Geothermal response test
Preparations for the thermal response test.
Preparations for the thermal response test.

The thermal response test determines the heat conducting abilities of the underground and the thermal borehole resistance (and/or the heat conducting ability of the borehole filling).

For the installation of geothermal probes, knowledge of the thermal properties of the underground is essential. For smaller systems the values are generally estimated and safety margins are included in the installation, or installation is done according to prior experience, but for larger systems underground tests and even sample borings are required.

Such sample borings allow the thermal response of the underground to be established through two processes:

• Determination of the conducting abilities in samples that are untouched as far as possible (e.g. drilling cores); in this process all rock-specific units of the drill log must be tested and particularly also the natural water content of the core samples. This is a fairly costly exercise.

• Determination with a thermal response test (in a ready-installed geothermal probe); the advantages of this method are that measurements can be done along the entire length, that the borehole filling can also be tested and that thus the quality of the geothermal probe can be established and that the test can be done in undisturbed underground conditions; it can also be established whether underground water flows exist.

The thermal response test thus is an instrument that allows the optimisation and safe instalment of even medium-sized geothermal probe systems directly on site.

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