Solid-liquid phase change materials (PCMs) consisting of multicomponent fatty acids have been developed. The thermodynamic properties of PCMs were investigated in detail with a differential scanning calorimeter (DSC). PCMs were prepared using two saturated fatty acids. The phase transition temperature of the binary system composed of capric and lauric acids was able to be freely controlled. In addition, the additive effect of surfactants with fatty acid properties ( sodium oleate or sodiumlaurate) was investigated. In particular, the addition of more than 15 wt% sodium oleate or sodiumlaurate to the binary system was a very effective means of suppressing the supercooling and controlling the temperature of the phase change between 4 degrees and 7 degrees C. Furthermore, the phase transition behavior on a large scale was constant in 200 heating-cooling cycle tests using handmade experimental apparatus. Physicochemical degradation of PCMs was not observed after repeated tests by FT-IR.