Advanced Development of PV Encapsulants: Semiannual Subcontract Report, 1 January 1993 - 30 June 1993

This report describes the results of the literature search, interviews, and site visits conducted during the first six months of this subcontract. This survey was conducted to establish a baseline of information about thermal and photothermal degradation of EVA and case history surveys on discoloration (yellowing/browning) of EVA-based encapsulants in fielded flat-plate PV modules. The literaturesearch revealed that EVA will undergo thermolysis of the acetate groups at temperatures of 130 degrees C to 150 degrees C and above, leading to formation of double bonds in the backbone of the copolymer. The survey of case histories of EVA-based encapsulant discoloration in fielded modules in the United States revealed that the problem is limited to those areas of the west and southwest thathave comparatively high solar insolation and ambient temperature. It is clear that the discoloration problem is not limited to the modules of any one manufacturer. Discoloration in the EVA encapsulant was experienced in fielded modules from all major U.S. module producers.