Modelling physical controls on mine water heat storage systems

The use of abandoned mines as a heat source and store has been receiving increased attention as a renewable heat source and storage solution in the transition away from traditional gas heating. The hydraulic, thermal and geomechanical processes governing heat storage and extraction are complex and understanding these processes is critical to safe heat extraction and injection into mine water systems. This paper outlines the development of a fully coupled thermo-hydraulic-mechanical (THM) 2D model to understand the mechanical stability of room and pillar workings during heat injection and extraction. It was found that the cyclical injection and extraction of heat does have an impact on both the modelled displacements and mechanical stability of the system. The impact risk reduces with temperature and the operational processes (e.g. injection temperature and water level) have more of an impact than the underlying geological conditions. These results are significant and could be included in a regulatory system to reduce the likelihood of stability impacts in mine water heating and cooling schemes.