Dynamic modeling and control of a solar-powered Brayton cycle using supercritical CO2 and optimization of its thermal energy storage

Recompression Brayton cycles using supercritical CO2 as the working fluid appear as a prominent alternative for thermo-solar power applications. Also, solar energy's natural variability and intermittence make it difficult for solar plants to operate consistently and predictably. Thus, two of the most explored mitigating alternatives are thermal energy storage and auxiliary heating systems. Hence, this paper used actual meteorological data and transient numerical simulations to investigate the power output dynamics of a 10 MW plant. The modeling of an active control system of the working fluid mass inventory allowed the plant to operate in a stable manner while accounting for the significant variations in the fluid's thermophysical properties. Also, the study investigated the effect of the sizes of the thermal energy storage system and solar collectors field on the dynamics of the system. Finally, statistical analyses with actual meteorological data from Florianopolis/Brazil for nine days between 2017 and 2018 supported determining the optimal thermal energy storage system size. Hence, depending on the daily conditions, the results showed the operating settings that minimize the use of auxiliary heating with reductions of fuel consumption larger than 10%.

Automated summary

Recompression Brayton cycles using supercritical CO2 as the working fluid are a prominent alternative for thermo-solar power applications. Thermal energy storage and auxiliary heating systems are two widely explored mitigating alternatives to deal with the natural variability and intermittence of solar energy. This study used actual meteorological data and transient numerical simulations to investigate the power output dynamics of a 10 MW solar plant. The results showed operating settings that minimize the use of auxiliary heating with reductions of fuel consumption larger than 10%.