Solar thermal systems are technical devices from which solar radiation is absorbed and, with the help of the carrier medium, the energy is transported to heating systems or hot water boilers and delivered in a usable form. Medium temperatures of well over 160°C are the norm for larger systems.
A district heating system works in a similar way: with a closed circuit, i.e. a flow and return. The incoming hot water is used for heating and hot water production. The cooled water is then fed back into the district heating network.