United Downs Geothermal

Executive Overview

United Downs is the UK's first deep geothermal power plant, brought online on February 26, 2026 by Geothermal Engineering Ltd (GEL) at the United Downs Industrial Site near Redruth in Cornwall. The £50 million project drilled the deepest onshore wells in UK history — a production well to 5,275 metres and an injection well to 2,393 metres — accessing the Porthtowan Fault Zone in the Cornubian granite at temperatures of approximately 190°C. The plant generates 3 MW of gross electricity using an Organic Rankine Cycle turbine supplied by Exergy International, and simultaneously commenced commercial-scale lithium carbonate production at 100 tonnes per year from brine concentrations of 340 parts per million — the first co-located geothermal power and lithium extraction facility in the UK. Octopus Energy has signed a long-term PPA to purchase the full 3 MW output, sufficient to supply approximately 10,000 homes. The project holds a Contracts for Difference award at a strike price of £119/MWh (2012 prices, equivalent to ~£164 in 2023 prices) under Allocation Round 5, the first CfD ever granted to a UK geothermal project. GEL has planning permission for two additional Cornwall sites — Manhay and Penhallow — each targeting approximately 4.9 MW gross, with a combined 2030 target of approximately 20 MW geothermal capacity and 23,000 tonnes per year of lithium carbonate equivalent.

How It Works & Differentiation

Geothermal fluid at approximately 190°C is pumped from the production well at up to 60 litres per second using an electrical submersible pump at 1,400 metres depth. The hot brine passes through the ORC system — a radial outflow turbine — transferring heat to a secondary working fluid that drives electricity generation, before being reinjected via the shallower well. Heat flow at United Downs is approximately 120 mW/m², roughly double the UK average, and the geothermal gradient of 33–35°C/km makes the Cornubian granite one of the best-suited onshore geothermal resources in Europe. The lithium extraction process runs co-currently: after the ORC heat exchange, brine is processed to recover battery-grade lithium carbonate before reinjection in a fully closed loop. The system produces 24/7 baseload renewable electricity with an estimated carbon footprint of 5–15g CO₂ per kWh — genuinely firm power that solar and wind cannot replicate at this scale.

Commercialization & Traction

The project is the first operational deep geothermal plant in the UK and the first commercial-scale geothermal lithium carbonate producer in the country. GEL plans to scale lithium production to 18,000 tonnes per year over the next decade — approximately 65% of UK battery electric vehicle registrations in 2024 — positioning United Downs as both a power asset and a domestic critical minerals platform. The Automotive Transformation Fund supported the demonstration lithium extraction plant. Funding for the power project came from the European Regional Development Fund, Cornwall Council, Thrive Renewables, and Kerogen Capital. The UK's 2027 Rules of Origin requirements for domestic lithium content in electric vehicles provide additional commercial relevance for lithium production beyond the electricity sector. The UK government appointed its first dedicated geothermal minister in late 2025, signalling strengthening policy support.

Scalability & Strategic Context

United Downs demonstrates that Cornwall's granite can support commercially viable deep geothermal power, the key proof point for GEL's pipeline of Manhay, Penhallow, and further sites. GEL's 2030 target of 20 MWe and 23,000 tpa of lithium carbonate equivalent makes it not simply a power project but the UK's first integrated geothermal energy and critical minerals platform. The British Geological Survey estimates over 200 GW of onshore geothermal potential across the UK, with Cornwall the most developed resource area. The integrated power-and-lithium model, the CfD revenue certainty, and the Octopus Energy PPA give the project a multi-revenue structure that most early geothermal projects lack — a potentially important template for financing subsequent UK geothermal developments.