The use of renewable energies in Spain is growing; nevertheless, up to now, a very low use of geothermal energy is found. In this paper, the use of low enthalpy geothermal energy that consists of converting mine galleries in underground heat exchangers is described and analysed. The system would be used in those areas with mining works that with a near future closure, such as Asturias but also other regions of Spain or Europe. The described system, unlike other proposed ones, implies to act before the closure of the mines, when it is possible to access underground galleries. A prediction method for evaluating the system capabilities has been developed which has been calibrated with measurements taken in underground mines and which can be used and calibrated in any mine in operation. Finally, using the method, the capabilities of a typical system are analysed and its viavility from a technical, economic and environmental point of view is proved. (C) 2009 Elsevier Ltd. All rights reserved.