Thermodynamic Analysis and Structure Optimization of Compressed CO2 Energy Storage System based on Energy Cascade Utilization
To solve the problem of high efficient waste heat recovery and utilization in energy storage sys-tems,a compressed CO2 energy storage system based on step utilization of energy was proposed in this pa-per,and the deep utilization of energy was realized by means of hierarchical storage of waste heat under high pressure compression.A thermodynamic model of the system was established,and a comparative anal-ysis was made between the proposed system and the existing reference system.The result shows that after the improvement,the cycle efficiency of the system increases by 3.99％,the energy storage density increa-ses by 4.47(kW·h)/m3,and the relative exergy loss of heat exchange parts decreases by 6.80％.The new system can effectively improve the cycle efficiency by increasing the initial temperature of cooling wa-ter.The influence of CO2 outlet temperature on the cycle efficiency of high temperature heat storage heat exchanger has an optimal value of 434 K.When the outlet temperature of CO2 in the medium temperature heat exchanger is low,it is conducive to the improvement of cycle efficiency and energy storage density.The proposed system can provide a feasible scheme for further optimization of CO2 energy storage system.
CO2 energy storage systemstep utilizationcycle efficiencyenergy storage densitycom-pressed waste heat
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