General performance evaluation method of the heat aided liquid air energy storge system with waste heat utilization

Abstract

As a large-scale energy storage technology, liquid air energy storge (LAES) system is considered as a promising route to solve the instability of renewable energy. The heat aided LAES system with waste heat utilization (WHU) has been widely concerned for the high electrical efficiency. However, there is no unified theoretical evaluation method for such systems. In this study, the WHU-LAES systems are generalized and unified, and a comprehensive evaluation factor (efficiency improving ability) is proposed. The specific influence modes of the added heat energy on the WHU-LAES system are analyzed: the “allocation effect” shows the heat energy redistribution in the air expansion (AE) subsystem and the follower waste heat utilization system due to the heat integration in the AE subsystem; the “gain effect” is brought by the simultaneous heat integration of the “power increase” subsystems and “consumption reduction” subsystems; the “superposition effect” is revealed and shows the efficiency improving ability is comprehensively determined by the direct benefit, the explicit influence, the “allocation effect” and the “gain effect”. In the end, the efficiency improving ability is applied to the supplementary heat characteristic analysis and the comprehensive evaluation of 8 cases of WHU-LAES systems, which proves the effectiveness of the comprehensive evaluation factor.