Hydrogen generation system with zero carbon emission based on synergistic conversion of methane and solar energy

This paper proposes a hydrogen generation system with zero carbon emissions based on the synergistic conversion of methane and solar energy. It was divided into high-temperature reforming and low-temperature solar-assisted pre-reforming. The pre-reforming reactants were methane and a portion of the flue gas. The oxygen from the electrolyzer and the purge gas from the pressure-swing adsorption unit are burned to heat the reformer. The other portion of the flue gas was condensed and the carbon dioxide separated to achieve zero emission. The energy and exergy analyses indicate that the proposed system can achieve a methane chemical energy utilization rate of 91.48 % without sacrificing hydrogen recovery. Simultaneously, it was found that the conversion rate of solar energy to hydrogen chemical energy using photothermal-thermochemical technology was 32.66 percentage points higher than that using photovoltaic-electrochemical technology. The energy and exergy efficiencies of the proposed system were 42.88 % and 39.21 %, respectively, which were 4.76 and 4.53 percentage points higher than those of the reference system. The exergy utilization diagram analysis result then revealed the mechanism of irreversible loss formation during the combustion and reforming process. Finally, the influence of pre-reforming and reforming temperature on system performance was studied.