Computational study of performance of cascaded multi-layered packed-bed thermal energy storage for high temperature applications

Publication Type:

Journal Articles

Source:

Journal of Energy Storage, Volume 32, Issue 101930 (2020)

Abstract:

Continued effort towards decarbonizing the power sector has attracted enhanced research interest on the ideas revolving around different Coal-Concentrated Solar Power hybrid plant concepts. A few pre-feasibility studies indicate the importance of high-temperature (> 600 °C) latent heat packed-bed energy storage systems to ensure operational flexibility of the power plants, especially during the peak demand. In this study, a tractable and computationally fast numerical model comprising of two simplified non-equilibrium energy equations for the working fluid and the phase change material (PCM), respectively, is developed to account for the radiation effects at the high temperatures in the cascaded multi-layered packed bed latent heat thermal energy storage (PBLTS). The PBLTS is filled with spherical capsules of different diameters, containing PCMs having different melting temperatures, while air is chosen as the heat transfer fluid (HTF). The arrangement of different capsule diameters is found to affect the thermal performance of the storage significantly during the charging and discharging process. Equal bed heights with the capsule size arrangement of 10, 20, 30 mm from the inlet towards the oulet of the storage tank showed enhanced thermal performance during discharging operation. An aspect ratio between 4 and 4.5 leads to a better discharging performance of the storage, maintaining a stabilized high temperature at the storage outlet for a longer duration. It is found that the radiative heat transfer plays a significant role at high temperature (> 650 °C) in dictating the performance of the thermal energy storage system during the charging operation