LTDH 3-pipe solution (4GDH-3P) in a completely new residential area (Halmstad)

Testing and comparing advantages and disadvantages of a three-pipe system in terms of energy efficiency and construction. The circulation in the third pipe enables lower return temperatures. 



  • Halmstad Municipality: technical knowledge exchange during the design phase technical drawings based of engineering calculations
  • Other municipalities: the technical solution proposed can be exploited in other DH systems both in Europe or worldwide
  • Triple Helix approach: Halmstad University, HFAB (Halmstad Real Estate AB) and Halmstad Municipality
  • Interest from other municipalities, real estate companies, heating companies and citizines

Overall aims

The pilot measure aims to test and compare advantages / disadvantages with the three-pipe system in terms of energy efficiency, construction, etc. The second goal is to handle the challenge of designing and dimensioning of the grid for the three-pipe system. In practical terms, it is about dealing with the difference in construction design between the 3rd generation district heating and 4th generation.

Environmental and health benefits

Reduction of CO2, NOx, UHC and SO2 emission through lowered return temperature, which makes the incineration plants more efficient. A more efficient incineration plant saves energy and reduces emissions.

Innovative approach

Ranagård in Halmstad is a new residential area that will be provided with low temperature district heating. Measurements between 4th generation LTDH with 3 pipes (4GDH-3P) and LTDH with 2 pipes. The supply

Implementing Partner: Halmstads Energi och Miljö AB (HEM)


Contact person: Rolf Strandell,


Financed by LowTEMP project:

Design and coordination: 147.600 EUR


Financed by partner:

Design and coordination: 100 000 €

Construction: 2 500 000 €

temperature is 65 °C. The return temperature is expected to be 32°C for the LTDH and 28°C for the 4GDH-3P. The third pipe in 4GDH-3P is used to circulate the supply water when the heating demand is low, replacing the circulation in buildings. The circulation in the third pipe enables lower return temperatures. This is not built anywhere else in the world, by our knowledge at the moment. The networks in Ranagård will be connected to the conventional district heating network in Halmstad by two technical buildings. About 50 % of the return water is mixed with the supply water to obtain the desired temperature. In the future will the knowledge from this project be used to build new sustainable DH-networks in the Municipality of Halmstad and Sweden.

University of Halmstad will continuously use the data gathered from this DH-network over time in their future research in the field of LTDH.