Complementary Optimization of Hydropower with Pumped Hydro Storage-Photovoltaic Plant for All-Day Peak Electricity Demand in Malawi

Solar energy is currently dispatched ahead of other renewable energy sources. For the first time, this study presents a concept of exploiting temporary-periodical runoff discharge in the Shire River. Pumped hydro storage-photovoltaic plant (PHS-PV) was optimized to satisfy the all-day peak electricity demand in Malawi. The effect of varying the net head on the PHS system in both the generation and pumping operation modes was investigated. The bi-objective optimization evaluated the system reliability for day-time and night-time operation together with implied costs of investment for the whole system. The optimized system generated above 53% of added power as contrasted to single-source power generation from the existing hydropower plants. The estimated optimal capacities were 182 MWp (solar PV) and 86 MW (PHS plant). These additional optimal capacities achieved a 99.8% maximum system reliability (Loss of Power Supply Probability-LPSP-of 0.2%) and Levelized Cost of Energy-LCOE-of 0.13 USD/kWh. The overall investment cost of the PHS-PV system was estimated at 671.23 USD for an LPSP of 0.20%. The net head varies from 15.5 to 17.8 m with an impact on electricity generation of the PHS-PV system. More notably, the PHS-PV production matches with daily day-time and night-time peak loads and functions as a peaking plant.