基于能量梯级利用的压缩CO_(2)储能系统热力学分析及结构优化

Thermodynamic Analysis and Structure Optimization of Compressed CO_(2) Energy Storage System based on Energy Cascade Utilization

为了解决储能系统中余热高效回收利用的问题,本文提出了一种基于能量梯级利用的压缩CO_(2)储能系统,利用高压压缩余热分级存储的手段实现能量的深度利用。建立了系统的热力学模型,对所提出系统和现有参考系统进行了对比分析。结果表明:改进后的系统循环效率增加了3.99%,储能密度增加4.47(kW·h)/m^(3),换热部件相对火用损失下降了6.80%;提高冷却水的初始温度能有效提高循环效率;高温储热换热器中CO_(2)的出口温度对循环效率的影响存在最优值为434 K;中温段换热器中CO_(2)的出口温度较低时,有利于循环效率和储能密度的提升。本文所提出的系统能够为CO_(2)储能系统深入优化提供一种可行方案。

To solve the problem of high efficient waste heat recovery and utilization in energy storage systems,a compressed CO_(2) energy storage system based on step utilization of energy was proposed in this paper,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 analysis 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 increases by 4.47(kW·h)/m^(3),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 water.The influence of CO_(2) 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 CO_(2) 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 CO_(2) energy storage system.