Cell Performance

A large number of AES cells with plasma sprayed interconnections have been electrically tested for up to about 9,000 h with little performance degradation. The performance degradation has decreased from about 0.5% per 1,000 h for PST cells to less than 0.2% per 1,000 h for AES cells. Also, the change from PST cells to the AES cells has resulted in a power density increase of about 33%. In addition to improved performance, the AES SOFCs have shown the ability to thermally cycle to room temperature for over 100 times without any mechanical damage or performance loss.

Westinghouse in conjunction with Ontario Hydro Technologies has also tested AES cells at pressures up to 15 atmospheres on both hydrogen and natural gas fuels. Operation at elevated pressures yields a higher cell voltage at any current density due to increased Nernst potential and reduced cathode polarization, and thereby permits higher stack efficiency and greater power output. With pressurized operation, SOFCs can be successfully used as replacements for combustors in combustion turbines; such integrated SOFC-combustion turbine power systems are expected to reach efficiencies approaching 70% (3).

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