This article describes all experimental investigation oil the thermal characteristics of a thermal energy storage device. It utilizes the superior heat transfer characteristics of wick-less heat pipes and eliminates drawbacks found in the conventional thermal storage tank. This study purports to examine the functions of a thermal energy storage device having three operating modes, i.e., charge, discharge, and simultaneous charge and discharge. Different heat transfer mechanisms are identified in the thermal energy storage device under different operating modes. The thermal performance with alcohol and water as working fluid are also explored in the thermal energy storage device. The results show that a thermal energy storage device employing alcohol as the working fluid provides better performance. The system gives optimum charge and discharge performance under 35%-40% fill ratio and displays optimum charge efficiency of 73% and optimum discharge efficiency of 85%.