Thermodynamic analysis of a hybrid energy system based on CAES system and CO2 transcritical power cycle with LNG cold energy utilization

Abstract

Compressed air energy storage (CAES) is recognized as one of the most promising grid-scale energy storage technology due to the increasing share of intermittent renewable power sources. To utilize both the compression heat during charging and the waste heat in exhaust from turbines during discharging of CAES system, a hybrid energy system based on CAES system and CO2 transcritical power cycle (CTPC) with liquid natural gas (LNG) cold energy utilization is proposed. The LNG is used to chill the inlet air temperature of compressors during the charge process thereby reducing the power consumption, and thus making a shorter time to fill up the air storage cavern. On the other hand, the CTPC with LNG as its heat sink is employed to recover the waste heat in exhausted flue gas from expansion train to produce more electricity, which can increase the net energy output, resulting in a raised energy generated per unit volume of storage (EVR). Moreover, the parametric analysis shows that the air storage cavern temperature and turbine inlet temperature have positive effect on the system second law efficiency, whereas the inlet temperature of compressors has negative effect.