The Use of Energy Piles for Sustainable Energy

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

As global energy demands continue to rise, along with the production of harmful greenhouse gases, there is a critical need for research to advance innovative renewable green energy technologies. Geothermal energy, for instance, is a renewable energy source whose use in the US has been limited mainly to western regions where high ground temperatures near the surface have been exploited for residential heating and production of electricity. With the development of new technologies, we can exploit geothermal energy much more efficiently and broaden its applicability to almost any geologic and climatic condition, including areas where there is no geothermal heat source. That is, there is tremendous potential in simply utilizing the relatively constant temperature of the ground (i.e., "geothermal energy") in the upper 30 m of the soil profile, about 55F (13C) in most areas, to help regulate the temperature of buildings. This research will investigate the use of Energy Piles, a new geothermal energy concept designed to efficiently access the constant temperature of the ground for heating and cooling of buildings. In this new concept, the foundation piles that are already in place for support of the building are used conjunctively as geothermal cooling/heating elements. The piles, typically 20 to 30 m long, are installed with circulation tubes that act as heat exchangers where heat energy is circulated through the tubing with water or antifreeze. Heat energy from the building is fed into the ground for cooling in the summer and withdrawn from the ground for heating in the winter. The fluid circulation is performed via a heat pump similar to those used in conventional residential and commercial applications. Cost savings for heating and cooling could be as much as 80% for buildings outfitted with Energy Piles, especially in extreme climate regions. Pilot tests and limited applications for major buildings have been recently completed in Japan and Europe, respectively, but the Energy Piles concept is largely unknown. No major systems of this type are currently being used the US. This research will develop the data and expertise needed for wide-scale and efficient implementation of this promising new technology. The project will involve development of a full-scale field test section, advanced numerical modeling and a detailed cost-benefit feasibility analysis to study key aspect of Energy Pile systems, such as what factors affect their conjunctive performance as heat exchangers and as load bearing foundation elements, how their performance varies with differing ground and climatic conditions, and how they can be installed and operated most cost-effectively. The main intellectual merit is that the findings could lead to wide-scale implementation of a new alternative energy technology that is currently being underutilized. In terms of broader impact, the study represents an important new step toward the sustainable design of "green" buildings that use near-zero energy for heating and cooling. In addition to being an alternative renewable energy resource that reduces greenhouse gas emissions, Energy Piles offer the added advantage of being applicable in any climate or region, including those where wind and/or solar power have limited effectiveness. The findings of this study will be disseminated to a broad audience via journals, the Internet, and incorporated into academic courses and the PIs' frequent professional shortcourses for ASCE, FEMA, FERC, and USACE. Finally, there will be a diverse research team, including an ethnic minority, a disabled person, senior and junior faculty and an undergraduate student researcher.