Geothermal Well at Cornwall site due to complete in early 2025

The UK’s first geothermal power plant in due to complete in early 2025 in Cornwall, UK. The United Downs Geothermal Power Plant has been developed by GEL and will output power to the National Grid. The deep geothermal system utilises a fractured granite batholith via two directional wells (a 5,275m production well and 2,393m injection well) which intersect the Porthtowan Fault Zone. Bottom hole temperatures of 180°C have been identified. 

Part of the PUSH-IT project includes a study testing the feasibility for installation of mine thermal energy storage technologies in abandoned metalliferous mines adjacent to the United Downs plant. Future development at United Downs and other geothermal sites across Cornwall may provide opportunity for use of excess or recaptured heat from the power plant. Thermal energy storage projects have the potential to manage seasonal mismatches in heat supply/demand. 

cornwall building site UK United Down Geothermal Well
Figure 1: Photograph of an engine house forming part of the mine network adjacent to the United Downs Power Plant, alongside the drilling rig used to drill the geothermal wells.

The site targeted for such a development is the Great Consolidated Mines, an amalgamation of several 19th century copper and tin mines, in which several mineral lodes in the Mylor Slate Formation were worked. Workings extended to 475 m depth. The mines are intersected by the Great County Adit which outflows into the Carnon River. At depth, the mine workings are largely flooded. 

Cornwall has a long history of mining, dating back to the Bronze age, with the last mine closing in 1998. There is a strong relationship between local communities the historic industry. Whilst efforts are underway to reopen a number of mines in the county, mine water geothermal and mine thermal energy storage projects provide a unique opportunity to re-purpose abandoned mine workings to bring benefits to local communities and reduce reliance on fossil fuels used in space heating. 

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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