New Reuse: Old Mine Shafts as Geothermal Energy Plants
Village Image, Credit: Rodríguez et al. / SINC.
Mine shafts on the point of being closed down could be used to provide geothermal energy to local towns, according to two engineers from the University of Oviedo in Spain, whose research is being published in the journal Renewable Energy. They developed a method to estimate the amount of heat that a tunnel could potentially provide.
"One way of making use of low-intensity geothermal energy is to convert mine shafts into geothermal boilers, which could provide heating and hot water for people living nearby," said Rafael Rodríguez from the Oviedo Higher Technical School of Mining Engineering in a recent report.
The engineer and his colleague María Belarmina Díaz have developed a "semi-empirical" method (part mathematical and part experimental) to calculate the amount of heat that could be produced by a mine tunnel that is due to be abandoned, based on studies carried out while it is still in use.
Active mines can be accessed to gather data about ventilation, rock properties and to take samples and design better circuits. When planning for a geothermal application, engineers close off specific sections to use for this purpose.
The study looks into geothermal exploitation of a two-kilometer-long mine shaft, in which the temperature of the rocks 500 meters 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.
Rodríguez and Díaz highlight the benefits of building geothermal boilers in mine shafts in that, aside from their predictable energy production levels, they also function practically as an open tube system "but without any risk of heat contamination of aquifers."