Analytical Modeling of Diffusion of Moisture in Silicon Photovoltaic Module under Damp Heat Testing Condition

• DOI: 10.1007/s12633-021-01156-7
• Publication Date: 2021-07-15T14:02:41Z
• Authors: Shikha Marwaha; Kunal Ghosh
• Keywords: 02 engineering and technology; 0210 nano-technology; 7. Clean energy

The moisture ingression into photovoltaic module has significant impact on the reliability as it participates in multiple degradation pathways. Damp heat test is performed at a temperature 85°C and relative humidity of 85% for 1000 h to assess the ability of a photovoltaic module under humid conditions. In this paper, we have developed an analytical model to quantify the amount of moisture ingressing into a photovoltaic module with a breathable backsheet under damp heat testing condition. The analytical model is developed with the consideration that the vertical moisture diffusion in the ethylene vinyl acetate (EVA) layer is instantaneous. The comparison with numerical model validated the assumption. The analysis of the simulated profile with the developed analytical model showed that at 85°C, the moisture profile within the rear EVA and backsheet reaches a steady state value within 10 h. Considering that the damp heat test is performed for a span of 1000 h, to simplify we can consider that the moisture profile is temporally and spatially constant in the backsheet and rear EVA, with the moisture concentration being given by the product of moisture solubility (S) and permeability (P) for that particular material at 85°C. However, the moisture profile for top EVA in regions above the solar cell does not reach a steady state value even within a span of 1000 h. The non-uniformity of the moisture profile needs consideration for quantifying the degradation in the regions of top EVA that is directly above the solar cell.