Improvement of Thermal Response Test

• Unité de recherche: OFEN
• Numéro de projet: 101690

Mots-clé (Allemand)

TP0069;F-Geothermie

Description succincte (Allemand)

Improvement of Thermal Response Test

Rapport final (Anglais)

Thermal response tests are used to investigate thermophysical properties of the ground for the purpose of dimensioning borehole heat exchangers. In a conventional thermal response test (TRT), a fluid circulating in a borehole withdraws a constant heat capacity from the formation – or feeds a constant heat capacity to it. The temperature changes of the fluid associated with this process are recorded over a sufficient period of time and then analyzed for an integral of the thermal conductivity of the formation in the immediate borehole vicinity and the thermal resistance of the borehole. In general, the rock thermal conductivity is related to the slope of the average TRT temperature versus the natural logarithm of time. The fact that the results obtained from this simple and conventional method tend to be relatively poor with respect to the effort expended to perform the test hampers its application in practice. The consequence is that heat exchanger facilities are often dimensioned on the basis of rudimentary rules of thumb instead, thereby compromising the efficiency of this form of geothermal energy utilization. Recent technical developments in borehole investigation tools provide a promising prerequisite for improved estimates of thermal conductivity. The EPFL developed a minimodule (DIS-Projekt 101'189, 2005) which is suitable for fast and flexible thermal response testing. Geowatt developed a wireless miniature data logger for continuous temperature recordings in borehole heat exchangers up to a depth of 350 m (DIS-Projekt 47’974 2003) which allows for high resolution vertical temperature profiling in boreholes. The effective application of these tools requires adaptations in the analytical methods in order to pave the way for an advanced form of thermal response testing.

Auftragnehmer/Contractant/Contraente/Contractor:
Geowatt AG
AF-Colenco AG

Autorschaft/Auteurs/Autori/Authors:
Poppei,Joachim
Poppei,Joachim
Péron,Hervé
Wagner,Roland

Documents annexés

• Innovative Improvements of Thermal Response Tests - Schlussbericht [PDF] 2'735 kB