The US Department of Energy (DOE) has selected two projects for continuation within the Department’s Solid State Energy Conversion Alliance (SECA) Program research portfolio. The projects—led by FuelCell Energy, in partnership with VersaPower Systems, and Siemens Energy—have successfully demonstrated solid oxide fuel cells (SOFCs) designed for aggregation and use in coal-fueled central power generation.
The selections were based upon an assessment of demonstrated progress in developing high-performance, low-cost SOFC technology. FuelCell Energy is testing two ~10 kW SOFC stacks incorporating planar cells; each has surpassed 4,700 hours of operation to date. Similarly, Siemens is testing a ~10 kW SOFC stack incorporating its new higher power Delta cells, with 2,500 hours of operation to date.
With the continuation, these projects will pursue cell materials and design development to further improve performance, reduce cost, and integrate the cells into larger stacks for evaluation and incorporation into larger demonstrations beginning in 2012.
SOFCs operate by separating oxygen from air and transferring it across a solid electrolyte membrane, where it reacts with a fuel—such as synthesis gas derived from coal, biofuels, or natural gas—to produce steam and carbon dioxide (CO2). Condensing the steam results in a pure stream of CO2 gas, which can be captured for storage or other use in a central location.
This feature, coupled with very high efficiencies and the fact that fuel cells operate more efficiently at lower temperatures than combustion-based technologies, results in near-zero emissions. In addition, eliminating the need for steam bottoming cycles, and the ability to keep fuel and air streams separate, significantly reduce water withdrawal.
Projects in the SECA portfolio are conducting research and technology development to lower costs and improve reliability, ultimately culminating in the demonstration of fuel cell technologies that can support power generation systems as large as several hundred megawatts capacity. Key program goals, as defined by the Office of Fossil Energy and the US Office of Management and Budget, include:
- Cost of $175 per kilowatt (2007 dollars) for a minimum 40,000 hour fuel cell stack.
- Cost of $700 per kilowatt (2007 dollars) for an integrated fuel cell power block.
- Maintaining high power density in the large cells necessary for economic manufacturing.
SECA was established by DOE’s Office of Fossil Energy in 2000 to research and develop low-cost, modular, fuel-flexible SOFC systems by 2010. In early 2005, the SECA program was accelerated to deliver megawatt-class fuel cell systems in response to the emerging national need for low-cost carbon capture technologies, near-zero emissions, and the need to reduce water withdrawal in power plants. Demonstrations are planned for 2012, 2015 and 2020:
- 2012: Multiple 1 MW systems to demonstrate 5-year life by 2017.
- 2015: Multiple 5 MW systems to demonstrate system integration with heat recovery turbines, power electronics, and other system level features by 2017.
- 2020: Full scale 250–500 MW integrated gasification fuel cell plant as part of DOE’s Near-Zero Emissions Coal-Based Electricity Demonstration Program.