Thermo-economic optimization of an air driven supercritical CO2 Brayton power cycle for concentrating solar power plant with packed bed thermal energy storage

This work presents an innovative indirect supercritical CO2 - air driven concentrated solar power plant with a packed bed thermal energy storage. High supercritical CO2 turbine inlet temperature can be achieved, avoiding the temperature limitations set by the use of solar molten salts as primary heat transfer fluid. The packed bed thermal energy storage enables the decoupling between solar irradiation collection and electricity production, and it grants operational flexibility while enhancing the plant capacity factor. A quasi steady state thermoeconomic model of the integrated concentrating solar power plant has been developed. The thermo-economic performance of the proposed plant design has been evaluated via multi-objective optimizations and sensitivity analyses. Results show that a Levelized Cost of Electricity of 100 $/MWhe and a capacity factor higher than 50% can be achieved already at a 10 MWe nominal size. Such limited plant size bounds the capital investment and leads to more bankable and easily installable plants. Results also show that larger plants benefit from economy of scale, with a 65 $/MWhe cost identified for a 50 MWe plant. The receiver efficiency is found to be the most influential assumption. A 20% decrease of receiver efficiency would lead to an increase of more than 15% of the Levelized Cost of Electricity. These results show the potential of indirect supercritical CO2 - air driven concentrated solar power plant and highlight the importance of further air receiver development. More validations and verification tests are needed to ensure the system operation during long lifetime.