3 June 2009 – Plans for a GBP15m ($25m) geothermal power plant have been unveiled by the UK’s Eden Project near St Austell, Cornwall, and geothermal experts EGS Energy.
The developers expect the plant, the UK’s first power generating geothermal project, will produce up to 3 MW – enough to power nearly 5000 homes. The pilot plant will be created near the Eden Project’s vast greenhouses near St Austell.
Engineers will first drill two boreholes around 2.5 miles into the granite that lies underneath much of Cornwall. Each hole will taper – and will be 24 inches wide at the top, and around nine inches wide at its bottom.
Water will be pumped down one well and forced through the hot, porous granite to the bottom of the second well where it will return to the surface under pressure and at temperatures of around 150ºC.
At the surface, a heat exchanger will remove most of the heat from the water and use it to drive a turbine. Waste heat will be piped directly to offices, homes and the Eden Project’s domed greenhouses.
By now the water from the wells will have cooled to 50ºC and will be pumped back into the first well to repeat the cycle.
Guy Macpherson-Grant, managing director of EGS Energy, said the plant would be built on land no bigger than a football stadium.
‘I would hope to start drilling in a year and hopefully be generating electricity in 2012,” he said.
Tim Smit, Chief Executive of the Eden Project, said: ‘Powering the Eden Project site from a renewable source of energy is clearly a priority for us and we are very pleased to have the opportunity to bring our unique vision and environmental skills to the project alongside EGS Energy’s experience and skills in engineering geothermal systems.’