United Downs (United Kingdom)

Follower site for Mine Thermal Energy Storage (MTES).

The Mine Thermal Energy Storage follower site is located at United Downs, Cornwall where the UK’s first geothermal electricity plant is being developed. The MTES feasibility study at United Downs aims to evaluate the use of nearby United Mines to store excess heat from the geothermal power plant. United Mines comprises a mapped network of 130 kilometres of shafts and adits (passage to an underground mine), which are relics of 19th century tin and copper mining. The MTES project at United Downs is led by Geothermal Engineering Ltd. We aim to do the following:

  • Store residual heat from the deep geothermal power plant under development close by.
  • Manage the seasonal mismatch in the heat supply and demand.
  • Ensure continuity of heat supply during geothermal well maintenance downtime.
Photograph of an engine house forming part of the United Mines network, with the United Downs drilling rig in the background.

Project details

  • Location: United Downs, Cornwall
  • Energy infrastructure:
    • A deep geothermal power plant that will generate electricity is currently under development. Residual heat from this plant will be fed into a district heating system.
  • MTES heat source:
    • Heat from the deep geothermal power plant currently under development.
  • Objectives of the demo site:
    • Characterise the site’s physical properties, in particular its hydrogeology and thermal conductivity.
    • Explore how the local community may react to the development.
    • Identify and document the regulatory issues that may be encountered in using metalliferous mine workings for heat storage and determine requirements for viable heat storage.
  • Status:
    • The concept of a United Downs MTES facility is currently undergoing a feasibility study.


In the MTES feasibility study, integration with the planned geothermal power plant and district heating system at Geothermal Engineering Ltd.’s United Downs geothermal site. Any mine workings surrounding future geothermal projects could be considered as heat storage for integration into any heat supply system, to improve efficiency and better meet varying energy demands. Cornwall’s mining heritage and the public perception that exists around the reopening and reuse of historic mines will be an important aspect of the project.

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PUSH-IT is a project funded by the European Union’s Horizon Europe research and innovation programme under grant agreement No 101096566.
Funded by the European Union. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union. Neither the European Union nor the granting authority can be held responsible for them.

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