Quantification of solar inverter efficiency for Indian tropical climatic conditions

Project developers rely on the peak efficiency specified by inverter manufacturers to estimate the generation capacity of solar PV power plants. However, the varying nature of the DC input power to the inverters, caused due to varying irradiation, leads to deviations of the actual efficiency from the peak efficiency. Two weighted average efficiencies, namely the Euro efficiency and California Energy Commission (CEC) efficiency address this issue by weighting the major DC input power levels that the inverter is likely to operate in with respect to the amount of time in a year that the inverter resides in a particular operating level. Since the Euro efficiency and the CEC efficiency are location specific to Trier, Germany and Sacramento, California respectively, they would not yield accurate estimations of the inverter efficiency when used in other locations. The weighted average inverter efficiency will need to be formulated taking location specific irradiation profiles into account in order to arrive at a more reliable figure that can be used to estimate the annual generation capacity of solar PV power plants. This paper brings out the shortcomings of the Euro efficiency and discusses an approach to estimate the weighted average efficiency of inverters for tropical climatic conditions in India.