor and bifaciality ratio, which did have a strong linear impact on mismatch losses.

Original languageAmerican English
Pages (from-to)691-703
Number of pages13
JournalProgress in Photovoltaics: Research and Applications
Issue number7
StatePublished - 2020

Bibliographical note

Publisher Copyright:
© 2020 John Wiley & Sons, Ltd.

NREL Publication Number

  • NREL/JA-5K00-74844


  • bifacial photovoltaics
  • PV systems


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