7 - Energy geostructures

Abstract

Energy geostructures (eg, energy piles, walls and tunnels) incorporate the primary heat exchangers of ground-source heat pump (GSHP) systems through the foundation elements (eg, piles and basement walls) or into the tunnel linings. Concrete used for such structures is an ideal medium as the heat absorber in the ground due to its good thermal conductivity and thermal storage capacity. Thus, an energy geostructure functions not only to carry mechanical load but also as a heat exchanger, circulating cooler or warmer fluid liquid to extract stored geothermal energy from the ground. When designing such dual purpose structures, it is necessary to investigate the thermo-hydromechanical interactions between the heat exchanger–coupled foundation elements and the surrounding ground. In this chapter, the basic concepts of energy piles, walls and tunnels are introduced. The current understanding on the performance of such structures are summarised and some design considerations are discussed. More work is needed to build confidence in the use of energy geostructures. Once clear design guidance has been developed, the uptake of energy geostructures will increase from the current rate.