Long-term photovoltaic (PV) module reliability is highly determined by the durability of the polymeric components (backsheet and encapsulation materials). This paper presents the result of experiments on encapsulant degradation influenced by the backsheet permeation properties. Towards this goal, one type of ethylene/vinyl acetate copolymer (EVA) was aged in glass/EVA/backsheet laminates in accelerated aging tests (up to 4000 h for Damp-Heat (DH) and up to 480 kWh/m² for UV and UV-DH combined). The samples contained three backsheets with different permeation properties to examine their impact on EVA degradation. Thermal and chemical characterization shows that the EVA degradation is stronger with the glass–EVA–polyamide (PA)-based backsheet than with the polyethylene terephthalate (PET)-based backsheets. The higher oxygen transmission rate (OTR) of the PA-based backsheet may increase photo-oxidation and aggravating the degradation of EVA in the laminates. Furthermore, FTIR results were used to demonstrate the effect of damp heat exposure on the EVA interfaces, showing an accelerated degradation at the glass–EVA interface. The comparison of accelerated aging stress factors reveals that EVA suffers the strongest chemical and optical degradation when high UV, high temperature and high relative humidity are combined simultaneously.

The encapsulant browning degradation mode of photovoltaic (PV) modules is affected by ultraviolet irradiance, ambient temperature, and humidity of the installation site. In this article, the degradation rate for encapsulant browning, measured by short-circuit current degradation, is estimated for different PV module tilt and orientation angles in the Algiers region, characterized by a temperate climate. The activation energy for encapsulant browning is calculated using the acceleration factor modeling of the field-to-field degradation and physical models, in conjunction with the meteorological data of two locations in Algeria, where the same module type is fielded for 9–10 years. The tradeoff between the PV energy production and the PV module lifetime is carried out for different PV module positioning, assuming that encapsulant browning is the main failure mechanism experienced in the field. The results reveal that the orientation angle affects the PV module lifetime, where orienting the PV module from east to west increases the lifetime up to 30%, and the lifetime energy production up to 6%, due to reduced degradation. It is also presumed that although the Saharan region of Adrar receives more UV light and ambient temperatures throughout the year in Algeria, the PV modules fielded in the Mediterranean region of Algiers suffer higher degradation, which isexplained by the high humidity experienced in Algiers that accelerates the encapsulant browning failure mechanism.

The power degradation and failure of photovoltaic (PV) modules can be caused by changes in the mechanical properties of the polymeric components during the module lifetime. This paper introduces instrumented nanoindentation as a method to investigate the mechanical properties of module materials such as polymeric encapsulants. To this end, nanoindentation tests were carried out on ethylene vinyl acetate (EVA) surfaces, which have been separated from the glass panel. Two types of time-dependent indentation cycle modes, the time domain (creep mode) and frequency domain (dynamic mode) were performed to determine the viscoelastic behavior. For each mode, a corresponding model was applied to calculate the main mechanical properties. The general capability of nanoindentation as cross-linking determination method is investigated with the methodological advantages over bulk mechanical characterization methods. A large number of Glass/EVA/Backsheet laminates were built using different lamination conditions resulting in different degrees of curing. Both indentation modes indicate good modulus sensitivity for following the EVA crosslinking in its early stages but could not reliably differentiate between samples with higher EVA branching. Additional dynamic mechanical analysis (DMA) characterization was used as an established method to validate the indentation measurements. Both nanoindentation and DMA tensile mode produce similar quantitative viscoelastic responses, in the form of the damping factor parameter, demonstrated for three different frequencies at room temperature. A statistical study of the data reveals the advantages for the investigation of multilayer PV laminates by using nanoindenation as a surface method while also being applicable to field aged modules.