Michigan, USA:

Tapping into mine water for geothermal energy (Phys.org)

Old mine tunnel

Millions of miles of tunnels criss-cross the ground under old mining communities across the United States. Abandoned, falling apart and choked with water, the tunnels are often viewed as a dangerous legacy. But the water in these mines could actually be a major geothermal resource.

Student researchers at Michigan Technological University have put together the first comprehensive guidebook communities can use to explore the feasibility of using mine water for geothermal energy to heat and cool buildings. While there is great potential for this resource, there are less than 30 active mine water geothermal systems in the world. One is at Michigan Tech's Keweenaw Research Center just north of Houghton, Michigan.

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Millions of miles of tunnels criss-cross the ground under old mining communities across the United States. Abandoned, falling apart and choked with water, the tunnels are often viewed as a dangerous legacy. But the water in these mines could actually be a major geothermal resource.

Read more at: http://phys.org/news/2015-04-geothermal-energy.html#jCp