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Solid oxide fuel cell (SOFC) systems using anode off-gas and process heat for endothermic fuel reforming promise outstanding system efficiency for power generation from hydrocarbon fuels. A project team of four research institutions developed a stand-alone and thermally self-sustaining SOFC system with 830 Watt gross power and 54 % electrical system efficiency (gross, based on fuel LHV). A commercially available integrated stack module (Staxera ISM) of sunfire GmbH (Dresden, Germany) was used as SOFC.

Solid oxide fuel cell systems (SOFC) can improve the efficiency of electrical power generation from biogas compared to small scale CHP units. The SOFC requires a reforming step converting biogas into synthesis gas (hydrogen and carbon monoxide). . Dry reforming of methane with the carbon dioxide contained in biogas is a promising approach to produce high caloric SOFC fuel gas, but carbon formation is predicted for all typical biogas compositions. To avoid carbon formation and to compensate fluctuating biogas compositions additional supply of steam is essential leading to a combined dry and steam reforming. The paper describes the system approach, upfront analysis, biogas monitoring results, process unit design and evaluation as well as the system setup to demonstrate a biogas to electricity route with a gross efficiency of 45 % using a commercial 1 kW SOFC stack.

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A simple model for prediction of polarization losses occurring in a solid oxide fuel cell is presented. It is a one-dimensional model taking into consideration ohmic and fuel conversion losses, voltage drop due to fuel crossover and internal currents, losses due to gas diffusion through the porous electrodes as well as activation overpotential. The parameters for the modeling equations are derived from literature values which need only be supported by few initial measurements. The model can be implemented to identify separate experimentally found loss phenomena and to predict SOFC behavior -especially E(i) behavior -for most standard situations. Based on this model it is possible to describe results obtained in the laboratory fairly well.