Direct solar photocatalytic hydrogen generation with CPC photoreactors: System development

A new compound parabolic concentrator (CPC) for solar photocatalytic hydrogen production has been designed and estimated in the present study. Parameters of the CPC, i.e., the orientation, the acceptance angle and the absorber tube diameter are designed according to the local meteorological conditions. A north-south orientated, adjustable, single axis tracking truncated CPC with the concentration ratio of 4.22 is designed as one unit. An experimental system including 76 units with the total light area of 103.7m² is developed and installed. The units have four different angles with inclination being 25°, 35°, 45° and 55°, respectively. The system is operated under the natural circulation condition for most of the time, with high pressure gas perturbing the sedimentary photocatalysts from time to time. NiS-Cd_xZn_1−xS is used as the photocatalyst. Preliminary results show that the mean hydrogen productivity and cumulative hydrogen generation are 7.14 NL/h and 42.84 NL/day of the horizontal angle 25° row on a typical meteorological day. The average energy conversion efficiency is 0.087%. The daily hydrogen generation of the whole system is accumulated to be 160.34 NL.