Optical design and experimental characterization of a solar concentrating dish system for fuel production via thermochemical redox cycles

•High-flux concentrating concepts for solar fuel production are evaluated.•The optical designs enable the operation of two solar reactors side-by-side.•The selected design comprises a parabolic dish coupled to a rotating flat secondary.•On-sun characterization yields a peak solar concentration ratio of 5010 suns. The design, fabrication, and on-sun characterization of a solar dish concentrating system for performing the two-step thermochemical redox splitting of H2O and CO2 is presented. It comprises a primary sun-tracking 4.4 m-dia. solar dish concentrator coupled to a secondary planar rotating reflector. This optical arrangement enables the operation of two (or more) solar reactors side-by-side for performing both redox reactions simultaneously by alternating the solar input between them while making continuous and uninterrupted use of the incoming concentrated sunlight. On-sun characterization of the complete concentrating system revealed a peak solar concentration ratio of 5010 suns and an average of 2710 suns measured over the 30 mm-radius aperture of the solar reactor. A detailed optical analysis elucidates measures to increase the optical efficiency and concentration ratio.