DURABILITY, RELIABILITY, AND SERVICE LIFE PREDICTION OF POLYMERIC MATERIALS USED IN PHOTOVOALTAIC (PV) SYSTEMS
Kaipeng Liu, Xiaohong Gu
In practical applications of PV solar cells, long-term weathering durability and reliable performance are essential. In order to meet the desired service life of over 20-30 years, proper polymeric encapsulation is needed. However, the fundamental degradation mechanisms need to be understood and the service life prediction models need to be established for those polymers used in PV systems.
This work takes advantages of NIST SPHERE (Simulated Photodegradation via High Energy Radiant Exposure) as a powerful ultraviolet (UV) irradiation source. Under different exposure temperature and relative humidity, a series of accelerated laboratory tests for PV materials, such as ethylene vinyl acetate (EVA) and fluoropolymer, were carried out on the SPHERE. Multi-scale characterization of chemical and physical properties of aged and unaged PV polymers shows that EVA starts to degrade within 2-months UV exposure, while fluoropolymer barely changes even after 4-months exposure. Combined with the outdoor exposure results, a proper linkage between indoor and outdoor results can be established based on scientifically mathematical models and a reasonable service life prediction can be expected.