Steady-State Off-Design Modeling of the Supercritical Carbon Dioxide Recompression Cycle for Concentrating Solar Power Applications with Two-Tank Sensible-Heat Storage

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36 Scopus Citations

Abstract

Concentrating solar power researchers are evaluating the potential of the supercritical carbon dioxide recompression cycle to improve the thermal efficiency and decrease the capital costs of next-generation systems. This analysis investigates the steady-state off-design performance of a recompression cycle integrated with two-tank sensible-heat thermal energy storage as the ambient temperature and heat-transfer fluid (HTF) inlet conditions to the cycle change. This paper presents off-design component models and then cycle convergence and control models to maximize net cycle power output while constraining the high-side pressure and air-cooler fan power to their respective design values and fixing the cycle HTF outlet temperature to its design value. Results show that inventory control and air-cooler fan power are important control parameters that can be optimized to maximize off-design power output as the ambient temperature and HTF mass flow rate diverge from design. The high-side pressure and fan power constraints cause the cycle net power to degrade when the ambient temperature is warmer than the design value, and this study calculates a maximum mass flow rate for hot days above which the cycle cannot achieve the design HTF outlet temperature. Finally, the analysis shows that optimizing compressor shaft speeds can improve cold-day performance by around 1.5 percentage points and part-load performance by up to 2.5 percentage points versus a baseline case with no active compressor control.

Original languageAmerican English
Pages (from-to)19-33
Number of pages15
JournalSolar Energy
Volume212
DOIs
StatePublished - 2020

Bibliographical note

Publisher Copyright:
© 2020 International Solar Energy Society

NREL Publication Number

  • NREL/JA-5700-77064

Keywords

  • Concentrating solar power
  • Off-design
  • Recompression cycle
  • Supercritical carbon dioxide
  • Thermal energy storage

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