Evaluation and Field Assessment of Bifacial Photovoltaic Module Power Rating Methodologies

Chris Deline, Sara Macalpine, Bill Marion, Fatima Toor, Amir Asgharzadeh, Joshua S. Stein

Research output: Contribution to conferencePaperpeer-review

18 Scopus Citations


1-sun power ratings for bifacial modules are currently undefined. This is partly because there is no standard definition of rear irradiance given 1000 Wm-2 on the front. Using field measurements and simulations, we evaluate multiple deployment scenarios for bifacial modules and provide details on the amount of irradiance that could be expected. A simplified case that represents a single module deployed under conditions consistent with existing 1-sun irradiance standards leads to a bifacial reference condition of 1000 Wm-2 Gfront and 130-140 Wm-2 Grear. For fielded systems of bifacial modules, Grear magnitude and spatial uniformity will be affected by self-shade from adjacent modules, varied ground cover, and ground-clearance height. A standard measurement procedure for bifacial modules is also currently undefined. A proposed international standard is under development, which provides the motivation for this work. Here, we compare outdoor field measurements of bifacial modules with irradiance on both sides with proposed indoor test methods where irradiance is only applied to one side at a time. The indoor method has multiple advantages, including controlled and repeatable irradiance and thermal environment, along with allowing the use of conventional single-sided flash test equipment. The comparison results are promising, showing that the indoor and outdoor methods agree within 1%-2% for multiple rear-irradiance conditions and bifacial module types.

Original languageAmerican English
Number of pages6
StatePublished - 18 Nov 2016
Event43rd IEEE Photovoltaic Specialists Conference, PVSC 2016 - Portland, United States
Duration: 5 Jun 201610 Jun 2016


Conference43rd IEEE Photovoltaic Specialists Conference, PVSC 2016
Country/TerritoryUnited States

Bibliographical note

See NREL/CP-5J00-66496 for preprint

NREL Publication Number

  • NREL/CP-5J00-67931


  • albedo
  • bifacial solar photovoltaics
  • standards


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