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Companies sign contract for UK’s first deep geothermal power plant

21 July 2023

Exergy International and Geothermal Engineering Ltd. (GEL) have signed a contract for the supply of a 3 MWe of energy at the United Downs site, in Cornwall. This represents the first integrated deep geothermal project in the UK which will begin delivering energy by late 2024.

Image: Exergy International
Image: Exergy International

The turnkey engineering, procurement, and construction (EPC) contract awarded to Exergy, which specialises in Organic Rankine Cycle (ORC) systems, will include the design and engineering of the ORC system, the manufacturing of the equipment and the erection of the power plant.

Exergy’s technology will utilise the Radial Outflow Turbine to produce electricity exploiting the heat of the geothermal fluid. The condensing system chosen is air-cooled to avoid any water consumption. Being a closed loop cycle, the power plant will not release any vapour into the atmosphere and will have a small footprint and minimal visual impact, Exergy said in a statement.

The system will be delivered in 18 months, with commissioning of the plant expected by late 2024. Once in operation, this installation will save more than 6,500 tonnes of CO2 emissions per year compared to the production of conventional fossil fuel power, Exergy said.

The United Downs power plant is expected to be the first of many projects to be developed under a partnership and cooperation agreement signed between Exergy and GEL. The geothermal site, located near Redruth in Cornwall, utilises the naturally heat producing granite which underlies most of Cornwall. Two deep, directional wells have successfully been drilled for the purpose; the production well to a measured depth of 5,275m – the deepest onshore well in the UK – and the injection well to 2,393m. The naturally-heated geothermal fluid will be pumped to the surface, passed through the power plant to produce electricity, then returned underground via the injection well where it will percolate through the granite to reheat.

An ORC or binary power plant consists of a closed loop cycle which extracts the heat of the geothermal fluid coming from the production well, transferring it by means of heat exchangers to an organic fluid. The organic fluid is first heated in the preheater and then vapourised, absorbing the heat from the geothermal fluid. After being superheated, the vaporized fluid drives a turbine coupled to a generator to optimize the production of electricity. The vapour exhaust returns to liquid state through a condenser, thereby retaining the organic fluid within the closed loop system.

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