UK’s first geothermal plant opens in Cornwall

AFTER more than a decade of development, Geothermal Engineering Limited (GEL) has opened its United Downs power plant near Redruth, making it the UK’s first operational geothermal electricity facility.

The £50m (US$68m) proof-of-concept project uses a closed-loop system that pumps hot brine from granite reservoirs deep underground to generate electricity before reinjecting the cooled fluid back into the formation. The site will also extract lithium from the brine, combining renewable power generation with critical minerals production.

United Downs is expected to generate 3 MW of constant, weather-independent electricity – enough to power around 10,000 homes – and produce approximately 100 t/y of lithium carbonate equivalent (LCE).

Two wells

At the heart of the project are two deep wells: a 5.2 km production well and a 2.5 km injection well, drilled over seven months. Brine heated to around 190°C is brought to the surface to drive a turbine before undergoing direct lithium extraction (DLE). The remaining fluid is then reinjected underground, with no net loss.

Electricity from the plant will be supplied to customers of Octopus Energy, which has agreed to take the full output.

GEL has calculated that the geothermal brines contain more than 340 ppm of battery-grade lithium carbonate equivalent and says production could eventually scale to 18,000 t/y.

Geothermal potential

Geothermal is gaining attention in the UK energy mix, with research from the British Geological Survey suggesting that onshore geothermal resources could produce 200 GW of thermal energy hot enough to generate electricity.

Alison Monaghan, head of geothermal at BGS, said the UK already supports widespread shallow geothermal systems, including tens of thousands of ground source heat installations and mine water heating schemes.

“Globally, engineered geothermal systems (EGS) such as United Downs have generated commercial scale electricity for tens of years,” she said.”The technology is renewable and low carbon.”

GEL is developing two further deep geothermal sites in Cornwall, which it expects could add 10 MW of baseload capacity by 2030.