Energy Conversion Efficiency Enhancement of Polyethylene Glycol and a SiO2Composite Doped with Ni, Co, Zn, and Sc Oxides

Abstract

Doping the SiO2support with Co, Ni, Zn, and Sc improves the thermal conductivity of a hybrid PEG/SiO2form-stable phase change material (PCM). Doping also improves the energy utilization efficiency and speeds up the charging and discharging rates. The thermal, chemical, and hydrothermal stability of the PEG/Zn-SiO2and PEG/Sc-SiO2hybrid materials is better than that of the other doped materials. The phase change enthalpy of PEG/Zn-SiO2is 147.6 J/g lower than that of PEG/Sc-SiO2, while the thermal conductivity is 40% higher. The phase change enthalpy of 155.8 J/g of PEG/Sc-SiO2PCM is very close to that of the parent PEG. PEG/Sc-SiO2also demonstrates excellent thermal stability when subjected to 200 consecutive heating-cooling cycles and outstanding hydrothermal stability when examined under a stream at 120 °C for 2 h. The supercooling of the PEG/Sc-SiO2system is the lowest among the tested materials. In addition, the developed PCM composite has a high energy storage capacity and high thermal energy storage/release rates.