Storage for Community Electricity: A Comparison Between Batteries and Mini Pumped Hydro

Abstract

For electrification of rural communities that are remote from the grid distribution network, renewable energy-based mini-grids are a cost-effective option. These can be based on solar PV, wind or biogas/biofuels. In some cases, a hybrid system using a combination of different technologies makes sense in order to achieve a better match between supply and demand. However, the predominance of evening lighting loads means that energy storage is also required. For large-scale grid storage, pumped hydro is the most cost-effective option, but at smaller scale, this technology is not competitive with batteries. This investigation set out to find the crossover size at which batteries and pumped storage have similar overall costs, when used for off-grid communities.

The paper employs case studies where mini pumped storage would be an option, and compares the cost-effectiveness relative to batteries. Detailed costs were calculated for pumped hydro installations of different capacities, and compared with battery costs (for both lead-acid and lithium-ion technologies) using HOMER software. Energy losses in comparable systems were also taken into account in the evaluation. Depending on various factors, pumped storage appears to be competitive for off-grid community storage above around 200 kWh. Nevertheless, the likely reduction in lithium-ion battery costs mean that in the future, battery storage could be competitive with pumped storage at larger sizes.