Design issues tubular SOFCs

In contrast to stationary applications, portable applications require frequent start and stop procedures. Therefore for SOFC, a robust cell design and adapted electrode-electrolyte assemblies are an important issue. Frequent thermal cycles between room temperature and an operation temperature of about 600-800 °C pose challenges to the layered system consisting of solid anode, ceranfic electrolyte and solid cathode with respect to thermal and mechanical stability. For several years, different approaches to developing tubular nficro SOFC have been undertaken but did not lead to a commercial product yet. As SOFC can be operated with pure hydrogen, reformate and hydrocarbons as fuel as well - the latter option means direct internal reforming at the anode catalyst — various investigations focused on reduced operation temperature and a parallel conversion of fuels [21]. 

Structural issues related to the interconnect depend on the choice of the material. High-temperature SOFCs, such as the tubular design of Siemens-Westinghouse [111], make an exclusive use of ceramic materials, apart from the nickel felt used for current collection. The most common material, lanthanum chromite, is brittle and prone to non-uniform isothermal expansion when simultaneously subjected to reducing and oxidising atmospheres on different faces [131]. 

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