Improved quasi-steady-state power flow calculation for district heating systems: A coupled Newton-Raphson approach

Jonte Dancker and Martin Wolter

Applied Energy, 2021, vol. 295, issue C, No S0306261921004104

Abstract: District heating systems have a considerable storage capability due to their dynamic thermal behavior (i.e. the thermal inertia of the water flow). Using this storage can support a secure, reliable, and efficient integrated energy system operation with a high share of volatile renewable energy sources. To use this flexibility, a joint analysis is necessary that includes the dynamic thermal behavior. Existing methods determine the dynamic thermal behavior by separated hydraulic and thermal equation systems, which are solved consecutively. This complicates the analysis because dependencies between temperatures and mass flow rates are not depicted directly. Also, this decoupled representation does not allow an easy analysis of the interactions in an integrated energy system as is already possible in steady-state analysis. Thus, this paper extends the steady-state methods by including the dynamic thermal behavior. The equations describing the hydraulic and dynamic thermal behavior are joined in a single equation system and solved simultaneously in a coupled Newton-Raphson power flow calculation. For this, the dynamic thermal behavior is described by the node method. At the same time, the accuracy of the node method is improved by enhancing the temperature-gradient method. The validation shows a high accuracy independently of the simulation time increment. Because the method is based on the steady-state analysis it enhances the wide area of application by introducing the dynamic thermal behavior. With its high accuracy and its coupled approach, the method is suitable for future investigations of the interdependencies of integrated energy systems.

Keywords: District heating system; Newton method; Dynamic behavior; Node method; Temperature-gradient method (search for similar items in EconPapers)
Date: 2021
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Citations: View citations in EconPapers (12)

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DOI: 10.1016/j.apenergy.2021.116930

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