“Combining Geothermal Heat Pumps (GHPs) with Underground Thermal Energy Storage (UTES)" by Mr. Charles Hammock

This project supports ESTCP’s efforts to increase the energy security of Department of Defense (DoD) facilities by significantly reducing their energy consumption, water consumption and on-site emissions while simultaneously reducing the cost of deploying geothermal heat pump (GHP) systems and creating an inside-the-fence geo-utility that can serve the installation for decades. The objectives of the demonstration included a minimum 30% reduction in heating ventilation and air conditioning (HVAC) energy consumption, an 80 to 100% reduction in cooling water consumption, and a 100% reduction in on-site emissions and cost reductions over conventional GHP systems. Two architectures of Underground Thermal Energy Storage (UTES), namely borehole thermal energy storage (BTES) and aquifer thermal energy storage (ATES), were demonstrated with both featuring GHPs, adiabatic dry coolers and the reversibility of flow through the UTES such that both waste heat (for winter heating) and “waste cool” (for summer cooling) could be captured in the geology and used out-of-season. The BTES system utilized 306 concentrically-zoned boreholes, drilled 210 feet deep into the underground formation, and a 6-pipe heat recovery chiller that simultaneously created 45°F chilled and 105°F space heating hot water. The ATES featured 2 warm and 2 cold reversible-flow water wells that stored waste-heated and “waste-cooled” water 250 to 400 feet beneath the surface in the unconsolidated on-site aquifer. HVAC energy consumption was reduced almost 50% on both projects, on-site emissions eliminated and 4.6M gal/year of cooling water saved at the BTES site.

Mr. Chuck Hammock is a Principal/Founder and Mechanical Engineer with Andrews, Hammock & Powell, Inc., a Consulting Engineering firm established in Macon, Georgia in 1988. Mr. Hammock’s career began in 1980 and has been devoted to the design of HVAC systems for the built environment. As a practicing design engineer, his passion and focus have been on innovative deployments of GHPs. This specialty led to Mr. Hammock being selected as the Principal Investigator of ESTCP’s demonstration project combining GHPs with UTES. The project concluded in the Spring of 2017 with the installation of the first BTES system and first warm and cold ATES system in the United States. Mr. Hammock’s design efforts have extended to as far away as Cape Town South Africa, at that continent’s only Leadership in Energy and Environmental Design (LEED) Platinum hotel. Other successfully deployed technologies include the use of underground fiber optic cable for temperature monitoring and to conduct layered thermal response tests (TRTs) of the geology at the BTES site. Mr. Hammock is a graduate of Auburn University, Alabama, where he earned his Bachelors of Mechanical Engineering in 1983. He is a licensed Professional Engineer in multiple states and holds the LEED BD+C credential from the U.S. Green Building Council and the Certified GeoExchange Designer designation from the International Ground Source Heat Pump Association.