Solar Hydrogen Production Integrating Low-Grade Solar Thermal Energy and Methanol Steam Reforming

In this paper, a novel approach of middle-temperature solar hydrogen production using methanol steam reforming is proposed. It can be carried out at around 200–300°C, much lower than the temperatures of other solar thermochemical hydrogen production. For the realization of the proposed solar hydrogen production, solar experiments are investigated in a modified 5 kW solar receiver/reactor with one-tracking parabolic trough concentrators. The feature of significantly upgrading the energy level from lower-grade solar thermal energy to higher-grade chemical energy is experimentally identified. The interaction between the hydrogen yield and the energy-level upgrade of solar thermal energy is clarified. Also, this kind of solar hydrogen production is experimentally compared with methanol decomposition. The preliminarily economic evaluation of the hydrogen production is identified. As a result, in the solar-driven steam reforming, the thermochemical efficiency of solar thermal energy converted into chemical energy reached up to 40–50% under a mean solar flux of 550–700 W/m2, and exceeding 90% of hydrogen production is achieved, with about 70% higher than that of methanol decomposition. The thermochemical performance of solar-driven methanol steam reforming experimentally examined at around 200–300°C for hydrogen production may be competitive with conventional methane reforming. The promising results obtained here indicate that the proposed solar hydrogen production may provide the possibility of a synergetic process of both high production of hydrogen and effective utilization of solar thermal energy at around 200–300°C.