Effects of temperature and stress in laser-assisted sealing of vacuum photovoltaic modules

Abstract

One of the main issues that need to be addressed for the large-scale application of photovoltaic (PV) modules is ensuring their long-term stable operation. Conventional sealing methods cannot completely prevent the erosion of PV cells by water vapor and oxygen. We propose placing PV cells in a vacuum layer sandwiched between two glass sheets, with localized laser sealing around the perimeter. To this end, we constructed a transient three-dimensional model of PV module sealing using a laser heat source, studied the temperature and stress variations throughout the laser-assisted glass frit encapsulation process, and determined the basic mechanism of laser sealing for PV modules. Subsequently, we systematically investigated the laser sealing process parameters, exploring the impact trends of different process parameters on the weld morphology, deformation, temperature field, and stress field of the module. The results indicate that within the ranges of an average laser power of 10–30 W, sealing speed of 1–3 mm/s, and spot radius of 0.5–2.5 mm, the spot center temperature, maximum stress, and maximum deformation of the module increase with higher laser power, increased sealing speed, or smaller spot radius. The highest temperature and maximum transient thermal stress occur at the interface boundary of the upper glass, and there are significant differences in stress between the glass frit layer and the glass layer, with a correlation between thermal stress and thermal deformation. Different types of process parameters have varying impacts on temperature, stress, deformation, and the size of the molten pool. Experimental simulation results show that with appropriate laser process parameters, laser-assisted glass frit can efficiently seal vacuum PV modules, with the PV cells being sealed within a vacuum layer.