Introduction  Supercritical CO₂ (sCO₂) Brayton cycle is a promising technology to improve the efficiency of concentrated solar power systems.

  Method  This paper presented an equation-based nonlinear programming model for the analysis and optimization of the power tower concentrated solar power (CSP) coupled with supercritical CO₂ (sCO₂) Brayton cycles. The model included CSP subsystems, sCO₂ Brayton cycle, and high accuracy equation of state, enabling simultaneous optimization of the systems with arbitrary number of decision variables. Case studies of the integrated CSP-simple sCO₂ Brayton cycle and CSP-recompression sCO₂ Brayton cycle systems were carried out to determine their optimal design.

  Result  The results show that thermal efficiency of the CSP-recompression cycle system can reach a maximum of 29.4%, higher than the 24.9% of the CSP-simple cycle system. The optimal turbine inlet temperature is 901 K for the CSP-recompression cycle system, 826 K for the CSP-simple cycle system. The optimal expansion ratios of the CSP-simple cycle system are greater than 3.2 at the investigated temperature range, and are approximately equal to 3 for the CSP-recompression cycle system.

  Conclusion  There are optimal turbine inlet temperatures and compression ratios for the integrated systems.Additionally, the compression ratio has a greater impact on the thermal efficiency of the CSP-simple cycle system.