Last week, the Dutch city of Heerlen opened the world’s first geothermal power station that uses water heated in old coalmine shafts. The power station works by pumping water up from 800 meters deep in the mines. At that depth, the water reaches a temperature of 35 C (95 F). It heats 350 homes and is pumped back into the mines after use, where it recirculates two to three times a year.