Supercritical Carbon Dioxide Brayton Cycle Constrution And Its Application In Solar Energy

The sCO₂ Brayton cycle has the advantages of high efficiency,compact structure,environmental protection,and strong energy adaptability.Its combination with solar energy and geothermal energy can meet the requirements of improving energy efficiency and reducing environmental pollution,and has good application prospects.This paper takes the sCO₂ Brayton cycle as the research object,and studies the thermodynamic characteristics and technical economy of the cycle applied to the solar system through simulation.First,based on the modular modeling method,five different forms of sCO₂ Brayton cycle thermodynamic models were built,and the solving method and the optimal design method were proposed for the thermodynamic model.The thermodynamic analysis was carried out by simulation,and the results showed that the intercooling and recompression sCO₂ Brayton cycle was the most suitable cycle layout for the tower solar system.Key parameters which have the greatest effects on thermodynamic performance of intercooling and recompression sCO₂Brayton cycle were studied,and the thermodynamic performance was optimized by genetic algorithm with the goal of cycle thermal efficiency and the sCO₂ mass flow per kilowatt power.The results show that when the inlet pressure of the main compressor,the inlet pressure of the pre-compressor,and the split ratio are 9.81 MPa,7.46 MPa,and 0.66,respectively,the thermal efficiency is 40.06%,and the sCO₂ mass flow per kilowatt power is 43.63 kg/k Wh.Secondly,a sCO₂-ORC combined power generation system using tower solar energy and geothermal energy as heat sources is proposed to make full use of sCO₂ Brayton cycle waste heat and realize cascade utilization of energy.The thermodynamic model of the sCO₂-ORC combined power generation system was built,and the combined system with different geothermal resource types as auxiliary heat sources was simulated to realize the matching of the cycle and the heat source,and the adaptability of the sCO₂-ORC combined power generation system was verified.The results show that when CO₂-EGS is used as the geothermal auxiliary heat source,the recompressed sCO₂ Brayton cycle is the most suitable cycle,the sCO₂-ORC combined power generation system has the best thermodynamics.The thermodynamic key parameter analysis and optimization of the combined cycle with a net output power of 10MW in the topping cycle were carried out.The results showed that:when the main compressor inlet temperature,main compressor inlet pressure,turbine inlet pressure,and split ratio were 315.15K,7.4 MPa,20 MPa,and 0.559,the thermal efficiency is 35.07%,the net output work is 16.63MW.Finally,investment cost estimation model of the sCO₂-ORC combined power generation system was built,and the solving method and evaluation indexes were proposed.The technical and economic evaluation of the sCO₂-ORC combined power generation system with tower solar energy and CO₂-EGS as the heat source and the net output power of the topping cycle is 10MW is carried out,the optimization results of cycle parameters show that when the main compressor inlet temperature,main compressor inlet pressure,turbine inlet pressure,and split ratio are 314.33 K,7.78 MPa,18.52 MPa,and 0.66,respectively,the sCO₂-ORC combined power generation system is technique economic optimal,the system thermal efficiency is32.83%,and the levelized cost of electricity is￥0.719 per k Wh.