Pore characteristics and thermal conductivity enhancement of binary eutectic adsorbed into delignified wood for solar energy storage

In this work, two binary carbon-based composite phase change materials consisting of paraffin (PW), lauric acid (LA) and tetradecanol (TD) were prepared. Delignified wood flour (DWF) was obtained through treatment with a mixture of NaOH and Na₂SO₃. The pore volumes of DWF and wood flour (WF) are 0.01049 and 0.008955 cm³/g, respectively, and the pore volume of DWF increased by 17.16%. The adsorption capacity of DWF for LA-PW and LA-TD reaches 50%, which is 10% higher than the adsorption capacity of WF for LA-PW and LA-TD. The thermal conductivities of LA-PW/DWF and LA-TD/DWF are 0.3762 and 0.3580 W/m k, respectively. The phase transition temperatures of LA-PW/DWF and LA-TD/DWF are 40.86 ℃ and 19.68 ℃, respectively. The phase transition latent heat for LA-PW/DWF and LA-TD/DWF is 88.86 J/g and 62.31 J/g, which are 33.61% and 26.18% higher than those of LA-PW/WF and LA-TD/WF, respectively. After 200 cycles, the maximum value of the change rate in phase transition temperature for LA-PW/DWF and LA-TD/DWF is less than 2.64%, and the peak shape remains consistent before and after the cycle, which have good thermal stability.

The adsorption capacity of DWF obtained by alkali delignification of wood flour was enhanced. LA-PW and LA-TD were uniformly adsorbed in the pore structure of DWF by capillary force and surface tension. LA-PW/DWF and LA-TD/DWF have high phase transition latent heat and good thermal and stability.