Thermal Energy from Embedded Retaining Walls: Development of Analysis and Design Methods

The UK Government has a commitment to reduce greenhouse gas emissions by at least 80% by 2050. While the last five years has seen a 50% reduction in carbon density of the electricity grid, the target is unlikely to be met without also tackling the gas network. This is because gas, principally used to provide space heating delivers over twice the energy of the electricity grid.

With an ever decreasing carbon intensity of electricity, one of the best routes to decarbonise heating is through use of ground thermal energy storage coupled with ground source heat pump systems. However, heat pump systems retain high investments costs, mainly due to the expense of drilling dedicated ground heat exchangers (GHE).

Efforts to reduce these up-front costs include using dual purpose buried civil engineering structures as GHE and for structure support. This technique has been successful for foundation piles, but is now being developed for other infrastructure such as metro systems, underground carparks, and water and wastewater infrastructure.

Thermal energy storage via embedded retaining walls is the type of structure closest to industry implementation, having been trialled in notable case studies in Paris, London and Vienna. However, adoption of the technology is being held back by an absence of accessible analysis approaches and design tools to assess the amount of thermal energy which can be stored. This PhD project will provide those tools. It aims to:
- Develop novel analytical methods to relate heat exchanged with embedded retaining walls with the temperature changes within the structure;
- Test these methods against short to medium duration field data and longer timescale synthetic numerically derived datasets;
- Make recommendations for design methods and checks to be used in practice;
- Determine the types of projects and locations most suitable for long term operation of heating and cooling systems based on ground heat storage via embedded retaining walls.

As well as analytical analysis, the project will involve assisting in maintaining field sites and interpreting data from those sites. This will allow development of insights into the thermal behaviour of retaining walls used as heat exchangers which will guide choices on appropriate methods and boundary conditions for analysis and design. This PhD project forms part of a larger research project on energy from embedded retaining walls and the applicant will work with other researchers at the University of Leeds as well as a range of industrial and academic partners in the UK and overseas.