Performance Assessment of PV mini-grids for effective replacement of diesel based mini-grids at selected sites in Ethiopia
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Date
2023-09
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Addis Ababa University
Abstract
This study highlights the necessity of transforming diesel generator-only mini-grids into solar mini-grids due to their limited run time, high cost, and environmental impact. To achieve this, it is important to evaluate the operational performance of other nearby solar mini-grids in the same geographical area before designing and replacing the diesel generator-only mini-grid with a solar mini-grid at a specific location. The findings of the evaluation can help determine the operational performance of the newly designed solar mini-grid. Out of the 12-pilot solar mini-grids in Ethiopia, two were selected as benchmarks for designing and replacing the diesel-only mini-grid in Dolo Odo town with a solar, battery, and diesel generator hybrid mini-grid. Omorate town solar mini grid, which exhibited good performance, and Qorile town solar mini grid, which exhibited poor performance, are chosen for evaluation. Homer Pro software is used for optimizing the PV system, while PVsyst software is used for evaluating the performance of the PV system. The results indicate that Omorate system experienced 1027.7 kWh/day unutilized solar potential and had an average yearly PV efficiency of 10.28%, while the Qorile system had unutilized solar potential of 1405.8 kWh/day and average six months PV efficiency of 4.32%. Additionally, total system losses in the Qorile system were found to contribute to 6.84 kWh/kWp/day, which is much higher than the corresponding value of 2.9 kWh/kWp/day in Omorate system. Therefore, the performance analysis of both solar mini-grids showed that they are operating with poor performance, indicating that they are not meeting the expected energy output levels. From the benchmarking, it was found that determining and forecasting the energy requirement and sizing the PV system while considering all derating factors for the system equipment’s is necessary for efficient and optimal performance. The first optimized system for the Dolo Odo hybrid solar mini-grid system consists of a 2 MW PV module, an 8.06 MW battery pack, 2 MW grid inverter, 1.05 MW power conditioning system, and 0.6 MW diesel generator. This system provides 91% of the electricity demand from solar and Battery and the remaining from the diesel generator. The proposed hybrid mini-grid system not only uses less fuel and emits less CO2 than the base system but also has a lower levelized cost of energy of 0.211 USD/kWh and a reasonable net present cost of 16.5 million USD.
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Keywords
Solar mini-grid, diesel-only-mini-grid, HOMER Pro, PV syst, performance analysis, Ethiopia.