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A data-based comparison of methods for reducing the peak volume flow rate in a district heating system

Felix Agner, Ulrich Trabert, Anders Rantzer, Janybek Orozaliev

Abstract

This work concerns reduction of the peak flow rate of a district heating grid, a key system property which is bounded by pipe dimensions and pumping capacity. The peak flow rate constrains the number of additional consumers that can be connected, and may be a limiting factor in reducing supply temperatures when transitioning to the 4th generation of district heating. We evaluate a full year of operational data from a subset of customer meters in a district heating system in Germany. We consider the peak flow rate reduction that could be achieved with full a posteriori knowledge of this data. Three strategies for reducing the peak flow rate are investigated: A load shifting demand response strategy, an upper limitation in substation return temperatures, and an upper limitation on each substation's volume flow rate. We show that imposing up to to 18 % load flexibility for the customers provides an equal reduction in the peak system flow rate under the load shifting strategy. The limited return temperature strategy is less efficient at curtailing the peak flow rate, but provides an overall reduction of volume flow rates. Finally, the flow rate limitation method can introduce new, higher flow rate peaks, reducing performance.

A data-based comparison of methods for reducing the peak volume flow rate in a district heating system

Abstract

This work concerns reduction of the peak flow rate of a district heating grid, a key system property which is bounded by pipe dimensions and pumping capacity. The peak flow rate constrains the number of additional consumers that can be connected, and may be a limiting factor in reducing supply temperatures when transitioning to the 4th generation of district heating. We evaluate a full year of operational data from a subset of customer meters in a district heating system in Germany. We consider the peak flow rate reduction that could be achieved with full a posteriori knowledge of this data. Three strategies for reducing the peak flow rate are investigated: A load shifting demand response strategy, an upper limitation in substation return temperatures, and an upper limitation on each substation's volume flow rate. We show that imposing up to to 18 % load flexibility for the customers provides an equal reduction in the peak system flow rate under the load shifting strategy. The limited return temperature strategy is less efficient at curtailing the peak flow rate, but provides an overall reduction of volume flow rates. Finally, the flow rate limitation method can introduce new, higher flow rate peaks, reducing performance.
Paper Structure (17 sections, 4 equations, 8 figures, 3 tables, 1 algorithm)

This paper contains 17 sections, 4 equations, 8 figures, 3 tables, 1 algorithm.

Table of Contents

  1. Introduction
  2. Notation
  3. Method
  4. Dataset Description and Preprocessing
  5. Coordinated Optimal Load Shifting
  6. Individual Return Temperature Limitation
  7. Individual Flow Rate Limitation
  8. Pumping Power and Aggregate Return Temperature
  9. Results
  10. Duration Curves
  11. Partial Strategy Implementation
  12. Impact of Flexibility or Limitation Level
  13. Additional Benefits
  14. Discussion
  15. Conclusion
  16. ...and 2 more sections

Figures (8)

  • Figure 1: A conceptual scheme of the grid branch where the data used in this study was collected.
  • Figure 2: Bar plot of mean and peak heat loads by meter ID.
  • Figure 3: Mean hourly heat load for each consumer and hour of the day (1-24) taken over the full year of data. The profile for each consumer is normalized in the interval $\left[0, 1\right]$.
  • Figure 4: Duration curves of total flow rates using flow rate limitation (FL), return temperature limitation (TL) or coordinated load shifting (LS). The results are displayed over the full year (\ref{['fig:duration curves full year']}) and detailed over only the top 300 hours (\ref{['fig:duration curves zoomed in']}).
  • Figure 5: The effect on peak yearly flow-rate when including a larger number of substations.
  • ...and 3 more figures