Efficacy of passive cooling panels for silicon photovoltaic mini-modules using phase change material and expanded graphite

This study details the effectiveness of Phase Change Material (PCM) composite panels to improve the performance of solar devices through passive cooling realized by the phase transition in the range 30–50 °C. PCM-based panels (70 g) of thermal energy capacity 11–15 kJ (143–195 J/cm³) were obtained with three organic PCMs impregnating expanded graphite (EG). Commercial PV mini-modules were compared in outdoor experiments, with PCM panels at single, double or triple layer, by using dedicated 3D printed housings to position the panels in contact with the solar devices. Tests under sunlight exposure were conducted in Trento (Italy, 46° N, 11° E) during summer 2024 to estimate the efficiency increase. Thermal management parameters were used to quantify the positive performance of PCM panels in minimizing the maximum temperature, and to compare with literature data. In particular, the results were correlated to different temperature coefficient to extend the validity to a broader case history. The module temperature could be decreased by 15–30°C for hours, in some cases completely smoothing the daily temperature peak, guaranteeing an output energy enhancement of up to 11 %. The integrity of the panels was maintained during all the period of sunlight exposure. The obtained results of passive cooling have positively confirmed that these panels can be placed in contact with the PV devices by exploiting the unused empty space commonly present on the back side of PV panels and can be used either for new installations or for the retrofitting of existing systems.