Evaluation of operation safety of energy release process of liquefied air energy storage system

Abstract

In order to solve the safety problem caused by the abnormal load shedding of the liquefied air energy storage (LAES) system during expansion process, the dynamic simulation model of the 500 kW expansion unit was established. The model is used to simulate normal shutdown and emergency shutdown of the unit, and the changes of parameters such as unit load, valve opening, and rotor speed during the expansion process are analyzed. By studying the influence of valve closing time and rotor time constant on rotor speed and rotor downtime when the unit is shut down due to accident, the value range of valve closing time and rotor time constant which can meet the safety requirements of the unit was proposed. The simulation results show that during the process of shutdown, the highest rotor speed increases first and then decreases with the increase of valve closing time when the rotor time constant remains unchanged, and the valve closing time when the highest speed reaches the maximum value is related to the rotor time constant. When the valve closing time remains unchanged, the highest rotor speed decreases gradually with the increase of the rotor time constant, but the downtime increases. The rotor time constant should be set not less than 7s, and the closing time of the control valve should not exceed 1.5s to ensure the safe operation of the expansion process of the liquefied air energy storage system.