Engineers from the University of Oviedo believe that mines could provide geothermal energy — low-intensity geothermal energy, that is, providing heating and hot water for people living nearby:
The study looks into geothermal exploitation of a two-kilometre-long mine shaft, in which the temperature of the rocks 500m below the surface is around 30º C. This is typical of many of the mining areas in Asturias, although it could also be applied to other parts of the world. Water could be forced in through tubes at 7º C and return at 12º C, a big enough heat gain to be of benefit to towns located above the mines.
In Fahrenheit, the 86º rock would heat 45º water to 54º.