There is growing interest in the newly developed technology to store heat energy at the temperature of 200 degrees Celsius or lower from industrial plants, which has until now been dissipated. And also, it is important to utilize such waste effectively in order to save energy. A new thermal energy storage/retrieval system, which employs erithritol as heat storage medium and direct contact heat transfer technology as the method for the heat exchange between the heat medium and heat storage material, has been developed. In this system, it is important to evaluate and prove a heat output from the heat storage device. For instance, the performance to maintain heat output high will lead to good economical efficiency. In this study, in order to increase the heat output, tow types of the heat storage device, conventional and improvement type, were manufactured and compared the performance with each other. As a result, improvement type of device which include metal separate plate in the thermal storage media layer have a advantage of increasing heat output.