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Photovoltaic power is emerging as a major power resource, steadily becoming more affordable and proving to be more reliable than utilities. The photovoltaic effect is the basic principal process by which a photovoltaic (PV) cell converts sunlight into DC electricity. PV cells were developed as a spin-off of transistor technology. Photovoltaic modules are interconnected assemblies of photovoltaic cells (solar cells) packaged in a weather tight housing. The module is encapsulated with tempered glass on the front surface, and with a protective and waterproof material on the back surface. The edges are sealed for weatherproofing as photovoltaic modules have to withstand a number of environmental influences like irradiance, temperature, mechanical stresses, atmosphere, humidity, moisture in their long life time. It is very important to understand the mechanical stability of theses solar panels as they undergo various loading and environmental conditions such as thermo-mechanical loading, thermal cycling, wind loading, effect of hell storm etc. A three dimensional finite element model of a typical solar module assembly that consists of silicon cells and bus bars sandwiched between glass cover and backsheet using an EVA and adhesive is solved numerically to study the impact of stresses induced on mechanical integrity of the silicon and bus bar during cool down of the solar assembly. In this analysis, a stress free temperature of 60° C, while temperature range of −40° C to 120° C is applied to the module and stresses are calculated at the Si, bus bars, adhesive, solder pads and glass to assess the reliability of the overall package. A parametric study of critical geometric parameters such as Si, bus bar, adhesive and glass thickness as well as mechanical material properties (E and a) of adhesive is carried out to minimize the maximum stresses on the overall module. Recommendations are provided to minimize the overall stresses which eventually results in a productive design and installation of a solar module assembly. |
