Think of a castle moat, and you’ll probably imagine cold water meant to repel attackers rather than a heat source. Yet in two different castles in Belgium, water is being used to provide sustainable energy, thanks to heat pumps and aquathermal technology.
‘Aquathermal energy’ means using energy from rivers, lakes or canals to warm or cool buildings. Normally for still bodies of water, heat exchangers are placed in the water, forming a closed circuit with a heat pump. When there is a current, such as in a river, an open system with the heat exchanger in a separate building is more commonly used.
In the two Belgian cases – of the 14th century Merode stately home in Westerlo, and the water gardens of the Annevoie castle near Namur – engineering firm EXTRAQT and its partners developed a closed aquathermal system.
For the Merode stately home, the engineers implemented a closed loop heat exchanger in the moat, so that heat could be captured from the moat and transferred into the castle. Inside the castle a heat pump is used to boost the extracted heat of the moat at low temperature to a high temperature of 55 degrees. This has replaced the previous gas heating.
Owner Simon de Merode says: “We had been thinking for a long time how we could use natural energy to reduce our energy bills. When prices shot up in 2022, we decided to act. We have to heat the castle, both because we live there and to preserve it. For example at Christmas when there are many visitors, it needs to be warm and cosy inside.”
At Annevoie, the lake behind the castle provides the energy, with heat pumps connecting to both underfloor heating and radiators. As at Merode, the engineers were EXTRAQT and the installers were Eco-Technix.
Simon de Merode adds that they will have recouped their investment in seven to eight years.
What’s more, it’s good for the planet: “We’ve emitted 50% less CO2 than last year, thanks to this less ‘traditional’ heating system.”
Want to know more about aquathermal energy? Check out the EU-funded Waterwarmth project in which EHPA is a partner.
