Moisture ingress in photovoltaic modules: A review

Moisture ingress in photovoltaic (PV) modules is the core of most degradation mechanisms that lead to PV module power degradation. Moisture in EVA encapsulant can lead to metal grids corrosion, delamination and discolouration of encapsulants, potential induced degradation, optical and adhesion losses. The present work is a review of literature on the causes, effects, detection, and mitigation techniques of moisture ingress in PV modules. Literature highlights on determining the diffusivity, solubility, and permeability of polymeric components of PV modules via water vapour transmission rate tests, gravimetric, and immersion methods, have been presented. Electroluminescence, photoluminescence, and ultraviolet fluorescence spectroscopy, as well as dark lock-in thermography are some techniques used to detect moisture ingress in modules. Encapsulants with excellent moisture barrier and adhesion characteristics, desiccant-stacked polyisobutylene sealants, imbedded moisture sensors, and PV designs with/without breathable backsheets are ways of preventing/detecting moisture ingression in PV modules. Areas of focus for future research activities have also been discussed.