High-temperature thermal storage using a packed bed of rocks – Heat transfer analysis and experimental validation

High-temperature thermal storage in a packed bed of rocks is considered for air-based concentrated solar power plants. The unsteady 1D two-phase energy conservation equations are formulated for combined convection and conduction heat transfer, and solved numerically for charging/discharging cycles. Validation is accomplished in a pilot-scale experimental setup with a packed bed of crushed steatite (magnesium silicate rock) at 800 K. A parameter study of the packed bed dimensions, fluid flow rate, particle diameter, and solid phase material was carried out to evaluate the charging/discharging characteristics, daily cyclic operation, overall thermal efficiency and capacity ratio.

►High-temperature solar thermal storage in a packed bed of rocks was analyzed.►A transient two-phase heat transfer model was formulated and experimentally validated.►A parametric study of the dimensions and fluid flow rates was carried out.►The charging characteristics, daily cyclic operation, and capacity ratio were evaluated.►The overall thermal efficiency under optimal conditions exceeded 90%.