District heating tunnel with metro expertise 

In the spring of 2005, work will begin on a district heating tunnel which will run from Amager power station to Fredensgade. The tunnel is a much needed steam production modernisation project, through which Energi E2 will move a part of production from the H.C. Ørsted and Svanemølle power stations to Amager power station. The Copenhagen City Energy Water and Environment Committee has recommended a grant of DKK 750 million towards the project.

As a traditional district heating conduit would result in major traffic disruption and inconvenience for the public, it has been decided to sink the pipes in a four-kilometre long underground tunnel.

Part of steam production to be moved

The modernisation has been made necessary by the fact that parts of the old district heating production facilities are now antiquated and subject to high maintenance and operating costs. As a consequence, Energi E2 and Copenhagen Energy have decided that the best solution is to move parts of steam production to Amager power station and to sink a district heating tunnel from Amager power station to the steam area in Copenhagen where it adjoins the rest of the piping network.

The new heating tunnel will bring economic and environmental benefits, for instance through a reduction in CO2 and sulphur dioxide emissions from the new facilities, since the fuel used will consist of at least 40 percent biomass and as a result of enhanced production efficiency.

Major maintenance costs

“In order to maintain reliability of supply and ensure the safety of personnel the older type of steam producing facilities are associated with high maintenance costs. As a consequence of modernisation Copenhagen Energy will save a total of DKK 50 million annually,” says Astrid Birnbaum, who is heating manager with Copenhagen Energy (KE), which will install, own and be responsible for the operation of the heating tunnel.

COWI has signed a framework project planning and tunnel supervision agreement with Copenhagen Energy. When carrying out the assignment COWI consultants will draw on a large reservoir of experience in such areas as soil mechanics and groundwater management in tunnel bores such as the Great Belt, the Malmö City tunnel, Hallandsåsen and, not least, the Copenhagen Metro.

Experience from the Metro

Experience from the Metro has shown that a tunnel may be bored to great advantage in the intermediate limestone layer, situated 20-40 metres below Copenhagen, where there are relatively few problems with water and flint. Therefore the district heating tunnel will be sunk to this depth.

However, additional soil surveys will have to carried out along the actual line of the tunnel, and consultants must also, as was the case with the Metro, ensure that the water table is not lowered, as this might cause damage to buildings whose foundations rest on old timber pillars.