Three phase change nanocomposite materials made of stearic acid and different carbon additives (multi-walled carbon nanotube-MWCNT, graphene, graphite) are prepared to enhance the heat transfer performance for thermal energy storage applications. The SEM analysis shows that the carbon additives are uniformly distributed in the based phase change material of stearic acid, and the DSC analysis reveals that the melting onset temperature of nanocomposites shifts to a lower temperature. The experimental results indicate that the addition of carbon additives can improve the heat conduction of stearic acid effectively, but it also weakens the natural convection of stearic acid in liquid state. The graphite-based nanocomposite has the highest heat transfer performance during both the charging and discharging processes among three kinds of nanocomposites. In comparison with the pure stearic acid, the charging and discharging rates are improved by about 37% and 320%, respectively by using the graphite-based nanocomposite with the content of 5.0%. It appears that the graphite is a more effective additive for enhancing the heat transfer of phase change materials compared with MWCNT and graphene although the former additive has a lower thermal conductivity than the latter additives. (C) 2014 Elsevier Ltd. All rights reserved.