A model is presented to predict the fluid and solid temperatures in a packed bed thermal energy storage vessel using compressed gas as heat transfer fluid (HTF). The model is compared to data from an experimental vessel that is 10' tall with a 2.25 '' storage diameter filled with 6 mm diameter alpha-alumina beads, using air as the HTF. The model is validated against this data for two flow rates, and the exergy efficiency of the experimental data is also calculated. Developments in the model include an optimized fluid-solid heat transfer coefficient based on formulas in the literature, incorporating wall heat losses from natural convection on the exterior wall of the vessel, and using temperature-dependent relationships for the thermophysical properties of the gas and alumina. (C) 2014 Elsevier Ltd. All rights reserved.