Energy Geostructures for Reducing Energy Consumption in Hong Kong: An Example of Energy Diaphragm Wall

Energy geostructure is a green construction technology that turns geostructures such as piles, walls and tunnels to underground heat exchangers; by embedding polyethylene pipes in the concrete body of these geostructures, they could be used to inject heat into the ground in summer for space cooling and extract heat from the ground in winter for space heating, through the control of ground-source heat pump (GSHP). By exchanging ground energy, energy geostructures represent an advantageous technology to reduce energy consumption of air-conditioning nearby buildings sustainably. However, adoption of this technology in Hong Kong is slow primarily because of high cooling load and declining energy efficiency caused by ground thermal imbalances. This study presents a series of finite-element simulations to demonstrate the energy and structural performance of hypothetical, GSHP-coupled, reinforced concrete energy diaphragm wall panels, when operated under long-term extreme and realistic energy use scenarios in Hong Kong for an underground shopping mall. Changes in heat exchange efficiency due to continuous heat injection to the ground are presented. Implications in the engineering design of the diaphragm wall due to the additional thermal functioning through detailed analysis of soil-structure interaction are discussed.