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.

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. 

Cont..

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.

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

Cont..

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