A step towards dynamic: An investigation on a carbon dioxide binary mixtures based compressed gas energy storage system using energy and exergy analysis

Abstract

A dynamic model of a compressed gas energy storage system is constructed in this paper to discover the system's non-equilibrium nature. Meanwhile, the dynamic characteristics of the CO2 binary mixture (i.e., CO2/propane, CO2/propylene, CO2/R161, CO2/R32, and CO2/DME) based system are first studied through energy and exergy analyses. Performance indicators are considered, including round trip efficiency, exergy efficiency, energy density, discharge time, and average power output. The effects of tank volume and ambient temperature on the system performance are analyzed. According to the results, although the round trip efficiency of the CO2 mixture system is reduced by about 0.68%–11.97% compared to pure CO2, the compressor performance and the system pressure stability are improved. When the tank volume increases from 10,000 m3 to 15,000 m3, the system round trip efficiency increases by 0.16%–0.33%. A further improvement of round trip efficiency for the CO2 mixture is found compared to pure CO2 at higher ambient temperature. This paper demonstrates the dynamic operational characteristics of the compressed gas energy storage system when using different CO2 binary mixtures, providing a reference for optimizing related systems. Potential scenarios and applications for the CO2 binary mixture are discussed for future research.