Ground energy systems: from analysis to geotechnical design

Ground energy systems use the ground and groundwater beneath a site as a heat source or sink to reduce energy costs and improve the environmental performance of buildings. The design and performance of the ground element of these systems (boreholes and ground loops) are dominant factors in the capital and operating costs of the system, yet, at present, such systems are often specified with little geotechnical input. This paper reviews some of the existing design approaches from a geotechnical perspective, and identifies potential failure modes (short term, long term and regulatory related) for ground energy systems. Short-term failures may result from deficiencies in the capacity of the infrastructure forming the ground element and/or from poor connection between the infrastructure and the ground. Long-term failures may derive from misestimation of loads and/or ground parameters. Possible future directions in the design of ground energy systems are discussed, and the need for informed geotechnical input to ground energy system design is highlighted.