Introduction Many studies on thermal energy storage systems using ice have been reported for electricity load leveling [1]. In particular, in a dynamic ice thermal energy storage system, the cold thermal energy can be transported directly because the fluid ice slurry is used as a phase change material. Furthermore, ice slurries are applicable for heavy thermal loads because they have a high melting heat transfer rate. However, the characteristics of ice sludge in the fundamental processes, including generation, storage, transportation, melting and so on, have not yet been described. Therefore, ice thermal energy storage systems could be better understood by understanding these characteristics. In the past, the storage and generation of ice sludge have been carried out by many researchers. Hirata et al. [2] proposed a method to continuously produce an ice slurry using buoyancy force. Matsumoto et al. [3] used emulsions of silicone oil and water mixtures as thermal energy storage material and could produce an ice slurry with a high ice packing factor (IPF). Furthermore, some authors have demonstrated that the permeability of an ice/water mixture varies due to storage in water [4]. The transfer of heat of fusion of ice slurries has also been studied [5]. It is necessary to consider not only the fundamental processes but also the thermal properties of the ice slurry to develop the best system, and an amount of cold thermal energy must be controlled appropriately, for the design of a thermal energy storage system. Sawada et al. [6] attempted to measure the latent heat of fusion of ice slurry, but their study was not satisfactory regarding the heat of dilution due to variations in the concentration of the solutions. Some measurements using Differential Scanning Calorimetry (DSC) have also been...... half of the article...... 3.1. Heat of Dilution Effects The concentration of an aqueous solution varies with changes in the amount of ice, as ice melts or solidifies in aqueous solution. Thus, the change in the effective latent heat of fusion due to dilution must be considered. Therefore, the amounts of heat produced by different concentrations of aqueous solutions were taken from previous studies. Ulbig et al. [14] and [15] made precise measurements of the heat generated when propylene glycol (PG), ethylene glycol (EG) and ethanol (ET) were diluted with water, respectively. Hubert et al. [16] showed heat absorption by infinite dilution of a NaCl solution with water, and Khrenova et al. [17] showed heat absorption by infinite dilution of NaNO3 solution. Using these results, the heat from mixing or dilution at 25 °C for each solution was approximated using the least squares method respectively as follows: