Karlsruhe Institute of Technology

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About Karlsruhe Institute of Technology (KIT)
Institut für Werkstoffe der Elektrotechnik IWE

Karlsruhe Institute of Technology (KIT) is a higher education and research organization with almost 9,000 employees, 20,000 students, and a total annual budget of about 730 million Euros. KIT was established on 01/10/2009 as merger of Universität Karlsruhe (founded in 1825), one of Germany's leading research universities, and Forschungszentrum Karlsruhe (founded in 1956), one of the largest research centers in the Helmholtz Association.

Higher education, research, and innovation are the three pillars of KIT's activities. In establishing innovative research structures, KIT is pursuing joint strategies and visions. KIT is devoted to top research and excellent academic education as well as to being a prominent location of academic life, life-long learning, comprehensive advanced training, exchange of know-how, and sustainable innovation culture.

KIT's research profile is characterized by a strong focus on energy technology, nanotechnology and materials research, elementary particle and astroparticle physics as well as climate and environmental research. It has significant competencies in the fields of information and communication technologies, mobility systems, optics and photonics, and the inter-relations of humans and technology.

KIT builds on the extensive experience its predecessors have gained in EU-funded research from more than 1000 projects up to now.  

SOFC research activities
The IWE (Institute of Materials for Electrical and Electronic Engineering) is an institute within the Department of Electrical Engineering and Information Technology developing functional ceramics, as dielectrics, sensors and Solid Oxide Fuel Cells. The SOFC research activities of the IWE are based on the planar SOFC stack development which started in 1989 between Siemens Power Generation (KWU) and Siemens Corporate Research and Development in Munich and Erlangen.

Since 1996 the IWE research is dedicated to the development, electrochemical characterization and modeling of advanced types of solid oxide fuel cells for stationary and mobile (APU) applications with respect to improved performance, efficiency and long term stability. More than 40 refereed publications were co-authored on these issues during the last 8 years.

SOFC experience
There is a wide experience in the area of electrical and electrochemical testing of single cells, stacks and systems. Several setups for planar single cells and short-stacks, each of them designed to solve a special scientific or technological objective, are in use. Testing of planar cells (1 to 100 cm² electrode area) is possible in a wide range of operating conditions (different types of gas compositions: air, O2/N2-mixtures / H2, H2O, CO, CO2, hydrocarbons; temperature 500 to 1000 °C, in-situ impedance spectroscopy, in-situ gas analysis), including an automated entire monitoring of the cell and individual electrode properties for operating times up to some 1000 h. In-situ impedance spectroscopy is applied to analyze the electrochemical properties of electrodes and single cells as well as a diagnosis tool for fuel cell stacks and systems.

Project contribution
At IWE fundamental electrochemical studies to analyze the loss and degradation mechanisms in METSAPP-cells and repeat units will be carried out. These studies will provide an understanding of the electrochemical properties and degradation mechanisms in metal supported cells and support the material and cell developers (Sandvik, TOFC, DTU Risø) to improve performance and stability.

Next to experimental analysis of METSAPP-cells, at KIT the electrochemical model presented in (1),(2) will be applied to analyze the impedance spectra. The model provides quantitative information about the resistance contribution of individual loss mechanisms (gas diffusion in the metal support, electro-oxidation in the anode, ohmic losses in the electrolyte, oxygen surface exchange and O2--diffusion in the bulk, gas diffusion in the cathode). The model parameters will be applied in a 0-dimensional electrochemical model to simulate the current voltage behavior of the cell for arbitrary operating conditions (3). In case of a stack respectively a single repeat unit the non ideal contacting and gas supply results in additional losses as in plane ohmic losses in the gas channels and gas diffusion losses under the contact ribs.

At KIT, the FEM-model presented in (4) will be adapted to the flow-field geometry, the material parameters  and the electrochemical properties of the metal supported cell to evaluate the losses related to the flowfield geometry. By varying the flow-field geometry (width and shape of gas channels and contact ribs), the thickness of contact layers and their conductivity and porosity in the model and simulating the related performance values, a model based optimization of the repeat unit will be performed.

Based on experimental results parameters for the reforming reaction kinetics of the different metal supports and catalyst coatings developed in the project will be evaluated according to the method described in (5). These parameters as well as the electrochemical model for the metal supported cell will be integrated in a FEM-model (6) to simulate the catalytic and electrochemical reactions along the gas channel. Based on this model the different metal supports / catalyst coating developed in this project will be rated.

 (1)  A. Leonide, V. Sonn, A. Weber and E. Ivers-Tiffée, J. Electrochem. Soc., 155 (1), p. B36 (2008).
 (2)  P. Blennow, J. Hjelm, T. Klemensoe, S. Ramousse, A. Kromp, A. Leonide and A. Weber, J. Power Sources, 196 (17), p. 7117 (2011).
 (3)  A. Leonide, S. Hansmann and E. Ivers-Tiffée, ECS Trans., 28 (11), p. 341 (2010).
 (4)  M. Kornely, A. Leonide, A. Weber and E. Ivers-Tiffée, ECS Trans., 25 (2), p. 815 (2009).
 (5)  H. Timmermann, W. Sawady, R. Reimert and E. Ivers-Tiffée, J. Power Sources, 195, p. 214 (2010).
 (6)  A. Kromp, A. Leonide, H. Timmermann, A. Weber and E. Ivers-Tiffée, in First International Conference on Materials for Energy, Extended Abstracts - Book A, DECHEMA, Editor, p. 114 (2010).

More info: www.kit.edu