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Bergen, Norway

Ho T.X.,University of Bergen | Kosinski P.,University of Bergen | Hoffmann A.C.,University of Bergen | Vik A.,Prototech AS
International Journal of Hydrogen Energy | Year: 2010

This paper presents an analysis of the effects of heat sources on performance of a planar anode-supported solid oxide fuel cell (SOFC). Heat sources in SOFCs include ohmic heat losses, heat released by chemical and electrochemical processes and radiation. We take into account the first three types of heat source here while neglecting the last type as it is supposed to be negligibly small. The cell is working under conditions of direct internal reforming of methane and with co-flow configuration. The composite electrodes are discretized allowing the heat source associated with the electrochemical processes to be implemented in a layer of finite thickness. Two cases are investigated, one where the electrochemical heat source is implemented on the anode side (base case) and another where it is implemented on the cathode side. Results for temperature, current density and chemical species distribution of the base case are shown and discussed. Moreover, the effects of magnitude and location of the heat sources are discussed. The results show that including ohmic heating in the cell model does have a significant effect on the predicted cell performance. Comparisons between the two cases indicate that the location of the electrochemical heat source does not affect the cell performance. © 2010 Professor T. Nejat Veziroglu.

Weydahl H.,Norwegian University of Science and Technology | Weydahl H.,Prototech AS | Thomassen M.S.,Sintef | Borresen B.T.,Norwegian University of Science and Technology | And 2 more authors.
Journal of Applied Electrochemistry | Year: 2010

The load-following capability of a proton exchange membrane fuel cell was studied by measuring the cell voltage response to a sinusoidal current load with large amplitude and varying frequency. A mathematical model was developed, incorporating mass transport and capacitive effects as well as the membrane resistance. The model was capable of separating the faradaic and capacitive currents and predicting the observed hysteresis. At frequencies of the sinusoidal current load below 1 Hz, no appreciable hysteresis in the polarisation curve was observed. When increasing the frequency above 1 Hz, a hysteresis appeared at current densities below 0.2 A cm-2. The model related this hysteresis to capacitive effects. When using air as the cathode feed, hysteresis in the current density range 0.5 A cm-2 and higher appeared above 1 Hz compared to 100 Hz for pure oxygen. The model revealed that hysteresis observed in this current density range was caused by oxygen transport limitations. © 2010 Springer Science+Business Media B.V.

Razbani O.,University of Stavanger | Waernhus I.,Prototech AS | Assadi M.,University of Stavanger
Applied Energy | Year: 2013

Temperature distribution over a Solid oxide fuel cell (SOFC) surface is a crucial parameter for design of a SOFC stack. The selection of both materials and the operating point of a stack is heavily affected by temperature gradient. Temperature distribution can also be used for control and monitoring purposes. An experimental set-up consisting of a cross flow type stack of six cells was built to measure the temperature distribution in different current densities and in two oven temperatures. Five thermocouples were inserted inside the middle cell to measure temperatures in four corners and in the middle of the cell. Voltage was also measured for different cells using platinum wires. Low fuel utilization (meaning low current density) and high excess air caused maximum temperature at the fuel inlet-air outlet corner. Higher oven temperature caused more uniform temperature distribution, while increasing the current density resulted in higher temperature gradient over the cell surface. This paper provides measurement data and analysis of the results from the test runs. © 2013 Elsevier Ltd.

Waernhus I.,Norwegian University of Science and Technology | Waernhus I.,Prototech AS | Grande T.,Norwegian University of Science and Technology | Wiik K.,Norwegian University of Science and Technology
Topics in Catalysis | Year: 2011

The electronic charge carrier concentration in La1-xSrxFeO 3-δ was shown to depend on the partial pressure of O 2 (pO2). Chemical diffusion coefficient and surface exchange coefficient, kchem, were determined by conductivity relaxation in O2/N2 and CO/CO2 mixtures. kchem was proportional to pO2 1.06 in O2/N 2, while in CO/CO2 kchem was controlled by a reaction mechanism involving both CO and CO2. © 2011 Springer Science+Business Media, LLC.

Prototech As | Date: 2011-06-14

A power generation apparatus comprises a fuel cell and a reforming module, wherein the reforming module is adapted to reform hydrocarbon fuel into hydrogen and other components, and to separate the hydrogen from the other components. The apparatus is arranged so that the hydrogen is fed from the reforming module to the anode of the fuel cell. Carbon dioxide may be separated in the reforming module. Hydrogen may be recycled from the anode outflow back to the anode and/or tapped off. The apparatus may also contain a desorption module for releasing carbon dioxide. The absorption and release of carbon dioxide may be integrated and the carbon dioxide absorbent and/or desorbent may be recycled. Components of the apparatus may be thermally integrated. The apparatus may be used to generate electricity and produce hydrogen.

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