Reduction of PV Module Temperature Using Thermally Conductive Backsheets

Abstract

Photovoltaic (PV) modules typically operate at approximately 30°C above ambient temperature on clear sunny days, irrespective of their location. Since the average annual daytime temperature is typically higher than 20°C in most locations, where PV modules are installed, operating temperatures can exceed 50°C on clear sunny days. This translates to a 12% reduction in nameplate power for crystalline silicon modules. In addition, thermally induced degradation mechanisms have a higher probability of occurrence when operating temperatures increase, thereby reducing the module lifetime. The operating temperatures are impacted by the selection of packaging materials, e.g., backsheets and encapsulants. This paper demonstrates a significant reduction in the operating temperature of single-cell modules with innovative thermally conductive backsheet (TCB) materials vis-à-vis a baseline Tedlar/polyester/Tedlar (TPT) backsheet. Field results demonstrate that the nominal operating cell temperature of the TCB coupons is approximately 1°C lower than those of conventional TPT coupons. The daily average module operating temperature of TCB coupons was as much as 3°C cooler compared with the TPT coupons in summer months. Reducing the module temperature by 3°C results in a 1.5% relative efficiency increase. Finally, an empirical thermal model to predict the cell temperature for each backsheet type and a physical thermal model using ANSYS were developed and presented in this paper.