A tertiary building in Brussels opts for geothermal energy
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In the European Quarter of the Belgian capital, the office complex Commerce 46 has replaced fossil energies with geothermal power. Cegelec HVAC Commercial South has been entrusted with the HVAC installations and energy monitoring for this vast office block.
©Georges De Kinder ©ImmobelGroup
Developed by Immobel, Commerce 46 is a 12-storey office complex with three underground levels and total floor area of 14,200 sq. metres. Situated in the European Quarter of Brussels, the building has been occupied by European Commission services since June 2024. In addition to its premium-quality facilities (huge workspaces, private garden, rooftop terraces, etc.), it boasts the unusual feature of operating without fossil energies. Instead, it uses geothermal energy, with 64 boreholes, each 93 metres deep, operating with heat pumps in a closed system.
Cegelec has been entrusted with the HVAC (heating, ventilation and climate control) installations and systems energy monitoring for this vast office block. This VINCI Energies business unit – which previously worked with Immobel in Luxembourg on Project Infinity, a building complex incorporating offices, shops and apartments – drew here on its long experience of projects avoiding the use of fossil energies.
“We are currently managing several large-scale carbon neutrality projects,” says Ludovic Godon, Technical Manager at Cegelec HVAC Commercial South. “These include the head office for Fluxys, a Belgian energy infrastructure company; construction of the new HQRE defence headquarters in Brussels; and construction of the first digital control tower for airports in Wallonia, which will be energy-neutral.”
Optimised geothermal HVAC
On the Commerce 46 project, following a study by the engineering consultants CES, Cegelec installed a six-pipe heat pump for heating and cooling, another four-pipe heat pump for heating, and an air-to-water pump as a backup solution during peaks in demand for heat.
“The six-pipe geothermal heat pump operates simultaneously and reversibly,” explains Ludovic Godon. “It manages energy transfer into the building and automatically captures or returns excess energy to the ‘source’. Everything is recovered, and only the surplus energy is automatically drawn from or reinjected into the groundwater.”
The technical manager adds: “The aim is to prioritise operation of the six-pipe heat pump to cover the building’s heating and cooling needs, and to find a balance while limiting use of the geothermal source. The four-pipe geothermal heat pump is only used for peak shaving to meet any remaining demand for heat.”
Rooftop solar panels supply the heat pumps with green energy.
At the same time, Cegelec installed a 600 kW variable-speed chilled water production unit with a condenser linked to a 750 kW cooling tower to deal with heat spikes. This solution avoids overloading the geothermal system, balances out the ground temperature, and helps meet the requirements of low-consumption (and therefore environmentally friendly) buildings.
The Cegelec technical manager adds that: “The benefits of a variable-screw compressor compared with a scroll compressor are its superior capacity, better energy efficiency at large scale, longer life and greater reliability in heavy industrial applications, and better management of load variations.”
Technical challenges
This technically demanding project posed a number of challenges. The first related to the limited basement space available for the installation of technical HVAC equipment.
“To make maximum use of the space, we optimised the design by selecting modular and compact HVAC equipment,” explains Ludovic Godon. “We also created a custom design with 3D modelling of the available space so we could tailor each HVAC component to the physical limitations of the basement. The success of this solution also took close coordination with the other VINCI Energies trades (plumbing, electrical engineering, sprinklers, data).”
Cegelec HVAC Commercial South also had to find an innovative solution for locating the cooling tower within the basement rather than on the building exterior or roof as is generally the case with similar systems. This option freed up the space for rooftop solar panels, which supply the heat pumps with green energy.
In collaboration with the CES design office and using a tool developed by VINCI Energies Building Solutions, Cegelec HVAC Commercial South calculated that the technical enhancements to the HVAC installations and solar panels reduced emissions by 60.6 tonnes a year, earning the project BREEAM “Outstanding” certification.
01/16/2025
