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Scientists discover regions of the UK with greatest potential to use heat from deep thermal waters

BGS geologists have mapped the UK’s potential to use heat from thermal groundwater deep beneath central and southern Britain.

Map of the Carboniferous limestone formation with deep geothermal potential.
Map showing Carboniferous limestones with geothermal potential in the deep subsurface of Great Britain. Derived in part from DTM of Great Britain at 5m resolution © Bluesky International Limited.

Geothermal energy is the heat stored below the Earth’s surface. It has the potential to provide a stable supply of clean heat energy for Great Britain, helping to reduce carbon emissions, diversify from fossil fuels and improve domestic energy security.

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BGS geologists mapped where the Carboniferous limestone is buried at depths of over 4 km. This video shows how they did it. BGS © UKRI.

Natural thermal springs have been used since Roman times and towns such as Bath and Buxton have grown up around them. These warm waters, which are rich in minerals, have travelled from great depth from a rock formation called the Carboniferous limestone, which can be found beneath many regions of the UK such as the Mendip Hills and the Peak District.

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Rain falling onto hills and mountains percolates deep below the Earth’s surface, where it is stored for as long as 10 000 years and heated by the surrounding rocks. These warm waters are what we would call low- to medium-temperature geothermal resources in the UK.

We have known of these systems underground because the hot water comes to the surface in places like Bath Spa. However, little is understood about the wider extent and reach of these limestones, which lie deep below the surface of the ground, and about the potential to recover heat from their deep thermal waters.

Dr Timothy Kearsey, BGS Sedimentary Geologist.

Mapping the limestone

Now, the geothermal team at the BGS has mapped where the limestones are buried below the Earth’s surface at depths of over 4 km below the ground.

Using established 3D modelling methods, they assessed the depth, distribution and geothermal potential of regions in England, producing maps that demonstrate the total heat in place and estimate the recoverable heat distribution. They calculated that there is the potential to recover thermal heat of 106 to 222 GW from the rocks at depth under central and southern Britain. The largest potential resource is under the East Midlands and Greater Manchester, as well as the Humber and Cheshire regions.

A geologist wearing blue overalls and a white hard hat points at the rock ceiling in a cave
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BGS geologists inspecting the Variscan unconformity in Wookey Hole, Somerset. The underlying Carboniferous limestones are one of the main targets for deep geothermal potential in Great Britain. BGS © UKRI.

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Scientists are keen to stress that further work is needed to understand the resource and to identify areas with sufficient flow rates for successful development. 

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This is very exciting. Until now, Early Carboniferous limestones had not been fully quantified as a geothermal resource in Britain. Our research shows these limestones could play host to many active geothermal systems across central and southern Britain.

What we do know is that the Early Carboniferous limestone may offer significant potential as a resource for deep geothermal energy across large parts of central and southern Britain. Equivalent rocks have been successfully developed for geothermal energy in Belgium and the Netherlands, where they are used to supply heat networks or heat agricultural greenhouses, lowering fuel bills for heating and the food industry.

These maps are very encouraging, particularly as large-scale exploitation of heat is critical for the successful decarbonisation of the UK’s energy mix.

Dr Timothy Kearsey, BGS Sedimentary Geologist.

More information

Access the video by BGS to learn more.

The full paper is published in Science Direct: Deep geothermal resource assessment of Early Carboniferous limestones for central and southern Great Britain.

About the author

Timothy Kearsey Survey geologist and sedimentologist
Dr Tim Kearsey

Survey geologist and sedimentologist

BGS Edinburgh

Tim Kearsey is an expert in 3D geological modelling and Carboniferous stratigraphy and sedimentology. He has developed ranges 3D geological models for Glasgow, Singapore to address problems from hydrogeology to geotechnical properties and geothermal energy.

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