14 DAY TRIAL // Two researchers recently proposed in the journal Renewable Energy that mine shafts about to be abandoned could be used to extract alternative thermal energy from the ground, helping meet local towns' power demands even after the coal yield became insufficient to keep the mine open. The internal heat of the Earth is considered among renewable energy supporters as the only source of power that is virtually endless and able to be readily harvested. Scientists Rafael Rodriguez and Maria Belarmina Díaz are based at the University of Oviedo, in Spain.
“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,” expert Rafael Rodriguez, who holds an appointment at the UO Higher Technical School of Mining Engineering, explains the idea, quoted by SINC. The two argue that the new half-breed model they devised (half mathematical and half experimental) is able to predict fairly accurately the amounts of geothermal energy that could be collected, based on measurements done while the mine pit is still operational.
“When the mine is still active one can access the tunnels easily in order to gather data about ventilation and the properties of the rocks, as well as to take samples and design better circuits, and even program the closure of some sections in order to use them for geothermal energy production,” Rodriguez says. However, he adds that, once the system is set in place, it “is no longer possible by that stage to make any modifications, or to gather any useful data to evaluate and improve the system.” In other words, engineers who build it have to get it up right, and as efficient as possible, in the first attempt.
The new system, which is similar to using the shafts as boilers, has yet another advantage – it does not contaminate nearby aquifers with heat, as is the case with other geothermal exploitations. In their investigations on the efficacy of this method, the duo found that inserting water at 7 degrees Celsius in a mine shaft heated naturally at 30 degrees Celsius resulted, at the end of the pipe, in water being heated at 12 degrees Celsius. They say that the difference is great enough to be used by the populations around the abandoned mines.
Moreover, the new thermal collection method is completely carbon-neutral, and does not require any of its external sources of power to be powered by electricity brought from elsewhere. The applications for the heated water vary extensively. It can be used in homes, pools, fish farms, in various factories, and so on, and all at very low costs, ScienceDaily informs.