Pulse Transient Method as a Tool for the Study of Thermal Properties of Solar Cell Laminating Films

The paper reports a study on the possible influence of surroundings on thermal properties of various types of laminating films used in the design of photovoltaic (PV) modules based on crystalline silicon. The main purpose of cell encapsulation is to provide protection of PV panels against environmental damage (especially humidity). However, the laminating film can influence also the electrical behavior of the whole panel because of differences in the working temperature. It is well known that with increasing solar cell temperature the PV conversion efficiency is decreasing. Therefore, it is important to study the thermophysical properties of laminating foils which are used for PV cells encapsulation. These materials must possess low specific heat and high thermal conductivity. Therefore, by using a laminating film with low absorption, high thermal conductivity, and high emissive ability of the rear (not illuminated) side, the PV module working temperature can be lowered and thus the generated power is increased and the investment recovery time shortened. The method of measurement is relative. The goal is not to determine the thermophysical parameters of laminating foils, but only to compare the influence of selected types of laminating foils on heat flow from the PV panel. A planar heat source placed between two PMMA blocks with defined thermal properties was adopted as the model of a real PV panel. A measurement on real PV panels was carried out by thermal imaging with a thermocamera. The correlation between both measurements was found.