液氮和液空复合型空气储能系统热力学与经济性分析

Thermodynamic and economic analysis of liquid nitrogen and liquid air hybrid energy storage system

可再生能源存在间歇性和波动性,给电网的稳定运行造成了挑战,储能技术是解决此问题的有效途径。液态空气储能技术具有储能密度高,不受地理条件限制和常压储存的突出优势,但往返效率相对较低。提出了一种液氮和液空复合型空气储能系统(N-LAES),通过充注液氮,增加膨胀机中的气体流量,同时也提高膨胀机前的气体压力,从而提高系统往返效率。利用建立的热力学模型进行分析,结果表明:对于一个典型规模的N-LAES,其往返效率可以从单一液空储能系统的56.90%提高至66.47%,第30年的净现值从单一系统的5 807.74万元提高至12 021.35万元,平准化储能成本从单一系统的0.897 2元/(k W·h)降低至0.8094元/(k W·h)。表明,N-LAES的热力学性能和经济性能都优于单一系统,为液空储能技术的发展提供了新思路。

The intermittency and volatility of renewable energy poses significant challenges to stable operation of power grids.Energy storage technology can address these issues effectively.Liquid air energy storage technology offers significant advantages of high energy storage density,being unconstrained by geographical conditions and atmospheric pressure storage.However,its round-trip efficiency is relatively low.To solve this problem,a liquid nitrogen and liquid air hybrid energy storage system(N-LAES)is proposed.By charging liquid nitrogen during energy release process,the gas flow in the expander increases,and gas pressure in front of the expander rises as well,thus the system’s round-trip efficiency increases.A thermodynamic model is developed,and the analysis results indicate that,for a typical scale N-LAES,the round-trip efficiency is increased to 66.47%compared with 56.90%for a standalone LAES.The net present value at the 30th year increases to 120213500 yuan,compared with 58077400 yuan for a standalone LAES,and the levelized cost of storage decreases to 0.8094 yuan/(kW·h)from 0.8972 yuan/(kW·h)for a standalone LAES.These findings demonstrate that both the thermodynamic and economic performance of the N-LAES is superior to that of the standalone LAES,offering a new approach for development of the liquid air energy storage technology.