From Peter F. Green
Fred Pearce states that the Alsace project is the first time that cold water injected from the surface has been used in a geothermal project (3 April, p 23). I think he will find that the Geothermal Energy Project project in the UK in the 1980s used this method, with two boreholes, one for cold water down and the other for hot water up. I can find no references to it on the web, but remember it being fully covered in New Scientist at the time (18 August 1983, p 467).
I was involved in some mapping connected with the project. The boreholes were into the granite from an old quarry. The shattering of the rock between the boreholes was to be done by explosives, rather than high pressure water. I remember discussing with the cheerful gang on site the relative importance of the conduction of heat from the core of the Earth and the generation of heat within the mass of granite from the radioactive decay in the feldspar. I suppose that must be a factor in the French project as well. Even 30 years ago, the Hotrock folk said that they avoided mentioning radioactivity as it tended to cause panic in the press.
Naturally, being a British project, Hotrock was eventually cancelled, but I think that the efforts of all those involved should be remembered.
Henley-on-Thames, Oxfordshire, UK
