Volume 64

Performance comparison of discharge cycles in a cold storage Carnot battery Yuemao Jiang, Rui Xia, Wen Su, Shunsen Wang

Abstract

Cold storage Carnot batteries (CSCBs) have emerged as a promising solution for long-duration energy storage by integrating ice-based cold storage. However, existing architectures are constrained by limited efficiency caused by suboptimal discharge cycles. In this study, two modified discharge cycles, recuperated and regenerative configurations, are investigated within the CSCB system framework. Additionally, two low-GWP working fluids, R1234ze(E) and R1234yf, are evaluated. Results show that the regenerative cycle provides a higher efficiency improvement than the recuperated cycle (7.3% versus 4.2%), and R1234ze(E) outperforms R1234yf across all discharge configurations. Increasing the cold storage temperature can enhance the overall system round-trip efficiency (RTE). With ice/water as a storage medium, the proposed CSCB system achieves an RTE of approximately 78.3%. This study provides insights into modifying the CSCB system to achieve high-efficiency, sustainable, long-duration energy storage.

Keywords pumped thermal energy storage, ice-cold storage, organic Rankine cycle, low-GWP working fluid, Performance comparison.