SOFC Technology

Solid Oxide Fuel Cells Intended mainly for stationary applications with an output of 1 kW and larger They work at very high temperatures (some at 1000ºC) Due to the high operating temperature of SOFC's, they have no need for expensive catalyst. catalyst

Fuels for Fuel Cells The primary fuels directly utilized within fuel cell stacks today are – Hydrogen – Carbon monoxide – Methanol and – Dilute light hydrocarbons like methane, depending upon the fuel cell type.

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SOFC :The most inherently fuel flexible The presence of sulfur is not tolerated by fuel cells in general. SOFC is the most inherently fuel flexible of the fuel cell types. MCFC units are also quite fuel flexible.

Composition Every fuel cell has two electrodes, one positive and one negative, called, respectively, the cathode and anode. The reactions that produce electricity take place at the electrodes. Every fuel cell also has an electrolyte, which carries electrically charged particles from one electrode to the other, and a catalyst, which speeds the reactions at the electrodes.

Cont.. (SOFC) use a hard, ceramic compound of metal (like calcium or zirconium) oxides (chemically, O2) as electrolyte Efficiency is about 60 percent Operating temperatures of 800-1,000 °C (about 1,800 °F).

Simplified diagram of an SOFC

Operating Principle 1.Oxygen is dissociated at the cathode into O2- 2.O2- migrate thru the crystal structure of the electrolyte 3.Oxidize the hydrogen atoms at anode 4.Yields electrons and produces electricity

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SOFC Design types According to the type of cell configuration and developer- Three major configurations for stacking the cells together to increase the voltage and power are: –Tubular (as developed by Westinghouse and Mitsubishi Heavy Industries), –Flat plate (as developed by Ceramatec and Mitsubishi Heavy Industries), and –Monolithic (as developed by Allied Signal).

Applications Suitable for decentralized electricity production While the major application of SOFCs are seen in stationary plants, auxiliary power units in Transportation vehicles On-board power for aircraft Power packs- small enough to be carried by soldiers has been motivated by DARPA

Drawbacks The high temperature limits applications of SOFC units and they tend to be rather large While solid electrolytes cannot leak, they can crack. Complex materials Assembling Maintenance Design Cost & choice of material