Solid Oxide Fuel Cells
The FuelCell Energy Direct FuelCell® (DFC®) is the most widely adopted fuel cell technology in the world based on kilowatt hours of electricity produced commercially and the installed base of operating power plants. High electrical efficiency and high grade thermal output, combined with the ability to cost-effectively scale the power plants to multi-megawatt size has driven this success. For several years, FCE has been evaluating a higher temperature fuel cell system, the Solid Oxide Fuel Cell (SOFC) through a relationship with Versa Power Systems (Versa), previously a partner, now a wholly owned subsidiary. SOFC has the potential to achieve even higher electrical efficiency with high power density (i.e. more power per fuel cell and fuel cell stack) than the carbonate-based DFC technology.
Commercialization of the technology has been limited because acceptable performance could only be achieved from very small cells, and configuring commercial scale power systems with small cells is not cost effective. Versa has successfully scaled the technology to produce larger cells and stacks than any other planar SOFC developer. The potential target market for SOFC is sub-megawatt applications, which would be complementary to the megawatt-class market for DFC power plants.
We have incorporated the larger-scale SOFC components into fuel cell stacks as large as 60 kilowatts (kW) as part of FCE’s project under the U.S. Department of Energy Solid State Energy Conversion Alliance (SECA) program. The SECA program has a long term objective to introduce low-emission, high- efficiency SOFC based systems operating on coal gas in the size range of hundreds of megawatts. Smaller sub-megawatt scale natural gas or renewable biogas fueled systems are expected to be near term spin-off products from this developmental activity.
The high efficiency and fuel flexibility of SOFC technology also makes it attractive for select portable power applications as contracts with the U.S. Navy and a sub-contract to a U.S. Defense Advanced Research Projects Agency (DARPA) program illustrate. The U.S. Navy is evaluating the use of SOFC power for propulsion and ship power of unmanned submarine applications as the virtual lack of emissions, high efficiency, and quiet operating nature are well suited for stealthy operations. DARPA is evaluating SOFC based systems for unmanned airborne applications. The DARPA airborne system is an example of SOFC technology deployed for energy storage. The complete system incorporates both SOFC and solar power generation. During the day, the solar power generation is used to power the aircraft and excess solar power generation is converted to hydrogen by the fuel cells as they operate in electrolysis mode. At night, the fuel cells run in fuel cell mode, converting the stored hydrogen to power. SOFC based energy storage systems have the potential to provide unprecedented round trip energy efficiency as the storage application of the technology is further developed.