As a geologist and geophysicist, my research focuses on understanding whether Scotland radiothermal granites could help unlock a new source of sustainable geothermal energy for the UK. In summer 2024, I conducted a three-week field campaign to study the potential for geothermal energy in the Cairngorms with a team of other geoscientists. 

The Cairngorms: more than just mountains

Geothermal energy is often associated with places like Iceland or other volcanic hot spots, but Scotland ancient granites may also be able to supply sustainable heat. The Cairngorm Pluton, part of the East Grampians Batholith, is one of the UK highest heat-producing granites, with intriguing geothermal potential. My work combines geophysical surveying with laboratory experiments to explore this potential, whilst addressing uncertainties about the region geology. 

Using magnetotellurics to explore below the surface

Magnetotellurics (MT) is a deep-sounding geophysical technique that uses the Earth natural electromagnetic field to produce images of the conductivity properties of the rocks in the subsurface. It can also be used to map features like fluid pathways and fractures located several kilometres below the surface. These pathways are critical for geothermal energy because they act as conduits for the fluids transporting heat. 

During my fieldwork in the Cairngorms, we set up 24 MT stations using instruments on loan from the NERC Geophysical Equipment Facility across the region. These were deployed by a team comprising myself and: 

• 51ÁÔÆæ staff members 

• Heriot-Watt University staff 

• other postgraduate researchers 

• a Cairngorm ranger 

• a University of St Andrews undergraduate student 

The MT equipment uses two types of sensor:  (1) non-polarisable electrodes, which measure the ground electric field, and (2) induction coil magnetometers, which measure changes in the magnetic field. The setup at each site required us to bury the sensors to protect them from the fierce weather conditions.

The data collected from the sensors will allow us to produce images of the Earth electrical resistivity below the surface using a mathematical process called data inversion. Ideally, the images could show zones with lower electrical conductivity, where fractures in the rocks are present within the resistive granite. These could be potential geothermal reservoirs from which heat can be extracted.

Fieldwork challenges and discoveries

Conducting fieldwork in the beautiful but bleak Cairngorms is both rewarding and challenging. With no roads in much of the area, we had to carry our equipment, including a 20 kg battery, over many kilometres of hiking paths and sometimes beyond any trails. Navigating deep bogs, steep bouldery terrain and elevations of up to 1250 m while braving sudden weather changes was an adventure in itself. In June 2024 we had seven consecutive days of snow fall on the mountain!

In addition to the MT fieldwork, I surveyed the geological structures and outcrops and collected samples for later laboratory analysis. One memorable moment came when we discovered a zone of extensive hydrothermal alteration of the granite near Stob Coire an t-Sneachda. This is possible evidence of hot fluids chemically changing the rock many millions of years ago. This alteration is significant because it could enhance the porosity and permeability of the rock, which are crucial factors for geothermal reservoirs.

Why it matters

Geothermal energy offers a constant, low-carbon source of heat, making it a promising candidate for the UK renewable energy mix. Additionally, its small land footprint and minimal surface infrastructure requirements mean it can provide sustainable energy with reduced visual impact, preserving the natural landscape. My research aims to de-risk geothermal exploration in Scotland, providing the scientific basis for future projects that could benefit communities and combat climate change.

Next steps

With my first year of fieldwork complete, I’m back in the laboratory, analysing samples and processing the MT data to build a three-dimensional resistivity map of the Cairngorm Pluton. Combining geophysical models with laboratory-based analyses will bring us closer to understanding the geothermal potential of this region of Scotland.

Thanks

Thanks go to Nathaniel Forbes Inskip and Andreas Busch from Heriot-Watt University and Juliane Huebert from BGS.

All images kindly reproduced with permission. For enquiries about the images within this article, please contact the copyright team (IPR@bgs.ac.uk).

51ÁÔÆæ has broken ground on its geothermal heat pump project at its headquarters in Keyworth, Nottinghamshire, with the help of Ruth Edwards, MP for Rushcliffe. The ground-source heat pump and living lab project is costing £1.7 million and is majority funded by the Natural Environmental Research Council (NERC) with a further contribution from the Government Public Sector Decarbonisation Scheme. The scheme is run by the Department for Energy Security and Net Zero and delivered by Salix Finance.

The renewable energy system will be the largest system of its kind in Rushcliffe, consisting of an array of 28 boreholes drilled to a depth of 225 m. It will save approximately 30 tonnes of carbon dioxide (CO₂e) per year and reduce the organisation heating bill.

Forming part of BGS Keyworth campus decarbonisation plans, the proposed system will involve the removal of greenhouse gas-emitting gas boilers and will heat two buildings on the Keyworth site, where more than 400 members of staff work, including tenants and non-BGS staff.

The heating system will also benefit from advanced monitoring, which will assess the running costs and efficiency of the heat pumps and provide a case study for other organisations, such as schools and hospitals, that are thinking of switching from fossil fuel boilers to clean heat pumps.

The project will constitute a ‘living laboratory’, with state-of-the-art sensors deployed in the heat extraction boreholes and buildings. The technology will provide data in real time to help increase the public understanding of ground-source heat pumps and how they can be an effective solution for heating both new and existing buildings in the UK.

As part of this project, BGS will also be taking rock samples for further analysis to help get a better understanding of the flow of heat and water underground. The type of geology on site at Keyworth means that this information is transferable to a large part of the UK; the information generated will be of help to other, similar projects.

The installation of the ground-source heat pump is part of a wider project to help achieve UK Research and Innovation (51ÁÔÆæ) aim of reaching net zero by 2040. This also included the installation of 1000 solar panels above BGS car parking area in 2022. 

To mark the installation of this technology and the ground-source heat pump, BGS invited local MP Ruth Edwards to the site where she met with senior staff, scientists and members of the estates team at BGS to learn more about the project, as well as to see the borehole drilling taking place.

I was really honoured to be asked to break ground on the new geothermal heat pump at the 51ÁÔÆæ in Keyworth. This is a hugely exciting opportunity to help decarbonise the public sector estate. I’m thrilled that we are trialling the technology here in Rushcliffe and that the data generated by the trial will be used to inform other projects around the country. Many congratulations to all involved!

Ruth Edwards, Member of Parliament for Rushcliffe.

This inspiring project to decarbonise heat at the BGS Keyworth campus will reduce our reliance on fossil fuels. This is the first geothermal heat pump system to be installed on the 51ÁÔÆæ estate and will support our journey to net zero in 2040. What makes this project extra special is the ‘living lab’ feature, which will support data collection and knowledge sharing that could inform the heat pump sector as a whole.

Mike Potter, senior environment manager at NERC.

Geothermal energy is heat that naturally occurs under the ground and is available 24/7 across the UK. This project will demonstrate the deployment of ground-source heat pump technology to decarbonise existing buildings across the public sector estate.

David Boon, senior engineering and geothermal geologist at BGS.

This exciting project gives us the opportunity to blend our observation of the subsurface with leading low-carbon heating. The disruption to BGS staff will be kept to a minimum, with short closures of a couple of buildings to allow for the installation of heat emitters. The drilling and heat pump installation is due to last around three months. The borehole installation should not impact on Keyworth site operations due to the careful planning and specification involved in the project.

Daniel Crow, head of BGS Estates and Facilities.Ìý

Cenergist are proud to be supporting the 51ÁÔÆæ in their plans to achieve net zero by 2040.ÌýOur solution for this site will provide modernised futureproof low carbon heating and hot water systems to these two buildings, significantly reducing carbon emissions.

Steve Wilkinson, head of commercial projects at Cenergist.

We are delighted to work with the 51ÁÔÆæ on this fascinating project. The state-of-the-art technology and the innovation being deployed is hugely exciting and the impact this will have on reducing carbon emissions is inspiring. We cannot wait to follow the project progress and see how a ‘living lab’ with all its detailed data collection will work and benefit this site and all the people who use it.

Ian Rodger, director of programmes at Salix.

There are a number of Government grant schemes to help the public and organisations install ground-source heat pumps. The Government aim is to see 600 000 heat pumps installed in the UK every year by 2028, as part of the UK target to reach net zero by 2050.

A Government White Paper entitled ‘The case for deep geothermal energy — unlocking investment at scale in the UK‘ was commissioned by the North East Local Enterprise Partnership (LEP) and funded by the Department for Energy Security and Net Zero (DESNZ) and the North East and Yorkshire Net Zero Hub. Written by BGS and Arup in July 2023, it provided an evidence-based assessment of the opportunities and made recommendations for building the deep geothermal sector in the UK.

51ÁÔÆæ has subsequently written and released this supplementary , funded by UK Research and Innovation (51ÁÔÆæ), that underpins the White Paper and provides the original outputs from the North East LEP commission as well as additional information, including:

• a review of the international geothermal landscape, including financial incentives, risk sharing and regulation
• a more detailed assessment of UK geothermal prospects, including new data and analyses from recent BGS studies
• potential regional economic and social impacts of geothermal energy and how deployment could contribute to UK policy goals
• an analysis of key challenges within the context of international geothermal experiences
• descriptions of the methodologies adopted in developing the White Paper, including stakeholder engagement, and how evidence was collected, analysed and translated into a set of recommendations

Together, the evidence report and the White Paper highlight opportunities where deep geothermal energy could:

• help the UK meet its net zero objectives
• increase energy supply security
• deliver economic benefits
• create the green jobs of the future

Under the amended UK Climate Change Act, a reduction in the emission of greenhouse gases of at least 80 per cent from 1990 levels is necessary to reach net zero targets by 2050.

Geothermal energy, the energy generated and stored in the form of heat in rocks, groundwater and soils, can provide a unique opportunity to deliver a low-carbon source for heating, cooling and power generation.

This evidence report provides underpinning evidence, background, and data for the White Paper, which highlights the opportunities where deep geothermal energy could help the UK meet its net zero objectives.

Dr Corinna Abesser, BGS Director of Policy and lead author of the report.

Since its publication in July 2023, the White Paper has been updated to include a foreword by Lord Callanan, Parliamentary Under Secretary of State, DESNZ.

More information

Contact the BGS press office:

• email Lucy Bloor (bgspress@bgs.ac.uk)
• phone Lucy on 07745667169

51ÁÔÆæ, in collaboration with Arup, was commissioned by the North East Local Enterprise Partnership to develop a White Paper entitled ‘’. It provides an evidence-based assessment of the opportunities and makes recommendations for building the deep geothermal sector in the UK. The report was funded by the Department for Energy Security and Net Zero and the North East and Yorkshire Net Zero Hub.

Key recommendations from the report are:

• undertake a review of financial support for geothermal energy
• clearly outline the role of geothermal energy in the UK net zero efforts
• improve data availability and accessibility
• review the legal status, regulation and licencing of geothermal energy
• develop an understanding of the public perception of geothermal energy
• support communication between stakeholder groups

Geothermal energy provides a unique opportunity to deliver a low-carbon energy source to many areas of the UK, specifically for heating.

This White Paper highlights opportunities where deep geothermal energy could help the UK meet its net zero objectives, increase energy supply security, deliver economic benefits and create the green jobs of the future to improve our communities.

Dr Corinna Abesser, BGS Director of Policy and lead author of the report.

Geothermal energy is energy produced and stored as heat in the subsurface. It can provide an ultra-low-carbon source for heating, cooling and power generation.

The current high costs of drilling restrict the use of geothermal energy to areas with certain geological settings. As technologies improve and new extraction methods are developed, more areas should become economically viable for geothermal exploitation.

Most of the UK onshore deep geothermal potential is found in deeply buried (deeper than 500 m) limestones and sandstones in sedimentary basins. Groundwater within these rocks may reach temperatures of more than 100°C but more data from deep wells and from operational geothermal projects is  needed to estimate the economically usable portion of the energy. In some areas, hot granites provide a potential source for geothermal power.

There are currently two deep geothermal projects in development or operation in Cornwall for provision of heat and power, including the Eden Geothermal project, and three other UK sites are currently using geothermal water from springs or shallower wells for heat. 

Deep geothermal energy already delivers environmental, economic and technical advantages in countries with similar geology to the UK, such as the Netherlands, Belgium and Germany. Advantages include greenhouse gas emission reductions and job generation. They have also shown that deep geothermal sources are viable to provide long-term or large-scale district heating and cooling.

Contact

For media enquiries please contact the BGS Press Team: bgspress@bgs.ac.uk

Many countries have signed up to commitments towards net zero carbon dioxide (CO₂) emissions and, together with the continuing war in Ukraine and wider increases in energy prices, interest in all forms of secure, low-carbon energy sources is accelerating. We are starting to see how geothermal technologies can provide real solutions in the transition to net zero.

Using the world disused mining infrastructure to decarbonise the heating and cooling of buildings is one such technology. With heat demand commonly close to old mines, it is a solution through which people and communities can also be engaged in a just energy transition.

The Mine Water Energy Symposium

To share research, innovation, policy, application, licencing and regulation of mine-water energy schemes across the world, International Energy Agency (IEA) Geothermal and the UK Government supported the Mine Water Energy Symposium. Now in its third year, the free, online symposium has gone from strength to strength; the April 2023 event had to be extended in length due to the number of speakers offering talks! There were 215 attendees at Mine Water Energy 2023 from 18 countries.

Current schemes

Speakers from across industry, universities and regulators shared their knowledge and experience on a wide range of topics. One group of talks provided updates on mine-water energy schemes already in place or in the exploration stage from Germany, Spain, UK, USA and Canada. These talks demonstrated the size (hundreds of houses plus industrial or municipal buildings) of mine-water heat, cool and storage resources that are being used. An emerging theme was around successful integration with other technologies, for example solar-thermal and integration in fifth generation district heating and cooling networks.

Modelling mine-water energy systems

Cutting-edge modelling of mine-water energy systems was illustrated in several talks, applied to the size and sustainability of the heat resource as well as the geomechanical stability. Models were not theoretical; they were quantified using data from active mine-water schemes. The significant potential for further at-scale quantification, calibration and monitoring at the UK Geoenergy Observatory in Glasgow and the ‘Living Lab’ in Gateshead were also described. Experimental and analytical work examining changes in in-rock properties under heat and flow changes and geomicrobiological processes provided insight into controlling processes that could affect mine-water heat operations.

Thermal storage

An important emerging theme at the 2023 symposium was investigating thermal storage in disused mines and shafts for balancing intermittent electricity supply, for use of waste heat (for example from data centres) and to maintain long-term sustainability of temperature. The significant scale of potential storage was also highlighted. Interesting discussions included considering whether thermal storage would improve the economic case for mine-water heat schemes.

Raising awareness of mine-water energy

A number of talks covered economic, social and regulatory aspects. Community ownership and participation for a just, place-based energy transition provided a different perspective to speakers covering the opportunities offered by government-led heat zoning that could provide certainty to investors. The role of raising awareness with appropriate groups (for example housebuilders) was highlighted and a new mine-water heat resource map for Scotland was presented as a first step to guiding non-users to the opportunity.

Regulatory needs

Finally, a lively discussion followed presentations on an integrated regulatory and permitting regime in England, the needs of commercial operators and investors, and grant funding timelines for data and decisions. The symposium discussion ended with the aim of collectively articulating the data and regulatory needs for enhanced mine-water energy deployment and to raise awareness of these with decision makers.

Presentations

are available.

Thanks

Thank you to all the speakers and attendees for their contributions at Mine Water Energy 2023. We’re taking feedback from attendees and discussions are underway about next year, possibly for a hybrid event. We hope to see you all again next year.

Mine-water energy expert group

The aims to take forward these themes in its work throughout the year. Volunteers are welcome to join the group to contribute their knowledge and expertise by emailing MineWaterThermal_IEA@bgs.ac.uk (MineWaterThermal_IEA@bgs.ac.uk).

About the authors

Alison Monaghan leads mine-water energy research at BGS and is the science lead for the UK Geoenergy Observatory in Glasgow.

Gareth Farr is head of heat and by-product innovation at the Coal Authority.

Geothermal energy is the heat stored below the Earth 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.

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.

Rain falling onto hills and mountains percolates deep below the Earth 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 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.

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. 

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 energy mix.

Dr Timothy Kearsey, BGS Sedimentary Geologist.

More information

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The full paper is published in Science Direct: .

About the author