Increased reliability of modified polyolefin backsheet over commonly used polyester backsheets for crystalline PV modules

Abstract

The weathering stability of polymeric backsheets is very important for the reliability of photovoltaic (PV) modules. In addition to reliability, cost reduction and sustainability are upcoming challenges the PV backsheet industry is facing with. The most commonly used material for PV backsheets is poly(ethylene-terephthalate)-PET. However, PET is in general very sensitive to hydrolysis, which leads to chain scission and causes embrittlement, cracking, delamination, and dimensional instability of the backsheet. Compared to that newly developed modified polyolefin backsheets have favorable selective permeation properties and high mechanical flexibility, which could be key properties for backsheets in terms of higher PV module reliability. In this work, the weathering stability of PET/fluoropolymer backsheet and an alternative coextruded polyolefin-backsheet was investigated in terms of thermal and mechanical stability. Both materials were artificially aged and the changes caused by aging were investigated. The polyester-based backsheet showed embrittlement and reduced elongation at break for 70%. The polyolefin-based backsheet retained its mechanical flexibility even after 2000 h of aging under damp-heat conditions, with no significant physical or chemical aging processes occurring. The comparison of the results of both backsheets suggests that the polyolefin backsheet is a promising candidate for the reduction of cracks and delamination in the field.

Analysis of polyamide and fluoropolymer backsheets: Degradation and insulation failure in field‐aged photovoltaic modules

“…However, its use in the PV industry has proved that polyamide‐based backsheets have poor weatherability, mainly due to UV degradation. For this reason, some innovations are already appearing such as polyamide‐ionomer alloys 12 or even new approaches as the use of polyolefins like polypropylene 13 . However, while these products are being introduced in the market, polyamides have already been used massively in previous years and are present in PV plants that should last for around 25 years.…”

“…For this reason, some innovations are already appearing such as polyamide-ionomer alloys 12 or even new approaches as the use of polyolefins like polypropylene. 13 However, while these products are being introduced in the market, polyamides have already been used massively in previous years and are present in PV plants that should last for around 25 years. Thus, the understanding of the degradation modes of polyamides is still of high interest in order to have an early identification of this problem.…”

Peeling of Flexible Laminates—Determination of Interlayer Adhesion of Backsheet Laminates Used for Photovoltaic Modules

“…These range from fluoropolymer-based or fluoropolymer-free backsheets, to laminates, co-extruded films, monolayer and coated monolayer films. The primary materials used are PET, polyamide (PA), polyethylene (PE), and polypropylene (PP) as core layers and PET, PE, PA, and PP as inner or outer layers [8][9][10].…”

“…An additional problem that was reported was the fracture of the peel arm before delamination started [5]. and polypropylene (PP) as core layers and PET, PE, PA, and PP as inner or outer layers [8][9][10]. Delamination of one or more layers is one of the most critical failure modes of a PV module during its service lifetime [11][12][13], so its root causes have been investigated thoroughly [5,[14][15][16].…”

Repair options for PV modules with cracked backsheets

“…Several variations of backsheet compositions are available on the market, mainly laminated multilayer stacks and coextruded foils. 1,2 When looking at the reliability of glass/backsheet modules, it was noted that the most frequent backsheet failures are cracking, delamination, and yellowing. [3][4][5][6][7][8][9]…”