My geothermal project, step by step
Completing a geothermal project, regardless of scale, demands that certain essential steps be followed. The starting point of any new geothermal project is the estimation of the building's energy needs as well as of the ground's geothermal potential. Another key to success is having the system installed and maintained by qualified professionals.
Installing a geothermal system in six steps
The precise evaluation of the building's energy needs and of the ground's geothermal potential will determine which geothermal should be installed. It will also enable engineers to properly size the system, i.e. to decide how powerful the heat pump should be, how many geothermal loops or wells should be installed (for shallow vertical systems), and how deep they should be.
This evaluation is an essential step, as a proper balance between the building's energy needs, the ground's thermal potential, and the system's scale guarantees the lowest installation cost. It also helps optimise the operating costs of the heat pump while keeping the underground heat reservoir from being exhausted, which would reduce its coefficient of performance.
It is highly recommended to rely on qualified professionals for the evaluation (engineering firm, driller, heating specialist). Especially when preparing a project for an apartment building or an office building, it is crucial to call upon an engineering firm specialised in geothermics, given the complexity of the sizing process.
The building's energy needs
A competent heating specialist can evaluate the energy needs of the building. However, information and documents related to PEB certification (energy efficiency), such as those provided by Environment Brussels, can be very helpful.
The geothermal potential of the ground below Brussels
In order to determine the geothermal potential of the ground below Brussels, proper knowledge of the site's geology is essential.
For closed shallow geothermal systems (vertical geothermal loop fields), the ground's thermal conductivity is one of the key parameters; it depends on the types of soil and rock that will be drilled through. For instance, conductivity is generally higher in sandstone than in sandy clay, and it increases when water is present.
For open shallow geothermal systems (geothermal wells), the hydraulic properties of the aquifer (permeability, thickness) from which water is collected must be taken into account.
Eventually, a mapping tool for the geothermal potential of the ground below the Brussels-Capital region will be developed as part of the Brugeo project. It will be available on this website, providing vital information to anyone planning to install a geothermal system.
Currently, information can be found using the tool developed by the Belgian Building Research Institute (BBRI) for Flanders (only in Dutch) as part of the SmartGeotherm project. This can help provide an initial estimate of geothermal potential in Brussels.
In addition, a request for information and geological data on the ground below the Brussels-Capital region can be submitted to the Geological Survey of Belgium.
The type of geothermal system depends on many factors:
- Building type: single-family home, apartment building, industrial building, office building
- Energy needs: power required; heating and/or cooling
- Renovation or new system
- Building location: access for drilling equipment, surface area available
- Geological properties of the ground: presence of aquifers
For single-family homes in Brussels, geothermal systems are most often closed shallow systems (vertical loop fields). Provided that the heat follows certain criteria (see the section on permits), these systems generally do not require specific procedures other than a planning permit for drilling.
For larger buildings requiring a more powerful heat pump, a notification or a permit are generally required.
Owners who install a heat pump for domestic heating or hot water can receive an energy grant from the Brussels-Capital region.
Installing a geothermal system requires specific expertise and skills in order to avoid any problems during drilling and to maximise the system's efficiency. The parties involved (heating specialist, engineering firm, driller) must have solid references.
The heat pump can be an efficient and reliable piece of equipment, provided it is properly selected and installed, and subsequently maintained by an experienced heating specialist every 2 years. Geothermal installations must also be monitored regularly. The level of monitoring depends on the type of system.
For closed systems, the recirculation pumps must be checked every 2 years, and the heat transfer fluid must be changed every 5 years.
Open systems require more advanced monitoring, which will cover the wells and the aquifer (hydrodynamic properties, re-injection tests, water level, pumping rate, etc.).