Geothermal technology could help decarbonise the UK's heating and cooling

Diagram of the operational principle of low-temperature ATES in summer (L) and winter (R).

Geothermal technology has the potential to cut emissions by up to 94% for cooling and 41% for heating in the UK compared to other low-carbon systems.

The Imperial study showed that a cutting-edge technology capable of drastically reducing carbon emissions from the UK’s heating and cooling systems is being overlooked, despite already being available.

The new geothermal technology, known as Aquifer Thermal Energy Storage (ATES), provides low-carbon heating and cooling by storing warm water in an underground reservoir during the summer for winter use, and cold water during the winter for summer use.

The technology has already been successfully deployed, but the UK only has 11 systems in operation. These supply a tiny fraction of the UK’s heating and cooling demand – less than 0.01% and 0.5%, respectively. In contrast, countries like the Netherlands have over 3,500 systems in place, supplying a much larger share of their heating and cooling needs.

To carry out the research, Imperial College London researchers assessed the viability of the technology in the UK and are now calling for increased investment and government support to expand national deployment of ATES systems at scale.

The study is published in the journal Applied Energy.

Geothermal tech ‘overlooked’ in UK

ATES works by capturing and storing waste heat and cool underground in porous, permeable rocks. In winter, warm groundwater is pumped from the aquifer and used to supply heating in conjunction with a heat pump; the cooled groundwater is then pumped back underground in a nearby location and stored until summer. In summer, the cool groundwater is pumped from the aquifer and used to provide cooling; the warmed groundwater is then pumped back underground and stored until winter.

As part of the study, researchers analysed data from one of the ATES systems operating in London – the Wandsworth Riverside Quarter development operating in the Chalk aquifer – to assess the technology’s viability in the UK. 

They looked at the system’s performance and energy use and compared it to similar ATES systems in the Netherlands.

After analysing data from 2015 to 2021, the team concluded that the system is performing well. Their findings showed that the system stores and re-uses approximately equal amounts of energy for heating and cooling, which means it is sustainable over long timeframes – there is no net extraction of heat or cool from the groundwater.  They found that slightly more energy used is supplied for cooling (494 MWh annually) than heating (391 MWh).

Researchers also found that the system has reduced CO2 emissions by over 100 tonnes per year since its second year in operation, compared to conventional heating using natural gas.

Study leader Professor Matt Jackson, Professor of Geological Fluid Mechanics at the Department of Earth Science and Engineering at Imperial, said:

Our analysis suggests that scaling up ATES technology could make a major contribution to the UK’s heating and cooling demands. ATES has the potential to supply around 60% of the nation's current heating demand and around 80% of its cooling demand. Prof Matt Jackson Study leader

“Not only does this technology offer lower CO2 emissions, it also requires less electricity than rival heat pump technologies,  reducing demand on the electrical grid. The evidence shows that ATES could be suitable for widespread deployment across the UK.  We have the right climatic conditions, and widespread availability of suitable aquifers in which warm and cool water can be stored.  However, despite its potential and benefits, it remains almost unknown, with very few plans to expand its use.”

Reducing carbon emissions

As part of the new study, researchers also compared CO2 emissions from ATES with those from rival low carbon heating and cooling and heating technologies – including both ground- and air-source heat pump systems – and showed that it can further reduce emissions by 13-41% for heating, and 70-94% for cooling. 

Unlike conventional heat pump technologies, ATES stores and re-uses energy, rather than extracting energy from groundwater or air.  ATES systems therefore offer long term, sustainable heating and cooling. The researchers say ATES is suited to large-scale projects, such as hospitals, universities, office blocks and residential developments.

Co-author Dr Iain Staffell, from the Centre for Environmental Policy at Imperial, said:

“ATES technology provides lower emissions because it’s more efficient, as it captures, stores, and reuses waste heat and cool.

“In this way, cooling becomes a low-cost bonus, as it uses cool energy produced as a byproduct of heating, that would otherwise be wasted. This is crucial, as cooling needs are rapidly increasing as summer temperatures rise due to global warming – with London experiencing the highest rate of increase in cooling demand globally.”

Barriers to deployment

Despite confirming the efficient and sustainable operation of the Wandsworth ATES development in London, the team’s analysis of data from other UK ATES systems suggests some of them do not perform as well as they could. 

Some of the barriers to widespread deployment of the technology identified by the researchers stem from a lack of awareness and expertise regarding ATES, as well as a higher upfront cost and perceived risks associated with using a new technology.

Other issues the researchers also identified include incorrect operation of the ATES system after it has been installed, unbalanced supply of heating and cooling, and inaccurate predictions of how groundwater flows in areas with complex geological conditions. These barriers have been overcome in other countries and the researchers are developing solutions tailored to the UK market.

Call for a supportive regulatory framework

Given the potential of ATES, researchers are urging policymakers to remove regulatory hurdles and incentivise the use of the technology.

“Compared to other heating and cooling systems, including groundwater heat pumps, ATES systems are more efficient and sustainable. The potential for this technology is huge,” said Professor Jackson.

“Many countries are already using ATES, and we can learn from their experiences. To take full advantage of the benefits of this new technology we will need supportive policies and incentives, as well as a clear regulatory framework that supports the use of ATES,” said Dr Staffell.

“This will only be possible if UK regulators and policymakers work together with industry stakeholders and the public. We are working with these stakeholders to develop holistic strategies to support the uptake of ATES.”