Photo: © mylisa / Shutterstock.com
In addition to geothermal collectors, many system owners rely on geothermal probes to extract heat stored in the ground for their brine/water source heat pumps. There are several reasons for this.
Geothermal probes occupy a very limited area
One of the main reasons for using geothermal probes is the extremely small installation footprint. The diameter of an individual probe is barely larger than that of a compact disc. The only space required is the vehicle performing the drilling. Another advantage of geothermal probes is their high efficiency year-round, achieved due to the consistently warm temperature deep within the earth.
How geothermal probes work
To access thermal energy, one or more boreholes must first be drilled. Double U-shaped pipes are inserted into the boreholes and sealed with concrete. Brine (a frost-resistant liquid) circulates in the pipes, absorbing the thermal energy stored in the ground and transferring it to a heat pump. The heat pump then uses this heat to evaporate the refrigerant.
Next comes the compression process, typical of heat pumps. During this process, the evaporated refrigerant is compressed to the required temperature for use in heating and hot water production. You can learn more about how this process works in the “How a Heat Pump Works ” section.
Finding suitable geothermal probes
At a depth of approximately 15 meters, the temperature remains constant at 10 degrees Celsius and continues to rise the further you drill. For a brine/water heat pump to operate efficiently, the source must provide the highest possible temperature. In practice, geothermal probes are lowered to depths of 40 to 100 meters. The final length of the geothermal probes depends on the heat demand and the thermal conductivity of the soil. Alternatively, multiple geothermal probes can be used instead of one. Care must be taken to ensure that too much heat is not extracted from the soil at specific points, otherwise there is a risk of icing.
Subject to obtaining a permit, look for certified drilling companies.
Official permission is required for anyone wishing to extract heat from the ground using geothermal probes for brine/water source heat pumps. Local water authorities are responsible for approval. In the private sector, competent water authorities may commission expert testing if necessary. In this case, it is recommended to contact an expert before construction begins. This will ensure coordination of inspections and audits throughout the construction process.
Because improper drilling poses an environmental risk, the drilling company contracted must meet strict standards. Specifically, when searching for drilling companies, ensure they are certified according to the quality requirements of DVGWW120-2. This certification is also required to qualify for government subsidies of up to 35 percent of the eligible heat pump costs. More information on this can be found in the section on financing brine/water heat pumps.
The benefits of geothermal probes for brine/water heat pumps at a glance
In addition to the economic advantages already mentioned, there are other factors in favor of using geothermal probes. The most important of these are:
- Constant and high heat all year round
- Possibility of use for passive cooling in summer
- Safe and durable operation
