Gravity energy storage with suspended weights for abandoned mine shafts

This paper investigates the potential of using gravity energy storage with suspended weights as a new technology for redeveloping abandoned deep mine shafts. The technology has relatively low energy density, but has advantages including a power capacity decoupled from its energy capacity, no cycle-limit and the potential to be combined with compressed air energy storage. It is currently being trialled in the United Kingdom, targeting abandoned coal mines. The paper presents analysis for sizing the suspended weight to maximize the energy storage capacity, given a mine shaft's physical dimensions. In addition, it is shown that the power capacity of the system's motor and power electronics determine the maximum ramp-rate, and therefore the range of power system services that can be provided. A case study is presented, estimating the total energy storage capacity which could be obtained by converting abandoned mines in the United Kingdom Midlands, using geographic information system data from the United Kingdom Government Coal Authority Abandoned Mine Catalogue.