PV Module Durability -connecting field results, accelerated testing, and materials

This presentation will discuss the framework employed at DuPont for using the analysis of modules from the field to guide development of accelerated tests and understand aging and degradation of PV modules, components and materials. Our framework starts with analysis of the stresses that are applied to modules in the field and in accelerated tests, including UV irradiation, humidity, temperature, and temperature cycling, either applied singly or in sequences. It then examines the measurements or responses that can then be evaluated or measured to determine the effects of these stresses. Measurements and indicators of aging and degradation include visual and physical degradation and changes of polymeric and other components, corrosion of metallization and bus bars, loss of power, and changes in IV characteristics and electroluminescent imaging. To correctly analyze and compare the data to the field it is important to understand the evolution and changes in materials in modules over time. Comparisons of these characteristics from the field and from accelerated tests can then be used to develop accelerated tests and determine the stress levels that match the levels of aging and degradation mechanisms found in typical field exposures. We will illustrate this work with examples from our analysis of fielded modules from around the globe and show how we have used it to understand degradation mechanisms and develop accelerated test protocols that more closely match what is seen in the field.