Case Study: Thermal Conductivity Testing of a Kelix Thermacouple™, North Carolina

The Project:

Terraclime Geothermal was contracted to install and test a Kelix Thermacouple™ for a municipal recreation center in North Carolina.

The Thermacouple is a revolutionary and patented geothermal well design that maximizes heat transfer to the ground through increased turbulence and borehole geometry.

Due to limited field applications, the earth coupled properties of the Thermacouple are still being evaluated.  Terraclime Geothermal was contracted to install a Thermacouple to 300 feet, and perform a thermal conductivity test.

The Thermacouple consists of an approximately 4-inch diameter fiberglass composite outer casing, and a 3-inch diameter, finned PVC inner tube.  The borehole for the Thermacouple was drilled to a total depth of approximately 300 feet.  The borehole was backfilled with a thermally-enhanced cementitious grout (GeoSupergrout™).

After installation, the Thermacouple was tested for 48 hours according to American Society of Heating, Refrigerating & Air-Conditioning Engineers (ASHRAE) recommendations for Thermal Conductivity Testing.

The results of the testing suggested that the Thermacouple could provide up to 3 tons of heating and cooling, or approximately 100 feet of borehole per ton (12,000 Btu/hr).  This is an exceptional performance in a geographical location where typical boreholes yield approximately one ton per 200 feet of installed HDPE U-bend.  However, the long-term heat transfer capacity of the Thermacouple has not been evaluated.  Based upon ongoing research being conducted by Terraclime Geothermal, it appears that long-term performance may require an increase in the effective loop length from 100 feet per ton to at least 160 feet per ton to prevent premature loopfield failure.