Effect of torque-tube parameters on rear-irradiance and rear-shading loss for bifacial PV performance on single-axis tracking systems
Silvana Ayala Pelaez1, Chris Deline1, Joshua S. Stein2, Bill Marion1, Matthew Muller1
1National Renewable Energy Laboratory, Golden, CO, United States
/2Sandia National Laboratories, Albuquerque, NM, United States

Abstract  —  The emergence of cost-competitive bifacial PV modules has raised the question of the additional value of bifacial modules in 1-axis tracking arrays, in particular when considering rear-irradiance losses from the tracker system itself. In this work, the effect of different geometries and materials of torque tubes is evaluated and found to reduce rear-irradiance averages without any torque-tube shading by 0.1 to 12% for metallic and black absorptive torque tubes respectively for a clear-sky day. This paper will compare modeled to measured rear-irradiance profiles, and propose a recommended range of rear-shading loss factors for different geometry conditions. The effect of rear-irradiance distribution into electrical mismatch loss will also be explored.
Index Terms — bifacial PV module, single-axis tracking, irradiance, ray tracing, model, performance, torque tube