What is holding back the development of geothermal energy? There must be an awful lot of energy down there.
鈥� Geothermal energy for heating makes a great deal of sense in cold climates, and localised 鈥渄istrict heating鈥� systems that use it have been around for centuries.
If you want to generate electricity, then it鈥檚 best to find the hottest water you can. Very hot water is easily accessible in volcanic regions, but in most areas drilling and fracking are needed to access the heat deep in Earth鈥檚 crust. This becomes expensive, especially if you want water hot enough to drive state-of-the-art power plants that use steam at 600 掳C. Typically water from the ground is much cooler than if we used coal, oil or gas to make steam.
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Geothermal power will therefore always be expensive compared with fossil fuels, but perhaps carbon dioxide emissions will drive those out of fashion.
Hugh Hunt, Trinity College, Cambridge University, UK
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This article appeared in print under the headline 鈥淕etting off the ground鈥�