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Title: Differential degradation patterns of photovoltaic backsheets at the array level

There are relatively few field studies on the degradation of non-fluoropolymer-based backsheets, and understanding their in-field behavior is critical for further development of such products. In this paper, backsheet degradation of modules with one of these new types of backsheets (polyethylene naphthalate (PEN)-based) was documented at a four-year old utility-scale array located in Maryland (USA). Visual inspection, colorimetry, glossimetry, and Fourier-transform infrared spectroscopy (FTIR) revealed highly varied properties depending on module position within the array. Specifically, modules near the edge of the array and with higher mounting elevations underwent greater amounts of backsheet degradation, as indicated by yellowing and gloss-loss. The reason for these unique degradation patterns were differential backside exposure conditions, especially of ultraviolet light. This was strongly influenced by the array design, including array structural and environmental factors, such as module spacing and ground cover, respectively. Within the array, no clear link between backsheet degradation and module output or safety has been identified. However, such a relationship may be expected to become more pronounced with time, affecting system lifetime and ultimately the levelized cost of electricity (LCOE). Finally, the observed phenomena have implications for both backsheet product development and array design, especially for modules that utilize newer classesmore » of non-fluoropolymer-based backsheets which are typically more susceptible to environmental degradation.« less
ORCiD logo [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [3] ;  [1] ;  [2] ;  [1]
  1. National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States). Engineering Lab.
  2. Case Western Reserve Univ., Cleveland, OH (United States). SDLE Research Center. Materials Science & Engineering
  3. National Renewable Energy Lab. (NREL), Golden, CO (United States)
Publication Date:
Report Number(s):
Journal ID: ISSN 0038-092X; PII: S0038092X18300938
Grant/Contract Number:
EE0007143; AC36-08GO28308
Accepted Manuscript
Journal Name:
Solar Energy
Additional Journal Information:
Journal Volume: 163; Journal ID: ISSN 0038-092X
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States); National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Solar Energy Technologies Office (EE-4S); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Solar Energy Technologies Office (EE-4S), SunShot Initiative
Country of Publication:
United States
14 SOLAR ENERGY; photovoltaic array; field survey; reliability; backsheet degradation; exposure conditions; polyethylene naphthalate; 36 MATERIALS SCIENCE
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1423800