From Peter Laurie
In all the fuss and confusion about energy and carbon problems one dull but crucial fact has been overlooked: the oil industry can now routinely drill to depths of 10 kilometres. This means the Earth’s core, the 7000-kilometre-diameter ball of molten iron, is now available as an energy source, as this heat seeps out to the upper layers. A recent study at the Massachusetts Institute of Technology estimates that there is enough thermal energy at a depth of 10 kilometres in crystalline rocks (at temperatures of 200 to 300 °C) under the US alone to supply the whole world at its current consumption rate for 30,000 years.
The editor writes:
• We have reported an estimate that hot rock beneath the US could supply its energy needs for two millennia: see “Hot clean power under our feet” (27 January, p 4)
Abbotsbury, Dorset, UK
