A novel system of liquid air energy storage with LNG cold energy and industrial waste heat: Thermodynamic and economic analysis

Liquid air energy storage (LAES) is a promising technology for large-scale energy storage applications, particularly for integrating renewable energy sources. While standalone LAES systems typically exhibit an efficiency of approximately 50 %, research has been conducted to utilize the cold energy of liquefied natural gas (LNG) gasification. This approach, applied during the LAES energy storage phase of air compression and liquefaction, can reduce the power consumption of the compressor and enhance the performance of the integrated system. However, the improvement in the system's efficiency is constrained due to the low temperature of the air entering the turbine expansion during the energy release phase. Most studies only focus on the utilization of LNG cold energy, neglecting the proper utilization of the cold energy generated during the liquid air gasification process. This paper proposes an integrated system of LNG cold energy utilization and cement industry waste heat recovery (WHR) with LAES (LNG-LAES-WHR). A thermodynamic model is constructed, and the system is optimized by using four-stage compression, four-stage expansion, and R601 as the working fluid for WHR. The optimized integrated system has a round-trip efficiency (RTE) of 176.27 % and achieves a power output of 337.53 MW. Compared to the previously proposed system, this system has a high exergy efficiency of 74.49 % with a maximum energy storage capacity of 0.5918 kW/kg LNG. The economic analysis shows that the system has the best economic performance when constructed in Zhuhai: the dynamic payback period (DPP) is 4.2 years and the life cycle net present value (NPV) is 1170.72 million USD. This system realizes the cascaded utilization of energy, both in terms of heat and cold, which is safe, flexible, and highly efficient. This work provides a reference for the design of integrated systems for large-scale LAES for industrial applications.