Shallow geothermal energy represents a renewable resource that can be further developed via ground-source heat pumps (GSHPs). The costs of these systems 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.

Researchers at the Center for Geospatial Data Analysis and Indiana Geological Survey developed a comprehensive monitoring network that provides in-situ measurements of shallow subsurface thermal conductivity, temperature gradients, and soil moisture. Continuous measurements of 1) thermal gradients in the upper 6 feet of the ground, 2) thermal conductivity, and 3) volumetric moisture content are collected at six monitoring sites near Indianapolis and Fort Wayne, the two largest population centers in Indiana

Although software allows GSHP installers to calculate optimal lengths and configurations of ground-coupling geothermal systems, there are 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 in which the system is installed. The determination of thermal properties for typical unconsolidated sediments 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 systems to specific geological conditions and also to account for seasonal changes.

Site locations and data

Site name (click name for data)	Site #	Geologic setting	Texture at 4-foot depth	Bulk density (g/cm3)
Flat Rock River	1	alluvial terrace	sandy clay loam	1.11-1.32
Bradford Woods	2	alluvial terrace	silt loam	1.32-1.58
Shelbyville Moraine	3	moraine crest	silty clay loam	1.41-1.79
Eel River Valley	4	outwash terrace	sandy loam	1.46-1.71
Wabash Moraine	5	moraine crest	clay loam	1.64-1.80
Ball State Univ.	6	till plain	silt loam	NA

For more information contact Shawn Naylor (snaylor@indiana.edu).