The Department of Energy has encouraged the development of high temperature fuel cells in partnership with industry. These fuel cells are primarily designed for stationary power. Integrating a fuel cell with a gas turbine produces a “hybrid” system, which enhances power output and efficiency, while reducing overall system cost. Recent DOE studies on Solid Oxide and Molten Carbonate fuel cells have confirmed that the fuel cell hybrids can generate 70+% plant electrical efficiency. The studies were focused on >20 MW hybrids. The first commercial hybrids using currently available stacks are expected to exceed 60% efficiency and are likely to be of the 1-3 MW class.
Existing gas turbines are not compatible with performance or life requirements of a “hybrid.” In order to achieve these goals, a purpose-designed gas turbine was deemed necessary, which would:
• Drive oxidant flow (normally air) through the stack and cycle
• Pressurize the stack to raise its power output and efficiency
• Minimize internal gas velocities and associated parasitic losses
• Reduce system cost through a simpler overall balance of plant configuration
• Enhance and simplify balance of plant and system integration process
• Provide a means for converting fuel cell exhaust heat to as bonus electricity
The benefits of a purpose-designed gas turbine are:
• Total power improvement from 20 to 50%
• Fuel efficiency improvement of 20-30% from a given stack system
• System capital cost reduction ($/kW) of up to 40%
• Life target of approximately 100,000 hours
Fuel cells are expected to be used extensively for distributed generation application in base load mode, running predominantly steady state. The design stack life in this operating mode is 100,000 hours. The design of a fuel cell compatible gas turbine has been initiated. Results of this project will be presented at the conference. Turbogenerator configuration studies are continuing, under contract number DE-FC26-00NT40914, for the US Department of Energy.