Efficiency Analysis of an Arrayed Liquid Piston Isothermal Air Compression System for Compressed Air Energy Storage

Compressed air energy storage(CAES) is an important technology in the development of renewable energy. The main advantages of CAES are its high energy capacity and environmental friendliness. One of the main challenges is its low energy density, meaning a natural cavern is required for air storage. High-pressure air compression can effectively solve the problem. A liquid piston gas compressor facilitates high-pressure compression, and efficient convective heat transfer can significantly reduce the compression energy consumption during air compression. In this paper, a near isothermal compression method is proposed to increase the surface area and heat exchange by using multiple tube bundles in parallel in the compression chamber in order to obtain high-pressure air using liquid-driven compression. Air compression with a compression ratio of 6.25:1 is achieved by reducing the tube diameter and increasing the parallel tube number while keeping the compression chamber cross-sectional area constant in order to obtain a high-pressure air of 5 MPa. The performances of this system are analyzed when different numbers of tubes are applied. A system compression efficiency of 93.0% and an expansion efficiency of 92.9% can be achieved when 1000 tubes are applied at a 1 minute period. A new approach is provided in this study to achieve high efficiency and high pressure compressed air energy storage.