Single axis tracking with bifacial modules

I receive a warning (in the most recent SAM version) that results may not be accurate when I model bifacial modules on a single axis tracker. Does anyone know how significant the difference might be? Where can I find more information about modeling bifacials on trackers?

thanks, Robert

Hi Robert,

That message is misleading. The bifacial model should work fine with one-axis tracking as long as the tilt angle is zero. The model was developed from empirical data measured for systems with horizontal tracking axes.

That message should only appear if the tilt angle is not zero. We will fix that for the first update to SAM 2020.11.29: github.com/NREL/ssc/issues/364 .

Best regards,
Paul.

Greetings-
We are using BiFacials on Dual-axis trackers. The recent reports from field installs in Vermont appear to perform as expected. 
Can you please direct me to any reference of potential problems?
Many Thanks! J# for SES and STracker Solar

Hi Jeff,

SAM's simulation message is meant to explain a limitation in the way SAM  models bifacial models, not a limitation of how they work in a real system:



The model is descried in Marion et al. (2017) and available from the SAM website here: sam.nrel.gov/photovoltaic/pv-sub-page-2.html . The model was developed and tested for fixed arrays and one-axis tracking arrays with a horizontal tracking axis (tilt = 0), so SAM displays the message when those conditions are not met.

Best regards,
Paul.