Geothermal drilling
Drilling, design, and obtaining of permits
The purpose of geothermal drilling is the preparation of such boreholes in which geothermal probes can be installed. The boreholes provide annular spaces with 140-160 mm in diameter and 100 meter base depth. After the geothermal drilling we install geothermal probes into these boreholes. The probe can be of 32 mm diameter with four plastic pipes developed especially for this purpose, or of 40 mm diameter with two plastic pipes.
The drilling procedure:
The boreholes must be separated from each other by placing them within a circle of at least 6 meter radius, depending on the soil structure, and according to the design documentation. During geothermal drilling we use special environmentally friendly, so-called viscosity enhancing, sludge conditioning materials. In case it is justified, we also use protective piping.
After the installation of the geothermal probe, we fill up the borehole with bentonite cement to protect the soil and the water within the layers, and to enhance the heat transfer capability. Such a collector can provide 4.5-5 kW of power depending on the soil structure and the quality of the installation method. At the end of the procedure, after the completion of flow and pressure testing, the probes are connected to the main pipe, then finally they get connected to the heat pump. They can be used for heating, domestic hot water, and passive cooling purposes.
Thermal sealing
In case of a probe installation that is in accordance with the German VDI40 standard, the annular space must be sealed for optimal heat transfer and for the physical fixation of the probe into the soil. For this procedure we use frost resistant sealing materials developed specifically for geothermal probes. Such materials are available in various makes: between about 0.7 – 1.5 t/m3 utilization quantity and from 1.2 W/mK to 2.40 W/mK thermal conductivity.
The essence of the VDI 40 standard is that the boreholes must be refilled from the base up without any air inclusions through a borehole filling pipe, which remains in the borehole so that no damage is done to the installed piping during its retraction. For material conservation and efficiency enhancing reasons it is very IMPORTANT, that the suspension is mixed until an even consistency is achieved, using a colloidal mixer and injection equipment that are also developed for this purpose!
Geothermal probe test
The “Geothermal Response Test” provides the initial default values of the accurate mdetermination of the probe area. The essence of our service is to optimize the design of the probe area, providing cost-efficiency and long term reliability for the installation and operation of the system to be established.
Testing a geothermal probe through an existing probe:
- assembling and commissioning the testing equipment deaerating the probe
- startup of testing
- testing period: ~ 48h
- dismantling the testing equipment
- recording the temperature profile down to the full depth of the probe
- 4 times: in quiescent state; 1; 2 and 3 hours after testing
Determination of results (using the GeRT-CAL-2-0-10 program)
- determining the thermal conductivity of the soil (geological medium)
- quality inspection of the stepless testing
- determining the thermal resistance of the drill hole
- interpreting the temporal variation in the temperature profile