4DH partner Danfoss and the consortium of partners in this project developed and tested a concept of ultra-low-temperature district heating with the supply temperature as low as 40°C combined with instantaneous electric heater topping up the last few degrees of domestic hot water heating. The project was supported by Danish research program EUDP.

The concept was tested in the city of Odder, Denmark for period of nine months in five single-family houses from late 90's, equipped with floor heating. 

Satisfied end-users

The results show that the concept and the developed units are working very fine and with satisfied end-user comfort of temperature and flow rate of domestic hot water.

The share of the electricity for the domestic hot water preparation accounted in average for 30%, corresponding to only 3% of the total energy needed for the space heating and domestic hot water.

40°C during the whole year

However, the main benefit of the concept should be seen in the opportunity of supplying the district heating networks during whole year with 40°C, enabling the use of low-cost low-grade heat sources or heat from the return line of existing district heating networks.

Photo: Peter Kristensen.