Bifacial PV module operating temperature: high or low? A cross-comparison of thermal modeling results with outdoor on-site measurements

The PV module operating temperature has a significant impact on system energy yield, as well as on the module long term reliability performance. The IEC 61853-2:2016 defines the Nominal Module Operating Temperature (NMOT) as a simplified index to characterize the thermal performance of different PV module designs. This work focuses on the evaluation of the monofacial and bifacial NMOT, through a combination of modeling and experimental field testing. A previously built Finite Element 3D static thermal model is extended to account for bifacial module specificities, at the cell and the module levels. Simulated results show that the NMOT is similar within the uncertainty range for bifacial module compared to the incumbent monofacial design. Data analysis is then performed using IEC61853-2:2016 methodology for direct comparison of the temperature differences with outdoor measurements for the bifacial experimental test sites, which showed a consistent – 1.1°C lower for bifacial moduleand results. Finally, the field data has been justified with PVsyst simulation and recommended thermal parameters are given according to the RMSE/MBE enhancement.