Due to the large variability in time and quality, waste heat should be stabilized before use. Thermal energy storage (TES) system based on latent heat of phase change material (PCM) is attracting attention because of its capability to store waste heat and supply it at a certain load. In this study, the heat charging characteristics of PCM were investigated in a 10 MJ-scale TES unit having an internally and externally finned tube. Docosanol of organic fatty alcohol was chosen as a heat storage material, and hot water and low pressure steam (0.5~3 barg) were used as heat transfer fluids to simulate low-quality waste heat. Except for the charging effect of water and steam, the heat of 12.5 MJ and 17 MJ can be charged using hot water and steam at a rate of 2.5 kW and 17.6 kW, respectively. The results show that the charging rate and overall heat transfer coefficient of steam are higher than that of water and increase as the steam pressure increases.