Evaluation of the non-uniformity of rear-side irradiance in outdoor mounted bifacial silicon PV modules

Abstract

The bifacial crystalline silicon (Si) photovoltaic (PV) module market has grown significantly in recent years since they offer the opportunity for increased performance in comparison to conventional monofacial PV modules. This is because both sides of the cells can absorb solar radiation, utilizing the scattered light from the ground and surroundings. This however also implies a more difficult energy yield forecast due to the extra rear irradiance contribution that needs to be evaluated. Furthermore, the IEC technical specification (TS) 60904-1-2 indicates a threshold of 10% for rear side irradiance non-uniformity in outdoor characterization conditions. This work is a study of rear-side irradiance (Grear) non-uniformity essential to ensure meaningful characterization and long-term outdoor energy yield measurements for bifacial modules. The sky conditions, location on rack, rear irradiance sensor number and position that influence the rear irradiance non-uniformity for bifacial modules mounted on an open rack are studied. Finally, the minimum number and position of irradiance sensors needed to reliably describe the rear irradiance as a function of time for long-term monitoring of this PV system is proposed.The bifacial crystalline silicon (Si) photovoltaic (PV) module market has grown significantly in recent years since they offer the opportunity for increased performance in comparison to conventional monofacial PV modules. This is because both sides of the cells can absorb solar radiation, utilizing the scattered light from the ground and surroundings. This however also implies a more difficult energy yield forecast due to the extra rear irradiance contribution that needs to be evaluated. Furthermore, the IEC technical specification (TS) 60904-1-2 indicates a threshold of 10% for rear side irradiance non-uniformity in outdoor characterization conditions. This work is a study of rear-side irradiance (Grear) non-uniformity essential to ensure meaningful characterization and long-term outdoor energy yield measurements for bifacial modules. The sky conditions, location on rack, rear irradiance sensor number and position that influence the rear irradiance non-uniformity for bifacial modules mounted on an open r...