打破热集成泵送式热能存储系统性能限制：一种三重效率提升方法

Abstract The thermally integrated pumped thermal energy storage system has drawn growing attention for its high power-to-power efficiency, geographical independence, and low-grade waste heat utilization capability. However, there is an enormous gap between the actual and ideal systems, and it is unknown how to break the performance limitations of actual systems in light of that gap. Herein, leveraging energy and exergy analyses, this study taps into technological directions to break the performance limitations of the practical system towards the ideal system: improving energy conversion efficiency and enhancing waste heat utilization. To move towards these two directions, a three-way efficiency-boosting method is proposed, namely structure modification, discharging time extension, and application of the zeotropic mixture. First, a dual-pressure discharging cycle is developed to match the temperature profiles of the working fluid and the heat sources, reaching the power-to-power efficiency of 142 % compared to the baseline value of 107 %. Second, by extending the discharging time, the power-to-power efficiency of the system can be further boosted through superior waste heat utilization, realizing the power-to-power efficiency of 175 %. Third, by incorporating the optimized composition of the R1233zd(E)/ cyclopentane on the charging and discharging process separately, the pumped thermal energy storage system with dual-pressure discharging cycle and extended discharging time yields a maximum power-to-power efficiency of 220 %. The evaluation results confirm the availability of the proposed efficiency-boosting method.