With countries proposing the goal of carbon neutrality,the clean transformation of energy structure has become a hot and trendy issue internationally.Renewable energy generation will account for the main proportion,bu...With countries proposing the goal of carbon neutrality,the clean transformation of energy structure has become a hot and trendy issue internationally.Renewable energy generation will account for the main proportion,but it also leads to the problem of unstable electricity supply.At present,large-scale energy storage technology is not yet mature.Improving the flexibility of coal-fired power plants to suppress the instability of renewable energy generation is a feasible path.Thermal energy storage is a feasible technology to improve the flexibility of coal-fired power plants.This article provides a review of the research on the flexibility transformation of coal-fired power plants based on heat storage technology,mainly including medium to low-temperature heat storage based on hot water tanks and high-temperature heat storage based on molten salt.The current technical difficulties are summarized,and future development prospects are presented.The combination of the thermal energy storage system and coal-fired power generation system is the foundation,and the control of the inclined temperature layer and the selection and development of molten salt are key issues.The authors hope that the research in this article can provide a reference for the flexibility transformation research of coal-fired power plants,and promote the application of heat storage foundation in specific coal-fired power plant transformation projects.展开更多
Latent heat thermal energy storage systems can effectively fill the gap between energy storage and application, and phase-change materials(PCMs) are crucial media for storing thermal energy. Therefore, how to maximize...Latent heat thermal energy storage systems can effectively fill the gap between energy storage and application, and phase-change materials(PCMs) are crucial media for storing thermal energy. Therefore, how to maximize the utilization efficiency of PCMs has attracted widespread attention. In this study, the thermal behavior of two thermal storage units employing a spiral tube and straight tube as heat transfer tubes was experimentally researched and comprehensively compared. Stefan numbers were used to investigate the impact of the heat transfer fluid temperature on the PCM melting process. The temperature distribution of PCMs,temporal evolution of the melting front, and temperature variations of measurement points in both tanks were compared. The average temperature and energy storage of PCMs were calculated to evaluate the thermal performance of different configurations. The results indicate that compared to cylinder B(with a straight tube), the energy storage in cylinder A(with a spiral tube)increased by 78.8%, 38.5%, and 19.6% at Stefan numbers of 1.08, 1.28, and 1.48, respectively. Moreover, the increase in the Stefan number simultaneously ascended the average temperature and energy storage of PCMs in containers A and B, causing the shortening of the melting time. When the Stefan number was increased from 1.28 to 1.48, the storage capacity was raised from3233.18 to 3463.8 k J, and the total melting time was decreased by 34.2% from 547.5 to 360 min after the PCM was loaded in cylinder A. The research results lay a certain foundation for a deeper study of enhanced heat transfer in spiral tubes.展开更多
基金funded by National Key R&D Program of China,grant number 2019YFB1505400 and 2022YFB2405205.
文摘With countries proposing the goal of carbon neutrality,the clean transformation of energy structure has become a hot and trendy issue internationally.Renewable energy generation will account for the main proportion,but it also leads to the problem of unstable electricity supply.At present,large-scale energy storage technology is not yet mature.Improving the flexibility of coal-fired power plants to suppress the instability of renewable energy generation is a feasible path.Thermal energy storage is a feasible technology to improve the flexibility of coal-fired power plants.This article provides a review of the research on the flexibility transformation of coal-fired power plants based on heat storage technology,mainly including medium to low-temperature heat storage based on hot water tanks and high-temperature heat storage based on molten salt.The current technical difficulties are summarized,and future development prospects are presented.The combination of the thermal energy storage system and coal-fired power generation system is the foundation,and the control of the inclined temperature layer and the selection and development of molten salt are key issues.The authors hope that the research in this article can provide a reference for the flexibility transformation research of coal-fired power plants,and promote the application of heat storage foundation in specific coal-fired power plant transformation projects.
基金supported by the National Natural Science Foundation of China (Grant No. 51876147)。
文摘Latent heat thermal energy storage systems can effectively fill the gap between energy storage and application, and phase-change materials(PCMs) are crucial media for storing thermal energy. Therefore, how to maximize the utilization efficiency of PCMs has attracted widespread attention. In this study, the thermal behavior of two thermal storage units employing a spiral tube and straight tube as heat transfer tubes was experimentally researched and comprehensively compared. Stefan numbers were used to investigate the impact of the heat transfer fluid temperature on the PCM melting process. The temperature distribution of PCMs,temporal evolution of the melting front, and temperature variations of measurement points in both tanks were compared. The average temperature and energy storage of PCMs were calculated to evaluate the thermal performance of different configurations. The results indicate that compared to cylinder B(with a straight tube), the energy storage in cylinder A(with a spiral tube)increased by 78.8%, 38.5%, and 19.6% at Stefan numbers of 1.08, 1.28, and 1.48, respectively. Moreover, the increase in the Stefan number simultaneously ascended the average temperature and energy storage of PCMs in containers A and B, causing the shortening of the melting time. When the Stefan number was increased from 1.28 to 1.48, the storage capacity was raised from3233.18 to 3463.8 k J, and the total melting time was decreased by 34.2% from 547.5 to 360 min after the PCM was loaded in cylinder A. The research results lay a certain foundation for a deeper study of enhanced heat transfer in spiral tubes.
