Liquid CO₂ energy storage system is currently held as an efficiently green solution to the dilemma of stabilizing the fluctuations of renewable power. One of the most challenges is how to efficiently liquefy the gas for storage. The current liquid CO₂ energy storage system will be no longer in force for high environmental temperature. Moreover, the CO₂ storage pressure is usually high with resulting in the high requirements on component materials. A novel liquid CO₂ energy storage system with low pressure stores is thus proposed in this paper. The sensible cold energy is stored by liquid methanol and the latent cold energy is stored in the latent cold storage for the sake of liquefying the discharging CO₂ after expansion. The mathematical model of the system is established for thermodynamic study. The analysis results indicate that the round trip efficiency and energy density of the system can be respectively 51.45% and 22.21 kW h/m³ at the typical default conditions. The round trip efficiency increases with a rise in charging pressure first and then appears a level-off with a striking inflection point. Moreover, the inflection point moves toward right for a larger discharging pressure. There is a peak value of the system round trip efficiency and energy density when the discharging pressure is changed. The allocations of compression ratio and expansion ratio should equal to 0.7 to reach the maximum value of round trip efficiency.

液态CO ₂能量存储系统目前被认为是解决稳定可再生能源波动的高效绿色解决方案。最大的挑战之一是如何有效地液化天然气进行储存。当前的液态CO ₂能量存储系统将不会在高环境温度下生效。此外，CO _2的储存压力通常较高，从而导致对组成材料的高要求。因此，本文提出了一种新型的具有低压储能的液态CO ₂储能系统。显冷能量由液态甲醇存储，而潜冷能量则存储在潜冷存储器中，以使排放的CO ₂液化扩展后。建立了系统的数学模型用于热力学研究。分析结果表明，在典型默认条件下，系统的往返效率和能量密度分别为51.45％和22.21 kW h / m ³。往返行程效率首先随着充气压力的增加而增加，然后出现一个明显的拐点，并趋于平稳。而且，拐点向右移动以获得更大的排出压力。当排出压力改变时，系统往返效率和能量密度达到峰值。压缩比和膨胀比的分配应等于0.7，以达到往返效率的最大值。