FTC Analysis on a Current Project

Several of you blogged me and/or emailed me during the post intensive to discuss my proposed geothermal system on my studio project.

I just received the following formation thermal conductivity (FTC) analysis on a project that is under construction, that I am the Project Architect on. (same project that I showed the Day Light Factor Study on during the intensive and is blogged earlier on this blog).

The FTC analysis provides a measure of the thermal conductivity of a test bore; in other words, how well does the bore release heat generated by the heat pump system. The analysis that was provided indicates that a loop with 1" diameter piping, down and back up, was installed at a depth of 300 feet, and tested for 48 hours to determine how well the heat in the water would dissipate.

This project is in central Nebraska and the FTC value of 0.99 Btu/hr-ft-deg F is somewhat less than we typically see in the Omaha and Council Bluffs area, but not significantly. Normal values are 1.1 to 1.3 Btu/hr-ft-deg F. The loopfield we currently show on our geothermal well field site plan is designed for approximately 150 tons at the FTC value of 1.1. We actually only need about 130 tons, so we can probably reduce the number of loops and get a credit back from the contractor.

The Mechanical Engineer is going to run GeoCalc software to determine how many loops will actually be needed with this value, and we'll issue a cost deduct request to delete several bores from the project.

Below the report is the drill rig that is drilling the 300’ deep geothermal wells and the trailer pictures is the FTC test rig that was set up to give the report. The computer is inside the trailer and two pipes are running out of it and down the 300’ well.