In this study, the effect of the geometrical and operational parameters on vertical cylindrical shell-and-tube LHTES systems is investigated. Four different ratios of the shell-to-tube radius are considered with the phase change material (PCM) on the shell side and the heat transfer fluid (HTF) flowing through the tube. The PCM temperature distributions are measured and compared experimentally among the studied storage units. A weighting method is utilized to calculate the average PCM temperature, liquid fraction, and stored energy fraction to evaluate the performance of the storage units. The results show that a shell to tube radius ratio of 5.4 offers better system performance in terms of the charging time and stored energy in the studied LHTES systems. Furthermore, the effects of HTF flow rate and temperature on the storage performance are studied. The HTF flow rate does not show a significant effect on the storage performance; however, the HTF temperature shows large impacts on the charging time. As the HTF temperature increases from 70 to 80 degrees C, the charging time reduces by up to 68% depending on the radius ratio. (C) 2017 Elsevier Ltd. All rights reserved.