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Commissioning and Early Operation of the United Downs Geothermal Power Plant and Lithium Extraction Facility, Cornwall, UK
Ryan LAW, Thomas OLVER, Poppy EDGECOMBE, Amy PEACH-GIBSON
[Geothermal Engineering Ltd., United Kingdom]
Throughout 2025, construction and commissioning of the United Downs Geothermal Power Plant and demonstration-scale lithium extraction facility was completed. Both projects have been developed from conception by Geothermal Engineering Ltd (GEL). The power plant is the UK’s first geothermal power development and outputs generated electricity to the UK National Grid. The project is an important case study for the development of geothermal power and critical minerals projects both in Cornwall, and across the country. Learnings from the commissioning process and early operation of the plant will be utilised in the development of similar projects across Cornwall. The United Downs geothermal project accesses natural geothermal waters via a geothermal doublet drilled into a fractured granite reservoir. A 5,275 m production well and a 2,393 m injection well were directionally drilled into a subvertical fault zone to access hot ( greater than 180 °C) geothermal waters for power production. Well testing demonstrated an inherent permeability within the reservoir at depth, associated with targeted NNW-SSE aligned faulting, as well as the ability for low-pressure hydraulic stimulation to enhance reservoir properties. Furthermore, well testing enabled the first geochemical analysis of deep geothermal waters in Cornwall. The results of well testing were utilised in the design of the binary cycle ORC plant. The analysis of the geothermal waters has highlighted lithium concentrations greater than 300 ppm. In conjunction with power plant development, since 2021 GEL has completed a number of projects culminating in the design, construction and commissioning of a 100 tonne-per-annum lithium extraction facility. The facility includes a direct lithium extraction plant, which utilises adsorption to remove lithium from the treated geothermal water, and has capability to produce a high-grade lithium carbonate product. Learnings from this demonstration plant are informing the scale-up to commercial extraction of lithium at United Downs and have enabled the early assessment of feasibility of extraction of additional critical minerals.
Topic: General