A fuel cell power system requires the integration of many components. The fuel cell produces only dc power and utilizes only certain processed fuels. Besides the fuel cell stack, various components are incorporated in a fuel cell system. A fuel processor is required to allow operation with conventional fuels; a power conditioner is used to tie fuel cells into the ac power grid or distributed generation system; for high-temperature fuel cells, a cogeneration or bottoming cycle plant is needed to utilize rejected heat for achieving high efficiency. A schematic of a fuel cell power system with interaction among various components is shown in Fig. 9.13.