Continuous Solar Hydrogen and Syngas Production in Membrane Reactors

Satisfying the industry's growing demand for sustainable hydrogen requires the rapid development of a diverse mix of hydrogen production technologies. The membrane technology is capable of shifting the thermodynamic limits of water splitting to lower temperatures and thus into a technically feasible range. This thermodynamic limit was determined with respect to possible molar flow parameters and temperature, where biomethane is considered as reducing agent on the permeate side of the membrane or a purge gas dilutes the permeated oxygen concentration. In the second part of this study, a developed thermal model is used to analyse the integration of real solar flux distribution into a membrane stack reactor. To avoid failure of the joined membrane modules, a homogeneous temperature distribution (< 50K) along the reactor body is required. However, the solar flux distribution from a solar system is characterised by a Gaussian-shape with a peak in its centre, which results in the generation of hot spots. Our model consists of a cavity, the reactor and a set of plates, which are used to enhance the temperature distribution in the reactor. It was found that parameters such as the aperture diameter of the cavity, the distance of the cavity to the focal point and the material of the irradiated plates influence the temperature distribution on the reactor stack. An aperture diameter of 55 mm and a distance of 135 mm to the focal point met the temperature requirements of the membrane stack reactor.