High-performance molten salt packed bed for latent heat storage by applying the anisotropic thermal conductive material

The spatiotemporal variability of renewable energy highlights the need for thermal energy systems with strong peaking-shaving capability. Molten salt packed bed latent heat storage is a promising technology, but its performance is limited by the heat transfer rate between the fluid and the bed. This study introduces anisotropic thermal conductive materials into packed bed to achieve oriented heat transfer enhancement and improve heat storage efficiency using the same amount of enhancement material. Encapsulated particles with different high-conductivity orientations are arranged to identify the optimal configuration and enhancement mechanism. In vertical beds, horizontally aligned orientations significantly improve horizontal heat transfer between the fluid and bed, increasing power density by 12.19% compared with isotropic arrangements under the same material usage. A material fraction of 15 wt% achieves the best comprehensive performance (1.964) based on a newly proposed dimensionless index considering both power density and energy density. Further analysis based on the optimal fraction demonstrates that fully filled anisotropic configurations outperform partially filled ones in both heat transfer and overall performance. Fully filled configurations uniformly strengthen the heat transfer pathway between the fluid and bed, significantly reducing overall thermal resistance and substantially improving comprehensive performance. In contrast, partially filled configurations only reduce local thermal resistance, while overall heat transfer remains restricted by unreinforced regions, resulting in much smaller comprehensive performance improvements despite negligible advantages in energy density. This work identifies the key mechanism for enhancing packed bed performance and validates the effectiveness of anisotropic thermal conductive materials.