Shawn Naylor
Geological Research at the IGS

The Indiana Shallow Geothermal Monitoring Network: A test bed for facilitating the optimization of ground-source heat pumps in the glaciated Midwest

Status Start Date End Date Locations
completed May 9, 2011 Sep 15, 2013 All Counties
Director: Shawn Naylor
Other Researchers: Jack Haddan, Sally Letsinger
Funding: U.S. Department of Energy - USDE - No Specific Program
Issue: Shallow geothermal energy represents a significant renewable resource that can be further developed via ground-source heat pumps (GSHP), the costs of which can be minimized by allowing designers and installers to make decisions about construction technologies that take into account the appropriate thermal properties and predominant moisture regime of the geologic material being utilized.
Objective: A comprehensive monitoring network that provides in-situ measurements of shallow subsurface thermal conductivity, temperature gradients, and soil moisture has not been developed to date.
Approach: The study entails collecting continuous measurements of 1) thermal gradients in the upper 6 feet of the ground, 2) thermal conductivity, and 3) volumetric moisture content at six monitoring sites near the two largest population centers in Indiana (Indianapolis and Fort Wayne).
Products: The data will be compiled and made available through the National Geothermal Data System (NGDS), in addition to being summarized in an Indiana Geological Survey (IGS) publication that will provide relevant geotechnical information for heat pump installers in the state.
Benefits: Although software exists for GSHP installers to calculate optimal lengths and configurations of ground-coupling geothermal systems, uncertainties exist for input parameters that must first be determined for these applications, including soil thermal properties and earth temperatures. The fundamental control on heat transfer for a ground-coupled heat pump system is the thermal conductivity of the earth materials within which the system is installed. The determination of thermal properties for typical unconsolidated sediments that are present in the upper 6 feet of the ground will support the design of more efficient systems by allowing GSHP installers to efficiently tailor the configurations of their in-ground systems to specific geological conditions and account for seasonal changes.

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