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Title: Field Testing of Thermoplastic Encapsulants in High-Temperature Installations

Recently there has been increased interest in using thermoplastic encapsulant materials in photovoltaic modules, but concerns have been raised about whether these would be mechanically stable at high temperatures in the field. This has become a significant topic of discussion in the development of IEC 61730 and IEC 61215. We constructed eight pairs of crystalline-silicon modules and eight pairs of glass/encapsulation/glass thin-film mock modules using different encapsulant materials, of which only two were formulated to chemically crosslink. One module set was exposed outdoors with thermal insulation on the back side in Mesa, Arizona, in the summer (hot-dry), and an identical module set was exposed in environmental chambers. High-precision creep measurements (±20 μm) and electrical performance measurements indicate that despite many of these polymeric materials operating in the melt or rubbery state during outdoor deployment, no significant creep was seen because of their high viscosity, lower operating temperature at the edges, and/or the formation of chemical crosslinks in many of the encapsulants with age despite the absence of a crosslinking agent. Only an ethylene-vinyl acetate (EVA) encapsulant formulated without a peroxide crosslinking agent crept significantly. When the crystalline-silicon modules, the physical restraint of the backsheet reduced creep further and was notmore » detectable even for the EVA without peroxide. Because of the propensity of some polymeric materials to crosslink as they age, typical thermoplastic encapsulants would be unlikely to result in creep in the vast majority of installations.« less
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [2] ;  [3] ;  [4] ;  [4] ;  [4] ;  [5] ;  [6]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  2. Arizona State Univ., Mesa, AZ (United States)
  3. National Renewable Energy Lab. (NREL), Golden, CO (United States); National Inst. of Advanced Industrial Science and Technology (AIST), Tsukuba (Japan)
  4. National Inst. of Advanced Industrial Science and Technology (AIST), Tosu (Japan)
  5. DuPont Company, Wilmington, DE (United States)
  6. Underwriters Lab., San Jose, CA (United States)
Publication Date:
Report Number(s):
NREL/JA-5J00-62417
Journal ID: ISSN 2050-0505
Grant/Contract Number:
AC36-08GO28308; AC36-08-GO28308
Type:
Published Article
Journal Name:
Energy Science & Engineering
Additional Journal Information:
Journal Volume: 3; Journal Issue: 6; Related Information: Energy Science and Engineering; Journal ID: ISSN 2050-0505
Publisher:
Society of Chemical Industry, Wiley
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Solar Energy Technologies Office (EE-4S)
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; Encapsulant; Adhesives; Creep; Thermoplastic; Qualification Standards; Polymer
OSTI Identifier:
1233866
Alternate Identifier(s):
OSTI ID: 1233684; OSTI ID: 1233867