The theoretical potential for large-scale underground thermal energy storage (UTES) within the UK

Large scale storage of heat is critical for the successful decarbonisation of the UK’s energy mix and for grid-balancing. Heat generation currently accounts for 50% of all energy use in the UK and most of this is produced by burning fossil natural gas. Heat is regarded as a single-use commodity, discarded or dissipated when not required in summer yet a lifesaving necessity during the colder winter months. Here we estimate the theoretical potential capacities for the storage of heat in the subsurface using aquifers and flooded mines, with a consideration of seasonal storage of heat in particular. We set this against the theoretical potential volumes of waste heat and solar thermal energy that could be exploited. This contributes to the wider knowledge base of the capacity of different forms of energy storage available through other means and highlights the potential for the UK. Our calculations indicate that the theoretical potential for large-scale underground thermal-energy storage in the UK is substantial, much larger than which might ever be needed and the location of such storage is well matched to the places where people live and work and therefore where the demand for heat occurs.