Development of a Concentrator With a Rectangular Flat Focus Used for Hydrogen Production via Photocatalytic Water Splitting Employing Solar Radiation

Hydrogen is a promising energy carrier. A carbon-free option to produce hydrogen is the photocatalytic splitting of water, when solar radiation provides the photons needed for the reaction. The DLR develops a test bed to assess the activity of potential catalysts either in suspensions or in fixed-bed electrochemical cells under practical sun-light conditions, concentrated by a factor up to 20. A rectangular flat focus is required in order to guarantee a homogeneous distribution of concentrated radiation on the planar receiver plate, where the light enters the receiver. A low deviation of irradiation on the receiver plate promotes a reliable evaluation of the catalysts’ efficiency and quantum yields. This paper is focused on the development of a suitable concentrator concept. A concentrator/receiver-concept featuring a homogeneous distribution of radiation on the reactor surface was chosen after analyzing different options by means of a ray tracing tool. The favorite concept employs a 2-axis modified linear Fresnel collector. The overall dimensions were determined taking the optical properties of the irradiated surface of the reactor into account. A limitation of the angle of incidence ensures that only a marginal fraction of the radiation is lost due to reflection on the irradiated surface of the reactor.