Performance Assessment of 8.5 MW Grid Connected Solar PV Plant in Butwal, Nepal

Abstract

The rising energy demand in Nepal has prompted the matter of energy security. Further, to maintain the energy mix it is essential to use alternative renewable resources. Grid connected megawatt scale PV systems possibly are the best alternatives. The Butwal solar project is the leading large Solar PV project built and operated by an independent power producer in Nepal. The growth of investment in such a large grid connected solar project will ultimately depend on its performance. Hence the designed system and performance parameters are needed to be properly analyzed and studied so that it provides some guidelines for upcoming future installations. The performance analysis of an 8.5 MW grid connected PV power plant installed at Butwal, Nepal is worked out. By analyzing the plant’s first-year operational performance, it is found that final yield, reference yield, Capacity Utilization Ratio (CUF) and Performance Ratio (PR) vary from 2.33 to 3.80 kWh/kWp-day, 3.87 to 6.20 kWh/kWp-day, 9.7 to 15.8% and 54 to 77% respectively. The annual average final yield, CUF and PR are found to be 1140.4 kWh/kWp, 13%, 64.2% in close agreement with PVSYST estimated outcomes of 1372 kWh/kWp, 15% and 72% respectively. The performance of the plant is compared with PV systems installed in various parts of the world and found comparable. Financial analysis shows that plant discounted payback period is 16.3 years with the proper return of NRs. 58.88 million in its useful life. The LCOE is found to be 6.7 NRs/kWh. Carbon emission balance analysis shows that 952 tCO2 emissions are replaced in a plant’s useful life. The power flow from this plant impacts the injected 33 kV substation causing a substantial drop in power factor and a slight voltage dip in that 33 kV substation. The findings give insight into the solar power plant's long-term performance in Nepal’s Terai area under real working circumstances. The need for regular maintenance against array capture loss, making the grid more reliable and the use of MPP having a large voltage range in the inverter is highlighted to maximize energy generation and export to the grid. Additional, supplement research studies are also recommended.