The goal of this project was to heat nine existing homes and apartments at the historic watermill of Rotselaar (Belgium), the site where energy cooperative Ecopower was founded, entirely without fossil fuels.
Existing and heritage buildings are among the hardest to decarbonise. Deep renovation is often impossible, outdoor units are unwelcome on heritage sites, and individual heat pumps for nine separate households would be costly and inefficient. Small collective heat networks for existing homes did not yet exist in Flanders.
EXTRAQT designed an innovative solution where a submerged heat exchanger placed in the river Dijle, directly behind the mill’s water wheel, extracts heat from the flowing river (average flow ~5 m³/s). A cascade of water-to-water heat pumps upgrades it to 50–60 °C for space heating and domestic hot water, distributed through a 300 m insulated micro heat network. The heat pumps run on green electricity from the mill’s own hydropower plant, and an additional heat pump recovers waste heat from the turbine’s generator and gearbox.
The result is a fully local, 100% renewable heat supply on a now fossil-free site, owned by citizens through the cooperative, and the first aquathermal heat network for existing homes in Flanders.
