Investigation of a High-Temperature Packed-Bed Sensible Heat Thermal Energy Storage System With Large-Sized Elements

A high-temperature, sensible heat thermal energy storage (TES) system is designed for use in a central receiver concentrating solar power plant. Air is used as the heat transfer fluid and solid bricks made out of a high storage density material are used for storage. Experiments were performed using a laboratory-scale TES prototype system, and the results are presented. The air inlet temperature was varied between 300 degrees C to 600 degrees C, and the flow rate was varied from 50 cubic feet per minute (CFM) to 90 CFM. It was found that the charging time decreases with increase in mass flow rate. A 1D packed-bed model was used to simulate the thermal performance of the system and was validated with the experimental results. Unsteady 1D energy conservation equations were formulated for combined convection and conduction heat transfer and solved numerically for charging/discharging cycles. Appropriate heat transfer and pressure drop correlations from prior literature were identified. A parametric study was done by varying the bed dimensions, fluid flow rate, particle diameter, and porosity to evaluate the charging/discharging characteristics, overall thermal efficiency, and capacity ratio of the system.