*Article* **Salt Cavern Exergy Storage Capacity Potential of UK Massively Bedded Halites, Using Compressed Air Energy Storage (CAES)**

**David Evans 1,\* , Daniel Parkes <sup>1</sup> , Mark Dooner <sup>2</sup> , Paul Williamson <sup>1</sup> , John Williams <sup>1</sup> , Jonathan Busby <sup>1</sup> , Wei He <sup>2</sup> , Jihong Wang <sup>2</sup> and Seamus Garvey <sup>3</sup>**


**Featured Application: The work provides important data and information relating to future energy storage options and in particular the role CAES might play in load balancing and the integration of renewable energy technologies into electricity grids.**

**Abstract:** The increasing integration of large-scale electricity generation from renewable energy sources in the grid requires support through cheap, reliable, and accessible bulk energy storage technologies, delivering large amounts of electricity both quickly and over extended periods. Compressed air energy storage (CAES) represents such a storage option, with three commercial facilities using salt caverns for storage operational in Germany, the US, and Canada, with CAES now being actively considered in many countries. Massively bedded halite deposits exist in the UK and already host, or are considered for, solution-mined underground gas storage (UGS) caverns. We have assessed those with proven UGS potential for CAES purposes, using a tool developed during the EPSRC-funded IMAGES project, equations for which were validated using operational data from the Huntorf CAES plant. From a calculated total theoretical 'static' (one-fill) storage capacity exceeding that of UK electricity demand of ≈300 TWh in 2018, filtering of results suggests a minimum of several tens of TWh exergy storage in salt caverns, which when co-located with renewable energy sources, or connected to the grid for off-peak electricity, offers significant storage contributions to support the UK electricity grid and decarbonisation efforts.

**Keywords:** energy storage; exergy; CAES; salt caverns
