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 120 213 500 yuan

compared with 58 077 400 yuan for a standalone LAES

and the levelized cost of storage decreases to 0.809 4 yuan/(kW·h)from 0.897 2 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.