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

Abstract

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 study, 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). The observed phenomena have implications for both backsheet product development and array design, especially for modules that utilize newer classes ofmore » non-fluoropolymer-based backsheets which are typically more susceptible to environmental degradation.« less

Authors:
 [1];  [1];  [1];  [1];  [1];  [2];  [3];  [1];  [2];  [1]
  1. National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States)
  2. Case Western Reserve Univ., Cleveland, OH (United States)
  3. National Renewable Energy Lab. (NREL), Golden, CO (United States)
Publication Date:
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), SunShot Initiative; USDOE Office of Energy Efficiency and Renewable Energy (EERE), Solar Energy Technologies Office (EE-4S)
OSTI Identifier:
1424906
Alternate Identifier(s):
OSTI ID: 1423800
Report Number(s):
NREL/JA-5J00-71051
Journal ID: ISSN 0038-092X
Grant/Contract Number:  
AC36-08GO28308; EE0007143
Resource Type:
Accepted Manuscript
Journal Name:
Solar Energy
Additional Journal Information:
Journal Volume: 163; Journal Issue: C; Journal ID: ISSN 0038-092X
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; photovoltaic array; field survey; reliability; backsheet degradation; exposure conditions; polyethylene naphthalate

Citation Formats

Fairbrother, Andrew, Boyd, Matthew, Lyu, Yadong, Avenet, Julien, Illich, Peter, Wang, Yu, Kempe, Michael, Dougherty, Brian, Bruckman, Laura, and Gu, Xiaohong. Differential degradation patterns of photovoltaic backsheets at the array level. United States: N. p., 2018. Web. doi:10.1016/j.solener.2018.01.072.
Fairbrother, Andrew, Boyd, Matthew, Lyu, Yadong, Avenet, Julien, Illich, Peter, Wang, Yu, Kempe, Michael, Dougherty, Brian, Bruckman, Laura, & Gu, Xiaohong. Differential degradation patterns of photovoltaic backsheets at the array level. United States. doi:10.1016/j.solener.2018.01.072.
Fairbrother, Andrew, Boyd, Matthew, Lyu, Yadong, Avenet, Julien, Illich, Peter, Wang, Yu, Kempe, Michael, Dougherty, Brian, Bruckman, Laura, and Gu, Xiaohong. Sun . "Differential degradation patterns of photovoltaic backsheets at the array level". United States. doi:10.1016/j.solener.2018.01.072. https://www.osti.gov/servlets/purl/1424906.
@article{osti_1424906,
title = {Differential degradation patterns of photovoltaic backsheets at the array level},
author = {Fairbrother, Andrew and Boyd, Matthew and Lyu, Yadong and Avenet, Julien and Illich, Peter and Wang, Yu and Kempe, Michael and Dougherty, Brian and Bruckman, Laura and Gu, Xiaohong},
abstractNote = {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 study, 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). The observed phenomena have implications for both backsheet product development and array design, especially for modules that utilize newer classes of non-fluoropolymer-based backsheets which are typically more susceptible to environmental degradation.},
doi = {10.1016/j.solener.2018.01.072},
journal = {Solar Energy},
number = C,
volume = 163,
place = {United States},
year = {2018},
month = {2}
}

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Figures / Tables:

Figure 1 Figure 1: Layout of the NIST ground-mounted PV array (Google Maps, 2016) (a), and orientation of the modules within the array, including nomenclature labels utilized in this work (shed-row-column) (b). “RTD” in (a) marks the approximate location of modules where backside temperature was recorded, and red boxes show the locationsmore » of the bio-retention areas (refer to the online color version). Insets for (b) show the ground cover at the array, including grass and coarse rock.« less

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