Experimental study of tube-array-based liquid piston air compressor for near-isothermal compressed air energy storage system

Compressed Air Energy Storage (CAES) serves as a crucial technology supporting large-scale renewable energy development, offering environmental friendliness, extended service life, and substantial energy storage capacity. The compressor constitutes a major component in the CAES system, and its efficient performance could lead to good roundtrip efficiency. Isothermal compression mitigates specific compression work and enhances efficiency by heightening the heat transfer amount and maintaining a relatively constant compression temperature. In this study, a novel Liquid Piston Air Compressor (LPAC) is designed to integrate a liquid piston with a tube heat exchanger structure, facilitating effective sealing and an expanded heat transfer area. Both experimental and simulated studies were conducted with pressure from 0.67 MPa to 4.7 MPa. The effects of flow rate variation on near-isothermal compression parameters were investigated, which included pressure, temperature, entropy, heat transfer amount, indicated work, polytropic exponent, power density, and efficiency. Experimental results revealed that, in contrast to the adiabatic process, the air peak temperature can be reduced by 73 K, 97 K, and 120 K at flow rates of 1320 cm³/s, 660 cm³/s, and 330 cm³/s, respectively. This leads to a decrease in specific work by 5.8%, 11.2%, and 14.9%. The compression efficiency could reach 86.7% when the flow rate was 330 cm³/s.