Model and Validation of Single-Axis Tracking with Bifacial Photovoltaics: Preprint

Christopher Deline, Silvana Pelaez, Peter Greenberg, Josh Stein, Raymond Kostuk

Research output: Contribution to conferencePaper


Single-axis tracking is a cost effective deployment strategy for large-scale ground-mount photovoltaic (PV) systems in regions with high direct-normal irradiance (DNI). Bifacial modules in 1-axis tracking systems boost energy yield by 4% - 15% depending on module type and ground albedo, with a global average of 9%. This benefit is in addition to the 15%-25% energy gain already afforded by single-axis tracking relative to fixed-tilt deployments. Here we compare model results against field performance data for two side-by-side bifacial / monofacial tracked systems - one in Albuquerque NM, and one in eastern Oregon. The Albuquerque system shows monthly rear irradiance gain of 10-14.9%, and the Oregon bifacial system has an average performance ratio 9.4% higher than the monofacial system. Both results match bifacial irradiance model results within uncertainty. Simulations show that smart tracking algorithms can offer more than 1% improvement on annual energy yield by adjusting tilt angle under cloudy conditions. Finally, ray-tracing simulations investigated edge brightening, suggesting 15%-25% increase in rear irradiance at the ends of tracker rows, but up to 20% loss from center-mounted torque tubes, creating multiple shadows.
Original languageAmerican English
Number of pages10
StatePublished - 2019
EventWorld Conference on Photovoltaic Energy Conversion (WCPEC-7) - Waikoloa, Hawaii
Duration: 10 Jun 201815 Jun 2018


ConferenceWorld Conference on Photovoltaic Energy Conversion (WCPEC-7)
CityWaikoloa, Hawaii

NREL Publication Number

  • NREL/CP-5K00-72039


  • bifacial tracking
  • photovoltaics
  • solar


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