Effects of multiple insufficient charging and discharging on compressed carbon dioxide energy storage

Compressed carbon dioxide is a promising energy storage technology. However, renewable energy variability can lead to insufficiency during charging and discharging. The present work systematically investigates the effect of charging/discharging insufficiency on compressed carbon dioxide energy storage systems from the viewpoint of transient thermodynamic cycles. The insufficiency extent is defined based on the pressure at the high-pressure tank when disturbances occur. Then the effects of insufficiency extent are investigated in three typical scenarios. In the results, the effects of charging/discharging insufficiency on the efficiency, storage density and power output of the energy storage system during long-term operation are demonstrated. The efficiency of the system during the whole working period is 57.78%, lower than the design efficiency of 59.66%. In particular, the energy storage density is reduced dramatically to 197.60 kJ·m⁻³, which is 78.2% of the storage density of 252.68 kJ·m⁻³ at design conditions. Besides, the average output power of the turbine is reduced to 95.70% of the design value. The present work provides an improved understanding of the charging and discharging for compressed carbon dioxide energy storage, especially when renewables are integrated.