A review on the performance of geothermal energy pile foundation, its design process and applications

Geothermal energy piles (GEPs) are an environmentally friendly energy source which utilise the low-grade heat energy present in the shallow earth surface to provide heating and/or cooling to the supported structures e.g. buildings. The heat is extracted from or injected into the ground through the circulation of heat carrier fluid that flows in energy loops attached to the reinforcement cage of the pile foundation elements. Utilising the GEP system to achieve building thermal comfort need has proven to be environmentally sustainable, economically viable, and with great social benefits. This paper presents an extensive review of literature on the principles behind the different design considerations, current available design standards, and government legislation for installing the GEP system. Furthermore, the behaviour of the energy pile under working loads was found to be influenced by the magnitude of the heat energy extraction and injection rate. In addition, case studies from several countries around the world including Austria, Switzerland, Australia, UK, Spain, Hong Kong, USA, Japan, China and South Korea which highlights the practicality of the system installation, its associated benefits, limitations and overall energy performance were presented and discussed. Moreover, factors such as thermal conductivity, thermal diffusivity, specific heat capacity, groundwater flow, soil moisture content, number and configuration of energy loops, pile length and diameter have positive implication on the energy performance of the system. This paper found that the GEP system, if appropriately designed and carefully installed, provides a viable alternative in terms of an energy source with a positive energy footprint on the environment.