Liquid air energy storage flexibly coupled with LNG regasification for improving air liquefaction

Abstract

Liquid Air Energy Storage (LAES) stands out among other large-scale energy storage technologies in terms of high energy density, no geographical constraints, low maintenance costs, etc. However, the LAES has a relatively lower round trip efficiency, 50–60%, which is a big disadvantage. One of the main reasons is the lower liquid air yield, ∼70%, which is far from 100% due to the lack of cold energy during air liquefaction. Thus, in this paper, cold energy released during liquified natural gas (LNG) regasification is recovered and stored with pressurized propane, which is used to help air liquefaction in the LAES (denoted as LAES-LNG-CS). The LNG regasification process works independently of the LAES thanks to cold storage. Effects of various working conditions on the LAES-LNG-CS system are studied and three operation periods (off-peak, peak and full hours) of the LNG regasification process are considered. Comparisons are made between the LAES-LNG-CS and standalone LAES systems. The results show that the LAES-LNG-CS system could achieve a liquid air yield up to ∼89% and the power consumption per unit mass of liquid air is reduced by ∼32%, compared with the standalone LAES system. What’s more, the system exergy efficiency of the standalone LAES is improved by ∼28% as the air charging pressure is at 8 MPa under studied conditions. Year-round performance study indicates that the round trip efficiency of the LAES-LNG-CS is in the range of 78–89%. Therefore, the proposed LAES-LNG-CS offers a good option for the future development of the LAES system.