Performance of a CO2-based mixture cycled transcritical pumped thermal energy storage system

Yilun Zhang, Suzhen Yin, Xuewen Yan and Zhan Liu

Renewable Energy, 2025, vol. 238, issue C

Abstract: The transcritical CO2 cycle has the characteristics of high power density, high stability and high thermal energy transfer efficiency. It has been employed in pumped thermal energy storage system and ice slurry often serves as the cold storage material. However, ice slurry is not an optimal choice for cold storage due to its huge volume and high cost. In this study, an innovative transcritical pumped thermal energy storage system cycled with CO2-based mixtures is proposed. Temperature of the CO2-based mixture changes during the phase transition process, which means that simple two-tank cold energy storage arrangement with fluid heat materials is feasible to achieve the phase change of working fluid. R32, R161, propane, butane and pentane are screened to mix with CO2, respectively. Multi-parametric analysis of proposed system is conducted to assess its technical and economic performance. The Monte-Carlo method is employed to investigate the system uncertainty. Results display that for a 10 MW/8h scale the system cycled with CO2/R32 has the minimum levelized cost of storage of 0.1655 $/kWh, with a round trip efficiency of 65.51 %. The optimal levelized cost of storage is 0.1678 $/kWh, 0.1801 $/kWh, 0.1781 $/kWh and 0.1801 $/kWh for R161, propane, butane, and pentane, in sequence. The system investment cost decreases as the operating durations increase. The mean levelized cost of electricity and energy capacity cost are separately reduced by 29.35 % and 48.24 % as the installed capacity is extended from 10 MW to 10000 MW.

Keywords: Transcritical pumped thermal energy storage; CO2 mixtures; Low-temperature thermal energy storage; Uncertainty analysis; Monte-carlo method (search for similar items in EconPapers)
Date: 2025
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Persistent link: https://EconPapers.repec.org/RePEc:eee:renene:v:238:y:2025:i:c:s096014812401961x

DOI: 10.1016/j.renene.2024.121893

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