The United Downs Deep Geothermal Project is the first geothermal electricity project in the UK. It is located in Cornwall, at the United Downs Industrial Estate, near Redruth and is being developed by Geothermal Engineering Ltd. It is part funded by the European Regional Development Fund. The project has targetted a permeable geological structure called the Porthtowan Fault Zone, which lies approximately 800m to the southwest of the drilling site. Two two deep wells have been drilled at the site; one for production of hot water at a depth of 5,275m, which is the deepest onshore well in the UK and one for re-injection of this water at a depth of 2,393m. The temperature at the bottom of the production (deep) well is expected to be about 195˚C.
Water will be pumped from the production well, fed through a heat exchanger and then re-injected into the ground to pick up more heat from the granite in a continuous cycle. The extracted heat will be used to supply a standard, geothermal turbine at the surface to generate heat and power. The project aims to deliver power to the grid at the end of 2021.