Abstract
The traditional way of managing the supply and return water temperatures in a district heating system (DHS) is by controlling the supply water temperature. The return water temperature then becomes a passive result that reflects the overall energy efficiency of the DHS. A DHS with many poorly functioning district heating centrals will create a high return water temperature, and the energy efficiency of the DHS will be affected negatively in several ways (e.g., lower efficiency of the flue gas condenser, higher heat losses in pipes, and lower electricity production for a DHS with combined heat and power (CHP)). With a strategic introduction of low-grade heat customers, the return water temperature can be lowered and, to some extent, controlled. With the heat customers connected in parallel, which is the traditional setup, return water temperatures can only be lowered at the same rate as the heat customers are improved. The active management of some customers can lower the return water temperatures faster and, in the long run, lead to better controlled return water temperatures. Active management is defined here as an adjustment of a domestic heating system in order to improve DHS efficiency without affecting the heating service for the individual building. The opposite can be described as passive management, where heat customers are connected to the DHS in a standardized manner, without taking the overall DHS efficiency into consideration. The case study in this article shows possible efficiency gains for the examined DHS at around 7%. Looking at fuel use, there is a large reduction for oil, with 10–30% reduction depending on the case in question, while the reduction is shown to be largest for the case with the lowest return water temperature. The results also show that efficiency gains will increase electricity production by about 1–3%, and that greenhouse gas (GHG) emissions are reduced by 4–20%.
Highlights
Moriarty et al [1] examine different scenarios for how global energy use may develop until 2050.They show that to mitigate the problem of greenhouse gas (GHG) emissions, global energy use growth cannot continue
The results show that efficiency gains will increase electricity production by about 1–3%, and that greenhouse gas (GHG) emissions are reduced by 4–20%
The district heating system (DHS) system was represented in the model by four different kinds of nodes—fuel nodes, conversion nodes, demand nodes, and waste nodes
Summary
Moriarty et al [1] examine different scenarios for how global energy use may develop until 2050.They show that to mitigate the problem of greenhouse gas (GHG) emissions, global energy use growth cannot continue. Three views on a typical mature DHSs are presented, followed by a proposal for a technical improvement that would increase system efficiency. The three views are to represent fundamental aspects of a DHS, namely, process control, energy delivery, and storage. By chosen to represent fundamental aspects of a DHS, namely, process control, energy delivery, and examining these three aspects of a DHS, the efficiency improvement potential of the system will be storage. By examining these three aspects of a DHS, the efficiency improvement potential of the easier to analyse.
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