Fuel cells complete record runs

Two tubular solid-oxide fuel cells (SOFC) have been shut down after nearly eight years of failure-free operation at the Westinghouse Electric Corp.`s Science & Technology Center in Pittsburgh, Pa., USA.

“These are the longest running fuel cells of any type, anywhere,” said Aris Melissaratos, Westinghouse vice president for science, technology and quality. The cells were able to maintain a “very respectable” output voltage, Melissaratos said, losing less than 0.5 percent/1,000 hours of operation.

In a related and perhaps more significant milestone, an entire 25 kW electrical generating system powered by 576 SOFCs ran for a world record of more than 13,000 hours. This field test was also conducted at the Westinghouse facility, where the system was built using a new design for its tubular cells. It ran with no cell failures and small degradation in output voltage–0.1 percent/1,000 hours–until it was shut down and dismantled earlier this year to allow inspections contractually required by its sponsors, Tokyo Gas and Osaka Gas of Japan.

The durability and output performance of the SOFC generating system are attributed by Westinghouse developers to a design innovation in the tubular ceramic cells. The porous support tube that each cell previously used was eliminated, resulting in fewer layers. The new design uses the cell`s cathode layer–the air electrode–as its basic mechanical support structure. The design also generates a third more power for a given tube length, and it makes the tubes easier to manufacture.

During its record run of 13,194 nonconsecutive hours, which included one nonstop run of 6,500 hours, the Westinghouse generating system, using cells 50 cm long, produced 282,000 kWh of electricity. It was available 92 percent of the time and endured 10 thermal cycles from the cells` 1,000 C operating temperature down to room temperature and back.

The next step in the Westinghouse program is completion of its first 100 kW SOFC cogeneration system to be delivered later this year to a group of Dutch and Danish utilities. The unit will be the first to use 150 cm cells. Ultimately, the company hopes to commercialize an integrated SOFC/gas turbine combined-cycle power system with efficiencies as high as 70 percent.

Westinghouse is developing tubular SOFC technology under a cooperative agreement with the U.S. Department of Energy and with funding support from Southern California Edison, Ontario Hydro and a variety of other domestic and overseas utilities and agencies.