The potential of transcritical cycles based on CO[formula omitted] mixtures: An exergy-based analysis.

This paper focuses on the thermodynamic comparison between pure supercritical Carbon Dioxide and blended transcritical Carbon Dioxide power cycles by means of a thorough exergy analysis, considering exergy efficiency, exergy destruction and efficiency losses from Carnot cycle as main figures of merit. A reference power plant based on a steam Rankine cycle and representative of the state-of-the-art (SoA) of Concentrated Solar Power (CSP) plants is selected as base-case. Two different temperatures of the energy (heat) source are considered: 575 °C (SoA) and 725 °C (next generation CSP). Compared to SoA Rankine cycles, CO 2 blends enable cycle exergy efficiency gains up to 2.7 percentage points at 575 °C. At 725 °C, they outperform both SoA and pure CO 2 cycles with exergy efficiencies up to 75.3%. This performance is brought by a significant reduction in the exergy destruction across the compression and heat rejection process rounding 50%. Additionally, it has been found that the internal condensation occurring inside the heat recuperator for those mixtures with a large temperature glide improves recuperator exergy efficiency, supporting the use of simpler layouts without split-compression. Finally, CO 2 blends exhibit lower cycle exergy efficiency degradation than pure sCO 2 in the event of an increase in the design ambient temperature. • CO 2 mixtures enable exergy efficiencies up to 75% at high ambient temperatures. • CO 2 mixtures outperform both SoA steam-Rankine and pure sCO 2 technologies. • Exergy efficiency is significantly enhanced by WF condensation in the recuperator. • Maximum cycle pressure level beyond 250 bar are found to be of scarce interest. [ABSTRACT FROM AUTHOR]