Photovoltaic hot spot analysis for cells with various reverse-bias characteristics through electrical and thermal simulation

Hot spots result from localized heating in a string of photovoltaic (PV) cells due to mismatch that is often caused by partial shading or uneven degradation. Over time, this localized heating can result in permanent damage and degrade string performance. Bypass diodes are commonly employed in PV panels to mitigate this problem, but it does not eradicate the problem-hot spots can still form. This study investigates how the reverse-biased I-V characteristics and number of cells in series affect the potential for hot spotting. Using an electrical and thermal model in Matlab Simulink and Simscape, three distinct PV cells are modeled and simulated in various string lengths. Simulation results confirm that shorter strings reduce hot spot risk, but none of the cell types were immune to hot spotting, particularly in bypass. Bypassing even a short string can lead to hot spots and the temperature rise worsens as string length increases.