To calculate the heat transfer of a photovoltaic panel composed of different materials, one can utilize the concept of a composite plane wall, focusing on the thermal conductivity values of each material. The overall heat transfer coefficient can be determined by considering the thermal resistances of each layer, rather than using a single thermal conductivity value for the entire panel. When the panel is placed over a flowing water source, convective heat transfer must also be accounted for, in addition to conductive heat transfer. If a steel backing is added, its thermal properties must be integrated into the overall calculation to accurately assess heat transfer. Understanding these principles is crucial for optimizing the thermal performance of photovoltaic systems.