Although lowering the temperature of district heating is not a new idea, it is only recently that lower temperatures have become the perfect solution because the technology has now matured. This was the backdrop to a demonstration project which Sweco carried out in collaboration with AffaldVarme Aarhus (AVA) for the Danish Energy Agency. The purpose of the project was to test the concept which Sweco Denmark had developed in collaboration with the Technical University of Denmark (DTU) and Danfoss in the area of large-scale ultra-low-temperature district heating.
Customers: AffaldVarme, Aarhus (AVA), Danish Energy Authority
Location: Geding, Denmark
The project involved converting the existing conventional district-heating system in the small town of Geding outside of Aarhus to an ultra-low-temperature system where the supply temperature from the central unit was to be lowered from 70°C to 45°C. The temperature level at the central unit was set so that consumers would always have a minimum supply temperature of 30°C.
As this low temperature is not sufficient for hot water for domestic use, however, the initial phase, part-funded by the Danish Energy Agency, involved the installation of a district-heating unit with a small built-in heating pump unit in each dwelling. This made it possible to raise the district-heating temperature so it could produce hot utility water. At the same time, the temperature of the hot utility water no longer depended on the supply temperature of the district heating water in the main distribution system.
The district-heating unit with the small built-in pump unit, a so-called microbooster, was developed by Danfoss, the Technical University of Denmark and Sweco Denmark as part of an EUDP project which concluded in 2013. At present, four microboosters are installed in Birkerød and these microboosters are an improved version of the microbooster installed in Geding in the summer of 2014, where all dwellings have been converted, a total of 25 houses.
Concurrently with this project, Sweco Denmark has prepared a plan for phase 2 for AVA. This will involve replacing the existing centrally located oil-fired boiler, which produces heat for the distribution system using a combination of solar heat, heating pumps and energy storage. Geding will not only be fossil free, but also fuel free.