Modelling bifacial irradiance – Step-by-step comparison and validation of view factor and ray tracing models

This study presents a comprehensive comparative analysis of View-Factor (VF) and Ray Tracing (RT) models to evaluate their effectiveness in predicting bifacial irradiance in bifacial photovoltaic (PV) systems. The comparison was conducted using an experimental dataset from NREL (CO, USA), which included front and rear plane-of-array (POA) irradiance values measured by silicon solar cell pyranometers. This initial step established a baseline understanding of each model's predictive capabilities in a real-world context. The comparison with POA measurements indicates that for front illumination, both models are closely aligned with relative Root Mean Square Error (rRMSE) of 7.2% (VF) and 7.6% (RT). For rear illumination, the rRMSE increases to 20.9% and 22.9% for the VF and RT models, respectively. Additionally, both models show a similar relative Mean Bias Error (rMBE) for front illumination of −1.8% and − 2.0% for the VF and RT methodologies, respectively. However, for rear illumination, the RT model predicts with only −0.1% bias, while the VF model underestimates POA irradiance by 8.4%.