| In the context of global warming,the issue of carbon emission is very important.China is a major carbon emitter.Conforming to the trend of carbon emission reduction in the world,we actively develop and utilize renewable energy and put forward the goal of "double carbon".However,due to the intermittency and volatility of renewable energy,its large-scale grid connection is bound to cause the fluctuation of power grid and affect the security of power grid.In this context,energy storage technology stands out,which can effectively restrain the impact of renewable energy on the power grid.As a new energy storage technology,compressed carbon dioxide energy storage technology has the advantages of high energy storage capacity,low critical temperature of working medium,good heat transfer performance and environmental friendliness.Based on the traditional trans-critical carbon dioxide energy storage system,this paper aims to improve the energy storage density and work capacity of the system.An Compressed CO2 energy storage system coupled with solar thermal storage and organic is proposed Rankine cycle.CCES-STS-ORC),and corresponding thermodynamic and economic analyses were carried out.Specific work contents are as follows:(1)The thermodynamic model and economic model of CCES-STS-ORC system are established and the evaluation index is given.Based on the thermodynamic model,the whole cycle efficiency and energy storage density of the system under the design conditions were calculated,and the relationship between the system output work,energy consumption,whole cycle efficiency and energy storage density and the main parameters of the system was analyzed.The results show that the whole cycle efficiency of the system is up to 108.79%,and the energy storage density is up to 21.36kWh/m3.(2)Exergic loss of Exergic components in design conditions was calculated based on the Exergic model,and the relationship between Exergic loss of Exergic components and Exergic efficiency of the system and major system parameters was analyzed.The major exergic exergy loss sites are solar energy storage subsystem,organic Rankine cycle(ORC)subsystem,while the major exergy loss parts of CCES subsystem are throttle valves,coolers,high-temperature heat exchangers,compressors and expanders.The exergy efficiency is 34.58%.(3)Based on the economic model,the dynamic payback period and kilowatt-hour cost of the system under the design condition are calculated,the prices of each component and material are calculated,and the relationship between the net present value of the system,the dynamic payback period and kilowatt-hour cost and the main parameters of the system is analyzed.The results show that the dynamic payback period and kilowatt-hour cost of the system are the solar heat storage part,followed by the CCES part,and the ORC part has the lowest proportion.In terms of the cost ratio of the materials and components of the subsystem,the mirror field cost is the highest in the solar thermal storage system,the heat conduction oil cost is the highest in the CCES system,and the dynamic payback period and kWh cost of the system are 7.66 years and 0.131 $/kWh,respectively. |
