Quantifying the influence of encapsulant and backsheet composition on PV‐power and electrical degradation

Abstract

AbstractAlthough the technical and economic properties of the standard polymer photovoltaic (PV) materials (ethylene‐vinyl acetate (EVA) encapsulant and fluorine‐containing polyethylene terephthalate (PET) backsheet) meet the basic technical requirements, more sustainable polyolefin‐based encapsulants and backsheets have been developed. These new polyolefin materials have to prove their performance compared to the established standard materials in terms of the electrical performance of the modules and in terms of reliability. The long‐term stability of the new materials is tested and evaluated using accelerated aging tests and degradation modelling. Based on experimental results, the influence of the type of encapsulant and backsheet (i) on the electrical output power of PV test modules and (ii) on the aging‐related electrical and material degradation under accelerated stress tests was estimated using statistical modelling approaches. First results showing significant effects for encapsulant, backsheet and the combination of both on the initial power output are presented. In general, modules with polypropylene‐based backsheets have a higher initial power (PMPP) than those with PET‐based backsheets, with the combination of thermoplastic polyolefin (TPO) encapsulation material and polyolefin backsheet being superior to the other material combinations. A comparison of the material‐dependent degradation rates obtained from the mixed‐effects models clearly shows that the degradation rate upon damp heat exposure for modules with EVA is significantly larger than that using polyolefin encapsulants. The derived relations aim to provide valuable input for innovative material developments as well as predictive maintenance specifications.