Study of the Energy Efficiency of Compressed Air Storage Tanks

Abstract

This study focusses on the energy efficiency of compressed air storage tanks (CASTs), which are used as small-scale compressed air energy storage (CAES) and renewable energy sources (RES). The objectives of this study are to develop a mathematical model of the CAST system and its original numerical solutions using experimental parameters that consider polytropic charging and discharging processes, changes in the time of the temperature, flow parameters of the inlet and outlet valves under choked and subsonic conditions, and the characteristics of the air motor. This model is used to select CAST as an energy storage system for compressed air generated by compressors and recycling, as well as an energy source to drive DC generators and a pneumatic propulsion system (PPS). A measuring test rig is built to verify the polytropic pressure and temperature variations during CAST charging and discharging obtained from numerical solutions. The topic of discussion is the functional model of a high-pressure air system (HPAS) that contains a CAST connected to an air motor coupled to a mechanical drive for a DC generator or PPS. Such a system is used in small-scale CASTs, which currently respond to socio-economic demands. The presented CAST energy efficiency indicators are used to justify the storage of compressed air energy on a small scale. Small-scale compressed air storage in CASTs is currently important and relevant due to the balance between peak electricity demand and the development of wind energy, photovoltaics, and other renewable energy sources.