Impact of cracks on crystalline silicon photovoltaic modules temperature distribution

Abstract

A photovoltaic (PV) module experiences mechanical and thermo-mechanical stress in outdoor conditions, which leads to formation of cracks in solar cells. The cracks give rise to mismatch in the electrical output between the cells, which creates a non-uniform temperature distribution that can have an instantaneous effect on power and long-term effect on PV module reliability. The objective of present work is to investigate the impact of cracks on temperature distribution in a PV module. Based on the electrical behavior of cracked cells, they have been classified as crack with enhanced recombination (C-ER) and crack with loss of active area (C-LAA). The impact of these cracks on temperature distribution has been estimated using an electro-thermal model, which is validated using an experimental setup. Different crack scenarios have been simulated in PV module to analyze the effect of crack type, number of cracked cells, and their biasing on temperature distribution. Results show that under normal operating conditions, the temperature gradient does not change with number of cracked cells. However, when the cracked cell operates under reverse bias either due to change in maximum power point or shading, the temperature gradient decreases with increase in number of cracked cells. Relative comparison between the two types of cracks shows that temperature gradient in PV module is greater in case of C-LAA. The analysis of different crack scenarios presented in this investigation will be useful for detecting cracks in outdoor conditions based on their thermal distribution.