No abstract

The current paper reports the details of challenges and progress in the joint project on development of metal supported solid oxide fuel cells and stacks by the teams of German Aerospace Center (DLR), ElringKlinger, Sulzer Metco and Plansee. An account of the materials is given followed by the advances in the processing techniques which include alternative plasma spraying and colloidal spraying. Improvement in the cell and stack design is then discussed followed by challenges faced during stack building and operations and solution implemented.

Water electrolysis is considered as a suitable pathway for the production of large amounts of hydrogen to be used as energy carrier for electricity storage. Among the existing water electrolysis technologies solid oxide steam electrolysis exhibits the highest electrical efficiency. Moreover, from thermodynamic considerations the efficiency can be further increased when part of the energy demand is provided by the integration of external high temperature heat to reduce the electrical energy for the water splitting reaction. This paper reports on the successful integration of solar heat into a solid oxide electrolyzer. The experimental setup of the prototype system consisting of a solar simulator, a solar steam generator, a steam accumulator and a solid oxide electrolyzer as well as first results with regard to solar steam

No abstract

At the German Aerospace Center (DLR) in Stuttgart, a lightweight stack design for mobile applications was developed in cooperation with the automotive industry (BMW, Munich; Elring-Klinger, Dettingen; Rhodius, Weissenburg). This concept is based on the application of stamped metal sheet bipolar plates into which porous metallic substrate-supported cells (MSCs) are integrated. The paper concentrates on the one hand on the investigation of plasma sprayed button cells with a diameter of 48mm on porous metallic substrates during reduction/oxidation and thermal cycling. On the other hand, another focus lies in the electrochemical testing of short stacks in the cassette arrangement. The microstructure of the cells was characterized by optical microscopy, scanning electron microscopy (SEM), X-ray diffraction, and energy dispersive microanalysis (EDX) before and after operation. The cells and short stacks were electrochemically characterized mainly by long-term measurements (life cycle), by current-voltage measurements, and by impedance spectroscopy. In order to understand the nature of degradation mechanisms, the open-circuit voltages (OCV), the ohmic resistances, and the polarization resistances, during dynamic operation are compared and discussed. In order to distinguish between degradation effects due to the dynamic operation and usual stationary effects, these values are compared to values of noncycled cells. All of the cells investigated were able to withstand ten redox and ten thermal cycles without severe failure. Their redox- and thermal-cycling behavior are strongly dependent on their OCVs, which decrease during cycling. This proves that thermomechanical stresses in the electrolyte layer play a major role for the electrochemical performance of the cells during cycling. The improvement of the electrodes during the first 200h of operation and the ohmic resistance of the cells are not significantly influenced by the cycling. The first four-cell short stack with the cassette arrangement shows promising results with an OCV of ∼4V and an overall power of 92W at 800°C. The performances of the single cells are in the range of 180–220mW∕cm2. The differences in cell performance can be attributed to different polarization resistances of the cells in the cassettes, which might be caused by a nonuniform gas supply in the short stack.