Exergy International and Geothermal Engineering (GEL), the UK’s leading developer and operator of geothermal plants, have signed a contract for the supply of an organic Rankine cycle (ORC) power plant at the United Downs site in Cornwall.
The agreement represents the first integrated deep geothermal project in the UK. It aims to deliver around 3 MWe of baseload renewable electricity and up to 10 MWth of zero-carbon heat for a large housing development at Langarth Garden Village, a project being developed by Cornwall Council.
The turnkey EPC contract awarded to Exergy 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 a highly efficient radial outflow turbine to produce electricity by 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 won’t release any vapour into the atmosphere and will have a small footprint and minimal visual impact. The system will be delivered in 18 months, with commissioning of the plant expected by late 2024. Once in operation, the installation is expected save more than 6,500 tonnes of carbon dioxide emissions per year, compared to the production of conventional fossil fuel power.
‘We are excited to embark on this journey with GEL,’ said Luca Pozzoni, general manager of Exergy International. ‘The United Downs project will be a milestone in the development of the geothermal industry in the UK and will give us the valuable opportunity to contribute with our technology and expertise to kick-starting geothermal power generation in the country. Under a structured long-term agreement with GEL, we will be able to partner for the development of future geothermal initiatives to unlock Europe’s largely untapped geothermal potential and support the decarbonisation of our energy systems.’
‘Geothermal heat is an untapped renewable resource with the potential to provide huge amounts of energy-efficient and carbon-free electricity and heat,’ said Ryan Law, CEO of Geothermal Engineering. ‘Exergy is well known globally for their competence in the binary geothermal power sector and we are very pleased to be working with them on this landmark project in Cornwall. Our long-term agreement with Exergy will also enable us to develop a number of additional projects both in the UK and abroad.’
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 the two companies.
The geothermal site, located near Redruth in Cornwall, utilises the naturally heat-producing granite that underlies most of Cornwall. Two deep, directional wells have successfully been drilled for the purpose; the production well to a measured depth of 5,275 metres – the deepest onshore well in the UK – and the injection well to 2,393 metres. 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. This process means that geothermal energy produces clean, green power with no waste product.
An ORC or binary power plant consists of a closed-loop cycle that extracts the heat of the geothermal fluid coming from the production well and uses heat exchangers to transfer it to an organic fluid. The organic fluid is first heated in the preheater and then vaporised, absorbing the heat from the geothermal fluid. After being superheated, the vaporised fluid drives a turbine coupled to a generator to optimise the production of electricity. The vapour exhaust returns to liquid state through a condenser, thereby retaining the organic fluid within the closed-loop system.