For photoelectrochemical (PEC) water splitting, hydrogen production is achieved by concentrating sunlight using parabolic trough collectors and focusing it on PEC cells, which are in a transparent enclosure with water. Irradiation of the PEC cells leads to hydrogen and oxygen production on opposites sides of cell, so that pure hydrogen can be obtained (see Figure , PEC). State-of-the-art properties of the PEC cells are based on devices by Kistler et al. and Khan et al. using a III-V absorber. The layout of the hydrogen production plant is based on Pinaud et al. (type 4 -PEC). A detailed description of the process can be found In SI Section 5.1 and all input parameters are available in SI Section 6.5.