The image shows how the installation of the LTDH-service pipes in Osterby are close to the users' buildings in order to reduce the length of the network and consequently the heat losses.

A new low-temperature network has been designed to upgrade the old and obsolete traditional district heating-network in Østerby in Høje-Taastrup municipality. This report from the COOL DH-project provides information about the final design and the implementation of the low-temperature district heating network and can be used as a guideline of the installation process for future similar projects.

A new LTDH-grid is built in the Østerby district in Høje-Taastrup, Denmark. Nowadays, the standard and old district heating systems are replaced by low-temperature district heating (LTDH) or ultra-low-temperature district heating (ULTDH) networks, where the supply temperature will be respectively between 50-60°C in LTDH and below 50°C in ULTDH.

Plastic pipes and optimized network-design

We implemented the new plastic pipes developed in the COOL DH project (learn more). Following the inputs provided by the investigation presented in the deliverable D2.7 New design concepts for LTDH, the district heating network was designed to ensure the heat supply in the entire district and minimize the heat losses. Higher insulation level and twin pipes were used to limit the heat losses. Furthermore, the network was optimised from a length and a hydraulic point of view. For example, the installation of the service pipes are close to the users’ buildings in order to reduce the length of the network and consequently the heat losses – as seen in the image below.

The image shows how the installation of the LTDH-service pipes in Osterby are close to the users' buildings in order to reduce the length of the network and consequently the heat losses.

Installation of the service pipes close to the users’ buildings in the Østerby district.

The LTDH network will take advantage of the surplus heat from the cooling system that operates in the nearby shopping mall called CITY2. On CITY2 a 16,300 m² PV plant has been installed. The network is designed to ensure a temperature of 55°C on the supply side and 30°C on the return side.

The figure below shows the configuration of the network before and after the renovation process. Østerby district is supplied by a centralized heat exchanger located at the end of the main distribution network (red line) in the middle of the figure. From this point, an internal DH network guaranteed the direct connection of the Space Heating system for all the consumers, with different types of units implemented in each building for the domestic hot water production. The distribution pipes of the old DH network were placed under the buildings.

Old configuration of the DH network (left) and new low-temperature DH network (right)

Lessons learned

The implementation of the new LTDH network gave some insights about the practical issues related to the installation of the new pipes:

  • Twin pipes is rigid to work with during winter when outside temperatures are low. During the summer, shrink-fitting presents some challenges as the material in the connection is softer.
  • During the connection of the twin pipes, two people are required to move the two endpoints and keep them together for the connection. Thus, a larger work force is required with prefabricated branches, with a consequent increase of the installation costs.
  • Overall, there is a need for further development of connection methods, for example electro-welding sockets such as those used in water supply.

Read the report

You can read the entire report which is available for download on the following link:

Converting Østerby area from traditional District Heating to Low Temperature District Heating

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