Geothermal heat pumps (GHPs) can be used to heat and cool residential, commercial, and institutional buildings, providing consumers with significant energy savings. In fact, a report published by the U.S. Department of Energy’s (DOE) Oak Ridge National Laboratory (ORNL) notes that GHPs save more than $50 billion in domestic energy costs (48.2% savings) and reduce peak summer electricity demand by 216 gigawatts (56.1% reduction). Additionally, GHPs support thousands of manufacturing, installation, and inspection jobs.
Upfront installation costs, however, create a barrier for accessing GHPs. The Office of Energy Efficiency and Renewable Energy’s Geothermal Technologies Office took this challenge head on through the Small Business Vouchers (SBV) Pilot program. SBV funded a Cooperative Research and Development Agreement between ORNL and Geothermal Design Center, Inc., a small business that specializes in GHP system and product engineering, to develop a new method for reducing initial testing times during GHP installation. This new method helps reduce the cost (a major obstacle to GHP adoption) of the geothermal ground loop.
GHPs use natural heat stored in the shallow subsurface of the Earth to provide space heating and water heating, and they use the ground as a heat sink for space cooling. This new testing approach can quickly and more accurately determine the effective ground thermal conductivity (GTC) based on thermal response test results. GTC is an important parameter for sizing ground heat exchangers used by GHP systems to transfer heat. While conventional GTC testing typically requires a 48-hour test period with a constant electric power supply, ORNL and Geothermal Design’s new method reduces the required test time by 40% or more. It can also determine GTC even with an unstable or intermittent power supply.
Costs associated with GTC testing are significantly being reduced with this approach, in conjunction with increased usage, which enables a more optimal design of GHP systems. Further, ORNL and Geothermal Design’s approach provides more information about the thermal properties of the ground heat exchangers than previous techniques, which can lead to further advancements and cost reductions in the GHP field and eventual reductions in costs to U.S. consumers.