District Heating Development : Prosumers and Bottlenecks

Sammanfattning: The overarching objective of the studies in this thesis is to solve issues associated with the current district heating development in order to improve the efficiency, and thus the environmental performance, of district heating systems. More specifically, the aim is to solve issues related to prosumers and bottlenecks in district heating networks. Prosumers are consumers who also produce district heating. Prosumers could be used to introduce more renewable and recycled energy into the district heating network. Bottlenecks are areas in which it is difficult to keep a high enough differential pressure, often due to large pressure loss in the pipe leading to the area. Bottlenecks often cause the district heating system to work in a non-optimal way.The results show that there may be great potential for prosumers to deliver a substantial amount of district heating, especially in areas with mixed building types. Most of the prosumer potential is, however, present during the summer, which is why, for example, large seasonal thermal energy storages would be needed in order to utilise all the prosumer heat. Prosumers are often beneficial environmentally for the district heating network, but the environmental outcome is not obvious. It mainly depends on three factors: if the prosumer needs a substantial amount of electricity to function, if so, how the electricity is regarded, and which type of district heating production is outcompeted. Prosumers may also affect the differential pressure in the district heating network, increase the flow velocity, and decrease the local supply temperature.Regarding bottlenecks, the results indicate that the existing bottleneck choosing processes in district heating companies are often based on experience and focusing on the distribution system, even if other solutions are also possible to perform. Moreover, the economic calculations often lack a lifecycle perspective. This results in the most effective, both economically and environmentally, solutions often not being chosen. To shed more light on alternative bottlenecks, the results thus highlight alternative solutions, costs, risks, and added values for various bottleneck solutions and finally presents a methodical and comprehensive decision-making process for choosing bottleneck solutions.District heating developers may use the result to help increase district heating competitiveness and thus increase the possibility of district heating being an important part of a more energy-efficient society.