关键词: 压缩储能, 超临界二氧化碳, 热容量匹配, 换热温差, 热泵

Abstract:

To address the challenge of recovering low-grade compression heat in compressed carbon dioxide energy storage systems， a novel supercritical carbon dioxide（S-CO₂） energy storage system coupled with a heat pump is proposed， and its steady-state analysis model is conducted. Considering the heat capacity matching and heat transfer temperature differences of intercoolers and recuperators， the impacts of hot water flow rate， S-CO₂ temperature at the compressor inlet， temperature differences of intercoolers and recuperators， heat pump evaporating and condensing temperatures on the system performance are studied. To further explore the significance of the influences brought by the temperature differences of intercoolers and recuperators， four modes with different weighting factors of the temperature differences are analyzed. Under a constant total heat transfer temperature difference，four modes are classified with an increasing proportion of intercooler cold end temperature difference and consistent variation of heat transfer temperature differences at heat end and cold end. The research results indicate that， keeping the S-CO₂ flow rate at 50 kg/s and the system's round-trip efficiency （RTE） ranging from 78.2% to 79.6%， the optimal water flow rate range is 19.5 kg/s to 23.5 kg/s. The RTE will peak at 79.62% and the coefficient of performance（COP）of the system will reach 5.9 under mode 3 in which the variations of intercooler heat end and cold end temperature differences are consistent and the cold end temperature difference accounts for a smaller proportion. The fluctuation of the RET changing with pressure is merely 2.1%.

Key words: compressed energy storage, supercritical carbon dioxide, heat capacity matching, heat transfer temperature difference, heat pump