Field Retrieved Photovoltaic Backsheet Survey from Diverse Climate Zones: Analysis of Degradation Patterns and Phenomena

Raymond Wieser, Yu Wang, Andrew Fairbrother, Sophie Napoli, Adam Hauser, Scott Julien, Xiaohong Gu, Gregory O'Brien, Kai-Tak Wan, Liang Ji, Michael Kempe, Kenneth Boyce, Laura Bruckman

Research output: Contribution to journalArticlepeer-review

3 Scopus Citations

Abstract

Understanding the impact of climate stressors on photovoltaic (PV) backsheet degradation in real-use conditions is critical to improve the accelerated testing exposures, extend the backsheet lifetime, and increase the confidence in PV reliability. In this work, a total of 33 PV module backsheets were retrieved from six climatic zones worldwide with 2 - 28 years of exposure. These modules included five types of backsheet air-side materials (or outer layer): poly(vinylidene fluoride) (PVDF), poly(tetrafluoroethylene-co-hexafluoropropylene-co-vinylidene fluoride) (THV), poly(vinyl fluoride) (PVF), poly(ethylene terephthalate) (PET), and polyamide (PA). Attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) was used to identify air-side materials. The degradation induced color change, gloss loss, and chemical material changes analyzed using optical microscopy, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), colorimetry (yellowness index (YI)), and gloss measurements. PVDF, THV, and PVF air-side layer backsheets, in particular PVF, had minimal degradation in the air-side layer appearance and chemical structures after exposure in different climatic zones. The PET air-side backsheets exhibited obvious color increase (22.55 YI units after about 9 years exposure) and the PA/PA/PA backsheets showed large gloss loss (up to 76.4 %) relative to the unexposed backsheets. Severe cracks between cells that penetrated through the entire thickness of backsheets are observed on PA/PA/PA backsheets after 4-6 years of exposure in 6 climatic zones. The current indoor exposure standards were not sufficient to identify this degradation type. However, fluoropolymer based PV backsheets showed lower levels of degradation predictors and increased climatic resistance. Specific samples (PVF) showed little change from baseline after 28 years of outdoor exposure.

Original languageAmerican English
Pages (from-to)49-62
Number of pages14
JournalSolar Energy
Volume259
DOIs
StatePublished - 2023

Bibliographical note

Publisher Copyright:
© 2023 International Solar Energy Society

NREL Publication Number

  • NREL/JA-5K00-83714

Keywords

  • Anisotropic degradation
  • Backsheet cracking
  • Backsheet degradation
  • Climatic zones
  • Field exposures
  • Outdoor exposure
  • Photovoltaic module

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