Accelerated degradation studies of encapsulation polymers

The estimation of PV-modules lifetime facilitates the further development and helps to lower risks for producers and investors. One base for this extensive testing and simulation work is the knowledge of the chemical degradation processes and their kinetics, as well as of the permeation of water and oxygen into the module, especially of the encapsulant. Besides ethylen-vinylacetate copolymer (EVA), which is the dominant material for encapsulation, new materials become available and need the assessment of their properties and the durability impact. Accelerated durability tests were performed on different EVA materials. The paper reports on several measurement methods for analysis of the polymers that were used, FT-IR with attenuated total reflection (ATR), and Raman microscopy, e.g. It is very important to identify degradation products and intermediates in order to identify the leading degradation processes and their kinetics as well as potential interactions between different processes. Another important factor for the degradation of the PV-modules and the concerned polymers in particular is the permeation of reactive substances, especially of water vapor, into and inside the modules. The paper shows results of permeation measurements of the new materials, as well as FEM-based numerical simulations of the humidity diffusion within a PV-module what is an important step towards the calculation of the chemical degradation using numerical simulation tools in the future.