Deep drilling (geothermal probe)

With deep drilling, a geothermal probe is inserted vertically into the ground. It requires little surface area and provides consistent heat all year round.

For a geothermal probe, a drilling company drills one or more vertical holes into the ground. Plastic pipes are inserted into these, and the borehole is backfilled. Brine circulates through the pipes, absorbing heat from the ground and transferring it to the brine-to-water heat pump.

Advantages

• Requires little space in the garden compared to a horizontal collector.
• Deep underground, the temperature is quite constant throughout the year. According to klimaaktiv, the seasonal performance factor is higher than with air.
• In summer, gentle cooling is possible.

Sizing

The klimaaktiv guide specifies: geothermal boreholes may be designed for a maximum extraction capacity of 50 W per metre or 100 kWh per metre per year. Higher values are only permissible with a geological report. Calculation is performed according to VDI 4640 Blatt 2 or ÖWAV-Regelblatt 207 (2009). How deep drilling needs to be therefore depends on the heating load of your house.

Documentation

According to the Wegweiser (guide), you should receive at least the following documents after drilling: site plan with probe lines, drilling master's log, drilling process sheet with grouting log, and pressure test log of the probes. Keep them in a safe place.

Permit

In Upper Austria, geothermal probes require a permit in areas such as specially protected water areas, in the case of confined or artesian groundwater, and at depths of more than 300 m. Other federal states have their own rules. Clarify this early on with the Bezirkshauptmannschaft (district authority), see permits.

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