GIS-BASED ASSESSMENT OF GROUND-SOURCE HEAT PUMP POTENTIAL IN THE WILLIMANTIC QUADRANGLE, CONNECTICUT

Through the collection and digital manipulation of geologic and hydrologic data, ArcGIS was used to develop a resource map to model the potential for closed-loop, vertical column ground-source heat pump (GSHP) operation. Since Connecticut has a very diverse and complicated geologic composition, and the performance of a GSHP system depends largely on the local geologic and hydrologic environment, there is high variability of success among specific sites. To strengthen consumer confidence, it is necessary to distinguish among sites of high and low potential before investing in a GSHP system. The resource map that I developed provides the GSHP market and consumers with a valuable tool to easily and economically perform a preliminary resource assessment for a site in question.

GIS data on Connecticut’s surficial materials and bedrock were imported into ArcGIS and cropped to the Willimantic quadrangle. Data on the overburden thickness and the height of the water table were collected and compiled using archived well completion reports from the towns within the quadrangle. This data was imported into ArcGIS and an interpolation was performed to best approximate the overburden thickness and water table depth for all point locations within the quadrangle. A literature review was conducted to establish a set of criteria for successful and economical GSHP operation. These criteria include the thermal properties of the soil and rock layers, the thickness of these layers, the hardness of the bedrock, the hydrologic properties, and the subsurface temperatures. ArcGIS was used to manipulate the data according to the established criteria in order to distinguish among regions of lower and higher GSHP potential.

The resulting map is a resource assessment for closed-loop GSHPs in the Willimantic Quadrangle. Its accuracy was verified by visiting real GSHP sites within different performance boundaries and comparing the relative actual performances among those systems.