Dipl.-Geol. Clemens Lehr
- Shallow Geothermal Energy
Geotechnisches Umweltbüro Lehr
61231 Bad Nauheim
Evaluation of thermal response tests using a cylinder source approach (Type Curve Fitting Method)
A Thermal Response Test or Geothermal Response Test (TRT or GRT) is a field method to investigate thermo-physical properties of a borehole heat exchanger (BHE) drilled into soft or hard rocks. The resulting TRT temperature graph is demonstrating the relation between the injected heat energy and the thermal rock properties. This project addresses a quantitative approach to evaluate TRT data with an unsteady state solution following the cylinder source theory. Similar to groundwater pump test results, the early TRT phase behaviour shows especially the level of disturbance of the drilled BHE and requires an evaluation of the unsteady state period. The starting hours represent influences of the borehole grout, formation damage and water movement by thermal gradients. Furthermore, the numerical modelling of BHE fields is becoming more precise if the volumetric heat capacity can be introduced. Using the Type Curve Method, it is also possible to evaluate measurements with non stable heat input conditions by time based superposition.