Rosemanowes Quarry Rosemanowes Quarry , near Penryn , Cornwall , United Kingdom , was a granite quarry and the site of an early experiment in extracting geothermal energy from the earth using hot dry rock ( HDR ) technology . Quarry . In the nineteenth century the quarry provided stone for building projects in Britain and abroad as well as for the Ponsanooth viaduct near Penryn and the Carnon Valley viaduct between Truro and Falmouth . Geothermal energy research project . The site was chosen as the research site because the granite in the area has the highest heat flow in England ( 120 milliwatts per square metre ) . The trials began in 1977 in the wake of the 1973 oil crisis and an earlier trial in the United States at Fenton Hill . It concluded in 1980 , although studies continued until 1991 . Funding for the initial project was provided by the Department of Energy ( now the Department of Trade and Industry ) and by the European Commission . The research facilities and staff transferred to Camborne School of Mines Associates Limited in 1992 , the trading arm of the Camborne School of Mines . The project had two aims 1 ) To see if hot dry rocks could be fractured by water pressure alone , enabling a current of cold water from an inlet borehole to pass easily through the mass and to be collected at an outlet borehole some distance away . The trial proved to be successful , and showed that explosives were not required to fracture this Cornish hot granite at depth . 2 ) To find out if the rocks were hot enough to make steam for a turbine to generate electricity . This second aim was not achieved at the depths attained . Though the rocks did yield substantial quantities of hot water , to reach a temperature to generate steam hot enough to drive a turbine would have required drilling a further kilometre or more into the granite , an option which was too expensive to pursue at that time . With government and EU support the expertise of the scientists and engineers at Rosemanowes was used to support the European HDR project at Soultz - sous - Forêts and a number of commercial contracts ensued exploiting HDR techniques , such as microseismic monitoring , in the oil and gas industry . Rosemanowes Quarry and the assets of CSMA , including intellectual property , were acquired by Asea Brown Boveri in 1997 . In 2004 Schlumberger acquired the intellectual property and some of the staff most closely associated with microseismic monitoring and the quarry was sold off . In 2006 , the site was acquired by 3K Facilities . The company now offers deep borehole test facilities in one of the best - logged sites in the world . All the deep boreholes are now available to hire for a range of down hole testing . There are three deep boreholes ( 2350m , 2180m , 2800m ) , four uncased 300m holes and one 150m hole inclined at 30degrees , as well as micro seismic testing and a wind turbine test environment on this site . Although the energy has not yet been exploited commercially , the data provided by the tests has been widely used to test numerical simulation codes . The dataset contributed significantly to the geothermal power plant built with European Union sponsorship at Soultz - sous - Forêts . In March 2013 the quarry was put up for sale by the owners 3K Facilities . Use by US forces during World War II . During the Second World War , the Quarry was used for storage by US forces , preparing for the invasion of Europe , which started in June 1944 . Location . The quarry is at Herniss , to the north of the A 394 road , between Rame and Longdowns . Ordnance Survey , Explorer series , Map 103 , : .