Seminar 43 - New Advances in Ground-Source Borehole Thermal Response Testing and Storage Applications ✓ Most Recent

Track: Fundamentals and Applications
Sponsor: 6.8 Geothermal Heat Pump and Energy Recovery Applications
Chair: Cary Smith, Member, Sound Geothermal Corp., Sandy, UT

Borehole thermal resistance is the most important field measured component in the loopfield design. Advancements in measurement and heat storage/recovery enable more detailed information to the design engineer and adds forensic tools. The advanced analytical tool extracts more information from the thermal conductivity test in a shorter amount of time. Thermal regimes, such as grout conductivity, can be identified, and stability of the power source is less important. Advances in borehole thermal storage (BTS) management permit more precise use of the heat stored and being stored. This seminar presents the latest advancement in storage management and measurement.

1. Dynamic Determination of Ground Thermal Conductivity and Minimum Thermal Response Test Duration Using theLine Source Model
Xiaobing Liu, Ph.D., Member, ORNL, Oak Ridge, TN
The effective ground thermal conductivity (GTC) is a critical design parameter for sizing ground heat exchangers (GHXs) of ground source heat pump (GSHP) systems. GTC is usually determined with a thermal response test (TRT) and inverse modeling. The current practice requires extremely stable power supply for 36-48 hours during a TRT. A new method is developed to dynamically analyze the TRT data during the test. With this method, the TRT duration could be shortened by 20 to 40% while retaining similar accuracy in the determined GTC value as the current practice.

2. Simulation Correlation Analysis Method Capabilities and Continuous Line-Slope Method Findings
Rick Clemenzi, Geothermal Design Center Inc., Ashville, NC
Current TRT is limited to only determining approximate Ground Thermal Conductivity. Other ground parameters are assumed to be "as reported by the requester, driller, and grouter". Correct Grout TC is critical to an efficiently operating GHP system, yet poor grouting quality is common. The new Simulation Correlation Analysis Method for the first time also determines Grout TC and confirms loop type and length for test wells or for installation Quality Assurance. The new method also removes the necessity of steady power/heat input -- a requirement of the current Line-Slope TRT method, opening new doors for Commissioning and System Validation Testing.

3. Advanced Thermal Response Applications
Garen N. Ewbank, Member, Ewbank Geo Testing, LLC, Fairview, OK
Ground Heat Exchangers (GHEX) are a system component of a convective circulation circuit (or Ct3). The GHEX is a renewable resource of heat and a storage device for wasted heat. To quantify the performance, capacity, and duration of the resource and storage one should be capable of forecasting the thermal response within the Ct3 to insure performance and operation. The use of the Dynamic Determination of Ground Thermal Conductivity and Minimum Thermal Response Test Duration Using the Line Source Model allows the designer to model hourly responses within the heat flux of the Ct3.

4. Utilizing DTS for DTRS and Ghx/Btes Temperature Instrumentation
Chuck Hammock, P.E., Associate Member, Andrews, Hammock & Powel, Inc., Macon, GA
Traditional Thermal Response Tests (TRT), aka Thermal Conductivity Tests (TCT), are limited to determining only an average ground thermal conductivity "k" factor of the formation. By deploying fiber optic based Distributed Temperature Sensing (DTS) cable inside the U-bend, "distributed" thermal conductivity values can be resolved at much more granular levels (typically every two meters) via this "Distributed TRT" or DTRT methodology. DTS systems can also be utilized to instrument traditional/non-traditional Groundloop Heat Exchangers (GHX) for temperature monitoring/control of these systems. This session provides a brief introduction/overview of the technology and real world examples of their use.

Presented: Tuesday, January 23, 2018, 11:00 AM-12:30 PM
Run Time: 90 min.

This is a zip file that consists of PowerPoint slides synchronized with the audio-recording of the speaker (recorded presentation), PDF files of the slides, and audio only (mp3) for each presentation.