By Zhiyong Xia, Materials Scientist, BP Solar International, Inc.; Daniel Cunningham, Module Technology Manager, BP Solar International, Inc.; John Wohlgemuth, Solarex, BP Solar International, Inc.
Among the different packaging materials used in photovoltaic solar modules, ethylene vinyl acetate-based (EVA) encapsulants play an important role during the lifespan of the module assembly. Prior to lamination, EVA is a thermoplastics polymer containing a number of additives. During the lamination process, EVA cross-links into a three-dimensional network structure, i.e., a thermoset, which provides protection for solar cells against detrimental environmental conditions. Since EVA has a very low glass transition temperature and melting points, proper cross-link density has to be achieved through the lamination process to prevent the EVA from cold flowing in the field. As a result, module manufacturers constantly monitor the cross-link density or gel content of EVA after lamination. This paper proposes a new method of measuring this density value while avoiding many of the current pitfalls.
Includes 12 months of unlimited digital access to the Photovoltaics International content, full online archive, technical paper collection (over 700), and more.
Includes 2 upcoming issues in digital.