Renewable energy: Power beneath our feet

At first glance, geothermal energy seems almost too good to be true. It's clean, inexhaustible, provides predictable 24-hour power and you can get it just about anywhere. There is a snag, however. Outside of geologically blessed places like Iceland, Japan and New Zealand, where volcanically active rocks are close to the surface, the Earth's heat is locked away under several kilometres of rock.