Thermal Performance Analysis Of The Compressed Carbon Dioxide Energy Storage System

The renewable energy sources are currently an effective solution to the energy problems.However,a common shortcoming of these renewable energy sources is their unpredictable nature and dependence on weather and climate changes.To solve this problem,an energy storage technology is usually required to reduce power production fluctuations.Meanwhile,the energy storage technology is also an indispensable part of load shifting of power system and the development of distributed energy system.Thus,energy storage technology is regarded as the sixth value chain of energy revolution.Carbon dioxide storage technology is a new storage technology so far.Compared with existing storage technologies,high energy density,easy liquefaction,environmental friendly content and the like are the merits of the new technology.However,few researches have focused on thermodynamic characteristics of the carbon dioxide storage technology.In order to have a deep understanding of the carbon dioxide storage technology,this paper specifies in the aspects of theory analysis,system structure and parameter optimization.Firstly,through a summary of the flow of various compressed carbon dioxide energy storage systems,a thermodynamic model of compressed carbon dioxide energy storage system is established.Then,the relationship between key parameters and system efficiency is obtained and the potential value of the system under different setting conditions is analyzed.Secondly,five compressed carbon dioxide storage systems with different storage states and system configurations are proposed: gaseous and supercritical compressed carbon dioxide storage system,gaseous and liquid compressed carbon dioxide storage system,liquid and supercritical compressed carbon dioxide energy storage system,liquid and liquid compressed carbon dioxide energy storage system at atmospheric pressure and non-pressurized liquid and pressurized liquid compressed carbon dioxide energy storage system.And the evaluation indexes of carbon dioxide energy storage system are proposed.Thirdly,these five compressed carbon dioxide storage systems are simulated by Aspen Plus and typical operating condition of each system is proposed.The results reveal that the storage pressure,release pressure,compressor inlet pressure,throttle valve pressure drop,the efficiency of the compressor,expander efficiency and expander entrance temperature can affect the system performances.Finally,the optimization models of the five systems are established,the optimal parameters especially the efficiency of each system is obtained.Through the exergy analysis of the optimal system,the exergy loss distributions are achieved.This paper reveals the internal essence of the exergy loss of compressed carbon dioxide storage system.This research provides reference for the design and optimization of the compressed carbon dioxide energy storage system.