The challenge
A domestic hot water system with recirculation needs heat even when no one is drawing water. This is a known challenge for CO₂ heat pumps: they need a low return temperature to operate efficiently, while water returning from the recirculation loop is much warmer. This has been a problem that has frustrated engineers for a long time.
The solution
To charge a Thermal Box to 65°C at the same time as the heat pump produces domestic hot water in the conventional tanks. The Thermal Box takes over the recirculation load when the heat pump is not running, for example at night.
The results
The hotels' technical director, Terje Klyve, explains: “If you want to be part of the game, you have to stay a little ahead. You have to want something, and you also have to be willing to take some risks to succeed. You should not jump at every possible idea, but when something makes sense, it is great fun to try it,” he says. Together with Gert Nielsen, energy storage geek at Multiconsult, Klyve and the Cartesian team came up with this solution, and it is now running smoothly.