Construction and Operation of an Experimental Setup for the Demonstration of Chemical Pumping in a Solar Thermochemical Process

Kurzfassung

Considering the huge potential and eco-friendly nature of solar energy, solar fuel production by means of two step water splitting redox cycles has gathered attention in the research community. Reaching high cycle efficiency is one of the biggest challenges towards the development of such process cycles. The non-stoichiometric reduction extent of the water splitting material heavily depends on the partial pressure of oxygen. By lowering the partial pressure of oxygen during the reduction, the non-stoichiometric reduction extent will be increased, which in turn increases the amount of fuel production. A novel method has been developed to increase the efficiency of the partial pressure reduction. In this method, the partial pressure of oxygen was lowered by thermochemical oxygen pumping at reduced total pressure. The main aim of this study is to demonstrate the working principle of the thermochemical oxygen pump. Initially, a piping and instrumentation diagram was created based on the process requirements. Based on that, the components/sensors has been selected and procured accordingly. The experimental test stand was later constructed by integrating all the components together. The acquisition and storage of the measured sensor values is carried out by means of a LabVIEW program created for the test stand with necessary data acquisition modules. The experiments were carried out in the presence/absence of the pumping material. During the re-oxidation step, a carrier gas containing 1040 ppm was passed through the splitting material. Based on the outlet Oxygen concentration measured by the mass spectrometer, the amount of oxygen absorbed by the Splitting material was calculated. From this value, the non-stoichiometric reduction extent of the Splitting material was evaluated. The experimental results indicate that there was no significant improvement in the reduction extent of the material. The air leakage and the diffusion factors were found to be the limiting factors for the implementation of this technology. The experiments and the analysis of the results helped to understand the insights of the pumping process and the limitations of the current system design. By carefully addressing the issues, it is foreseen to demonstrate this pumping process in the near future.