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Title: Multi angle laser light scattering evaluation of field exposed thermoplastic photovoltaic encapsulant materials

As creep of polymeric materials is potentially a safety concern for photovoltaic modules, the potential for module creep has become a significant topic of discussion in the development of IEC 61730 and IEC 61215. To investigate the possibility of creep, modules were constructed, using several thermoplastic encapsulant materials, into thin-film mock modules and deployed in Mesa, Arizona. The materials examined included poly(ethylene)-co-vinyl acetate (EVA, including formulations both cross-linked and with no curing agent), polyethylene/polyoctene copolymer (PO), poly(dimethylsiloxane) (PDMS), polyvinyl butyral (PVB), and thermoplastic polyurethane (TPU). The absence of creep in this experiment is attributable to several factors of which the most notable one was the unexpected cross-linking of an EVA formulation without a cross-linking agent. It was also found that some materials experienced both chain scission and cross-linking reactions, sometimes with a significant dependence on location within a module. The TPU and EVA samples were found to degrade with cross-linking reactions dominating over chain scission. In contrast, the PO materials degraded with chain scission dominating over cross-linking reactions. Furthermore, we found no significant indications that viscous creep is likely to occur in fielded modules capable of passing the qualification tests, we note that one should consider how a polymer degrades,more » chain scission or cross-linking, in assessing the suitability of a thermoplastic polymer in terrestrial photovoltaic applications.« less
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [2] ;  [2] ;  [3] ;  [3] ;  [4] ;  [4] ;  [4] ;  [4] ;  [5]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  2. DuPont Company, Wilmington, DE (United States)
  3. Arizona State Univ., Mesa, AZ (United States)
  4. National Institute of Advanced Industrial Science and Technology, Ibaraki (Japan)
  5. Underwriter Lab., San Jose, CA (United States)
Publication Date:
OSTI Identifier:
1234272
Report Number(s):
NREL/JA-5J00-64515
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: 4; Journal Issue: 1; 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; adhesives; creep; EVA encapsulant; polymer; qualification standards; thermoplastic