Off-Design Performance of Molten Salt-Driven Rankine Cycles and its Impact on the Optimal Dispatch of Concentrating Solar Power Systems

William Hamilton, Alexandra Newman, Michael Wagner, Robert Braun

Research output: Contribution to journalArticlepeer-review

32 Scopus Citations


This paper presents a model for improving off-design performance predictions for molten salt-driven Rankine power cycles, such as in concentrating solar power tower applications. The model predicts cycle off-design performance under various boundary conditions, including molten salt inlet temperature, mass flow rate, and ambient temperature. The model is validated using industry performance data and benchmarked with results from the literature. A complete concentrating solar power plant, inclusive of solar heliostat field and receiver, is then considered, by implementing the Rankine cycle off-design performance results into the National Renewable Energy Laboratory's System Advisor Model software, which includes a tool that determines optimal power production schedules. The work improves upon the current System Advisor Model by updating off-design performance characteristics. A case study demonstrates the impact of cycle off-design behavior on annual performance for a stand-alone concentrating solar power system and a concentrating solar power-photovoltaic hybrid system. In addition, we demonstrate how cycle off-design performance influences optimal operator dispatch decisions and, thereby, overall system design and economics. We conclude that off-design cycle performance impacts “optimal” sub-system sizing, especially for a concentrating solar power-photovoltaic hybrid configuration in which concentrating solar power must dispatch in conjunction with photovoltaic generation.

Original languageAmerican English
Article number113025
Number of pages16
JournalEnergy Conversion and Management
StatePublished - 2020

Bibliographical note

Publisher Copyright:
© 2020 Elsevier Ltd

NREL Publication Number

  • NREL/JA-5500-77433


  • Concentrating solar power (CSP)
  • CSP-PV hybrid systems
  • Dispatch optimization
  • Off-design performance
  • Steam Rankine cycle
  • Thermal energy storage (TES)


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