Energy distributing and thermodynamic characteristics of a coupling near-isothermal compressed air energy storage system

Intermittent renewable energy generation systems bring serious adverse impacts to the stable operation of the grid. In this regard, large-scale compressed air energy storage (CAES) systems with the potential to serve as long-term could be a solution for their optimal utilization. However, in a conventional CAES, most of the electricity is transformed into heat which passed into heat exchange mediums leads to serious heat transfer losses. In this study, a novel CAES system employing a Kalina cycle to effectively utilize the pre-compression heat in a near-isothermal compressed air process, is proposed and its holistic dynamic model is developed and presented for a deeper understanding of performance. The results showed that a near-isothermal compression undertakes the responsibilities of storing pressure potential energy, and the adiabatic pre-compression process helping in raising the inlet pressure of the liquid piston is primarily for storing thermal energy. In addition, the Kalina cycle working in the adiabatic pre-compression process achieves a 2.7 % improvement in the electrical efficiency. The thermal energy storage temperature was highlighted as the key factor in the energy allocation among the Kalina cycle, the thermal energy storage component, and the energy releasing sub-system in the proposed system. Through a systematic analysis of the proposed system performance, the highest electrical efficiency attained was 65.1 % with a 353 K storage temperature.