Boost for hot rocks power

Press, 22 July 1989, Page 22

Boost for hot rocks power

Plans to produce electricity from underground hot, dry rocks have taken a step forward in Britain with the goahead for new work to assess commercial prospects, the London Press Service reports. Experimental work is being carried out on an existing hot, dry rock reservoir two kilometres below ground in a quarry in Cornwall, western England. Engineers from the nearby Camborne School of Mines have spent more than $9O million developing a technique of tapping the heat of the underground rocks by pumping water down a bore hole and forcing it through a network of explosive fractures made in the rocks. The water is then returned to the surface via another bore hole as steam or hot water. The aim is to use this steam to drive the generators of a power station that would be built near the hot rock reservoir. The British Government has already given $25 million backing to the latest hot rocks research, and has allocated of this money for a study $1.4 million to design a commercial system to exploit hot rocks beneath Cornwall at a depth of six kilometres. Cornwall has an abundance of granite rock on and under the surface, but there is a need to drill several kilometres down in order to tap rock temperatures high enough for commercial exploitation. The temperature typically rises by 20 degrees Celsius for each kilometre down but in the Cornish granite the temperature rises by 30 degrees per kilometre. At six kilometres, the temperature is thought to be over 200 degrees. The previous phase of the work in Cornwall has identified a potential hot rocks resource of between 750 and 3000 terawatt hours.