Finite Element Modeling, Thermal-Mechanical Coupling Analysis, and Demonstration of Multibusbar Half-Cell Double-Glass Overlapping Photovoltaic Module During Lamination

The gap-free interconnect using structural round ribbons in overlapping photovoltaic modules is an effective measure to improve module efficiency. Cells in the overlapping module are interconnected by round ribbons with local flattened parts rather than conductive adhesive. The structure of overlapping modules has a crucial effect on the thermal-mechanical stress of crystalline silicon cells during the laminating process of modules. Excessive stress will produce microcracks in the cells, which will adversely affect the long-term reliability of the modules. In this article, the coupled temperature-displacement is used to simulate the stress evolution of the double-glass multibusbar overlapping modules during lamination and comparative experiments were carried out. The results show that in the overlapping area, the cell near the solder band will be subjected to more concentrated stress than other regions, resulting in local bending of the cell. Large stress concentration may induce the generation and propagation of microcracks. The cell stress is sensitive to the dosage of encapsulating agent and the thickness of the flattened ribbon. Increasing the amount of encapsulating agent and reducing the thickness of the flattened section will help to relieve stress concentration. Finally, we demonstrate the overlapping process with modules interconnected by 0.12-mm flattened round ribbons and encapsulated by 0.65-mm ethylene vinyl acetate. The overlapping modules pass 200 thermal cycles and 3600-Pa mechanical load without cracks.