HEAT STORAGE MATERIAL

PURPOSE:To obtain the heat storage material utilizing latent heat and having a melting point of less than 25 deg.C by a method wherein the heat storage material is made to contain at least sodium thiosulfate pentahydrate and urea. CONSTITUTION:The heat storage material contains at least sodium thiosulfate pentahydrate (Na2S2O3.5H2O) having a melting point of 48 deg.C and urea [(NH2)2 CO] having a melting point of 132 deg.C which are preferably mixed together with a mol ratio in the range of 1:2 to 1:8. The heat storage material has a heat storage capacity of higher than 25-30cal/g at a temperature of less than 25 deg.C. Further, as Na2S2O3.5H2O and (NH2)2CO are materials that can be obtained at low cost and in large amounts and also as they are harmless and non-combustible, the heat storage material is available for a passive solar heat heating system.