Simulation and Experimental Analysis of Temperature Profiles and Crosslinking in PV Module Lamination

Abstract

The lamination process plays a crucial role in the long-term reliability of photovoltaic (PV) modules. Monitoring the degree of encapsulant crosslinking in the modules can help ensure the quality of the lamination process, which is affected by factors like lamination temperature and process time. A consistent vertical temperature distribution during lamination is important for achieving uniform crosslinking across the module depth. In this study, thermocouple measurements were conducted to obtain temperature profiles and assess the degree of encapsulant crosslinking in glass-backsheet and glass-glass (GG) modules with and without cells. Four different encapsulants were analyzed, including two types of ethylene-co-vinyl acetates (EVA) and two types of polyolefin elastomers (POE). The measurements data were compared with simulations that allow to determine the temperature profile of the different layers of the module as well as the degree of crosslinking of the encapsulants over the process time. The simulation results showed good agreement with the measured values, effectively capturing the temperature trends during lamination. It was found that inadequate processing led to a crosslinking discrepancy between the front and back sides of the modules of 6.5% for EVA, and 14% for POE. To address this issue, a 1) plate-plate chamber was used for GG modules or; the 2) process time was extended in the plate-membrane chamber. The study also highlighted the significant influence of the cells on the degree of crosslinking, whereas the implementation of the cells decreases the crosslinking by up to 12.8%. In addition, the simulated encapsulant crosslinking was validated against Soxhlet extraction results.