Solid-liquid phase change materials (PCMs) have been preferred for solar passive thermal energy storage (TES) applications. However, low thermal conductivity and leakage issue of molten PCMs considerably restrain their TES potential. In this framework, n-Heptadecane (HD) as a solid-liquid PCM was incorporated with carbonized lemon peel (CLP) for development of a novel leak-proof composite PCM. Chemical compatibility between the constituents of the leak-proof composite PCM was examined by using FTIR spectroscopy and XRD diffraction analyses. The DSC results revealed that the developed leak-proof CLP/HD composite PCM had a melting temperature of 19.79 degrees C and LHS capacity of 141.8 J/g. The composite PCM exposed venerable thermal degradation stability after a 1000-cycling heating-cooling process. Thermal conductivity of the CLP/HD composite PCM (0.46 W/m.K at 10 degrees C) was measured as approximately 77% higher than that of pristine HD (0.26 W/m.K at 10 degrees C). (c) 2021 Elsevier B.V. All rights reserved.