Measuring and simulation of water vapour permeation into PV modules under different climatic conditions

This paper is dealing with measuring the water ingress to PV-modules under different climatic conditions and simulating it over an expected lifetime of 20 years. Furthermore different kinds of back sheet / encapsulant combinations were considered. For this purpose an own developed high sensitive test device composed of a climate cabinet and a mass spectrometer was used to investigate the temperature dependent permeation and diffusion processes that takes place in the polymers. Furthermore the results - permeation and diffusion coefficient - were used to simulate the mass transport through the back sheet and inside the encapsulant materials. In a second part the amount of absorbed water was analysed by a gravimetric method. For this study encapsulant materials were exposed to different ambient climates to quantify the sorption isotherme. With these results - permeation / diffusion coefficient and absorbed water amount - the mass transport and water concentration were simulated over the lifetime of a PV-module under different climatic conditions. Additional the influence of various tight back sheets on water ingress will be shown.