Britain is home to a large number of disused coal mines dotted across the landscape. To make use of these currently unused plots of land, technology is being developed that will be able to tap into geothermal hot water deep underground.

The production of central heating in the UK is currently dominated by natural gas, supplying around 70% of the UK’s heat demand.

Compared with electricity there are far fewer alternatives for low carbon heat production. Solar hot water and biomass are two of the main alternatives being touted; solar hot water is usually produced at a domestic level but requires access to a south facing roof whilst biomass is constrained by availability and the transportation of the fuel.

In trying to find a low carbon, secure and continuous energy source, experts have looked to the disused coal mines of Britain. Countries such as Iceland and New Zealand utilise their volcanic landscapes by capturing the steam and hot fluids produced by deep-lying tectonic activity. Although Britain lacks tectonic activity, the mining boom saw 15 billion tonnes of coal extracted from beneath the land surface. Over time these mines have filled with water due to inactivity and that water has reached deep enough to be heated to over 100°C.

These geothermal fluids are hot enough to drive turbines, produce electricity and also supply heat to homes. Extracting geothermal energy from such depths can only be possible if the water is present and it is able to flow from the rock.

The flooded galleries and shafts left behind by old mining ventures provide the perfect situation for geothermal energy extraction.

Although coal production in the UK has declined to zero, we are still a huge importer of coals for producing electricity and for use as house coal. Having celebrated their first coal free day of power generation in April 2017, utilising coal mines for geothermal energy could become more popular in the future.