Optimized planning of isolated renewable energy systems for rural electrification in Uganda

Abstract

Though there is a high potential for electricity generation in Uganda, 80% of the population cannot afford the costs of grid connection or the other forms of energy. Research has also shown that most of the cost in both standalone and mini-grid systems include the capital costs; with PV-panels and batteries contributing to approximately 60% of a typical mini-grid budget. This research therefore focuses on an optimization-based approach to minimize the overall installed generation required of a mini-grid, hence minimizing the associated capital expenditure. This will ultimately provide an insight into the technical and economic viability of mini grids for rural electrification. HOMER software was used to determine the optimal system for the provision of electricity to Nakasengere community at the least cost. Input information included: village demand, renewable resources, component technical details, costs, and constraints. Different configurations and technologies were also considered in this analysis namely, Solar Home Systems, Mini grid, and Grid extension. The network was also modeled in DigSILENT software to assess the amount of losses in the distribution. From the simulation results, it was observed that the system simulated at 5% capacity shortage is the most technical and economical feasible system. This system consists of a 95.4 kWp monocrystalline PV array with 19 parallel strings of 2 V 515 Ah lead acid battery bank and a 25 kW genset) The total annual electric production of this system obtained is 189,706 kWh/yr that meets the load satisfactorily with a Cost of Energy (COE) of 0.339$/kWh. If only priority loads are connected to ensure a system reduction of 40% then a 100% renewable energy system can be implemented with a COE of 0.283$/kWh. The system when further modeled in DIgSILENT also produced an optimal power flow with minimal losses. Conclusively, the research found that the optimal (least cost) solution to electrifying off-grid areas is firstly dependent on the abundance of renewable energy sources in an area, i.e., the greater the renewable energy resources, the more economically feasible the system becomes. Priority should be given to productive use applications as this will boost the customers’ income and enable them to afford the tariff and connection fees sustainably. The distance from the grid is also key; For Nakasengere, a distance less than 7.6 km makes grid extension more economical. Solar Home Systems also become technically and economically viable when the population is scattered and not very economically productive.