DFI Supports U.S. Energy Pile Research Efforts Energy Piles are an innovative renewable energy technology being studied at Virginia Tech as part of recently funded National Science Foundation (NSF) projects. Energy Piles are deep foundation elements designed to access and exploit the relative constant temperature of the ground for efficient heating and cooling of buildings. Ground temperature below a depth of about 10-20 C (50-70 F) in most regions. Circulation loops are integrated into the deep foundation element. Fluid is circulated through the tubing as heat energy from the building is fed into and withdrawn from the ground for cooling in the summer and heating in the winter. Although Energy Piles have seen exponential growth in Europe and Japan over the last decade, they have received little attention in the U.S. This is partly due to a lack of awareness about their benefits, along with a lack of U.S. case studies that demonstrate their cost-effectiveness. The Virginia Tech research team is about 5 m (20 ft) remains relatively stable at o o working with DFI, and its member firms, to investigate Energy Pile behavior. Our overall aim is to develop simplified design guidelines for widespread and efficient implementation of this new technology in the U.S. We are performing full-scale field tests, laboratory tests, advanced numerical modeling, and transferring technology from Europe where Energy Piles are used more commonly. The Energy Pile research program at Virginia Tech began in the fall of 2009 following a $260,000 research grant from the NSF. In this phase we partnered with Layne GeoConstruction and installed a full- scale field test setup at the Virginia Tech Geotechnical Research Facility. The field test consists of a total of five micropiles, four of which are equipped with circulation loops for heat exchange. The piles are 25 cm (10 in) in diameter and extend 30 m (100 ft) deep. The piles are instrumented with strain gauges and thermistors. Several observation boreholes, ranging from 18 to 36 m (60 to 120 ft) in depth, were formed around the test piles to monitor ground temperatures during heat exchange 78 • DEEP FOUNDATIONS • JAN/FEB 2012 operations. The circulation loops within the Energy Piles are pressure tested against punctures and possible leakage. In addition, thermal conductivity testing was performed to evaluate the heat exchange capacity of the soils at the test site. Insulated loops are connected to the circulation tubes in the test pile. Heated fluid is pumped through the Energy Pile and temperature change during the test is monitored to evaluate thermal conductivity. U. S. Army Corps of Engineers, NSF and others. The group indicated that one of the main obstacles to wider use of Energy Piles in the U.S. is the relative lack of field proof testing and reliable field performance data, particularly U.S.-specific field data. Those at the session identified critical areas for additional work and formed a project team including industrial participants. The inclusion of industrial partners made it possible to submit a proposal for a large Components of an Energy Pile The research team, along with Mary Ellen Bruce, DFI’s technical manager, organized a planning session on Energy Piles in June 2010. This event, in Virginia, convened stakeholders, including pile foundation and drilled shaft contractors, engineering firms, heat pump manu- facturers, and representatives from government agencies such FHWA, National Institute of Building Sciences, AUTHORS: C. Guney Olgun, Ph.D., Research Assistant Professor of Civil and Environmental Engineering, Virginia Tech James R. Martin, II, Ph.D. Professor of Civil and Environmental Engineering, Director of the Disaster Risk Management Institute, Virginia Tech grant to a specific program at NSF that required university-industry collaboration. As a result, the research team was recently awarded a $600,000 grant to expand the scope of the earlier study. This recent award will build on the initial research study and involves additional field testing of Energy Piles at four additional sites across U.S. (Gary Ind., Baltimore Md., College Station and Houston in Texas). Several industrial participants are providing in-kind contributions by building full-scale field tests, donating materials, instrumentation and heat pumps. Berkel & Company and Thatcher Foundations are installing the Energy Piles at the test sites and assisting with the field testing. Geo-Instruments is assisting with field instrumentation and providing the necessary sensors for the field tests. Piping for the geothermal loops and heat pumps for the field tests are
