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@PHDTHESIS{Schwager:1010743,
      author       = {Schwager, Christian},
      othercontributors = {Hoffschmidt, Bernhard Franz and Mitsos, Alexander},
      title        = {{O}perating assistance system for transitioning between
                      operating modes of molten salt receivers},
      school       = {Rheinisch-Westfälische Technische Hochschule Aachen},
      type         = {Dissertation},
      address      = {Aachen},
      publisher    = {RWTH Aachen University},
      reportid     = {RWTH-2025-04295},
      pages        = {1 Online-Ressource : Illustrationen},
      year         = {2024},
      note         = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
                      University 2025; Dissertation, Rheinisch-Westfälische
                      Technische Hochschule Aachen, 2024},
      abstract     = {Molten salt solar tower (MST) power plants represent a
                      concentrating solar power (CSP) technology already in
                      commercial use. Nevertheless, they still have great
                      potential for efficiency improvements and cost reductions.
                      In contrast to conventional power plants, CSP plants are
                      subject to highly volatile boundary conditions facing
                      components with a wide range of inertias. Hence, to
                      realistically predict and increase the actual yields of an
                      MST, complex simulation models and algorithms are required
                      to pay particular attention to the operation of the receiver
                      system. Within the scope of this work, it was fundamentally
                      investigated how an operating assistance system can support
                      the receiver operation concerning availability and net
                      yield. An assistance function, which provides
                      model-prediction-based decision proposals for transitioning
                      from normal receiver operation to drained standby, was
                      developed and tested. As a basis, a detailed dynamic process
                      model of an MST receiver system, including a
                      three-dimensionally discretized receiver, less detailed
                      other components, a distributed control system for start-up
                      and shutdown procedures as well as control loops, was
                      developed and implemented in Modelica. For this purpose, a
                      thermo-hydraulic two-phase model for molten salt and air as
                      well as specific component models, were implemented, which
                      enabled complying with local limits in the receiver during
                      and after flood or drainage of the receiver. To reduce the
                      computing time of the yield prediction, simplified models
                      and a heuristic decision algorithm were developed and
                      implemented in Modelica and Python, respectively. In this
                      context, a virtual net power approach for the receiver
                      system was developed, which allows realistically predicting
                      the net output while considering the com-plex dynamic
                      behavior and quickly finding the optimal timing without
                      iterations. This operating assistance function quantifies
                      the yield gain/loss achieved by a temporary receiver standby
                      and serves as the basis for the decision proposal. The test
                      results show that one single maneuver proposed by this
                      operating assistance function can increase the net yield of
                      a utility scale plant by several megawatt-hours, depending
                      on the cloud situation. Uncertainty analyses show a
                      particular sensitivity for forecasting errors, which is why
                      better forecasting accuracy is needed, especially for larger
                      prediction horizons, compared to the examined data.
                      Furthermore, there is still a need for research on the
                      accurate modeling of the local convective heat loss at such
                      a receiver to predict the thermal losses during start-up and
                      shutdown and thus its duration reliably.},
      cin          = {421010},
      ddc          = {620},
      cid          = {$I:(DE-82)421010_20140620$},
      typ          = {PUB:(DE-HGF)11},
      doi          = {10.18154/RWTH-2025-04295},
      url          = {https://publications.rwth-aachen.de/record/1010743},
}