Over half of UK's energy demand is from heat, and most of it is provided by fossil fuels. While coal mining has stopped, the water within flooded abandoned mines provide a huge source (2.2 million GWh) of low-carbon, geothermal heat for the future, enough to heat all UK houses for >100 years! The mine water is only lukewarm (12-20 degC), but with heat pumps, temperatures are increased to a more comfortable 40-50 degC. Heat pumps produce 3-4x the energy than they use, making mine water geothermal heating (MWGH) an efficient energy source.

But research is required to make MWGH competitive, technically and logistically feasible, and desirable: which collieries are suitable for sustainable heat extraction? MWGH requires district heating networks between premises, so how can we overcome the associated hurdles for setting those up? Can MWGH handle seasonal heat demands reliably? Can MWGH financially compete with the established gas boiler? Do local communities want such change to greener heat? This project will examine these components of MWGH, from the initial geothermal heat extraction, to the logistics of heat storage and delivery, the political and financial landscape for MWGH, and involving local communities in all this.

Detailed knowledge of mine water circulation and thermal interaction with the rocks is essential for the success of MWGH. Prior to expensive drilling, numerical models help predict how suitable a mine system is. WP1 will address this using innovative, detailed mine thermal flow models that are fast, so can easily run thousands of flow scenarios to find optimal settings, and are easily tailored towards individual mine plans to investigate case studies. Simulations will be calibrated against flow experiments at GGERFS, the UKGEOS Geothermal Research centre, while project partners provide mine plans, pumping and geological data from several sites. Valuable, unrecorded mine information available within former mining communities will be collected to supplement the mine knowledge and accuracy of the simulations.

Heat pumps will increase the temperature of the extracted mine water for local heating purposes. But to meet seasonally fluctuating heat demands, heat storage is essential. WP2 will address this through novel solar-geothermal heat collection that utilizes both underground and overground storage. Solar heat drives sorption reactions, and access heat is released to mine water and stored underground, thereby supporting the long-term heat capacity of the mines. The experimental design of such storage system will be tested and optimized at GGERFS.

The success of introducing MWGH depends on many political, financial and social aspects too. Without a favourable regulatory and financial landscape, the major undertaking of installing a MWGH system may be too risky. And without closely working with local councils, the Coal Authority, the Environmental Agency, and local communities, these schemes often fail. WP3 addresses these aspects, by critically analysing the regulations and procedures to start new mine geothermal heating schemes, map out and analyse the financial landscape, and investigate how local communities, scientists, and government agencies can work together to create financially successful and socially just interventions. Present and historic case studies from NE England and Wales will serve to test all aspects of the proposal.

So MWGH projects require an interdisciplinary approach as we are proposing here. WP4 will oversee the project and ensure, 1) that learning within and across WP's is shared and integrated to enrich the whole and, 2) that the communities, various research groups, local industries and project partners have opportunities to fully integrate and collaborate across the entire project. In summary, this project provides technical, logistical, political, financial, and social solutions for MWGH projects to decarbonize heating in the UK.