Field performance and degradation rates of different types of photovoltaic modules: A case study in Thailand

This paper provides field performance and degradation information of Si wafer-based and thin film photovoltaic (PV) modules in a tropical region. We address the importance of temperature coefficient (TC) and the significance of the degradation rate (DR) of the modules operating under tropical climate. The PV modules with TC for power below −0.31%/°C have a great advantage in terms of energy yield. The DRs of various PV module types are widely different, ranging from 0.5 to 4.9%/year, which greatly affect their long-term performance. This paper also presents the degradation behavior of electrical characteristics such as I-V curve, open circuit voltage (Voc), short circuit current (Isc), fill factor (FF) and maximum power output (Pmax) for each PV type. The DRs of the field-test PV modules in Thailand are first reported in this study. The level of degradation we found in this study suggests a reduction of output power 10-50% over a twenty-five year lifetime, possibly increasing the levelized cost of electricity by up to double cost. The database of this case study is informative and useful for a further study on performance degradation in the tropics and a comparison study with other environmental conditions.