A Rational Strength Prediction Approach to the Design of Double-Glass Photovoltaic Modules

A rational and systematic approach to estimate the load resistance and strength of various double-glass photovoltaic modules is demonstrated. The approach consists of three steps: 1) calculation of module stiffness based on a laminate effective thickness theory; 2) calculation of the highest stress concentration in the two glass plies of the module using a modified plate theory; and 3) estimation of glass breakage probability of the module against specified loads by comparing the stress concentration calculated in step 2 with allowable glass stress and associated breakage probability. In the modified plate theory, a parameter that incorporates stress mitigation by a peripheral frame and installation is introduced to enable simple and fast calculations. The allowable stress of glass in step 3 is obtained by the Weibull analysis of glass breakage data obtained by a ring-on-ring test. The calculation methodology has been validated experimentally using load tests and direct measurements of glass principal stress in a real module under load. The approach can be used for fast screening and initial design of various structures to resist specified imposed mechanical loads.