We are exploring the provision of low-carbon heating and cooling to buildings using the ground as a thermal battery. Our research spans the mechanical and thermal behaviour of thermo-active geostructures, data-driven design tools, and whole-system analyses of ground source energy deployment — with the aim of removing technical, economic, and regulatory barriers to widespread adoption.
Our work in this area has been driven in large part by the SaFEGround (Sustainable, Flexible and Efficient Ground Source Energy Systems) project, funded by UKRI between 2021 and 2025 and conducted in collaboration with the University of Cambridge, the University of Leeds, and De Montfort University,
Thermo-active structures
The central focus of our ground source energy research has been the development of rigorous yet practical design methods for thermo-active piles — structural foundation elements that also function as ground heat exchangers. A key challenge is quantifying and managing thermal interference when piles operate in groups, as adjacent heat exchange elements compete for the same thermal resource. introduced a simplified methodology for determining the thermal performance of individual thermo-active piles, avoiding the computational expense of full three-dimensional thermo-hydraulic finite element analyses. This was followed in 2024 by two companion papers: characterised the effects of thermal interference on pile group performance in Renewable Energy, and presented a design methodology that explicitly incorporates those interference effects in Geomechanics for Energy and the Environment. Together, these works provide practitioners with a coherent framework for moving from single-pile assessment to group-scale system design.
Parallel conference contributions have examined the influence of pipe arrangement and improved thermal conductivity on pile response (), the thermal performance of pile groups (), and the effect of pile spacing on group behaviour ().
2D Single U-loop video
A thermo-active pile with a single U-loop is analysed using a 2D thermal analysis, which provides the correct distribution of temperature in a section far from any of the boundaries. The temperature along the circle that contains the pipes is subsequently averaged and converted into a time-series that can be used in 2D coupled THM analysis to determine forces and displacements arising from thermo-active pile operation. The integral of the temperature distribution in the full 2D section can also be used to establish the thermal performance of the pile in W/m, enabling more accurate thermal design of these heat exchangers.
2D Heat transfer with 3 u-loops
When a larger number of U-loops is used, heat transfer from the pipes to the pile and the surrounding ground accelerates and overall larger temperatures are obtained. This indicates a considerably larger thermal performance in W/m and explains that current designs maximise the number of pipes within the cross-section of the thermo-active pile. However, with greater heat transfer, mechanical forces within the structure increase and need to be acknowledged in its design, as seen in the work by [] for thermo-active piles and [] for thermo-active retaining walls. There are also implications in terms of thermal interference when thermo-active piles are arranged in pile groups - read more about this in and .
Data-Driven Design Tools
More recent work has extended our research into machine-learning-assisted design. presented a surrogate neural network model — trained on a Latin hypercube sample of thermo-hydraulic finite element analyses — capable of predicting the long-term thermal performance of a thermo-active pile at a fraction of the computational cost. This enables the optimisation of large ground source energy systems involving many piles with diverse configurations, in a way that was previously impractical. A companion paper by introduced a method for incorporating heat pump coefficient of performance directly into the geothermal pile design process, linking the subsurface thermal response to the electricity consumption of the surface plant.
An overview of the full SaFEGround programme and its interdisciplinary design approach is presented in .
Whole-System and Policy Analysis
The interdisciplinary scope of SaFEGround extends to energy systems analysis and policy. Collaborators from 51³Ô¹ÏÍø's Chemical Engineering department and Centre for Environmental Policy have examined system optimisation of integrated thermal storage and ground source heat pump systems under time-varying electricity prices (), the impact of the energy crisis on the UK's net-zero transition (), and energy import security within optimal UK decarbonisation pathways (). A review of recent progress in the design and integration of domestic heat pumps is provided in , and assessments of ground source heat pump deployment at household and national scale in the UK appear in and . The integration of photovoltaic systems, heat pumps, and energy storage in buildings is explored in .
Publications and open datasets are available through and the .
Contact Geotechnics
Geotechnics
Civil and Environmental Engineering
Skempton Building
51³Ô¹ÏÍø
South Kensington Campus
London, SW7 2AZ
Telephone:
+44 (0)20 7594 6077
Email: j.otoole@imperial.ac.uk
Alternatively, you can find a member of Geotechnics staff on the Department of Civil and Environmental Engineering website.
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