In-Situ Thermal Conductivity Testing for Ground-Coupled Heat Exchangers

Abstract

Geothermal heating and cooling systems do work well in most any venue if designed correctly. Load calculations and other mechanical design data are more easily acquired than geologic conditions. Formation Thermal Conductivity Testing (aka: “insitu” testing) is the proven means of measuring soil properties and predicting loop performance at a given site. Mobilization of a drill rig and cost of running a 48-hour thermal test are relatively high and speculative at early stages of a project, so pre-modeling of loads and proposed loops should proceed testing. Results facilitate design of ground-coupled heat exchangers and specifications for drilling contracts. Failure to plan test loop parameters inhibits subsequent design as testing data may or may not reflect conditions in shorter or deeper boreholes. Testing of ground conditions for geothermal design is technically simpler and less costly than geophysical logs and deep well measurements using similar terminology in production drilling industries.