What potential is there for geothermal heat pumps in cities?

Last updated on 28 August 2024

Many city-dwellers are wondering how they can reduce their environmental impact. Geothermal heat pumps offer an interesting alternative, but their installation in urban environments raises a number of issues.

With proper planning and the expertise of a professional, the installation of a geothermal heat pump can be a wise choice for reducing your energy consumption and carbon footprint.

However, there are some specific factors that need to be considered in urban environments:

In the city, space is limited. There are, however, suitable solutions such as vertical probes, which require very little ground surface area.
Some cities may have specific restrictions on boreholes.
Drilling possibilities also depend on the nature of the subsoil. If the ground is rocky, for example, the drilling depth may be limited, which increases the footprint.
In the specific case of apartment buildings, the impact of boreholes on foundations will also need be taken into account. It will also be necessary to obtain the agreement of the co-owners.

Advantages and disadvantages of geothermal energy

If you have the required budget and a suitable outdoor space, geothermal energy can be an excellent option for more sustainable heating in the city.

Here are the main points to bear in mind:

Advantage of geothermal energy

Excellent energy efficiency: High COP, often between 4 and 5 (compared with between 3 and 4 for aerothermal energy).
Stable performance: Relatively unaffected by outdoor temperature variations.
Longer life span: Around 20-25 years for the underground section.
Quiet: No external noise.
Aesthetics: No visible outdoor unit.
Cooling possible in summer.
Low operating costs over the long term.

Disadvantages of geothermal energy

High installation cost: 2 to 3 times more expensive than aerothermal energy.
Complex installation: Requires earthworks or drilling.
Space required: Significant for horizontal loops.
Regulations: Specific authorisations for drilling.
Disturbance of the land: Impact on the garden or surroundings.

Horizontal or vertical collectors?

There are 3 main methods for collecting heat from the ground and transferring it to a home.

Horizontal collection

Pipes buried between 60 and 120 cm deep form a closed loop.

Vertical collection (ground)

A pipe, also called a "geothermal probe", is inserted in a borehole that is 50 to 150 m deep.

Vertical collection (water)

An initial borehole is drilled to collect the heat from the water.
A second one is drilled to discharge the cold water.

Horizontal collectors are simpler to install but take up a significant amount of space. In urban environments, vertical probes are often the preferred solution because of their small footprint.

What do the Brussels regulations say?

An environmental permit is required for the installation of a geothermal heat pump in Brussels. It aims to ensure compliance with environmental standards, particularly with regard to groundwater protection and borehole management.

A planning permit is also required. Its purpose is to verify that the installation takes into account aspects such as landscape integration and the visual impact of the system.

It is advisable to consult Brussels Environment or a geothermal expert before starting any project, as regulations may evolve and specific requirements may apply based on the location and nature of the project.

Geothermal heat pump prices

A horizontal collection system will tend to be less expensive, with an average cost of 14,000 to 22,000 euros. By contrast, a vertical collection system will cost around 16,000 to 25,000 euros.

However, because of its efficiency, this system is eligible for various forms of financial assistance, such as the Renolution Grant in the Brussels region. the Brussels region. The final cost for a residential building in Brussels may therefore range between 8,000 and 19,000 euros..

A system worth considering

A geothermal heat pump requires substantial investment but is the most efficient heat pump system available. It is therefore worth considering, especially as it is eligible for financial aid and does not cause noise nuisance for the neighbours.

In cities, geothermal heat pumps are particularly suitable for existing buildings with gardens. It is also an interesting alternative for new builds, as integration can be planned right from the project design phase.

For those who are not lucky enough to have a garden, aerothermal models (air/water or air/air) are an alternative that is - admittedly - less efficient but easier to implement.