{"title":"Thermal-economic analysis and optimization of a novel segmented energy storage Carnot battery","authors":"Yuchen Li, Peng Hu, Hui Ni","doi":"10.1016/j.applthermaleng.2025.125713","DOIUrl":null,"url":null,"abstract":"<div><div>As a new type of energy storage technology using thermal energy, the Carnot battery (CB) is one of the most promising large-scale energy storage technologies due to its unlimited geographical conditions, simple structure, and high energy storage density. Previous research has mainly focused on the individual analysis of the working fluid or the conventional CB system, and the comprehensive thermal economy analysis of the system is lacking. In this work, a novel CB system with segmented energy storage using zeotropic working fluids is proposed, and the effects of the working fluid mass fraction, waste heat temperature and heat storage temperature on system performance are investigated. The multi-objective optimization problem of maximizing the power recovery efficiency and minimizing the initial investment cost is studied, and systematic Pareto-optimal solutions are obtained. The novelty of this work is the use of segmented condensation at the saturated liquid phase point of the working fluids. The temperature matching of the heat exchanger is modified by adjusting the mass flow rate of the heat storage water to reduce heat transfer exergy losses and improve the system performance. Compared with the conventional CB system, the novel system improves the power recovery efficiency by 3.31–24.07 % and the economic index, the levelized cost of storage (LCOS) by 2.87–17.25 %. The zeotropic working fluid R245fa/pentane (mass fraction of 40/60) shows the best thermal performance, with a power recovery efficiency of 74.13 %, which is 23.51 % greater than that of pure R245fa and 18.97 % greater than that of pure pentane. The zeotropic working fluid R245fa/pentane (40/60) achieves the minimum LCOS of 0.213 $/kWh at a waste heat temperature of 80.0 ℃ and a storage temperature of 94.2 ℃, which is 8.06 % higher than the LCOS of 0.232 $/kWh for pure pentane, and 10.83 % higher than the LCOS of 0.239 $/kWh for pure R245fa. The selection of a zeotropic working fluid with an appropriate temperature glide can effectively improve the thermal and economic performance of the system.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"266 ","pages":"Article 125713"},"PeriodicalIF":7.5000,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Applied Thermal Engineering","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S1359431125003047","RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"2025/1/25 0:00:00","PubModel":"Epub","JCR":"Q2","JCRName":"ENERGY & FUELS","Score":null,"Total":0}
引用次数: 0
Abstract
As a new type of energy storage technology using thermal energy, the Carnot battery (CB) is one of the most promising large-scale energy storage technologies due to its unlimited geographical conditions, simple structure, and high energy storage density. Previous research has mainly focused on the individual analysis of the working fluid or the conventional CB system, and the comprehensive thermal economy analysis of the system is lacking. In this work, a novel CB system with segmented energy storage using zeotropic working fluids is proposed, and the effects of the working fluid mass fraction, waste heat temperature and heat storage temperature on system performance are investigated. The multi-objective optimization problem of maximizing the power recovery efficiency and minimizing the initial investment cost is studied, and systematic Pareto-optimal solutions are obtained. The novelty of this work is the use of segmented condensation at the saturated liquid phase point of the working fluids. The temperature matching of the heat exchanger is modified by adjusting the mass flow rate of the heat storage water to reduce heat transfer exergy losses and improve the system performance. Compared with the conventional CB system, the novel system improves the power recovery efficiency by 3.31–24.07 % and the economic index, the levelized cost of storage (LCOS) by 2.87–17.25 %. The zeotropic working fluid R245fa/pentane (mass fraction of 40/60) shows the best thermal performance, with a power recovery efficiency of 74.13 %, which is 23.51 % greater than that of pure R245fa and 18.97 % greater than that of pure pentane. The zeotropic working fluid R245fa/pentane (40/60) achieves the minimum LCOS of 0.213 $/kWh at a waste heat temperature of 80.0 ℃ and a storage temperature of 94.2 ℃, which is 8.06 % higher than the LCOS of 0.232 $/kWh for pure pentane, and 10.83 % higher than the LCOS of 0.239 $/kWh for pure R245fa. The selection of a zeotropic working fluid with an appropriate temperature glide can effectively improve the thermal and economic performance of the system.
期刊介绍：
Applied Thermal Engineering disseminates novel research related to the design, development and demonstration of components, devices, equipment, technologies and systems involving thermal processes for the production, storage, utilization and conservation of energy, with a focus on engineering application.
The journal publishes high-quality and high-impact Original Research Articles, Review Articles, Short Communications and Letters to the Editor on cutting-edge innovations in research, and recent advances or issues of interest to the thermal engineering community.
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