The current paper describes the design of a prototype system to explore the feasibility of the adsorption thermal energy storage. Water was chosen as the adsorbate, and three different adsorbents were tested. Zeolite 13X, NaLSX zeolite, and an activated alumina (AA)/zeolite 13X composite adsorbent were used as adsorbents. Experiments were performed at varying flow rates and different relative humidities to determine the optimal operating conditions for the system. The regeneration of the adsorbents also was explored by performing repeated runs on the same adsorbent sample. The results indicate that complete regeneration was achieved. A maximum energy density of 160kWh/m3 has been achieved with the AA/13X adsorbent, and this adsorbent was chosen for further studies. After this adsorbent screening, the system was modified to improve the data recording and system performance. Tests were performed on AA/13X, and a maximum energy density of 200kWh/m3 was achieved, which was much higher than the maximum energy density reported in the literature for adsorption thermal energy storage systems (165kWh/m3). Copyright (c) 2012 John Wiley & Sons, Ltd.