Thermodynamic and exergoeconomic analysis of combined supercritical CO2 cycle and organic Rankine cycle using CO2-based binary mixtures for gas turbine waste heat recovery

Combined cycle system is an effective technical mean for waste heat recovery (WHR) of gas turbine to improve energy efficiency and decelerate environmental pollution. A combined cycle system including two supercritical CO2 (S-CO2) cycles and one organic Rankine cycle (ORC) using CO2-based binary mixtures for WHR of gas turbine is proposed. Firstly, thermodynamic and exergoeconomic analyses are conducted for the proposed system. Then parametric study is carried out to investigate the influences of decision parameters on the system performance including thermal efficiency, exergy efficiency and unit cost. Besides, optimization is performed for the system from the viewpoints of thermodynamics and exergoeconomic. The results indicate that the highest total exergy destruction and capital cost occur in the gas turbine subsystem, followed by two S-CO2 cycles and ORC. The obtained results demonstrate that using Propane as additive in CO2-based binary mixture can not only benefit thermodynamic performance, but also is conductive to its exergoeconomic characteristic. Moreover, thermal efficiency, exergy efficiency, unit cost and exergoeconomic factor of proposed system can achieve 48.56%, 51.90%, 3.66 cent/kWh and 28.30% after the optimization of exergoeconomic, respectively. Furthermore, the superiority of proposed systems is verified compared with other systems in the literatures.