Carbon Aerogel/Myristic Acid Palmitic Acid Phase Change Composites With High Solar/Electro‐Thermal Conversion for Thermal Energy Storage

ABSTRACT Phase change materials (PCMs) have garnered significant attention in thermal storage owing to their high latent heat, near‐constant phase transition temperature, and negligible volumetric change during phase transition. However, their inherent disadvantages, such as leakage during melting, low thermal conductivity, poor photothermal response, and electrical insulation, have considerably limited their practical application in solar energy utilization and electrothermal conversion systems. In this study, we propose for the first time the design and fabrication of a lightweight biomass‐derived carbon aerogel (CKA) with a highly porous structure and superior light absorption, prepared via controlled carbonization process using natural kapok fibers (KF) with sodium silicate as the structural binder. The resultant CKA was employed as the encapsulation of myristic acid‐palmitic acid (MA‐PA) binary PCM by a vacuum impregnation method. The obtained CKA/MA‐PA composite PCMs (CMPPs) exhibit excellent form stability, enhanced thermal properties, and high energy storage density. These results show that the unique three‐dimensional network structure of CKA enables a high PCM loading ratio (> 80%) and outstanding thermal cycling reliability. The carbonized structure forms continuous heat conduction pathways, yielding a thermal conductivity of 1.676 W m −1 K −1 , which is 3.37 times higher than that of the noncarbonized samples (KMPP). Moreover, CMPPs demonstrate a high enthalpy of phase change (165.7–166.2 J/g) and significantly improved photo/electro‐to‐thermal conversion performance. The design offers a novel biomass‐carbonization‐based strategy for developing high‐performance composite PCMs, which show great potential for applications in solar energy storage and building energy efficiency.