Your recent item on geothermal heating (NCE 15/29 December) set me thinking. If the facts I have gleaned from elsewhere are correct, temperature within the earth's crust increases with depth at a rate of 2°C-3°C every 10m although there are areas where the increase is greater.
Drilling down 30m would therefore only be likely to produce heat at a degree or so over the ground surface temperature. Even taking the latter as the 15° world average the resulting hot water would scarcely be warm enough for a bath!
An article in NCE setting out the opportunities for geothermal heating in the UK - giving the appropriate figures and perhaps, maps - would be very welcome.
Robert Holland (F), dduuttcchh44@hotmail. com