The choice of fatty acids as shape-stabilized phase change materials (PCMs) will increase the feasibilities of PCMs in practical applications due to the low price of the fatty acids. Compounding different fatty acids for each other is an effective way to obtain a PCM with a suitable phase-transition temperature. In this study, a series of binary fatty acids composed by capric acid, lauric acid, palmitic acid and stearic acid for each other were prepared using the phase diagram thermal dynamics calculation method. Then these binary fatty acids are absorbed in four kinds of diatomites with different specific areas, which act as a supporting material, to prepare shape-stabilized PCMs. The prepared shape-stabilized PCMs are characterized by the Scanning electron microscope (SEM) and the differential scanning calorimetry (DSC) analysis method. The results show that there is an optimum absorption ratio between binary fatty acids and the diatomite. The latent heat of capric-lauric acid/diatomite decreases to 57% of that of capric-lauric acid, and the phase-transition temperature rises from 16.36 to 16.74 degrees C when the capric-lauric acid is absorbed in the diatomite. The prepared capriclauric acid/diatomite composite PCM has proper melting temperatures and latent heat for thermal energy storage application in buildings. (C) 2011 Elsevier B.V. All rights reserved.