Holistic performance appraisal of a photovoltaic system

During this research, performance of a 2.45 kWp PV system was evaluated over a period of 5 years. International electrotechnical committee (IEC) standard, IEC 61724: 1998 and a robust mathematical model were used as a guide for the purpose. Performance of the system was closely monitored during the dry winter season. Annual production decreased from 3463.8 kWh to 3370.9 kWh and the capacity utilisation factor decreased from 16.14% to 15.71% over the period. Monthly production was stochastic, but the average monthly production curve followed the same trend as incident global horizontal radiation with low production during dry winter months. Performance ratio was above 90% at the beginning of dry winter month, it then decreased to less than 70% after three months. A mathematical model based on five parameter model and one diode equation was then used to extract essential cell parameters and simulate performance of the system. Statistical indices were computed to assess performance of the model against measurement data. Hence the quality factor of the PV system was computed and was found to be between 60% and 100% with an average of 87% in the dry winter month.