Modelling Mine Energy Systems: A Feasibility Study of the Implementation of a Minewater Heating System on the University Estate

Abstract

Minewater heating is a form of shallow geothermal energy provision that exploits abandoned subsurface mines that have since flooded after mining activity ceased. Groundwater that occupies the void space left from material extraction is warmed to ambient temperatures by heat transfer exchanges with surrounding rock. Using ground source heat pumps, the temperatures of these waters can be lifted to those suitable for domestic heating with efficient electrical input.
This thesis assesses the feasibility of implementing a minewater heating system on the Durham University campus, specifically Van Mildert College. Assuming abstraction and reinjection of the minewater, the available subsurface heat resource was investigated using numerical modelling. The model calculated minewater flow through the void space of the mines and thermal interaction with the surrounding rock. A new methodology was developed for the digitisation of historic mine plans provided by the U.K.'s Coal Authority, which have then been modelled to provide 3D visualisation of technical factors critical to the success of such a project.
Preliminary results indicate over 11 million kWh of heat in place resource available at temperatures of 13.5°C. However, modelling suggests that Van Mildert College would not be a suitable candidate for minewater heat. Mine plans indicate a shaft connection between the Hutton and Busty Seams close to the case study site, resulting in thermal breakthrough when modelled. This occurred in all modelled configurations, with extracted water being up to 2°C cooler after one year of operation.
After reviewing these model results, a different site was assessed. The Teaching and Learning Centre is a recently constructed educational facility approximately 420 m North-East from Van Mildert College. Due to the layout of the mine workings beneath the site, a sustainable, secure heat supply was identified, with no temperature reduction over time.
Calculations of the project's economic feasibility were performed, considering current energy market prices and potential CO₂ emissions reductions. A social acceptance study was also undertaken with members of the University's senior leadership and staff, identifying stakeholder motivations and concerns regarding minewater heat on the University estate.