Conventional geothermal power needs hot rock, natural water and permeable ground in the same place, which is why it is concentrated in volcanic regions such as Iceland, Kenya and Indonesia.
For decades, enhanced geothermal systems were the energy technology that was always ten years away: engineer a reservoir in hot, dry rock anywhere, and you could have clean power around the clock.
Most people picture geothermal energy as steaming volcanic power stations. In Sweden, it is a 200-metre hole in the garden and a fridge-sized box in the utility room.
Turkey has become one of the world's fastest-growing geothermal markets in the past fifteen years, and most of its plants rely on equipment designed by a single company that started in a small workshop in Israel in 1965.
Most of the world's untapped geothermal heat is not hot enough to make steam. Below about 180°C, the water that comes out of a well cannot efficiently spin a conventional steam turbine.
