Thermodynamic analysis of methane to methanol through a two-step process driven by concentrated solar energy

Converting solar energy into liquid fuels such as methanol is the vision of efficient utilization of solar energy. We proposed a solar-powered methane reforming and methanol synthesis hybrid system. The methane reforming system is driven by solar energy, converting methane, CO2 and H2O into syngas, which are then used in the methanol synthesis system. Our numerical thermodynamic analysis shows that when the ratio of CO2/H2O in the methane reforming is 0.76, the H2/CO ratio obtained from the reforming reaction is most conducive to subsequent methanol production. We obtained experimentally a 73% methane conversion at a reforming reaction temperature of 875 °C. Starting from the experimental reforming effluents, we simulated methanol conversion obtaining a total methane-to-methanol conversion rate of 71%. The hybrid system demonstrates a 49% overall energy conversion efficiency when operating at an optimized condition that synergizes temperature, ratio of CO2/H2O in the methane reforming, and cycling parameters. By integrating the solar-driven methane reforming and methanol synthesis process, we provide a new pathway for further study of the conversion of methane-to-methanol by using solar energy efficiently.