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kW
Kilowatt (1,000 watts). A measure of electric power.

kWh
Kilowatt-hour (1,000 watts for one hour). A measure of electric power consumption.

Matrix
A framework within a fuel cell that supports an electrolyte.

Membrane
The separating layer in a fuel cell that acts as electrolyte (a ion-exchanger) as well as a barrier film separating the gases in the anode and cathode compartments of the fuel cell.

Molten Carbonate
A type of fuel cell electrolyte that contains carbon, oxygen and another element. Solid at room temperature, it must be melted in order to function.

MW
Megawatt (1,000,000 watts). A measure of electric power.

MWh
Megawatt-hour (1,000,000 watts for one hour). A measure of electric power consumption.

Nafion
A sulfuric acid in a solid polymer form. It is usually the electrolyte of PEM fuel cells.

O&M Costs
Operations and Maintenance. The cost of keeping a power plant running and in good repair.

Oxygen
A chemical element consisting of eight protons, eight neutrons and eight electrons. Two hydrogen atoms combine with one oxygen atom to form a molecule of water.

Phosphoric Acid
A solution of the elements phosphorus, hydrogen, and oxygen that serves as the electrolyte for one type of fuel cell. Chemically: 4H3PO4.

Polymer
A natural or synthetic compound composed of repeated links of simple molecules.

Potassium Hydroxide
A solution of the elements potassium, hydrogen, and oxygen that serves as the electrolyte for one type of fuel cell. Chemically: KOH.

Proton Exchange Membrane (PEM)
A polymer sheet that serves as the electrolyte in one type of fuel cell.

Reformer
A device that extracts pure hydrogen from hydrocarbons.

Regenerative Fuel Cells
Several fuel cell types in which fuel and, in some types, the oxidant are regenerated from the oxidation product.

Solid Oxide
A solid combination of oxygen and another element (often zirconium) that serves as the electrolyte for one type of fuel cell.

Stack
Individual fuel cells connected in series within a generating assembly.

Water (H2O)
A colorless, transparent, odorless, tasteless liquid compound of hydrogen and oxygen. The liquid form of steam and ice. Fresh water at atmospheric pressure is used as a standard for describing the relative density of liquids, the standard for liquid capacity, and the standard for fluid flow. The melting and boiling points of water are the basis for the Celsius temperature system. Water is the only byproduct of the combination of hydrogen and oxygen, and is produced during the burning of any hydrocarbon. Water is the only substance that expands on freezing as well as by heating, and has a maximum density at 4ºC.

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