Utilization of carbonized water hyacinth for effective encapsulation and thermal conductivity enhancement of phase change energy storage materials

In this work, a biochar carrier was developed to adsorb phase change materials and enhance thermal conductivity. Six kinds of modified carbonized water hyacinth were prepared by freeze drying (or vacuum drying) combined with high-temperature carbonization. The pore volume and specific surface area (SSA) of FC900 are the highest, reaching 0.3153 cm3/g and 479.966 m2/g, which are 32% higher than those of VC900. The load rates of FC900 and VC900 on lauric acid-myristic acid-paraffin section (LMPS) are 75% and 65% respectively. Meanwhile, the phase transition enthalpy of LMPS/FC900 is 104.36 J/g, which is 20.75% higher than that of LMPS/VC900, and the phase transition temperatures are 25.93 and 26.77 °C respectively. After 500 times of heat storage and release experiments, LMPS/FC900 maintains a stable phase change peak, which has good thermal performance stability. Notably, the thermal conductivity of LMPS/FC900 is 0.4168 W/(m·K), which is 56.93% higher than that of LMPS. Otherwise, under the constant temperature environment of 50 °C, the heating time of LMPS/FC900 is 11.89% longer than that of LMPS/VC900, which has more excellent temperature control performance. This study concludes that the carbonization temperature of 900 °C and freeze-drying measures are the best preparation process for carbonized water hyacinth, and LMPS/FC900 has good thermal conductivity and phase change energy storage performance.