TY - GEN
T1 - A field evaluation of the potential for creep in thermoplastic encapsulant materials
AU - Kempe, Michael D.
AU - Miller, David C.
AU - Wohlgemuth, John H.
AU - Kurtz, Sarah R.
AU - Moseley, John M.
AU - Shah, Qurat
AU - Tamizhmani, Govindasamy
AU - Sakurai, Keiichiro
AU - Inoue, Masanao
AU - Doi, Takuya
AU - Masuda, Atsushi
AU - Samuels, Sam L.
AU - Vanderpan, Crystal E.
PY - 2012
Y1 - 2012
N2 - There has been recent interest in the use of thermoplastic encapsulant materials in photovoltaic modules to replace chemically crosslinked materials, e.g., ethylene-vinyl acetate. The related motivations include the desire to: reduce lamination time or temperature; use less moisture-permeable materials; use materials with better corrosion characteristics or with improved electrical resistance. However, the use of any thermoplastic material in a high-temperature environment raises safety and performance concerns, as the standardized tests currently do not expose the modules to temperatures in excess of 85°C, though fielded modules may experience temperatures above 100°C. Here 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 designed to chemically crosslink. One module set was exposed outdoors with insulation on the back side in Arizona in the summer, and an identical set was exposed in environmental chambers. High precision creep measurements (±20 μm) and performance measurements indicate that despite many of these polymeric materials being in the melt state during outdoor deployment, very little creep was seen because of their high viscosity, temperature heterogeneity across the modules, and the formation of chemical crosslinks in many of the encapsulants as they aged. In the case of the crystalline silicon modules, the physical restraint of the backsheet reduced the creep further.
AB - There has been recent interest in the use of thermoplastic encapsulant materials in photovoltaic modules to replace chemically crosslinked materials, e.g., ethylene-vinyl acetate. The related motivations include the desire to: reduce lamination time or temperature; use less moisture-permeable materials; use materials with better corrosion characteristics or with improved electrical resistance. However, the use of any thermoplastic material in a high-temperature environment raises safety and performance concerns, as the standardized tests currently do not expose the modules to temperatures in excess of 85°C, though fielded modules may experience temperatures above 100°C. Here 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 designed to chemically crosslink. One module set was exposed outdoors with insulation on the back side in Arizona in the summer, and an identical set was exposed in environmental chambers. High precision creep measurements (±20 μm) and performance measurements indicate that despite many of these polymeric materials being in the melt state during outdoor deployment, very little creep was seen because of their high viscosity, temperature heterogeneity across the modules, and the formation of chemical crosslinks in many of the encapsulants as they aged. In the case of the crystalline silicon modules, the physical restraint of the backsheet reduced the creep further.
KW - Creep
KW - Encapsulant
KW - Polymer
KW - Qualification Standards
KW - Thermoplastic
UR - http://www.scopus.com/inward/record.url?scp=84869411024&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84869411024&partnerID=8YFLogxK
U2 - 10.1109/PVSC.2012.6317958
DO - 10.1109/PVSC.2012.6317958
M3 - Conference contribution
AN - SCOPUS:84869411024
SN - 9781467300643
T3 - Conference Record of the IEEE Photovoltaic Specialists Conference
SP - 1871
EP - 1876
BT - Program - 38th IEEE Photovoltaic Specialists Conference, PVSC 2012
T2 - 38th IEEE Photovoltaic Specialists Conference, PVSC 2012
Y2 - 3 June 2012 through 8 June 2012
ER -