Fuel-Flexible Fuel Cell Power System Debuts

Solid Oxide Fuel Cell Power Unit
(Photo: Delphi Corp.)

Together with DOE's Office of Fossil Energy personnel, the Delphi-led team met all the Phase I goals of the Solid-State Energy Conversion Alliance (SECA); the results were validated by the Agency this past May. DOE identified the SOFC as one of the more promising ways to generate cleaner and more efficient electrical power for a number of stationary and mobile power applications. 

Coordinated by the DOE, SECA is currently undergoing a three-phase, 10-year program that began in 2001. Its goal is to develop the SOFC technology to help reduce U.S. dependence on foreign oil while mitigating environmental concerns. SECA's Phase 1 goals called for industry-led development teams to make meaningful progress in achieving cost, performance and durability improvements.

In addition to its compactness, another key advantage of the SOFC is its high system fuel-efficiency, particularly when its high-temperature co-product heat can be used in combination with its high electrical output. For example, SOFCs can be teamed with gas turbines driven by the SOFC's co-product heat to potentially generate power at 55 percent to 80 percent thermal efficiency, depending on the scale of the project and the fuel used. 

This is significantly more efficient than today's typical coal-fueled power plant's thermal efficiency of 35 to 40 percent. By co-generating power on-site at industrial facilities, commercial businesses and even residences, this co-product heat could enable up to 90 percent efficiency in distributed, combined heat and electrical power (CHP) generation. 

Similarly, heavy-duty trucks could use SOFC auxiliary power systems for both heat and electrical power when parked, to save 85 percent of the billion gallons of fuel that they consume today when idling their main engines. In addition, idling emissions will also be greatly reduced.

While size and efficiency advantages are important for many potential applications, perhaps the SOFC's most significant advantage overall is its very broad applicability because of its inherent fuel flexibility. With relatively small changes, SOFC systems can potentially operate on a full range of conventional and alternative fuels, says Delphi. This includes natural gas and conventional petroleum-based fuels, such as low-sulfur gasoline, diesel and propane; high-sulfur military fuels like JP-8 and jet fuel; low-CO2 renewable fuels from biomass like ethanol, methanol and biodiesel; synthetic liquid fuels from coal and natural gas; and non-hydrocarbon fuels such as hydrogen and ammonia.

The team now moves onto Phase 2 of the SECA program: a three-year, $45 million, cost-shared contract between Delphi and DOE. Phase 2 goals will be to reduce the SOFC system factory cost to less than $600 per kilowatt, increase efficiency to 40 percent or more, and to further increase power density. The Delphi team will also work on increasing durability, particularly to withstand more thermal cycles.

Ultimately, SECA's final Phase 3 goal is to deliver a SOFC power system capable of 40 percent or greater efficiency at a factory cost of $400 per kilowatt. This performance will open up a wide range of mobile and stationary applications for this ultraclean power generation technology, from small-scale multikilowatt auxiliary power systems for vehicles and homes to larger-scale multimegawatt industrial and utility fuel cell power plants.

(Source: Delphi)