Degradation Analysis of Field-Exposed Photovoltaic Modules with Non-Fluoropolymer-Based Backsheets: Paper No. 1037003

Michael Kempe, Andrew Fairbrother, Scott Julien, Kai-Tak Wan, Liang Ji, Kenneth Boyce, Sebastien Merzlic, Amy Lefebvre, Greg O'Brien, Yu Wang, Laura Bruckman, Roger French, Xiaohong Gu

Research output: Contribution to conferencePaper

10 Scopus Citations

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 greater than or equal to 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.
Original languageAmerican English
Number of pages13
DOIs
StatePublished - 2017
EventSPIE Optical Engineering + Applications 2017 - San Diego, California
Duration: 6 Aug 201710 Aug 2017

Conference

ConferenceSPIE Optical Engineering + Applications 2017
CitySan Diego, California
Period6/08/1710/08/17

NREL Publication Number

  • NREL/CP-5J00-68229

Keywords

  • backsheet
  • degradation
  • failure analysis
  • photovoltaic module
  • polyamide
  • polyethylene naphthalate
  • polyethylene terephthalate
  • polymeric materials
  • reliability

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