Screening of mine shafts for future energy technologies: a case study from the Scottish coalfields

Abandoned mine shafts could be retrofitted for future energy technologies. We provide a high-level assessment of the potential for recorded mine shafts in the Scottish coalfields to be utilized for seven future technologies: geothermal heat extraction, thermal energy storage for waste heat and curtailed wind energy, gravity storage, underground pumped storage, compressed air energy storage, and CO2 loop power generation. Screening is based on depth, volume and geographical criteria using GIS data from the Mining Remediation Authority. The theoretical resource was estimated for the 6298 shafts that had information on depth and diameter. Heat extraction and thermal energy storage have potential capacities of 45 and 33 GWh, respectively. Nearly 10 GWh of surplus electricity could be stored as heat in 288 mine shafts within 1 km of a primary substation. The capacities of potential energy storage technologies were considerably lower. We apply the concept of reserve and resource commonly used in extractive industries to illustrate the theoretical resource. However many of these shafts may be inaccessible, have incurred damage that renders them unusable, or require significant engineering intervention. If this resource is to be realized as reserves, future work should focus on identifying and testing safe technological solutions.