Integration And Optimization Of Supercritical Carbon Dioxide Cycle Power Generation System Based On Mathematical Programming

Low percapita occupancy of fossil energy and serious environmental pollution has always been important factors restricting China's economic development.Recycling waste heat and developing renewable energy is one of the effective ways to solve the current energy and environmental problems.Supercritical carbon dioxide?SCO₂?cycle has the characteristics of compact structure,high cycle efficiency and wid e available heat source range,and is one of the most potential power generation technologies in utilizing industrial waste heat,geothermal energy,solar energy,etc.The simulation,optimization,structural improvement and system integration of SCO₂ cycle have important theoretical significance and practical value for improving the comprehensive performance of SCO₂ system.Aiming at the deficiencies in the current study,such as obtain CO₂ properties relying on REFPROP and other databases,difficulty in effectively dealing with pinch constraints,iteration and random algorithm limited by variable size,etc.,the integrated and optimized method of SCO₂ cycle power generation system based on CO₂ precise equation of state and mathematical programming method is proposed,to improve the integrated performance of SCO₂ through racking pinch point which synchronized with system optimization,and integrated system optimization of SCO₂ and ORC.A CO₂ property model based on EOS is established.The accuracy is verified by comparing the calculation results with the REFPROP Based on EOS,a multi-objective mathematical model of SCO₂ heat transfer process for automatic positioning of pinch points and synchronous optimization of system parameters was established.The reliability of the model and the proposed solution strategy,the optimization of the solution and the advantage of the calculation time are verified from the two perspectives of system efficiency and output work by compared with the traditional method of preset pinch at the inlet and outlet of the heat exchanger.The integrated system of SCO₂ and Organic Rankine Cycle?ORC?is established.A method to reduce heat sink loss and improve system efficiency of the power generation system is proposed,and the global optimization model of the system is established.With the efficiency of the integration system as the goal,three SCO₂ system parameters,ORC system parameters and SCO₂+ORC coupling parameters were synchronously optimized,and the integration system advantages were verified by comparing with SCO₂independent system.The influence of working medium and heat source inlet temperature and cold source temperature rise on ORC system and integrated system was analyzed.The results show that the integrated system can effectively improve the system efficiency,and the ORC working medium and heat source/sink parameters have a great impact on the advantages of the integrated system.The solar driven air-cooled SCO₂ power generation system is constructed,and the global optimization models of solar tower heating system,SCO₂,ORC and air-cooling system are established.The effects of molten salt type,receiver outlet temperature and regional solar radiation characteristics on system performance were studied.