FUEL-CELL POWER-PLANTS .2.

The presence of the fuel cell makes the power plant a fuel cell power plant. These plants contain several different technologies, including subsystems for fuel processing and the stacks themselves. Some utility systems also incorporate gas turbines, boilers, and steam turbines in addition to the chemical and electrochemical units. Performance of the fuel cell plant is governed by the complete flow sheet. The basic philosophy should be simple: Select the fuel cell option that gives highest electrical efficiency, make the most of this device for power generation, and minimize the contributions of other subsystems operating at lower efficiency; de-emphasize cogeneration except when waste heat can be utilized directly with no constraints on electricity generation. The flow sheet for a combined cycle plant is presented as is a flow sheet for a molten-carbonate fuel cell (MCFC). The MCFC flow sheet can be described as a combined-cycle flow sheet with an added topping MCFC system. Flow sheets for intermediate size plants are presented. The author shows that since fuel cells have a modular design, this principle can be used in the design of other components for small and medium-sized fuel cell plants thereby permitting standardization. Factors governing flow sheet optimization are delineated.