Measured RPOA Equivalent

[David Bowersox]

Pertaining to capacity or PR testing, the following equation is frequently referenced for total irradiance calculations:

E_Total = E_POA + E_Rear * 𝜑

...where 𝜑 is equal to the module bifaciality factor.

My question concerns the E_Rear term: if a PV system has a pyranometer installed in the rear plane of array in such a way that it is unobstructed by structures such as the torque tube, and the E_Rear used for the physical PV system is the measured RPOA from this pyranometer, what do you recommend using for the E_Rear term to calculate an equivalent model-side E_Total? Would the E_Rear term be the output variable GlobBak, a combination of factors such as GlobBak + BackShd, or something else? 

 

Reference: Waters, Martin, Chris Deline, Johan Kemnitz, and Jeffrey Webber. 2019. Suggested Modifications for Bifacial Capacity Testing: Preprint. Golden, CO: National Renewable Energy Laboratory. NREL/ CP-5K00-73982. https://www.nrel.gov/docs/fy20osti/73982.pdf