Abstract : In the present work, the performance of a thermal energy storage module made of cast steel is evaluated using air as the heat transfer fluid (HTF). A cast steel module of length 740 mm and diameter 267 mm is fabricated with 19 cylindrical channels of diameter 12.7 mm for HTF flow. The module charging and discharging performance data are reported for an operating temperature range of 393.15 K to 473.15 K and the effect of HTF flow velocities on module performance is analysed. The estimated maximum storage capacity of the cast steel module is 13.76 MJ. The charging and discharging temperature profile across the module is measured to analyse the heat transfer phenomenon and it is observed that conduction varies predominantly in the axial direction, whereas, there is minimal variation in the radial direction. From the experimental results, it is comprehended that both charging and discharging rates are enhanced by increasing the HTF velocity from 2.5 m/s to 4.5 m/s. For a velocity of 4.5 m/s, the average module temperatures achieved at steady state condition for charging and discharging are 468 K and 398 K respectively. © 2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of ICAE2018 - The 10th International Conference on Applied Energy.