Improving the reliability of Rwanda's electricity grid with solar PV micro-grids and battery energy storage support

Abstract

The importance and need for energy in the modern world continue to increase daily. This increase in energy demand goes with the necessity of its reliability and continuity of its supply. However, increasing energy use from conventional sources raises environmental and global warming issues. To mitigate the traditional energy sources’ negative impacts, environment-friendly renewable energy sources (RES) have been promoted and used due to their environmental benefits and availability. Energy harvesting from RESs plays an essential role toward energy sustainability. To achieve the continuity of energy supply, given the intermittent nature of RES, Energy Storage Systems (ESS) such as Battery Energy Storage Systems (BESS) must be integrated with RESs. Furthermore, integrating RES into power systems has the capability to upgrade the system's reliability. In many developing countries, including small residential areas, the inadequacy of distribution networks often leads to frequent interruptions in grid-supplied electrical energy. This situation significantly impacts the life quality and productivity of the local population. However, this challenge can be addressed by introducing RESs and BESS in the distribution network to ensure a reliable and energy supply continuity. Particularly in Rwanda, for radial distribution network, the reliability improvement in electricity supply requires rectifications of power system infrastructure, including transmission, distribution system, and an increase in energy generation capacity. To assess the influence of RES on Rwanda's electricity grid reliability, solar photovoltaic (PV) systems with BESS are integrated into Gatumba and Ntongwe feeders. The results from conducted studies showed that the potential of solar energy can achieve a level of self-sufficiency of up to 64.38% and a performance ratio of up to 86.65%. To enhance the grid's reliability at the feeders integrated with solar PV system and BESS, protection switches are configured to allow the load demand to be supplied by PV system and BESS when the grid is unavailable thereby supplying the energy demand and reducing interruption frequency and duration. Simulation results from DigSILENT and PV*SOL simulation tools showed that by integrating solar PV systems with BESS to Gatumaba and Ntongwe feeders, the system reliability ameliorates by 71.6% and 95.5% for system average interruption frequency and duration, respectively