Abstract
Scientific innovation and relevance: Humidity is a crucial factor for the degradation of PV modules. It has been linked to various degradation modes. The consequences range between minor power losses in the best cases, and severe yield losses and safety issues in the worst cases. Thus, it is important to predict the amount of water ingress in fielded modules with different encapsulants. Simulations in literature are commonly based on Fickian diffusion in a homogeneous material with one diffusion coefficient. However, it has been shown that the model fails to accurately describe the measured ingress curves. Water uptake shortly after a change in the humidity outside is underestimated, whereas it is overestimated at later times. It is concluded, that two main mechanisms drive the diffusion, one faster and one slower than Fickian diffusion in a homogeneous material.