Energy piles: current state of knowledge and design challenges

Energy piles offer a promising and eco-friendly technique to heat or cool buildings. Energy piles can be exploited as ground heat exchangers of a ground source heat pump system. In such application, the energy pile and its surrounding soil are subjected to temperature changes that could significantly affect the pile-soil interaction behaviour. The aim of this paper is to review the current state of knowledge on the design of energy piles in terms of the geostructural and heat exchanger functions. Furthermore, a conceptual understanding of the potential temperature effects on the mechanical behaviour of piles is proposed in this paper. Based on this conceptual understanding as well as the reported thermo-hydro-mechanical behaviour of saturated clays in the literature, the challenging geotechnical aspects facing the energy pile design are highlighted, and further research efforts to refine them are recommended.