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Brine-to-water heat pump (geothermal energy)

The brine-to-water heat pump extracts heat from the ground via probes or collectors. It is more efficient than an air-source heat pump, but more complex.

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Heat from the ground: three variants
  1. Deep drilling: probes reach vertically deep into the ground.
  2. Horizontal collector: pipes lie horizontally just below the surface and require a lot of garden space.
  3. Groundwater: one well extracts water, a second one returns it.
Schematic, not to scale. Drill holes and wells often require a water rights permit.

With a brine-to-water heat pump, a frost-resistant liquid, the brine, circulates through pipes in the ground. It absorbs heat there and transfers it to the heat pump in the house. The heat is accessed via a vertical borehole with a geothermal probe, via a horizontal ground collector or a trench collector.

Advantages

  • The ground has a relatively constant temperature all year round. According to klimaaktiv, the seasonal performance factor (JAZ) is therefore higher than with an air heat source.
  • In summer, gentle cooling is possible without the heat pump itself having to start up.
  • There is no noisy outdoor unit and no defrosting.

Disadvantages

  • According to klimaaktiv, installation is more complex than for an air source heat pump.
  • You need space for the borehole or collector and potentially a permit.

Guide values

The klimaaktiv guide recommends a COP B0/W35 of over 4.5 for ground source heat pumps. Boreholes must be designed for a maximum of 50 W per metre, collectors for a maximum of 25 W per m². Design is based on a calculation according to VDI 4640 Blatt 2 or ÖWAV-Regelblatt 207 (2009).

Permit

Whether a water rights permit or notification is required depends on the federal state and location. Find out more under Permits. You can find the comparison with air in Air or geothermal energy.

Related terms

Borehole (geothermal probe)Ground collector (horizontal collector)Air-to-water heat pumpWater-to-water heat pump (groundwater)Seasonal performance factor (JAZ)

Sources

All terms · Heat pump knowledge