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Proceedings Paper

Degradation analysis of field-exposed photovoltaic modules with non-fluoropolymer-based backsheets
Author(s): Andrew Fairbrother; Scott Julien; Kai-Tak Wan; Liang Ji; Kenneth Boyce; Sebastien Merzlic; Amy Lefebvre; Greg O'Brien; Yu Wang; Laura Bruckman; Roger French; Michael Kempe; Xiaohong Gu
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Paper Abstract

The selection of polymeric materials utilized in photovoltaic (PV) modules has changed relatively little since the inception of the PV industry, with ethylene-vinyl acetate (EVA), polyethylene terephthalate (PET), and fluoropolymer-based laminates being the most widely adopted primary components of the encapsulant and backsheet materials. The backsheet must serve to electrically insulate the solar cells and protect them from the effects of weathering. Due to continued downward pressure on cost, other polymeric materials are being formulated to withstand outdoor exposure for use in backsheets to replace either the PET film, the fluoropoymer film, or both. Because of their relatively recent deployment, less is known about their reliability and if they are durable enough to fulfill the ≥25 year warranties of current PV modules. This work presents a degradation analysis of field-exposed modules with polyamide- and polyester-based backsheets. Modules were exposed for up to five years in different geographic locations: USA (Maryland, Ohio), China, and Italy. Surface and cross-sectional analysis included visual inspection, colorimetry, glossimetry, and Fourier-transform infrared spectroscopy. Each module experienced different types of degradation depending on the exposure site, even for the same material and module brand. For instance, the polyamide-based backsheet experienced hairline cracking and greater yellowing and chemical changes in China (Changsu, humid subtropical climate), while in Italy (Rome, hot-summer Mediterranean climate) it underwent macroscopic cracking and greater losses in gloss. Spectroscopic studies have permitted identification of degradation products and changes in polymer structure over time. Comparisons are made to fielded modules with fluoropolymer-based backsheets, as well as backsheet materials in accelerated laboratory exposures. Implications for qualification testing and service life prediction of the non-fluoropolymer-based backsheets are discussed.

Paper Details

Date Published: 23 August 2017
PDF: 13 pages
Proc. SPIE 10370, Reliability of Photovoltaic Cells, Modules, Components, and Systems X, 1037003 (23 August 2017); doi: 10.1117/12.2272488
Show Author Affiliations
Andrew Fairbrother, National Institute of Standards and Technology (United States)
Scott Julien, Northeastern Univ. (United States)
Kai-Tak Wan, Northeastern Univ. (United States)
Liang Ji, Underwriters Labs. Inc. (United States)
Kenneth Boyce, Underwriters Labs. Inc. (United States)
Sebastien Merzlic, Arkema, Inc. (United States)
Amy Lefebvre, Arkema, Inc. (United States)
Greg O'Brien, Arkema, Inc. (United States)
Yu Wang, Case Western Reserve Univ. (United States)
Laura Bruckman, Case Western Reserve Univ. (United States)
Roger French, Case Western Reserve Univ. (United States)
Michael Kempe, National Renewable Energy Lab. (United States)
Xiaohong Gu, National Institute of Standards and Technology (United States)

Published in SPIE Proceedings Vol. 10370:
Reliability of Photovoltaic Cells, Modules, Components, and Systems X
Neelkanth G. Dhere; Keiichiro Sakurai; Michael D. Kempe, Editor(s)

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