Thermo-economic analysis of the integrated bidirectional peak shaving system consisted by liquid air energy storage and combined cycle power plant

Highlights: • A combined cycle power plant for bidirectional peak shaving is proposed. • Waste heat and cold energy are used by cascade in the liquid air energy storage. • Thermo-economic sensitivity and comparative analysis are performed. • The power conversion efficiency of the integrated system can reach 99.39%. Natural gas peak shaving power station with gas-steam combined cycle is widely used to meet the demand of peak load regulation of the power grid. However, the exhaust heat of the system and the high-grade cold energy from the nearby liquified natural gas terminal are not fully utilized. Liquid air energy storage is a load leveling method suitable for grid scale but the system efficiency needs to be further improved. Therefore, a system that flexibly integrates the combined cycle power plant and liquid air energy storage to maximize the recovery of the wasted heat and cold energy is proposed, achieving the bidirectional peak shaving. The system realizes the cryogenic compression during the charging process and adequate exploitation of the exhaust heat from the power station during the discharging process. The effects of compressor and air turbine inlet temperatures, ambient temperature and natural gas pressure on the system are investigated by the thermodynamic analysis. The highest system efficiency can reach 99.39%. Also, it is demonstrated that the integrated system is economically preferable. Moreover, within the inlet temperature ranges of the compressor and air turbine studied, the systemic economics performance deteriorates as the temperature increases.