The effects of copper nanowires (Cu NWs) with ultra-high aspect ratio and sponge-like structure on the properties of an organic phase change material (PCM) were investigated. Tetradecanol (TD) was selected as the organic PCM. The sponge-like Cu NWs clusters were randomly dispersed in the TD matrix and were wrapped by TD to form a new kind of composite PCM. The phase change enthalpy (6,H) of the composite PCMs was decreased linearly with the increasing of Cu NWs loading, while the melting speed was accelerated. The thermal conductivity of the composite PCMs was greatly enhanced by Cu NWs. The Delta H of the composite PCM containing 58.9 wt% (corresponding to 11.9 vol%) of Cu NWs was 86.95 J/g, and the thermal conductivity attained to 2.86 W/m K, which was nearly 9 times higher than that of the TD. The thermal conductivity enhancement of Cu NWs on the composite PCMs showed a turning point at the Cu NWs loading of 1.5 vol%. When Cu NWs loading exceeded 1.5 vol%, the thermal conductivity of the composite PCMs increased significantly faster with the increasing of Cu NWs loading. (c) 2012 Elsevier B.V. All rights reserved.