Degradation of photovoltaic module backsheet materials in desert climate
Amir Abdallah, Mohamed Abdelrahim, Mohamed Elgaili, Mujaheed Pasha, Kamal H. Mroué, A. Abutaha
Abstract
To improve the Photovoltaic (PV) module design for desert climates, it is important to understand the typical failure mechanism observed and the main cause of failure. This paper reports on PV backsheet degradation in desert climates. Field inspections reveal that backsheet degradation was found to be one of the most frequent PV system failures observed at the Outdoor Test Facility (OTF) in addition to hotspots, snail trails, and encapsulant yellowing. Degradation of two different polyamide (PA) and two different polyethylene terephthalate (PET) backsheets were investigated in real outdoor testing conditions. The observation of material changes due to degradation was studied using scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. Backsheet crack initiation, propagation, and chalking were monitored. We found that the embrittlement of the PA-based and PET-backsheet materials is caused by a combination of prolonged exposure to high ultraviolet (UV) radiation, high operating temperature cycling, and relative humidity resulting in cracking of the top UV-blocker layer and subsequent chemical and physical degradation of the underlying layers. The PET-2 showed only chalking powder with no backsheet cracking, which indicates an early stage of backsheet degradation. The green spot observed on the PA backsheet was found to be antlerite (greenish hydrous copper sulfate mineral Cu 3 (SO 4 ) (OH) 4 ) resulting from the reaction of the chalking and the solar cell interconnections. • This paper analyzes two polyamide and two polyethylene terephthalate backsheets degradation of PV modules installed in desert climates. • PA and PET-1 showed crack initiation, propagation, chalking, and delamination, but PET-2 exhibited chalking without cracks. • Analysis of PA-1 chalking powder via XRD revealed evidence of partial decomposition, indicating core layer degradation. • The chalking powder collected from the degraded PA-1 backsheet was found to be antlerite resulting from the reaction of the chalking and the interconnections.