There is a great reservoir of natural heat in the UK that could supply hot water and electricity round the clock, all year, whatever the weather and with the minimum of greenhouse gas emissions, if only it were fully used. This is geothermal energy stored under the Earth’s surface, and Cornwall has lots of it.
This year the old copper mining region at Redruth is set to become the UK’s first commercial geothermal power station using geothermal energy, generating enough electricity for about 6,000 homes, as well as hot water for heating. The production well is more than three miles deep, the deepest onshore well in Britain and four times the height of Ben Nevis. The temperature at the bottom of the well is about 180C and a second borehole will inject water into the hot rocks, absorbing the heat before the water is pumped back up to the surface, where it is turned to steam to drive a power turbine and generate electricity 24 hours a day.
The Redruth power plant is a prototype and the company behind it, Geothermal Engineering, is planning a larger geothermal power station at nearby Penhallow that would be capable of generating electricity for 11,000 homes, saving more than 700,000 tonnes of CO2 compared with an equivalent gas-fired power station. And the company has its eye on several other sites in Cornwall to develop more geothermal power stations.
The potential to expand this energy resource is immense. Almost all of Cornwall and parts of Devon have the hottest rocks in the UK, with a vast expanse of granite beneath the ground that gives off natural heat. It is estimated these hot rocks could provide about 5 per cent of the UK’s electricity, as well as substantial heating. Much of the granite in this region is also rich in minerals, and the Redruth well will tap into concentrations of lithium that can be used to make batteries.
The UK has, quite literally, barely scratched the surface of exploiting hot rocks, but the gas crisis is making it all the more attractive.
