Numerical modeling as a basic tool for evaluation of using mine water as a heat source

In 2007 research on the possibilities of using mine water as a heat source started. Major research goals were: a) model evaluation of the heat transfer in the rock containing selected mines; b) model prediction of the temperature change due to the heat pump operation. A database containing data from abandoned mines covering the Czech Republic area was created. It contains mine water volumes, chemical parameters and temperatures. Two types of simulation software were used. For the Plzeňska basin region the heat transfer and groundwater flow were calculated using MODFLOW and MT3DMS simulation software. Their numerical code is based on the finite difference method (FDM). For the Přibram region the FEFLOW code was used. FEFLOW numerical code is based on the finite element method (FEM). Model results show that the mining water temperature decrease due to the groundwater abstraction for the heat pump will be relatively small. Temperature decrease originates from the fact that colder shallow groundwater will inflow into mine spaces mixing with the warmer mine water. The time scale of the mine water temperature decrease is over several centuries. The temperature conditions of the mine water could be very stable. Abandoned mines are supposed to be a suitable geothermal energy source.