This paper demonstrates a novel sebacic acid/expanded graphite (SA/EG) composite phase change material for medium-temperature solar heat storage. The optimal mass percentage of SA in the SA/EG composite PCM is determined to be around 85%, at which not only SA exhibits a uniform distribution into the pores of EG but also the liquid leakage can be effectively prevented. The composite PCM with the SA mass percentage of 85% has a phase change temperature of 128 degrees C with the latent heat as high as ca. 187 J/g. The combination of SA and EG effectively prevents the low extent of subcooling inherent in SA. Compared to SA, the SA/EG composite PCM has the advantages of negligible subcooling as well as better thermal reliability and stability. The SA/EG composite PCM can easily be formed into various shapes by dry pressing, with little loss in thermal properties but a remarkable increase in thermal conductivity. The good thermal properties and formability make the SA/EG composite PCM show great potential in latent heat storage systems. (C) 2013 Elsevier Ltd. All rights reserved.