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Geothermal energy has a great potential to provide a constant source of clean and reliable energy to both residential and commercial sectors of our society which consume a major portion of this nations energy demand. The implementation of geothermal energy is fairly simple since heat can be extracted from the earth’s surface at relatively shallow distances. In combination with structural pile foundations, geothermal energy can be used as an alternative energy solution for buildings. This type of ground-source heat extraction has existed for many years in Europe and Asia and has been a clean energy technology with a reported 50% CO2 emissions reduction and a decreased need for primary energy sources to operate . It has been implemented not only in residential but multi-story commercial buildings as well. They are also beneficial since they can provide the structural and heating/cooling needs within one system and requiring less land usage and upfront costs. Geothermal energy piles are typically laid out in a pattern suitable to support the structure above and a typical cross section consists of concrete, steel reinforcement and high density polyethylene tubing. The tubing and steel reinforcement are arranged together before being lowered into a drilled shaft or borehole and filled with concrete. Once all piles are in place, the tubing is connected to a ground source heat pump which circulates a heat transferring medium throughout. As it is pumped the medium is heated by the ground through heat transfer processes and it is then pumped back into the building and distributed throughout. Energy pile foundations have the ability to use ground source heat and raise the relatively low temperature to a usable level.
The objective of this research project is to understand the thermo-hydro-mechanical effects of ground source heat pump systems on structural pile foundations. It is important to understand what effect heating and cooling cycles have on the behavior of concrete foundations in order to determine their long-term structural stability. Questions arise about the structural integrity of the pile when subjected to heating and cooling cycles since the pile will expand when heated and contract when cooled. The thermo-hydro-mechanical response of the soil-pile interface must be understood for better design practices and standards.
|Figure 1: A Typical Geothermal Energy Pile System||Figure 2: Geothermal energy pile construction |
1. Banks, David. An Introduction to Thermogeology: Ground Source Heating and Cooling. Oxford: Blackwell Ltd, 2008. Print.