ABSTRACT Storage of energy in the packed beds is experimentally investigated. Experiments are carried out to measure the time dependent temperature distributions inside two vertically oriented packed beds constructed from PVC cylinders with 0.15 and 0.25 m inside diameters, respectively. Rock grains of two irregular sizes ranging between 15 to 20 mm and between 30 to 35 mm, respectively, are packed inside the beds at different aspect ratios ranging from 1.0 to 4.5. For each bed, temperatures at different axial and radial positions as well as the axial pressure distribution are measured at different operating parameters. The stored energy, exergy and the bed efficiencies based on both the 1st and the 2nd laws of thermodynamics are calculated utilizing the present measurements. The influence of bed diameter, bed aspect ratio, packing grains size, air flow rate, and the inlet air temperature on the system storage characteristics are investigated. The present results for the stored energy, exergy per unit storage volume, system efficiencies and the charging duration are correlated as functions of the different operating and design parameters.