| Title | Could Cyclical Heat and Hydraulic Demand in Abandoned Mine Workings Lead to Surface Subsidence? |
|---|---|
| Authors | Fiona TODD, Chris MCDERMOTT, Andrew FRASER HARRIS, Stuart GILFILLAN, Alexander BOND |
| Year | 2020 |
| Conference | World Geothermal Congress |
| Keywords | mine water, low enthalpy, THM modelling, |
| Abstract | Mine water heat schemes are being investigated in the UK and other countries as potential low energy geothermal sources in the drive to decarbonise the energy sector. Abandoned coal mines can provide higher temperatures and increased (man-made) permeability compared to regular ground source heat pumps. Both of these attributes make mine-source heat pumps interesting as a potential geothermal resource or as an energy store in seasonally balanced systems. A high level estimate of the geothermal heat flow and the area mined in the Midland Valley of Scotland indicates the amount of natural energy available annually is 9.8e9 MJ. This is equivalent to around 8% of Scotland’s annual domestic heating demand. If these schemes are to contribute to a significant proportion of the annual heat demand, seasonal energy storage will be important to make them truly sustainable. One of the risks of using abandoned mine workings as a heat source or store is the potential for surface subsidence. The theory explored in this research is that changes in pressures, temperatures and water flow caused by mine source heat pump systems will impact the integrity of the existing mine workings and possibly cause subsidence at the surface. A coupled thermal-hydraulic-mechanical model has been developed to understand the controlling mechanisms in these systems and to determine the level of possible risk to surface structures. |