A ground source heat pump system is a highly efficient renewable heating, cooling, and ventilation system that utilizes the ground as a heat source or sink via ground heat exchangers. Energy pile is an energy geotechnical structure that couples a ground heat exchanger with a geotechnical structure, leading to low capital cost. The design of energy piles can be challengeable due to their complicated geometries and the requirement of mechanical load. This study focuses on the heat transfer across the concrete–soil interface of energy piles in urban areas. Case studies from two projects, the Lambeth College and Shell Centre projects, are presented and discussed. The back analysis of two energy pile cases illustrated that the heat transfer coefficient at the pile–soil interface can differ between the cooling mode and the heating mode. It can be concluded that the difference in the heat transfer coefficient is influenced by a number of factors such as soil properties, concrete (grout) properties, and the installation method.

To meet long-term climate change targets, the way that heating and cooling are generated and distributed has to be changed to achieve a supply of affordable, secure and low-carbon energy for all buildings and infrastructures. Among the possible renewable sources of energy, ground source heat pump (GSHP) systems can be an effective low-carbon solution that is compatible with district heating and cooling in urban areas. There are no location restrictions for this technology, and underground energy sources are stable for long-term use. According to a previous study, buildings in urban areas have demonstrated significant spatial heterogeneity in terms of their capacity to demand (C/D) ratio under the application of GSHP due to variations in heating demand and available space. If a spatial sharing strategy can be developed to allow the surplus geothermal capacity to be shared with neighbors, the heating and cooling demands of a greater number of buildings in an area can be satisfied, thus achieving a city with lower carbon emissions. In this study, a GSHP district system model was developed with a specific embedding sharing strategy for the application of GSHP. Two sharing strategies were proposed in this study: (i) Strategy 1 involved individual systems with borehole sharing, and (ii) Strategy 2 was a central district system. Three districts in London were selected to compare the performance of the developed models on the C/D ratio, required borehole number and carbon emissions. According to the comparison analysis, both strategies were able to enhance the GSHP application capacity and increase the savings of carbon emissions. However, the improvement levels were shown to be different. A greater number of building types and a higher variety in building types with larger differentiation in heating and cooling demands can contribute to a better district sharing performance. In addition, it was found that these two sharing strategies were applicable to different kinds of districts.

Ground-source heat pump systems are renewable and highly efficient HVAC systems that utilise the ground to exchange heat via ground heat exchangers (GHEs). This study developed a detailed 3D finite element model for horizontal GHEs by using COMSOL Multiphysics and validated it against a fully instrumented system under the loading conditions of rural industries in NSW, Australia. First, the yearly performance evaluation of the horizontal straight GHEs showed an adequate initial design under the unique loads. This study then evaluated the effects of variable trench separations, GHE configurations, and effective thermal conductivity. Different trench separations that varied between 1.2 and 3.5 m were selected and analysed while considering three different horizontal loop configurations, i.e., the horizontal straight, slinky, and dense slinky loop configurations. These configurations had the same length of pipe in one trench, and the first two had the same trench length as well. The results revealed that when the trench separation became smaller, there was a minor increasing trend (0.5 °C) in the carrier fluid temperature. As for the configuration, the dense slinky loop showed an average that was 1.5 °C lower than those of the horizontal straight and slinky loop (which were about the same). This indicates that, when land is limited, compromises on the trench separation should be made first in lieu of changes in the loop configuration. Lastly, the results showed that although the effective thermal conductivity had an impact on the carrier fluid temperature, this impact was much lower compared to that for the GHE configurations and trench separations.