Thermodynamic analysis of a near-isothermal compressed air energy storage system based on internal combustion engine assistance

Compressed Air Energy Storage (CAES) systems have long faced challenges related to the waste of compression heat during the energy storage process and the inefficient utilization of pressure potential energy during the energy release process. Although the current integration of large-scale thermal storage devices and multi-stage expansion units has partially addressed these issues, it significantly compromises system flexibility. To resolve these limitations, this paper proposes a novel near-isothermal compressed air energy storage system based on Internal Combustion Engine (ICE) assistance. The system integrates a Kalina cycle module, an internal combustion engine, and a liquid piston near isothermal compression module. Thermodynamic and sensitivity analyses of the proposed system are conducted. Results indicate that under design conditions, the round-trip efficiency, electrical efficiency, and exergy efficiency reach 87.42 %, 55.15 %, and 52.57 %, respectively. Compared to traditional ICE-integrated CAES systems, the electrical efficiency is improved by 15.7 %. The effect of the pressurized intake air of the internal combustion engine module on the system is emphatically studied. When the ICE inlet pressure reaches 0.3 MPa, the electrical efficiency and exergy efficiency reach their maximum (55.68 % and 53.2 %) respectively. At the operational condition of 0.35 MPa intake pressure, the round-trip efficiency reaches its maximum value of 90.4 %. These findings provide theoretical foundations for the engineering application of the proposed system.