The Belgian AquaCOM pilot site has been successfully brought to life. After three months of work, the aquathermal energy installation at the Rotselaar water mill is fully operational since the end of 2025, and the mill's residents have enjoyed their first winter with 100% green heating - a major step forward on the road to a carbon-free society, which is particularly relevant given the current geopolitical context.
But how do you set up such a cooperative heating project? Join us for a look behind the scenes of the construction and installation of this pioneering initiative, illustrated with a photo gallery.
1. Excavation works
In early October 2025, the excavation for the heating pipes starts in the mill’s inner courtyard. Openings are drilled into the walls to bring the district heating network into the buildings.
2. Press event
On 8 October 2025, Flemish media were invited to the mill site for the ceremonial first pipe‑laying. The event gained the attraction of important Flemish media such as VRT or Het Nieuwsblad. In the image below, VRT News interviews Ecopower Project Manager Colette Van Loy. Learn more about this day and the beginning of the works in this previous blog post.
3. Terrendis training
Terrendis, the heat pipes supplier, provides on-site training at the mill for Heatco’s technicians who will install the pipes. The Terrendis heat pipes consist of a red pipe, which carries the hot water flowing into the heating network, and a blue pipe returning the cooled water. They are both neatly enclosed in a single insulated outer casing.
4. Installation of the heat network
The heat pipes are laid in the ground. As there were already many existing cables, pipes and conduits underground that had to be worked around, over and under, the job proved challenging. Heatco’s technicians pulled, manoeuvred and persevered, and the district heating network was installed successfully!
5. Installation of the heat exchanger
At the end of October, the heart of the aquathermal system is installed: the heat exchanger. Using a crane, Eco‑Technix technicians move and position it precisely. For this operation, the branch of the Dijle next to the mill is temporarily drained.
The heat exchanger is installed beneath the walkway, just behind the debris screen. This screen protects the hydroelectric turbine (and now also the heat exchanger) from debris carried by the water.
6. Installation of the utility room
The utility room hosts the core technical components of the aquathermal heating system, including the heat pump, buffer tanks, circulation pumps, and control units. It serves as the central hub where heat extracted from the water source is processed and distributed to the buildings' heating network.
7. Connecting the heat consumers
Finally, the technical room is completed and the cooperative heating network is up and running - and the residents of the Rotselaar water mill can enjoy 100% sustainable heating!
