It has taken a decade of hard graft – and some bold, imaginative thinking – but a plume of steam finally exploded into the clear Cornish air, a signal of what is being heralded as a breakthrough for an energy project that taps into the hot rocks of the far south-west of Britain. The blast of steam at the United Downs site near Redruth, once a global mining capital, is being billed as proof that deep geothermal power can be part of the solution to the UK’s search for alternative sources of energy. By next year, the company behind the project, Geothermal Engineering Ltd (GEL), says it will have built a power plant to produce electricity and heat from the hot rocks. It plans to feed electricity into the grid and send heat to a local rum distillery and a new housing estate. On Thursday the company also announced plans to build four more sites in Cornwall by 2026, potentially creating hundreds of jobs in one of the most deprived areas of southern England. Ryan Law, the managing director of GEL, described the blast of steam as a tipping point in the UK for an industry that is well established in places such as Italy, Iceland and the west coast of the US. “It’s really quite a powerful thing to see,” said Law. “It’s almost like feeling the power of a jet engine. It’s a very dramatic thing – you get a sense of how powerful the earth is and how we’re just sitting on a tiny piece of its crust.” There is potential for similar geothermal power stations in other parts of the UK, including Cheshire and Staffordshire. But the geological structure of the granite masses beneath Devon and Cornwall makes it fertile territory for geothermal energy. GEL has worked with 26 universities and Cornwall council on the project. Two wells, one three miles down, have been drilled into the granite of the Porthtowan Fault Zone. Water is pumped up from the deeper well, where temperatures are 180C. The steam produced drives a turbine that produces electricity. Water is re-injected into the ground to pick up more heat from the rocks, and the cycle goes on. Heat can also be piped away to be used by businesses and homes. The project has received backing from the European Regional Development Fund and Cornwall council. The council’s cabinet portfolio holder for the economy, Stephen Rushworth, said: “The new plants will benefit local communities.” The council is hoping the heat will be used to supply a proposed housing development for up to 10,000 people, Langarth Garden Village. There have been concerns that the underground operations could cause earthquakes, but GEL has installed a network of seismometers that can detect earthquakes hundreds of times too small to be felt at the surface, which will allow it take mitigating action if necessary. Mike Childs, head of science, policy and research at Friends of the Earth, said: “Geothermal energy has great potential in some areas of the UK, particularly in Cornwall, but also other old mining areas where heat can be captured from mine water.” Childs added that in most parts of the country, air-source heat pumps would be the best option for heating people’s homes as the UK transitions to a fossil fuel-free future. Fin Thompson, 20, who works in the GEL office, had been planning to leave Cornwall in search of work. “There aren’t that many jobs in this area,” he said. “It’s good if this give more jobs for more young people. And it’s exciting that underground exploration is going on in Cornwall again.”