Design and operation of direct heat exchange type thermal energy storage unit in an actual-size liquid air energy storage system

Abstract

This study examines the design specifications and operational parameters crucial for integrating thermal energy storage unit (TESU) within a demonstration-scale liquid air energy storage (LAES) system. The LAES system’s storage capacity of 6 MWh and power generation of 2 MW serve as performance benchmarks. To satisfy these criteria, a TESU with a mass flow rate of 26 kg/s and a duration of 2 hr to 4 h is deemed essential. Ensuring an effectiveness exceeding 0.9 necessitates adherence to specific design principles. Firstly, optimal spatial configuration of heat exchange parts, approximately double the thermal penetration depth, is essential to maintain high performance. Deviations from this guideline can lead to decreased heat exchange efficiency and thermal interference. Moreover, as TESU duration increases, the relative heat capacity of the shuttle mass rises, diminishing overall effectiveness. Adequate heat capacity within the TESU is thus crucial to sustaining desired performance levels throughout the duration. Additionally, optimizing the aspect ratio of the TESU improves effectiveness by mitigating axial heat conduction losses, facilitating efficient energy storage and retrieval. By incorporating these design considerations, the performance and effectiveness of the TESU within LAES systems can be optimized, enabling seamless energy management.