Storing energy in disused underground mine voids: comparing pumped water- and compressed air-based technologies

Abstract

Large scale energy storage is becoming ever more important for balancing loads due to increased intermittent electric energy supply from wind and solar power plants. This paper explores how abandoned mine voids can be utilised for this purpose comparing the technological and economical suitability of two different technologies: underground pumped hydro energy storage (UPHES) and compressed air energy storage (CAES). By integrating these technologies into post-closure development concepts mine voids can be prevented from becoming environmental liabilities thereby averting costs associated with the indefinite pumping and treating of polluted water emanating from flooded mines. Apart from differing in construction costs, profitability, energy storage capabilities and grid-related flexibility each technology also requires different geological conditions that are to be considered when selecting the best suited one for a specific mine.