Evaluating the performance of photocatalysts with regard to spectral irradiation using the SoCRatus

Kurzfassung

Photochemical or photoelectrochemical processes can be employed for simultaneous treatment of waste water and hydrogen production. Thereby abundant but unsteady solar radiation is used to produce a potent chemical energy carrier. The development and demonstration of suitable reactor devices are addressed in the scope of the German project DuaSol. DLR’s test facility SoCRatus (Solar Concentrator with a Rectangular Flat Focus) – see Fig.1 – will be employed in the experimental assessment of developed devices with respect to solar efficiency and stability. First ideas concerning the concentrator were presented in [1]. The SoCRatus specified by a geometric concentration ratio of 20.2 provides homogeneous concentrated solar radiation in the rectangular focus extended to 2500 mm x 100 mm. A representative local standard deviation of irradiation relative to the mean of 2.4% could be determined. [2] The inlet optics of a spectrometer covering wavelengths in the range from 250 nm to 850 nm is directly located in the focal plane. Additionally a pyrheliometer for DNI measurement mounted at the concentrator structure allows the calculation of the total solar input on the photochemical system. As a result the solar-to-hydrogen efficiency can be contrasted with efficiencies respecting specific wavelength ranges. Four identical fluid cycles are available for connection to reactors. The product gas leaving the reactors is analysed by micro gas-phase chromatographs. The UV-part of incoming solar radiation varies significantly during a day. First experimental findings confirm that the productivity of the applied TiO2 based photocatalysts correlates rather with the UV irradiation than with the DNI.