Progress of TRT measurements
Thermal response tests (TRT) are an important technique to gather information on the underground properties for the dimensioning of shallow geothermal systems for 30 years. The used devices are still custom-made items. Due to that, a comparison of the measurements with different devices is not possible at the moment. A group of experts from Central-European companies, public authorities and research institutes set the objective to make the results of TRT measurements comparable and to validate them. In the following 18 months, TRTs will be performed by the project partners with different devices at several borehole heat exchangers in some of the pilot areas. The comparison of the results shall lead to new knowledge about relevant boundary conditions.
In March this year in Prague during the GeoPLASMA-CE knowledge exchange workshop this initiative was started. In the following month a test site was looked for to perform a ring test with the TRT devices of the Geological Survey of Austria, the Polish Geological Institute and the company geoENERGIE Konzept GmbH.
The experts agreed that the intersected geology by drilling is not decisive for the selection of the test site. Rather the knowledge of the geology and the documentation of the drilling is essential. Besides for the selection of the test BHE the time between two validation tests needed to be determined. Thereby, effects of the previous Thermal Response Test on the following ones should be excluded and similar undisturbed underground should be created.
Report on harmonized standards
A standard for the TRT measurements performed within the project was developed referring to the VDI guideline 4640 Vol. 5 which is available as a draft version since August 2016. The joint report on chosen approached and methods for calibration aims to make field measurement data within the project GeoPLASMA-CE comparable. In the report a general strategy and an action plan in which way and extend comparative measurements will take place in the project is provided. It also gives an overview about the principles of TRT measurements as well as possible source of errors. Furthermore, it defines quality criteria for performing comparative TRT measurements.
Measurements already done
The first measurements of the thermal conductivity and the underground temperature have already been done in the pilot area Vogtland, Germany by our project partner geoENERGIE Konzept this summer. The results will be included in calibrating the potential maps for this particular pilot area. Additionally, on two test sites validation measurements of the three TRT devices have been performed. The first validation test round was started by geoENERGIE Konzept in August in Vienna. Later this year, the test devices of the Geological Survey of Austria and the Polish Geological Institute will perform TRT measurements at the same borehole heat exchanger. The other test site is located in the Krakow area, where the Polish Geological Institute and geoENERGIE Konzept performed the second validation tests. The data is going to be evaluated and interpreted currently. After that, an analysis of possible sources of differences in the results will be done.