The UK uses around 50 GW of energy to heat and cool buildings with only 6% delivered from renewable sources. Heating of buildings represents almost a quarter of UK carbon emissions, while demand for cooling is projected to increase as the climate warms and summers become hotter. The UK Heat and Buildings Strategy is clear that action to reduce emissions is required now to facilitate compliance with legally binding 2050 Net Zero targets. Moreover, the current geopolitical uncertainty has highlighted the risks associated with importing energy. However, heat is challenging to decarbonise due to its extreme seasonality. Daily heat demand ranges from around 15 to 150 GW, so new green technologies for inter-seasonal storage are essential. Geothermal resources offer natural heat energy, very large-scale seasonal energy storage, cooling as well as heating, and steady, low carbon energy supply. Widespread exploitation of urban geothermal resources could deliver a significant component - and in some cases all - of the UK's heating and cooling demand, supporting UK self-sufficiency and energy security. However, barriers remain to uptake of geothermal energy, especially at large-scale in urban areas. There is uncertainty in the size of the underground resource, the long-term sustainability of urban geothermal deployments, and potential environmental impacts. New methods and tools are required to monitor and manage installations to ensure the resource is responsibly used. These knowledge gaps, along with lack of awareness and guidance available for stakeholders and decision makers, result in higher than necessary risks and therefore costs. In this project, we will remove obstacles to uptake by reducing uncertainty about how the ground behaves when used to store and produce heat and cool at a large scale in urban areas. We will focus on relatively shallow (<400m depth) geothermal resources and open-loop systems in which groundwater is pumped into and out of porous, permeable aquifer rocks underground, because these offer large storage capacity and can deliver heat and cool. Shallow, open-loop systems are also deployable in most UK urban areas and have lower investment costs than technologies which require deeper drilling. We will conduct advanced field experiments with state-of-the-art monitoring, supported by laboratory experiments, to determine the response of aquifers to storage and exploitation of heat and use the results to understand how temperature changes over a wide area as groundwater flow transfers heat within the aquifer. We will compare two different aquifers, with contrasting types of underground flow regimes, that can be exploited across much of the UK. We will also determine how temperature changes impact groundwater quality and stress ecological environments and sensitive receptors, as well as understand any risks of ground movement caused by use of the resource. The field data will be used to create calibrated heat flow models, which we can use as a 'numerical laboratory' to simulate and explore the capacity of urban geothermal and how different installations within a city might interact. The results will support planning of future resource use and assess the capacity of geothermal resources to store waste heat from industrial processes and commercial buildings and return it later when needed. We will explore the use of AI-based models that can 'learn' from data provided by geothermal operators to actively manage the resource in a responsible and integrated way. Together, this research will permit regulators to plan and permit installations to ensure fairness and prevent environmental damage, as well as ensuring system designs realistically predict the amount of energy available. Recommendations will be made for resource assessment, safe and sustainable operation and management, to stimulate the widespread development of low carbon, geothermally heated and cooled cities.

The UK uses around 50 GW of energy to heat and cool buildings, only 6% of which comes from renewable sources. Reducing building sector emissions is an essential part of the UK's decarbonisation strategy for achieving net zero carbon emissions by 2050. However, heat is challenging to decarbonise due to its extreme seasonality. Daily heat demand ranges from around 15 to 150 GW, so new technologies with inter-seasonal storage are essential. Heating buildings in winter and cooling them in summer produces waste heat or cool that is currently lost. We propose a technology to instead store this and re-use when required, by warming or cooling groundwater that is pumped underground and stored in an aquifer (porous rock mass). In summer, warm water is stored to provide heating in winter; in winter, cool water is stored to provide cooling in summer. This technology is termed aquifer thermal energy storage (ATES) and has been widely applied in other countries, notably the Netherlands where there are over 2500 ATES installations. These have shown that the technology is highly efficient, recycling up to 90% of the energy that would otherwise be wasted. ATES can be deployed with renewable electricity sources, storing excess output to help ease the challenges of integrating >40 GW of intermittent offshore wind energy. The UK has only a handful of projects, mainly located in London and supplying less than 0.025% of UK demand. Yet it has high potential for ATES: there are seasonal variations in temperature and widespread aquifers where heat and cool can be stored. Moreover, there is increasing demand for cooling as well as heating, as summers become hotter and longer. Experience in other countries has shown that widespread deployment of ATES can be prevented by technical, economic and societal barriers, such as uncertainty in the response of aquifers to energy storage, a lack of knowledge of the economic value and decarbonisation potential of the technology, and lack of public understanding or acceptance. This project brings together geoscientists, geoengineers, economists and social scientists to address key barriers to deployment of ATES in the UK, proposing solutions that inform government policy, the regulatory framework, planning authorities, and energy and infrastructure companies. The project integrates four key strands, combining technical geoscience and geoengineering research with economics and social science research. This integrated approach is essential to address deployment barriers. Our overall goal is to deliver solutions and recommendations that facilitate an increase the capacity of ATES in the UK to several GW (a thousand-fold increase on current capacity) with projects widely deployed across the UK. Our research will determine the UK capacity for ATES, linking supply and demand and creating maps for policy makers and planners. We will understand how a key UK aquifer responds to ATES by conducting field trials and laboratory experiments. We will identify strategies to deploy and operate ATES systems that maximize storage capacity and efficiency, while accounting for uncertainties in aquifer behaviour that are inevitable when engineering natural systems. Our economic research will quantify the economic value of ATES, accounting for the lifecycle costs of installation and operation, and the added value that ATES can deliver to the wider energy system storing excess renewable energy from wind and solar in times of low demand. We will quantify the decarbonisation potential of ATES in a lifecycle context, so it can be objectively compared against other low carbon heating and cooling options. Our social science research will ensure responsible deployment of ATES, promoting the co-design of ATES projects in line with societal priorities and values. It will use international examples to identify best practice, and identify and quantify broader societal benefits, such as the potential to develop a demand for skilled jobs.