The ingenious combination of thermal energy storage and temperature visualization of binary fatty acid eutectic/eucalyptus wood fiber skeleton composites

The adjustment of temperature, reduction of supercooling, combination of energy storage characteristics and color change visualization are very valuable for integrating phase change materials into practical energy storage applications involving the optical field. In this respect, delignified eucalyptus (DEW) used as the supporting structure, and the binary fatty acid eutectic used as the phase change and discoloration temperature determining component, a series of red/green dibasic fatty acid reversible thermochromic phase change composites (CPCMs) were prepared by the vacuum impregnation method. Among them, two types of CPCMs (MPR-DEW and MPG-DEW) show the suitable phase change temperatures (42.1 °C, 42.3 °C), high latent heat values (130.3 J g−1, 130.6 J g−1), the supercooling degree (0.2 °C, 0 °C) lower than that of single fatty acid of MA (3.8 °C) and PA (2.9 °C). SEM, FTIR and XRD analysis show that the phase change-discoloration components are completely immersed in the honeycomb pore structure of the DEW and that no chemical reaction occurred during the impregnation process. After heating, the color of MPR-DEW and MPG-DEW changed from dark red to light red and dark green to light green, respectively. The difference between the red and green colors of MPR-DEW and MPG-DEW is reflected in the slight difference between light and heat absorption and storage. Moreover, MPR-DEW and MPG-DEW have very small changes in phase transition temperature and latent heat value before and after 50 heating-cooling cycles, maintaining good thermophysical properties and thermal stability, and have broad application prospects in building thermal management.