Local overheating of a photovoltaic module junction box: analysis and recommendations

Abstract Local overheating of the junction box on photovoltaic modules is a major barrier to achieving uniform cooling of the entire panel. Even when effective cooling methods are applied, this area often remains a hotspot, limiting the overall cooling performance. We performed outdoor tests on two identical 290-W modules: one without cooling and one with evaporative cooling applied to the backside using ten stitched layers of gauze. Temperatures were monitored by sensors and infrared cameras, including at the junction box. To eliminate the hotspot, the junction box was relocated from the module backsheet to the frame, enabling full-surface cooling coverage. Evaporative cooling reduced the average panel temperature by about 10°C. However, the junction box area remained overheated (50°C–55°C), similar to the uncooled module. After relocating the junction box to the frame, the hotspot disappeared and the backside temperature became uniform (33°C–35°C). Cooling the panel alone does not ensure uniform temperature distribution due to junction box overheating. Relocating the junction box to the frame is an effective design measure that enables complete cooling coverage and uniform temperature reduction across the entire photovoltaic module.

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