First published in Cleantech magazine, February 2011. Copyright Cleantech Investor 2011
By Mel Poluck
It is estimated that geothermal power from the south west of England alone could meet 2% of the UK’s annual electricity demand. Two companies are gearing up to tap Cornwall’s extensive potential resources of deep geothermal energy and look set to convert the English county into a hot spot for enhanced geothermal systems.
Traditional geothermal energy is derived by pumping naturally occurring hot water from underground to the surface. Enhanced geothermal systems (EGS) manufacture geothermal resources by creating similar conditions to traditional geothermal energy in hot dry rocks. This is achieved by pumping high pressure cold water down into rocks at depths of around three miles (five kilometres). The rock then fractures, allowing the water to circulate and heat up – and subsequently re-emerge from a second borehole as very hot water to be converted into electricity.
Cornwall was the location for Europe’s first deep geothermal R&D initiative, the Hot Dry Rock (HDR) project, which took place in Rosemanowes. Triggered by the 1973 Middle East oil crisis and subsequent search for alternative energy sources, Cornwall was identified because its geothermal resources are large: the geothermal gradient (i.e. the temperature increase with depth) is higher than elsewhere in the UK (see chart).