Thermodynamic Analysis of an Indirect Supercritical CO2-Air Driven Concentrated Solar Power Plant with a Packed Bed Thermal Energy Storage

The present work assesses the thermodynamic performance of an indirect supercritical CO2 - air driven concentrated solar plant with a packed bed thermal energy storage. A specific focus has been devoted to the flexibility requirements on both air and supercritical loops, highlighting key limitations and challenges that need to be addresses prior fruitful development of proposed cycles. The introduced plant design enables a supercritical CO2 turbine inlet temperature of 800 degrees C, overcoming the temperature limits imposed by the use of solar molten salts as primary heat transfer fluid. Furthermore, the packed bed thermal energy storage permits the decoupling between thermal power collection from the sun and electricity generation. Besides, it grants operational flexibility and enlarges the plant capacity factor. Results show that the proposed indirect supercritical CO2 air driven with a packed bed thermal energy storage concentrated solar plant leads to improved thermodynamic performance with respect to the molten salts driven design, particularly when working at high temperature, above molten salts limit. Enhancements in the power cycle efficiency and in the overall electricity production can be achieved, with a consequent increase of the capacity factor. Furthermore, the proposed system seems viable for the coupling with other power sources as PVs or secondary, low temperature, power cycles.