SOFC Manoeuvrability

For all-ceramic HT/SOFCs the rate of preheating will be slow compared with IT/SOFCs with flexible metallic structural parts between the MEAs. In future SOFCs capable of direct oxidation of hydrocarbons (Section 4.1.11) and without a reformer, the preheating manoeuvres will be simplified by the absence of the reformer. An exception is the small-tube SOFC (Sections 4.11 and 4.12), which can be preheated rapidly. 

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The beginnings of the SOFC are recorded in an early East German University patent (Mobius and Roland, 1968) which shows awareness of many of the variables still being worked upon today. The oxides of lanthanum, zirconium, yttrium, samarium, europium, terbium, ytterbium, cerium and calcium are mentioned as candidate electrolyte materials. The proposed monolithic planar arrangement has, however, been abandoned by many companies, on the example of Allied Signal. One notable exception is a reversion to a circular planar concept by Ceramic Fuel Cells of Australia, UK (Section 4.7). The Rolls-Royce all-ceramic fuel cell (Section 4.3), which is monolithic and has one compliant feature, namely a gap, is a major exception. One modern trend is towards lower SOFC temperatures, with the intermediate-temperature IT/SOFC allowing the use of cell and stack arrangements with some flexibility and manoeuvrability based on new electrolytes, metallic flow plates, electrodes and interconnects. 

The small-tube SOFC (Section 4.9) remains outside the latter trend, since it is already very manoeuvrable and indeed shockable. 

In the same way, the result of competition amongst the three surviving PEFC, SOFC and MCFC fuel cell types is not predictable. For example, the SOFC has the nascent ability to oxidise natural gas directly, and the MCFC is fuel omnivorous as a result of its mature 600 °C isothermal anode reform capability. Those latter attributes are in contrast to the confinement of the PFFC to hydrogen of minimal CO content, from hydrocarbons processed in an inefficient combustion-driven reformer (inefficient relative to anode reform). The Ballard PFFC has, however, achieved high power density with good, but not unlimited, manoeuvrability. 

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