The role of EVA encapsulation in the degradation of wafer based PV modules

This paper investigates the effects of ethylene vinyl acetate (EVA) encapsulation on PV module ageing and how crosslinking degree of encapsulation influences module durability under damp-heat (DH) and thermal cycle (TC) stresses. Results show that the high crosslinking samples favoured TC stresses, while the low crosslinking samples performed better under DH stresses. The primary mechanism of DH-induced degradation is series resistance (RS) increase and parallel resistance (RP) decrease due to moisture ingress and grid/contact corrosion. Comparison analysis of the result indicates that the lower cross-linked EVA appeared to be able to accommodate a smaller amount of the generated acetic acid and thus resulted in a lower corrosion rate. The primary effect of TC is to impose thermal expansion/compression on device. The EVA with lower crosslinking degree is less compact and the freedom of motion of EVA macromolecules is higher, which appeared to be less resistant to the effect of expansion/compression