Lessons from mine water geothermal projects across Central Scotland

The University of Strathclyde (situated in the city of Glasgow, UK) has participated in several mine water geothermal projects across a range of budgetary scales from impact accelerator scoping studies (< £10,000 GBP) to major research projects (> £1 million GBP). This paper brings together the findings from these projects and summarises important learning points for the delivery of mine water heating, cooling and thermal storage projects. In collaboration with industry, government organisations (such as data-holders and permitting organisations), and local council authorities, our team has experience with delivery of e.g., resource exploration, feasibility studies, site surveys, subsurface models, drilling, operational planning, and demonstration trials; all whilst maintaining conscientious dialogue with key stake holders. Most of our efforts to date have focused on Central Scotland, which corresponds to the geological region known as the Midland Valley. The volume of mine worked area from the Carboniferous Coal Measures in this region is approximately 600 km3, with most extraction activities from c. 1800 following the introduction of steam power and mechanised mining techniques. Like other mining regions across the world, local wealth was strongly linked to mining activity, and hence modern population and industrial centres are situated above the legacy mine infrastructure. The impact of mine closures throughout the mid to late 1900s reverberates to the present day- c. 80% of Scotland’s most deprived communities live above abandoned, flooded coal mines and energy poverty is a major challenge. Some of our cross-project pooled learnings to date include:

• Each mine is different, therefore accessing diverse datasets and where possible local knowledge is key for de-risking. Surviving miners testimonies are only relevant to relatively recent mines, which are deeper, but the local knowledge may well offset drilling risk. Archival data is often available for older mines, though it is not systematic across mines.
• The variability of the mine infrastructure in terms of mine construction techniques, depth, geology means that each mine offers different opportunities and risks for heating, cooling and heat storage, but these opportunities and risks can be traded off to optimise a scheme.
• Integration with surface energy systems is ideally baked in from the start of a project as the variability in opportunity means that the risks can be managed or offset against different, and potentially evolving, surface end-uses.

We hope that the lessons detailed in this paper can help contribute to socially and environmentally responsible development of low-carbon mine water geothermal in Scotland and around the world.