This work presents an experimental study of thermal energy storage by the use of PCM. The aim of the study was to establish the influence of the different inlet temperature of heat transfer fluid (HTF) and the different Reynolds number of HTF on the intensity of the charging and discharging processes. The PCM used in this study was stearic acid and water was used as HTF. A copper helical coil mounted in a cylindrical container served as a heat transfer surface.