Bottlenecks in district heating networks and how to eliminate them - A simulation and cost study

To optimise district heating (DH) systems and simplify the transition towards the fourth generation of district heating, it is important to remove any bottlenecks existing in the DH network. DH bottlenecks are in this study defined as pipes with too high flow relative to the pipe diameter, resulting in difficulties to maintain sufficient differential pressure in the area beyond the pipe. The aim of this study is to investigate how well possible measures to solve bottleneck problems work in different DH network configurations and how much they cost. This was achieved by a simulation study and a cost analysis. The results showed that DH systems with a lower flow rate demanded more extensive measures than other systems and that different problems might arise in different types of networks. The economic results showed that a lot of varying parameters, such as the internal rate of return, the fuel and electricity prices and the annual utilisation time of the measure could have a large impact on the outcome. An increase of the supply temperature could however easily become very expensive. Before any bottleneck measures are implemented in a DH system, calculations and analysis based on the local situations should thus be performed.