Thermo-mechanical aspects of pile heat exchangers: background and literature review

Pile heat exchangers are thermo-active ground structures with built in geothermal heat exchanger pipes. As such, the foundation of the building both serves as a structural component and a heating/cooling supply element. The existing geotechnical and structural design standards do not consider the nature of the thermo-active foundations, what hampers their implementation. Several studies tackle different aspects of the thermo-mechanical behaviour of pile heat exchangers by experimental and numerical approaches. This document aims to compile the main literature in the field. We depart from understanding how an energy pile behaves under mechanical and thermal loads and then, we look into the different aspects affecting the phenomena. It is concluded that, even though the thermal loads resulted from the geothermal use applied to the energy piles are not likely to lead to geotechnical or structural failure, they need to be considered in the analysis and design of such structures. More data under operational conditions will ease the development of regulations and unified guidelines.