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 and Consolidated Mines to store excess heat from the geothermal power plant.  The MTES project at United Downs is led by Geothermal Engineering Ltd (GEL). GEL aim to explore the feasibility of storing residual heat from a deep geothermal power plant to aid management of the seasonal mismatch in the heat supply and demand and 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 being constructed at Geothermal Engineering’s United Downs site, which is due for commissioning in early 2025. Currently, GEL are exploring the possibility for the use of residual heat in a district heating system in Cornwall.
  • MTES heat source:
    • Heat from the deep geothermal power plant once commissioned.
  • Objectives of the demo site:
    • Characterise the site’s physical properties, in particular its hydrogeology and thermal conductivity.
    • Engage with local communities, providing information on the PUSH-IT project and potential future MTES projects.
    • 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.
    • Engage with relevant stakeholders.
  • Status:
    • Archive work has been undertaken to obtain maps of mine workings local to the United Downs project.
    • Early sampling of mine waters and United Downs geothermal fluids have been conducted. Further sampling and analysis has been scheduled.
    • A subsurface model of target mine workings is in development which will provide a basis for computational modelling.
    • An initial review of regulatory processes and initial discussions with relevant stakeholders have taken place.


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.

Take a look:

Would you like to know what an abandoned mineshaft looks like from the inside? Chris Rochelle (British Geological Survey / Geothermal Engineering Ltd) and his team made the following video at the Consolidated Mines site in United Downs:

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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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