Performance assessment of PV modules after long field exposure in north eastern of Thailand

The weather of Thailand is generally known as humid topical and seasonal rain by monsoon. In early twenty first century for installing photovoltaic system in the northeast of Thailand, the cumulative wattage of photovoltaic (PV) water pumping units in rural areas was close to 1 MWp, and the PV battery charging system was also nearly 0.2 MWp. However, an assessment of performance parameters has not been wide investigated for carrying out the deterioration of PV modules under long-term field exposure in northeastern Thailand. Fortunately, there were 39 used single-crystalline silicon PV modules over ten years from the northeast of Thailand that have been collected at Clean Energy Systems Group (CES), King Mongkut´s University of Technology Thonburi (KMUTT). Consequently, this paper focuses on the assessment of PV module performance parameters after degradation from real operating in the field. Dielectric encapsulations are diagnosed by visual inspection and electrical performance parameters of PV modules are measured at standard test condition by an indoor flash simulator. The diagnosis on physical deterioration in front of PV modules can be characterized into 7 categories. The results of I-V characteristics and performance parameters of the deterioration modules compose of initial performance degradation up to the worst-case degradation condition. Moreover, these results of I-V characteristics are directly correlated with the physical degradation such as browning and delaminating in front of the modules. We also found that, different browning and delaminating patterns in front of the modules may result in a decrease of both I-V characteristic shape and performance parameter.