Preparation and thermal properties of octyl, decyl, dodecyl and tetradecyl stearates as phase change materials for thermal energy storage

A homologous series of n-alkyl stearates CnS (C17H35COO(CH2)n-1CH3, n = 8, 10, 12, 14) was synthesized as solid-liquid phase change materials (PCMs) by esterification of stearic acid with 1-octanol, 1-decanol, 1-dodecanol and 1-tetradecanol. Molecular structures of CnS were confirmed by fourier transform infrared (FT-IR) and 1H nuclear magnetic resonance (1H NMR) spectra. Differential scanning calorimetry (DSC) measurements revealed that the melting temperatures of CnS were in the range of 21.4 ∼ 44.4 °C and increased with the increase in alkyl chain length. The latent heats of fusion were in the range of 165.8 ∼ 191.1 kJ kg−1. The comparable solidifying temperatures and latent heats of solidification were also observed. The phase change temperatures and latent heats changed little after repeated melting/solidifying cycles. Thermogravimetric analysis suggested that CnS was thermally stable at temperatures up to 215 °C. The volumetric latent heat storage capacities of CnS ranged from 146 to 159 MJ m−3. The latent heat storage/release performance of CnS in a ceramic cell suggested the potential application of the n-alkyl stearates for passive thermal energy storage to reduce the indoor temperature fluctuation.