Thermomechanical Stress Distribution Analysis of Junction Box on Silicon Photovoltaic Modules Based on Finite Element Analysis

The electrical failure associated with concentration of heat and thermomechanical stress inside junction boxes is one of the main failure modes of photovoltaic (PV) modules. Three types of potting junction boxes with partial 72 Si cells PV panel are modeled under a constant current steady-state condition. The temperature distribution results are verified through thermal dissipation tests. It is found that when one diode is in the ON-state, the split kind of junction box shows the highest temperature distribution on the surface, which is nearly 15 °C higher than the other two types under 25 °C with 11 A current applied. When three diodes are working, the other two types of junction box with three diodes inside will be intensely heated. The internal temperature distribution shows that bigger size and more copper coverage can help improve the thermal dissipation. Thermomechanical stress analysis based on the steady-state conditions is then carried out. The results show stress concentration on the side wall of the type I junction box while the other two types having conspicuous impact to the backsheet.