Modelling moisture ingress and impact on PV module degradation

Development of a FEM model to predict the moisture ingress and module degradation under different conditions

Master thesis (2023)

Authors

D. Jimenez Pelarda Electrical Engineering, Mathematics and Computer Science

Contributors

M.R. Vogt Photovoltaic Materials and Devices - EEMCS (supervisor 1)
Y. Blom Photovoltaic Materials and Devices - EEMCS (supervisor 1)
Faculty
Electrical Engineering, Mathematics and Computer Science
Copyright: © 2023 Daniel Jimenez Pelarda
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Published Date

28-08-2023

Language

English

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Faculty

Electrical Engineering, Mathematics and Computer Science

Abstract

A moisture ingress model is developed using the FEM software COMSOL. The model uses Fick’s second law of diffusion to model the diffusion of moisture in the module. The model also reflects the temperature dependent nature of parameters affecting moisture ingress by using an Arrhenius equation. The model is validated with experimental and simulated data from literature showing a good agreement. A brief comparison with alternative models such as analytical models and a simplified numerical model is also made. The model allows to simulate the moisture ingress into different PV modules in different conditions. The moisture ingress in 11 different locations with different climatic conditions is simulated. The moisture ingress is also simulated using 4 different encapsulants and 4 different backsheets. Finally, the model is adapted to simulate the moisture ingress into impermeable backsheet modules.\

These results are used to find a relation between ambient conditions and the results delivered by the COMSOL model. A simplified relationship is found that holds for the different climates and encapsulants. It is found that the effective relative humidity in the environment is the key parameter in determining the amount of water that will be in the module once it reaches equilibrium. The time that it takes for a module to reach its moisture equilibrium content is determined by the temperature. The presence of these simplified relations can help in estimating the moisture ingress behaviour of a model without the need of carrying out a full FEM simulation. However, the dynamics of the system when using different backsheets does not follow the same simplified relations.\

The degradation caused by water in the module is also studied. An analytical model is used to predict the degradation observed during damp heat tests. Due to the properties of the analytical model a different approach has to be followed for real life conditions. The degradation model is used to compare the expected degradation under different conditions. This shows that the expected degradation is larger in hot and humid climates while it is minimized in colder climates. The general degradation trend observed for the different climates is: Tropical > Arid > Temperate > Continental > Polar.