Polyethylene glycol/wood-derived porous carbon composites for solar–thermal energy storage

To address the high cost, low thermal conductivity, and limited solar-thermal conversion efficiency of conventional composite phase change materials, this study develops a wood-derived composite phase change material based on polyethylene glycol and a wood-derived porous carbon skeleton. Wood chips and phenolic resin were used as carbon sources to fabricate an integrated porous carbon framework through dry pressing and carbonization, and polyethylene glycol was subsequently incorporated as the phase change component. The phenolic resin promoted the formation of a continuous and mechanically stable carbon skeleton, resulting in a thermal conductivity of 0.57 W/(m·K), approximately three times that of pure polyethylene glycol, and a compressive strength of 0.85 MPa. As a further enhancement, silicon carbide nanowires were generated in situ by introducing silicon powder into the carbon skeleton. The nanowires improved heat-transfer pathways and regulated the pore structure, increasing the thermal conductivity to 1.13 W/(m·K) while enabling a polyethylene glycol loading of 62%. The resulting composite exhibited good shape stability during phase transition, which were attributed to the capillary confinement and interfacial interactions provided by the porous carbon framework. In addition, the combined effects of the biomass-derived carbon skeleton and silicon carbide nanowires contributed to a solar–thermal conversion efficiency of 78.7%. These results demonstrate that wood-derived porous carbon can serve as a low-cost and effective supporting framework for polyethylene glycol, while the in-situ-formed silicon carbide nanowires provide an additional route for improving heat transfer and solar–thermal conversion. This study offers a practical strategy for developing biomass-based composite phase change materials with favorable thermal storage, mechanical, and solar-thermal conversion performance.