Simultaneous charging and discharging performance for a latent thermal energy storage system with a microencapsulated phase change material

[Display omitted] •Simultaneous charging/discharging performance for a latent TES system is studied.•Heat transfer rate is sensitive to flow rate combinations of cooling/heating water.•Direct heat transfer between cooling/heating water is found in the stable state.•System reaches stable states in 7500 s for initially solid phase change material. A latent thermal energy storage system may operate under a simultaneous charging and discharging condition due to the mismatch between intermittent renewable energy supply and unpredictable energy demand. Adopting a microencapsulated phase change material in a thermal energy storage system can prevent material leakage during the phase change process. In this study, an experimental system is established for latent thermal energy storage, in which microencapsulated phase change materials mixed with carbon fibers are used as a latent energy storage material. The objective of this study is to investigate the performance of a latent thermal energy storage system under simultaneous charging and discharging conditions. The variations in the temperature and stored energy quantity in the energy storage unit and the charging/discharging power are analyzed under different charging/discharging flow rate combinations and different initial states of the phase change material. Depending on the initial state of phase change material, the dominant heat transfer mode is gradually transferred from a process of energy storage or energy release to a direct heat transfer between heating water and cooling water in stable states. The time duration is about 7500 s to reach the stable state for the system with initially solid phase change material. Under the same flow rate combination, the stable temperature of the energy storage unit is higher for initially melted phase change materials. The results show a promising potential in practical applications for thermal energy storage systems. The system design and material selection may be helpful in energy storage applications.