Mine Water for Energy and Water Supply in the Central Coal Basin of Asturias (Spain)

The Asturian Central Coal Basin (NW Spain) is generally characterized by moderately porous and permeable rocks, such as sandstone, limestone, and shale. Groundwater mostly flows through open fractures, voids, and decompression zones associated with coal mining. Exploitation of water resources in former coal mines could contribute to the economic well-being of communities affected by closure. The potential value of mine water associated with the flooded Barredo and Figaredo mine shafts near the town of Mieres was studied. This reservoir could supply water for 60,000 people; this could possibly be doubled by co-managing the river flow and underground resources. We studied the potential recovery of energy from the thermal value of this mine water (using water-to-water heat pumps). Two district heating systems are proposed: a low-temperature network (35 A degrees C) for domestic heating and a very-low temperature network (20 A degrees C) for large users, such as shopping centres, that need both heating and cooling. Return flow to the reservoir can generate electricity by means of micro-turbines. Preliminary estimates of profitability appear favourable, along with a sizable reduction in CO2 emissions compared to natural gas heating. Extrapolation of these results to other mine water reservoirs in Central Asturias implies a potential of 40 million m(3) per year for water supply, and an energy supply capacity close to 260,000 thermal MWh per year.