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.