Development of a Methodology for Service Lifetime Prediction of Renewable Energy Devices

Emerging advanced multilayer renewable energy devices, such as reflector materials and photovoltaic modules, are expected to exhibit significantly increased service lifetimes compared to existing devices. Such devices must be capable of 20 to 30 years of operation under harsh outdoor weathering conditions. Industrial manufacturers cannot afford to wait extended periods of time to determinewhether such lifetimes are realistic. Consequently, a flexible, robust, and accurate method for predicting the service lifetime of such devices is essential. Two requirements for developing such a method are first, to correlate the accelerated lifetime test methods with anticipated life under real-world operating environments; and second, to establish statistical models for predicting servicelifetimes based on environmental stress factors. The relative significance of the weathering stress factors ultraviolet light (UV), temperature (T), and relative humidity (RH) was ascertained. Optical properties of new reflector materials were measured and their loss of performance with exposure time was modelled as a function of an appropriate combination of stress factors. Then, the functionalrelationship between performance measurements and time in accelerated lifetime tests was investigated. The basic framework of this approach is SPt analysis because it tends to explain the bridge functions from Stresses (S) to Performance (P) and from Performance to lifetime (t) of the materials. The results show that the cumulative dosage of ultraviolet radiation between 290-320 nm (UV-B) withsynergistic effects of T and RH is a very critical factor in inducing performance loss. Finally, the SPt model developed for accelerated laboratory data was verified for data obtained from outdoor sites, and excellent agreement was found.