Thermal analysis and exergy evaluation of packed bed thermal storage systems

Thermal energy storage in a packed bed is analyzed for dynamic temperature response during cyclic storage and recovery. A robust system-scale heat transfer model for the packed bed is developed and accounts for wall heat transfer and intra-particle diffusion effects. Based upon the temperature field modeling, recovered and lost exergy are calculated. The analysis shows that, for packed beds, sensible heat storage systems can provide much higher exergy recovery as compared to phase change material (PCM) storage systems under similar high temperature storage conditions. The roles of axial dispersion and wall heat losses are considered.