Weathering and durability of PV backsheets and impact on PV module performance

Abstract

Polymeric backsheets form the outer protective layer of most crystalline and multi-crystalline silicon cell photovoltaic panels. The mechanical, electrical, optical and chemical properties and durability of these backsheets are critical to the long term reliability, durability and safety of the photovoltaic modules. The stability of these backsheet properties is typically determined based on accelerated testing using individual stresses. However, the impact of multiple stresses applied sequentially or simultaneously can lead to changes in materials properties that are more predictive of performance in the field. An important consideration in the development of accelerated test protocols is the level and duration of the stress, including temperature variation, light intensity & spectral power distribution, humidity, rainfall and powered module current. In this paper, we discuss observations of the aging and degradation of solar panel from the field. Then how these changes correlate to accelerated testing results, and how accelerated tests can be modified to better match observations in the field.

Depth profiling of degradation of multilayer photovoltaic backsheets after accelerated laboratory weathering: Cross-sectional Raman imaging

“…Polymeric packaging materials are important to the safety, performance, durability, and reliability of photovoltaic (PV) modulesduring field operation. The backsheet, the outermost packaging material on the back side of a PV module that directly adheres to encapsulant, is the first line of back side defense against environmental aging in the field [1,2]. In general, the backsheet is a polymeric multilayer laminate system engineered so that each layer can address multiple purposes such as weatherability, insulation, adhesion promotion, and light reflection.…”

“…Polyethylene terephthalate (PET) is often used as an insulation layer (usually core layer of the backsheet) because of its low cost, low electrical conductivity and high mechanical strength [1][2][3]. Moreover, to block ultra-violet (UV) from the back side and redirect reflected sunlight from the front side of a PV module, white inorganic pigments, such as titanium dioxide (TiO 2 ) and barium sulfate (BaSO 4 ), are widely used in backsheet layers to modify opacity and reflectivity of polymeric layers [2].…”

Optical properties of PV backsheets: key indicators of module performance and durability

“…The failures have included failure directly attributable to backsheet performance such as backsheet cracking and delamination, as well as other failure mechanisms that may be related to backsheet performance and durability. To better understand the performance of backsheets in the service environment, we have evaluated PV panels in a variety of climates and have shared results from several studies in previous papers [3,4]. We have also used analytical methods to better understand the mechanisms of panel failures and the role different materials play.…”

Chemical depth profiling of photovoltaic backsheets after accelerated laboratory weathering

“…Practical in-field testing results show that significant backsheet failures such as cracking, yellowing and delamination occurred in even less than five-year service. 2,[5][6] For this reason, more in-depth understanding and investigation on polymeric multilayer backsheet degradation are needed.…”

“…1 Backsheet, the outermost packaging material on the back side of a PV module that directly adheres to encapsulant, is the first line of back side defense against environmental aging in the field. 2 Backsheet is a polymeric multilayer laminate system engineered so that each layer has a different purpose such as weatherability, insulation, adhesion promotion, and light reflection. Fluoropolymers are commonly used as the outer-most weather resistance layer of backsheets due to their remarkable chemical and thermal stability, and polyethylene terephthalate (PET) is often used as an insulation layer (usually core layer of backsheet) because of its low cost, low conductivity and high mechanical strength.…”