Evaluating the Impact of Edge-Seal on the Performance of Double-Glass Solar Photovoltaic Modules

Solar energy is a vital component of the renewable energy landscape. Nevertheless, photovoltaic (PV) modules face numerous challenges during operation due to environmental stress factors, which can lead to various degradation issues such as delamination, encapsulant discoloration, corrosion of cell metallization, and potential-induced degradation. Ethylene-vinyl acetate (EVA), despite being a prominent encapsulant material, is notably vulnerable to moisture. Upon degradation, EVA releases acetic acid, severely impacting the long-term performance of PV modules. This study investigates the effectiveness of using a polyisobutylene-based edge-seal to minimize moisture ingress in double-glass modules. One-cell mini-modules encapsulated with EVA, with and without edge-seal, are subjected to damp heat testing (85°C / 85% RH) for up to 5000 hours and their performance are evaluated though current-voltage characteristics. Mini-modules without edge-seal exhibit a significant 70% loss in power, primarily due to a 37% decrease in short-circuit current, a 56% decrease in fill factor, and a staggering 650% increase in series resistance. However, mini-modules with edge-seal see only a 33% loss in power, driven mainly by a 21% decrease in fill factor and a 76% increase in series resistance. The use of edge-seal does not completely prevent but effectively reduces moisture ingress and mitigates its detrimental effects on module performance. Additionally, the Network Structural Equation Modeling approach is applied to analyze current-voltage characteristics, enabling the identification of statistically significant relationships, the construction of degradation pathway diagrams, and the determination of key factors contributing to power degradation. This analysis reveals increased series resistance and reduced fill factor as primary causes of power degradation for both mini-module configurations. Although the encapsulant materials exhibit minimal degradation in optical, chemical, and thermo-chemical properties, the presence of moisture within the module construction can still cause corrosion of cell metallization. This results in a decline in power performance even without substantial acetic acid formation. This study highlights the critical importance of preventing moisture ingress to enhance the durability and reliability of PV modules, ensuring their optimal performance throughout their intended service lifetime.