Electrical Transmission and Distribution Systems 415 Fuel cell stacks are the devices that actually chemically convert the fuel into direct current (DC) electricity. Substantial numbers of fuel cell stacks, much like batteries in a flashlight, must be electrically connected to generate a sufficient amount of electrical energy to operate electrical equipment. Also, since the energy produced by those devices is DC, electrical ``inverters'' and ``power conditioning'' equipment must also be employed to produce alternating current (AC) electricity. Voltage amplitude, frequency, and harmonic content must be controlled during that power conditioning and DC to AC conversion process. The DOE [6] lists the following available categories of fuel cells: Polymer Electrolyte Membrane (PEM) Fuel Cell Direct Methanol Fuel Cell Alkaline Fuel Cell Phosphoric Acid Fuel Cell Molten Carbonate Fuel Cell Solid Oxide Fuel Cell