Title: A non-destructive method for crack quantification in photovoltaic backsheets under accelerated and real-world exposures

Abstract

The long-term durability of photovoltaic modules is paramount for the continued growth of the industry. Polymer backsheets are of particular concern since they provide electrical insulation and an environmental barrier. In this paper, 23 freestanding, multilayer backsheets with nine unique material combinations underwent four different weathering exposures under accelerated and real-world conditions. Besides changes in color and gloss, the induced degradation included parallel or mudflat cracks on 11 backsheets, sometimes in combination with delamination or blistering. Similar degradation has been observed in previous studies and is concerning since cracks compromise the mechanical integrity and electrical safety of backsheets. Quantitative parameters are desirable to reliably classify categories of cracks and supply unbiased features for statistical analysis in predictive lifetime models. We developed an analysis technique that utilizes surface profilometry data to quantify the depth, width, area, spacing, and number of cracks. Parameters are automatically extracted from the raw data by an algorithm running on a high performance distributed computing cluster. Our algorithm excelled at characterizing parallel cracks with minimal de-adhesion, and only an estimated 4% of crack detections were false positives. The addition of humidity and temperature variation formed up to three times as many cracks on a photodose basis comparedmore » to dry, constant temperature exposures. Cracks in real-world and accelerated exposures propagated to similar depths with equivalent photodoses; however, the number of cracks formed in accelerated exposures was far greater on a photodose basis. Of samples that cracked, the best performing backsheet configuration was polyvinyl fluoride/poly (ethylene-terephthalate)/polyethylene (PVF/PET/PE) while the least durable was PET/PET/ethylene-vinyl acetate. Finally, none of the six PVF/PET/PVF backsheets cracked in any of the exposures.« less

Authors:

Klinke, Addison G.  ^[1];

• Search DOE PAGES for author "Klinke, Addison G."
• Search DOE PAGES for ORCID "0000-0002-6985-7657"

Gok, Abdulkerim  ^[2];

• Search DOE PAGES for author "Gok, Abdulkerim"
• Search DOE PAGES for ORCID "0000-0003-3433-7106"

Ifeanyi, Silas I. ^[1]; Bruckman, Laura S.  ^[3]

• Search DOE PAGES for author "Bruckman, Laura S."
• Search DOE PAGES for ORCID "0000-0003-1271-1072"

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+ Show Author Affiliations

1. Case Western Reserve Univ., Cleveland, OH (United States). SDLE Research Center. Dept. of Materials Science and Engineering. Dept. of Mechanical and Aerospace Engineering
2. Case Western Reserve Univ., Cleveland, OH (United States). SDLE Research Center. Dept. of Materials Science and Engineering; Gebze Technical Univ. (Turkey). Dept. of Materials Science and Engineering
3. Case Western Reserve Univ., Cleveland, OH (United States). SDLE Research Center. Dept. of Materials Science and Engineering

Publication Date:

Tue May 08 00:00:00 EDT 2018

Research Org.:

Underwriters Lab LLC, Northbrook, IL (United States); Case Western Reserve Univ., Cleveland, OH (United States)

Sponsoring Org.:

USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office

OSTI Identifier:

1501895

Alternate Identifier(s):

OSTI ID: 1437110; OSTI ID: 1599243

Grant/Contract Number:  

EE0007143

Resource Type:

Accepted Manuscript

Journal Name:

Polymer Degradation and Stability

Additional Journal Information:

Journal Volume: 153; Journal Issue: C; Journal ID: ISSN 0141-3910

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

14 SOLAR ENERGY; photovoltaic; backsheet; cracking; data science; predictive lifetime models; degradation science