Preparation of novel microencapsulated phase change material with Cu-Cu2O/CNTs as the shell and their dispersed slurry for direct absorption solar collectors

In this study, a novel microencapsulated phase change material paraffin@Cu-Cu2O/CNTs was successfully prepared by hydrothermal reduction and in situ deposition method, in which paraffin as the core, Cu, Cu2O and carbon nanotubes (CNTs) as the shell. SEM and TEM results proved that the microcapsules have a core-shell structure, the CNTs were irregularly wrapped on the shell, and the diameter of the microcapsules was about 600-800 nm. The melting temperature and latent heat of the paraffin@Cu-Cu2O/CNTs microcapsules were 61.17 °C and 81.31Jg-1, respectively, and the encapsulation rate of the microcapsules was calculated to be 41.53% from the results of the DSC measurement. Due to the shell material, the paraffin@Cu-Cu2O/CNTs microcapsules displayed excellent thermal stability, its thermal decomposition temperature is increased by 97 °C compared to paraffin. Moreover, the paraffin@Cu-Cu2O/CNTs microcapsules were dispersed in water to form a new kind of slurry, such fluid exhibited great improvement in terms of thermal conductivity, specific heat capacity, light absorption performance and photo-thermal conversion efficiency than that of paraffin@Cu-Cu2O microcapsules slurry. Therefore, the high heat storage capability and excellent photo-thermal conversion performance of the paraffin@Cu-Cu2O/CNTs microcapsule slurry make it to be the most potential heat transfer fluid for direct absorption solar collector. •Microencapsulated PCM with paraffin as the core, Cu, Cu2O and CNTs as the shell was prepared.•The microcapsule slurry achieved high optical absorption property and high thermal conductivity.•The photo-thermal conversion performance of the microcapsule slurry was enhanced.