The spider web of modified wheat bran captured PEG to form stabilized phase change composites for temperature regulation and waste heat storage

Biomass based phase change composites (PCCs) have potential application prospects in the field of thermal energy storage (TES). Environmentally friendly development could be realized by recycling and reusing wheat bran (WB) of the agricultural and forestry waste. Distinguished from conventional biomass derivatives and/or carbonization methods, multi-walled carbon nanotubes (MWCNT/OH) modified wheat bran aerogels (MWB) with 3D entanglement structure was fabricated by utilizing physical pasting incorporating chemical cross-linking and functional modification, and then followed by freezing method. The fabricated MWB exhibited a graded and "spider web" entangled special porous structure, which could adsorb polyethylene glycol (PEG) effectively to form stabilized PCCs (MWB/PEG). This non-carbonized, thermally conductive biomass PCCs play a positive role in energy and environmental recycling. Experimental results indicated that MWB possessed 87.9 % adsorption efficiency and excellent anti-leakage property. Enthalpy efficiency embodied through thermal storage capacity reached 86.5 %. Besides, the outstanding temperature regulation and heat transfer characteristics were verified by thermal infrared imaging. Two clear phase transition buffers appeared as well as the temperature distribution mainly concentrated in the phase transition temperature range from vertical view during heating/cooling process. Thermal conductivity and thermal diffusion coefficient of MWB/PEG increased to 0.26 W/m center dot K and 0.19 mm2/s from 0.15 W/m center dot K and 0.11 mm2/s for pure PEG, respectively. The MWB/PEG could store thermal energy by illumination and corresponding photothermal conversion rate reached up to 80.4 %. This composite showed a remarkable waste heat storage and/or reuse through electrothermal testing with integrated conductive fabrics, which would provide a potential development of green and high performance of TES technology in wearable flexible sensors and other fields.