Research On Thermodynamic And Thermoeconomic Properties Of Super-critical Compressed Carbon Dioxide Energy Storage

The rapid development of the world economy is inseparable from the power,huge electricity demand consumes a lot of fossil energy,resulting in energy crisis,environmental pollution,global climate change and other serious resource and environmental problems.Many countries are vigorously developing energy-saving,efficient,clean,low-carbon renewable clean energy power generation technology.But in recent years with the renewable energy development,renewable energy power generation has become an urgent problem to be solved.China has also emerged a serious abandon the wind energy,abandoned solar energy problem.Energy storage technology,especially large-scale energy storage technology is a key factor that solves the large-scale grid-connected renewable energy a key factor.Compressed air energy storage technology is considered to be one of the most promising large-scale energy storage technologies.But the storage density of the compressed air energy storage system is lower,which serious obstacles to its large-scale development and utilization.This paper analyzes a compressed carbon dioxide energy storage system based on compressed air energy storage technology and carbon dioxide.The system combines the advantages of compressed air energy storage technology and the physical properties of carbon dioxide,which can enhance the energy storage system performance of compressed gas energy storage density.In this paper,the following research works about the super-critical compressed carbon dioxide energy storage system were carried out.(1)The thermodynamic properties of compressed CO2 energy storage system based on underground gas storage were proposed and analysed.The thermodynamic model of compressed CO2 energy strorage system was established.The compressed CO2 energy storage system was divided into trans-critical compressed CO2 energy storage and super-critical compressed CO2 energy storage according to the working fluid status.Round-trip efficiency,exergy efficiency,storage density,and the complexity of the storage system were used as the evaluation indicator.The results show that the super-critical compressed CO2 energy storage has an excellent thermodynamic performance and simple system structure,which is suitable for large-scale development and utilization.(2)The super-critical compressed CO2 energy storage system and conventional compressed air energy storage system were analysed using advanced exergy analysis method that the exergy destruction was divided into endogenous exergy destruction and exogenous exergy destruction from the perspective of the system topology and the structure of the component itself,and was also divided into avoidable exergy destruction and unavoidable exergy destruction.The results showed that the exergy destruction of super-critical compressed CO2 energy storage was mainly decided by both the system topology and the structure of the component itself,while the exergy destruction of conventional compressed air energy storage was mainly decided by the structure of component itself.Therefore,improving the performance of the system topology and structure of the component itself is the best way to improve the performance of super-critical compressed CO2 energy storage,and improving the performance of structure of component itself can make conventional compressed air energy storage performance better.(3)An exergy cost analysis model of super-critical carbon dioxide storage system was established.The thermoeconomic analysis of the energy storage system was carried out.Based on the actual operating characteristics of the energy storage system,an improved exergy cost analysis method was proposed.Thermoeconomy and sensitivity analysis of the energy storage system were analyzed.The results show that the exergy cost of output electricity is raised compared with the input electricity.The exergy destruction within energy storage process comes from electricity,while the exergy destruction within regenerator and heater come from heat exergy.The variations of input fuel and electricity price will not affect the exergy cost ratio of the electricity exergy current and heat exergy current,and the electricity exergy destruction cost.(4)Based on orthogonal design and variance analysis,the signaficance factors influencing the exergy efficiency and thermoeconomic characteristics of the super-critical CO2 energy storage system are found.The analysis results show that although the interactions between the system components affect the thermodynamic and thermoeconomic performance,the signaficance factors affect the thermodynamic and thermoeconomic properties of super-critical compressed CO2 energy storage system are the components'own performance.