Is coal the unlikely answer to the low carbon heat conundrum?

Charlotte for blog 2

Dr Charlotte Adams, Durham University

Geothermal energy could mean a new, low carbon role for the UK’s abandoned coal mines. The EI’s 2019 Energy Champion award winner Dr Charlotte Adams of Durham University explains…

I was delighted to receive the Energy Institute Energy Champion award this year. It is often difficult for more applied research to achieve recognition within academia therefore being recognised by a professional society is a real honour and I’m very grateful to those who nominated me.

My interest in mining goes back to my school days when we had a field trip to an abandoned lead-zinc mine in Cumbria. We had an opportunity to raid the spoil heaps for the jewel bright minerals discarded by the miners in favour of the more valuable metals they sought. My interest in mining remained with me throughout my degree and doctorate culminating in my research on the treatment and management of water flowing from abandoned mines. Whilst taking minewater samples I noticed that these waters were tepid and wondered if they could be a source of heat.

After undertaking postgraduate research and working in the renewable energy industry for a few years, I returned to academia when I joined Durham University in 2009. Since then I have been researching and promoting the UK’s geothermal resources with a particular focus upon flooded abandoned coal mines for decarbonising heat. The political decision to rapidly abandon coal mines during the 1980s led to high levels of unemployment and social deprivation in mining areas. These communities were further affected by rising water levels underground which threatened surface and groundwater. The UK now has around 23,000 abandoned deep mines and water is pumped at strategic locations to keep water levels in the mine safe and intercept and treat any potentially problematic minewater discharges.

Over the past century, 15 billion tonnes of coal were extracted from the subsurface. This would create a layer of coal 5cm deep if spread over the UK land surface. This is important because it gives us an idea of the amount of water contained within the mines that could be used for heat supply and storage. Allowing for post abandonment subsidence, we estimate that there is enough heat for 180 million homes. Many towns and cities developed as a direct result of their coal reserves creating a good overlap between former coalfields and areas of heat demand.

The water in the mines is accessed by drilling boreholes, the tepid waters occurring there are not hot enough to take a bath in or heat a room but by using a heat pump, temperatures can be increased to a more comfortable 40-50°C. Although the heat pump requires an electrical input, it is an energy efficient device because you can expect to get 3-4 kW of heat output from the heat pump for every 1 kW of electrical input. There are around 30 projects globally that use abandoned mines for heating and this research proves that we don’t need to be in a volcanic setting to develop geothermal energy. We now have the potential to develop our mining legacy to meet our future heat demands, reduce national carbon emissions and provide opportunities to regenerate former mining regions.

* Dr Charlotte Adams is a Fellow of Durham University’s Durham Energy Institute (DEI), Assistant Professor (Research) in  Durham’s Department of Earth Sciences, Research Associate in the Department of Engineering and Research Manager at BritGothermal.


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