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Abstract

In the context of climate change and increasing energy conversion efficiency solid oxide fuel cells (SOFCs) are likely to play an important role in the production of electricity. The tubular SOFC configuration is considered to be the most advanced and is approaching commercialisation. A major advantage of SOFCs over other types of fuel cells is that they can utilise a wide spectrum of fuels (natural gas, coal and biomass syn-gas). This is due to its high operating temperature, which also makes them suitable for integration with gas turbines and for cogeneration. A R&D project is underway to develop a computer simulation model of a tubular SOFC that can accurately predict performance under various conditions and using a range of fuels. A model is developed using the process simulator aspen plus. The software uses unit operation blocks, which are models of process operations. The user places these blocks on a flowsheet, specifying material and energy streams. There is no built in model that can represent a SOFC, however it is possible to construct one using the built in unit operation blocks. This method is an alternative to developing a fuel cell model using programming languages. The model is based on Gibbs free energy minimisation. Data available in the literature on the Siemens Power Generation tubular SOFC was used to validate the model. The model predicts thermodynamic condition and chemical composition of the stack exhaust gases, heat generated, voltage, current, and electrical efficiency. Fuel composition and operating parameters were varied over a wide range. Operating parameters such as fuel utilisation factor, current density, and steam to carbon ratio were found to have significant influence. In a future study this SOFC stack model will be integrated with a biomass gasifier model and balance of plant models all developed in aspen plus. From examination of the sensitivity analyses’ results optimum conditions are established.

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