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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. • Problem on renewable energy variability effects on carbon dioxide energy storage is proposed and formulated. • Insufficient charging/discharging effects on efficiency, power and energy storage density are evaluated. • Cycle efficiency can be maintained at 57.78% but energy storage density reduced to 78.2%. • Necessity to consider renewable energy efficiency in economic analysis is suggested. [ABSTRACT FROM AUTHOR]