Understanding the behaviour of energy geo-structures

The heating and cooling of buildings represents a big chunk of global energy needs and a significant cause of carbon dioxide emissions. There is thus growing use worldwide of so-called ‘energy geo-structures’ – particularly piles – which take advantage of the relatively constant temperature of the underlying ground to reduce building energy requirements. Fluid circulating in pipes in such structures can extract heat from the ground to help heat a building in winter and can expel excess heat from air conditioning in summer. However, this introduces potentially serious additional stresses and strains which need to be considered during design – though they seldom are. This paper describes recent research into the thermo-mechanical behaviour of energy piles to help ensure they are properly designed.