The integration of liquid air energy storage (LAES) and air separation unit (ASU) not only enables large-scale energy storage on load side but also significantly reduces the operational electricity costs of the ASU. A discrete-integrated ASU and LAES (ASU-LAES) represents one form of their integrations, where the two systems are arranged independently but integrated by using liquid air from LAES as part of the feedstock and cold source for the ASU, thereby overcoming constraints of shared integrated systems such as limited storage capacity. However, its exergy loss mechanisms and the influence of some factors on performances are not yet clear, restricting further performance improvement. This study systematically investigates the exergy destruction characteristics of the discrete-integrated ASU-LAES, and innovatively elucidates the critical influence of the interstage compression ratio in the LAES and the nitrogen export ratio of the ASU on the overall performances. Using a nitrogen export ratio of 20% as baseline, a 20% increment in the nitrogen export ratio increases the energy storage scale by an average of 12.22 MWh per 10,000 Nm 3 O 2 , along with average improvements of 2.97% in electricity cost saving ratio and 44 million CNY in net present value. Total exergy efficiency during discharging (45.21%) is higher than that during charging (42.3%), with compressors and the distillation system identified as the main exergy destruction components, respectively. The optimal economic performance is achieved at an inter-stage compression ratio of 1.78, corresponding to a net present value of 250 million CNY. This study can provide theoretical references for the future design and application of the integrated ASU-LAES systems.
He et al. (Wed,) studied this question.