Design and performance analysis of a novel liquid air energy storage system with a liquefaction capacity replenishment subsystem

Abstract

In the context of the rapid transition of the global energy system to a clean and low-carbon renewable energy framework, the technology of liquid air storage is a competitive solution to the intermittency of renewable energy owing to its relatively low cost and high energy density, capacity flexibility without strict geographical limitations and suitability for various scales of deployment. In this paper, a novel liquid air energy storage system with a subcooling subsystem that can replenish liquefaction capacity and ensure complete liquefaction of air inflow is proposed because of the inevitable decrease in the circulating cooling capacity during system operation. The release and storage of cold energy through valve switch coordination in the proposed system is an effective measure for eliminating intermediate media to reduce the heat transfer temperature difference and cold loss. Energy and exergy analyses are carried out, and round-trip efficiency and exergy efficiency are used as evaluation indices to study the performance of the proposed system, with results of 0.592 and 0.653 for the base case, respectively. Then, the matching of cold and hot composite curves and the identification of the bottleneck locations of the heat exchangers and cold storage tank are presented through pinch-point analysis. Furthermore, the comparative analysis results of combining the compression and expansion stages show that 2-stage compression and 4-stage expansion are the optimal scheme configurations, with a round-trip efficiency of 0.615 for the proposed system.