Investigation of thermal properties and enhanced energy storage/release performance of silica fume/myristic acid composite doped with carbon nanotubes

Myristic acid (MA) with a melting temperature around 54 °C has huge prospects for solar passive thermal energy storage applications. However, like all other fatty acids (FA), it is also suffers from issues like leakage and low thermal conductivity (TC), when considered for latent heat thermal energy storage (LHTES) applications. Here, to overcome the seepage problem, MA was incorporated within the silica fume (SF) using simple direct impregnation method. To deal with the TC issue, prepared SF/MA pre-composite was doped with carbon nanotubes (CNTs) at three different weight percentage (0.3, 0.5 and 1.0 wt%) and eventually enhanced its TC by about 9.4%, 21.9% and 43.8%, respectively. The chemical and morphological structures of the SF/MA/CNTs developed as novel shape-stabilized composite PCMs (SS-CPCMs) were evaluated by FTIR, XRD, SEM and DSC analysis. The heat storage capacities of the doped and undoped SS-CPCMs were found in the range of about 87–91 J/g with good thermal stability up to 190 °C. Long standing-thermal cycling study was performed with the selected SS-CPCM doped with CNTs (1.0 wt%). No visible degradation or chemical changes were observed even after 1000 thermal cycles. CNTs doping significantly improved the heating and cooling performance of SF/MA composite.