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Fundamental thermo-economic approach to selecting sCO2 power cycles for CSP applications
Francesco Crespi, David Sánchez, José María Rodríguez, Giacomo Gavagnin
Session: Session 1A: CO2 Power System
Session starts: Wednesday 13 September, 10:30
Presentation starts: 11:30
Room: Building 27 - Lecture room 01

Francesco Crespi (University of Seville)
David Sánchez (University of Seville)
José María Rodríguez (University of Seville)
Giacomo Gavagnin (University of Seville)

The interest in sCO2 power cycle has grown exponentially in the last decade, thanks to distinctive features like the possibility to achieve high thermal efficiencies at intermediate temperature levels, small footprint and adaptability to a wide variety of thermal sources. In the present work, the potential of this technology is studied for Concentrated Solar Power applications, in particular Solar Tower systems with Thermal Energy Storage (TES). A thorough sensitivity analysis based on Turbine Inlet Temperature (TIT) and Pressure Ratio (PR) is done for twelve sCO2 cycles, considering their effects on thermal efficiency (ηth) and specific work (Ws), along with the Solar Share (SS) and the temperature rise across the solar receiver (ΔTsolar). The most important conclusions of this section are that: a) maximum values of ηth, Ws and ΔTsolar are obtained for different PRs; b) ΔTsolar and Ws, unlike ΔTsolar and ηth, are almost directly proportional within technological limitations; c) for a given TIT, an increase in the PR always produces a strong growth of ΔTsolar, but the effect on ηth is uncertain as this can either increase or decrease, depending on the cycle considered. A deeper analysis of ηth and ΔTsolarl is therefore mandatory, given that these parameters strongly affect the capital cost of CSP power plants. On one hand, a higher ηth implies a smaller solar field, the largest contributor to the plant capital cost; on the other, the temperature rise across the receiver ΔTsol is directly proportional to the size of the thermal energy storage systems, as it is also the case for state of the art steam turbine based CSP plants. An economic analysis is developed using an in-house code and the open-source software System Advisor Model (SAM) to evaluate the trade-offs between these two effects. The results obtained for the two most representative sCO2 cycles, i.e. the Transcritical Simple Recuperated and the Supercritical Partial Cooling cycles, are provided in the present work.