Bottlenecks in district heating systems and how to address them

Problems with bottlenecks in district heating networks occur when the pipes have too small dimensions to sufficiently meet customer needs. This may result in insufficient differential pressure in DH areas attached to these pipes. Bottlenecks are especially common in expanding DH networks, as previously sufficient pipe diameters may become too small when more DH consumers are connected to the DH network. Historically, bottlenecks have often been addressed by increasing the supply temperature or by exchanging the pipe to a larger dimension. Other techniques are however available to solve bottleneck problems. Such techniques are for example installation of local heat supply on the other side of the bottleneck (LHS), demand side management (DSM), or installation of thermal energy storage (TES). The aim of this study was to identify different techniques for addressing bottlenecks and to see what solutions were used by the DH companies in Sweden. A literature study of the different techniques available was performed and a survey study with the DH distribution companies in Sweden that are members of the Swedish DH association was carried out. The survey was sent out to in total 131 companies, of which 89 answered. The results showed that the most used techniques in Sweden are a higher supply temperature and installation of a new pipe to increase the pipe area, whereas for example DSM and TES were more rarely used techniques. This work is an introduction to the different techniques used to address bottleneck problems and shows the bottleneck situation in Swedish DH networks. More research and tests are however necessary in order to more thoroughly evaluate which techniques that should be used in different situations.