ESTCP Geothermal Foundations Project

Project Overview
The objective of this project sponsored by DoD ESTCP (project EW-201153) was to construct a new building at the US Air Force Academy with several geothermal foundations having different designs. Data is currently being collected to demonstrate the feasibility of using geothermal foundations to heat and cool buildings, and to compare the energy efficiency of a ground-source heat pump system with a conventional heating and cooling system. The results from this project are being used to enhance the design methodologies used for geothermal foundations. As the importance of energy dependence for buildings is a growing priority for the Department of Defense (DoD), new technologies are being developed in order to reduce the need of external energy requirements in all aspects of building operations.  Geothermal foundations are building foundations that serve the dual purpose of supporting building loads as well as providing access to geothermal energy. Tubing is embedded into the concrete of the deep foundation system that allows energy to be exchanged with the ground as a means of building heating and cooling. 

One of our specific objectives is to understand soil-structure interaction in full-scale geothermal foundations. As a foundation element is heated and cooled, it will expand and contract, which can lead to load distribution within the foundation that could potentially compromise the structural integrity of the building. Although no significant structural issues have been reported in previous research, analytical tools are needed to validate designs with respect to load distribution in the foundation element. Since the soil conditions at every site vary, an in-situ testing device has been developed to determine site-specific design parameters that could be implemented in a computer model in order to more accurately predict load distribution patterns in the foundation during heating and cooling. This research aims to further advance tools to aid in the safe design of geothermal foundations in order to have more widespread usage with the DoD and throughout the world.