Using groundwater as an energy source is complex but offers great potential. Anyone planning a water-to-water heat pump will inevitably come across the term “well system”. Here you can find out what is behind it, how the system works and which regulations you must comply with.

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What is a well system for a heat pump?

A well system consists of a production well and an absorption well, which together provide groundwater for a water to water heat pump Make it usable. The extraction well removes the groundwater and directs it to the heat pump, while the suction well returns the cooled water back into the ground.

How does a suction and absorption well for heat pumps work?

The suction well delivers groundwater to the heat pump, where it transfers its heat to a refrigerant in the evaporator. The evaporated refrigerant is compressed in the compressor, causing it to heat up strongly. In the condenser, this heat is transferred to the heating system and condenses. The expansion valve then lowers the refrigerant pressure before the cycle starts all over again. The cooled groundwater is returned to the ground via the absorption well.

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Construction of suction and absorption wells for heat pumps

Each suction and absorption well for heat pumps consists of a vertical pipe system that reaches into groundwater.

• The suction well contains a delivery pipe with a submersible pump or submersible pump, which directs the water to the heat pump.
• The Schluckbrunnen is designed in such a way that it returns the cooled water back to the ground via an open pipe system.

Both wells must be hydraulically effective, i.e. allow sufficient water flow.

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What is the required distance between the wells?

The distance between suction and absorption wells is usually 10 to 15 meters so that the returned cold water is not immediately sucked back in and a thermal short circuit is avoided. The suction well must always be located in front of the absorption well in the direction of groundwater flow.

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How deep does a suction or swallow well have to be?

A suction or absorption well for a heat pump is usually 5 to 20 meters deep, depending on the local groundwater level. It is crucial that the suction well supplies enough water — 250 to 300 liters per hour are usually required per kilowatt of heating output.

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Approval, Requirements, and Legal Requirements

For a well system with a heat pump, a Water permit required by the competent lower water authority. The permit regulates whether and to what extent groundwater may be withdrawn and discharged again.

To the editions These include maintaining the minimum distance between suction and absorption wells, proof of sufficient water quantity and quality, and regular maintenance and inspection of the system.

Legally appliesthat in water protection areas or hydrogeologically sensitive areas, the construction of a well system is either severely restricted or completely prohibited. A preliminary geological survey is also required in many federal states.

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Well drilling: Draining and construction of a well system

The construction of a well system for a heat pump is carried out in several precisely coordinated steps — from planning and drilling to connection to the heating technology.

1. Preliminary geological survey: A specialist company checks the site for groundwater availability, soil layers and flow direction. This data is the basis for the approval and planning of the wells.
2. Obtaining approval: Before starting work, a water permit must be obtained from the responsible water authority. Without this, drilling is not permitted.
3. Suction well drilling: First, the extraction well is drilled. A drill rig drives the pipe system up to the groundwater-carrying layer. The well pipe with filter section and gravel pack is then inserted.
4. Installing the pump: A submersible or submersible pump is installed in the suction well, which later delivers groundwater to the heat pump.
5. Drilling of the swallow well: The suction well is drilled at a prescribed distance of 10 to 15 meters and in the direction of flow behind the suction well. An open pipe system is also being installed here.
6. Pumping test and testing: Both wells are tested for their function. It checks whether enough water can be pumped and seeped away again, without pressure backflow or backflow.
7. Connection to the heat pump: The suction well, heat pump and suction well are hydraulically connected together. The system is put into operation and professionally documented.

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How much does a well cost for a heat pump?

A well for a heat pump usually costs between 8,000 and 15,000 euros, depending on depth, soil conditions and effort. Each meter of drilling costs around 80 to 150 euros. For the complete system with suction and absorption wells, water-water heat pump and installation, the total costs are usually between 25,000 and 40,000 euros.

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Can I use a well for my heat pump?

An existing well can only be used for a heat pump if it supplies sufficient water, the water quality is suitable and a second intake well is available or can be retrofitted. In addition, use as an energy source must be approved by the water authority.

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Advantages and disadvantages of the well system

A well system for heat pumps offers high efficiency and low operating costs, but requires extensive approval and high initial investments.

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What alternatives to well systems are there?

Alternatives to well systems for heat pumps include in particular geothermal probes, surface collectors and air-water heat pumps. Geothermal probes use geothermal energy from deeper soil layers via vertical boreholes, while surface collectors extract near-surface heat from the ground via a large pipe system. Air-water heat pumps do not require any earthwork and obtain their energy directly from the surrounding air. Each of these alternatives has its own requirements, advantages and disadvantages in terms of efficiency, space requirements and investment costs.

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