液态存储跨临界CO2储能系统的能量转换机理及调控机制研究

The large scale compressed gas energy storage system is useful to increase the fluctuant renewable energy penetration level. In order to overcome the drawbacks of low energy storage density and relying on geologic structure of conventional compressed air energy storage system, a transcritical carbon dioxide energy storage system with liquid storage by combining the advantages of liquid air energy storage and supercritical/transcritical carbon dioxide power cycle will be proposed, which has the features of compact structure, high round trip efficiency, high energy density and the independent of geologic conditions. To understand the operation mechanism of the proposed energy storage system deeply is the main purpose of this project. The system energy conversion and coupling principle will be illustrated based on the associated relationships between the changes of thermophysical properties and phase states of carbon dioxide, and the characteristics in compression, expansion and heat exchange processes. The optimal cycle layout of specific power/energy rating system is obtained after exploring the law of system energy flow affecting by improvements of system structure configurations. Meanwhile, the behaviors characteristics of design and off-design conditions are also revealed. Upon the system unstable state evolution behaviors under high randomness power requirement and complex physical constraint conditions, the predictive control strategy to implement the quick tracking after load change and stable control process is established and finally the active control mechanism with best system performance is developed. This project can help enrich and improve the theory of compressed gas energy storage, which has important theoretical and academic significances.

大规模压缩气体储能技术将有助于提高波动性可再生能源的并网容量等级。针对传统压缩空气储能系统储能密度低、依赖于地质构造等缺点，本项目结合液化空气储能技术与超（跨）临界二氧化碳动力循环的优点，本着结构紧凑、充放电效率和储能密度高且不依赖地质构造的原则，提出液态存储跨临界CO2储能系统。以深入理解该储能系统的运行机理为目标，在获取CO2物性变化、相态变化与其压缩特性、膨胀特性和传热特性的关联关系基础上，阐明系统能量转换与耦合机理；探索系统结构配置形式改进对能量流动的影响规律，获取特定功率/能量等级系统的最佳循环布局，并揭示不同储能、释能功率下系统的全工况行为特征；探究高随机性能量需求与复杂物理约束条件下的系统非稳态演变行为，构建能够实现负荷快速跟踪和控制过程平稳的预测控制策略，获取系统性能优化的主动调控机制。本项目的实施为有助于丰富和完善压缩气体储能技术理论体系，具有重要的理论和学术意义。

压缩气体储能利用其能量分时管理特性，可以平抑规模化间歇性可再生能源并网对电力系统的冲击，可实现电力系统深度调峰，助推能源利用低碳转型。鉴于CO2的优良物性，以CO2为工质的液态存储跨临界CO2储能系统具备结构紧凑、储能密度高、充放电效率高等优点，是压缩气体储能技术发展的新方向。.本项目为深入理解液态存储跨临界CO2储能系统的能量转换与耦合机理，针对CO2在拟临界区的物性突变现象，在典型跨临界CO2储能系统结构上探究了储能系统内部气-液与液-气相变过程的能量传递与转换过程，获取了CO2跨越拟临界区时蓄热器中的传热特性，探悉了压缩比与膨胀比的匹配关系对系统热能、内能和冷能的存储与转换的影响规律。针对不同的应用场景，提出了多种液态存储跨临界CO2储能系统的配置形式，探究关键参数对系统性能的影响机理，获取系统内部不可逆损失形成与分布规律，获取系统在完整充放电循环中的全工况行为特征。考虑高随机性功率需求与复杂物理约束条件下系统部件的动态耦合与匹配特性，选取典型风电场功率及区域负荷时间序列作为输入，仿真分析了系统在多运行模式间的切换规律及切换时的过渡行为，同时基于系统动态模型以及不平衡功率序列，探悉动态过程中旋转部件的最优性能曲线跃迁路径，获取系统负荷快速跟踪和平稳控制机理。此外，根据CO2储能系统相关研究工作启示，针对储能系统内部多能流耦合的特性，深入开展了基于压缩气体储能的区域级综合能源系统应用研究。