Review on heat transfer and thermo-mechanical behaviour of energy geostructures

Abstract

Energy geostructures represent a novel building energy-saving technology derived from ground source heat pump technology. Heat transfer and thermo-mechanical response characteristics stand out as pivotal issues in the investigation and design of such energy geostructures. This paper provides an overview of the research on heat transfer models, factors influencing heat exchange performance, and thermo-mechanical behaviour concerning energy piles, energy walls, and energy tunnels. The future perspectives are also presented. Four types consisting of ten basic heat transfer models for energy piles were summarized, and their advantages, limitations, and applicable scenarios were comprehensively discussed from multiple aspects. The heat transfer models for energy walls and energy tunnels are scarce, and only one model was introduced for each of them. The influences of some controllable design parameters on the thermal performance of energy geostructures and the thermal-induced mechanical behaviour were summarized. The key conclusions are that the fluid flow rate should not be too high or too low, which is generally considered sufficient to ensure that the flow state is turbulent; and properly intermittent operation is beneficial to the recovery of geothermy, thereby improving the heat exchange performance. Due to the differing conditions considered, it is not possible to draw a definitive conclusion regarding whether heating can increase or decrease the shaft resistance or bearing capacity of energy piles. Generally, thermal effects within energy walls are unlikely to cause severe damage to structural stability. The issues related to thermal-induced ground deformation are considered more critical than those concerning the energy tunnel structure deformation. This paper highlights the aspects that require further research and the new aspects worth exploring in the future. Energy geostructures are not limited to new construction projects, and combining with other renewable energy utilization methods and integrating into district energy networks are the future development trends.

Keywords

Energy geostructure / Energy pile / Energy wall / Energy tunnel / Heat transfer / Thermo-mechanical behaviour

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

CRediT authorship contribution statement

Duofeng Cen: Writing - original draft, Visualization, Methodology. Caichu Xia: Writing - review & editing, Supervision, Conceptualization.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

This work was supported by the Key Project of Zhejiang Provincial Natural Science Foundation of China (Grant No. LZ22E080008) and Ningbo Natural Science Foundation of China (Grant No. 2024J091).

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