{"title":"Thermodynamic performance analysis of upper-and-lower cascaded latent heat thermal energy storage device under unsteady inlet temperature conditions","authors":"Zhongbin Zhang, Tianqi Zhu, Lihua Cao","doi":"10.1016/j.est.2025.118712","DOIUrl":null,"url":null,"abstract":"<div><div>Latent heat thermal energy storage (LHTES) is critical for solar thermal utilization due to its high energy density, yet the impact of unsteady heat transfer fluid (HTF) inlet temperatures on cascaded LHTES units remains underexplored. This study numerically compares four unsteady inlet temperature profiles (<em>T</em><sub>A</sub>, <em>T</em><sub>B</sub>, <em>T</em><sub>C</sub>, <em>T</em><sub>D</sub>) with their steady counterparts (<em>T</em><sub>a</sub>, <em>T</em><sub>b</sub>, <em>T</em><sub>c</sub>, <em>T</em><sub>d</sub>) by assessing phase change material (PCM) liquid fraction, temperature distribution, melting uniformity, and heat/exergy storage capacity. Results demonstrate enhanced melting uniformity under all unsteady conditions. Specifically, the peak value of liquid fraction increased by 12.06 % (<em>T</em><sub>A</sub>), 22.01 % (<em>T</em><sub>B</sub>), 15.16 % (<em>T</em><sub>C</sub>) and 41.95 % (<em>T</em><sub>D</sub>), respectively, heat storage capacity increased by 2.12 % (<em>T</em><sub>A</sub>), 16.89 % (<em>T</em><sub>B</sub>), and 12.14 % (<em>T</em><sub>D</sub>) but decreased by 5.93 % (<em>T</em><sub>C</sub>); concurrently, exergy storage rose by 0.883 % (<em>T</em><sub>A</sub>), 20.388 % (<em>T</em><sub>B</sub>), and 13.993 % (<em>T</em><sub>D</sub>) yet declined by 7.862 % (<em>T</em><sub>C</sub>). A novel cut-off time determination method is proposed to optimize thermodynamic performance of cascaded LHTES under both steady and unsteady operations, providing critical theoretical guidance for real-world system efficiency.</div></div>","PeriodicalId":15942,"journal":{"name":"Journal of energy storage","volume":"138 ","pages":"Article 118712"},"PeriodicalIF":8.9000,"publicationDate":"2025-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of energy storage","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S2352152X25034255","RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ENERGY & FUELS","Score":null,"Total":0}
引用次数: 0
Abstract
Latent heat thermal energy storage (LHTES) is critical for solar thermal utilization due to its high energy density, yet the impact of unsteady heat transfer fluid (HTF) inlet temperatures on cascaded LHTES units remains underexplored. This study numerically compares four unsteady inlet temperature profiles (TA, TB, TC, TD) with their steady counterparts (Ta, Tb, Tc, Td) by assessing phase change material (PCM) liquid fraction, temperature distribution, melting uniformity, and heat/exergy storage capacity. Results demonstrate enhanced melting uniformity under all unsteady conditions. Specifically, the peak value of liquid fraction increased by 12.06 % (TA), 22.01 % (TB), 15.16 % (TC) and 41.95 % (TD), respectively, heat storage capacity increased by 2.12 % (TA), 16.89 % (TB), and 12.14 % (TD) but decreased by 5.93 % (TC); concurrently, exergy storage rose by 0.883 % (TA), 20.388 % (TB), and 13.993 % (TD) yet declined by 7.862 % (TC). A novel cut-off time determination method is proposed to optimize thermodynamic performance of cascaded LHTES under both steady and unsteady operations, providing critical theoretical guidance for real-world system efficiency.
期刊介绍:
Journal of energy storage focusses on all aspects of energy storage, in particular systems integration, electric grid integration, modelling and analysis, novel energy storage technologies, sizing and management strategies, business models for operation of storage systems and energy storage developments worldwide.