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What are fuel cells?

Fuel cells are galvanic cells that produce electricity from irreversible chemical reactions. They can provide energy to systems as large as utility power plants and those as small as portable computers. They produce much smaller quantities of greenhouse gases and no air pollutants.

What are hydrogen fuel cells?

Hydrogen fuel cells are fuel cells that use the electrochemical reaction between hydrogen gases and oxygen gases to produce electricity.

Hydrogen is considered to be a potential alternative to fossil fuels, which can provide clean electricity and heat energy. The energy content in hydrogen is higher than any other known fuel, along with being a clean and sufficient energy carrier. This source of energy is expected to generate power, provide heating and be an effective fuel for transportation. In internal combustion engines and turbines, hydrogen has the potential to be used as fuel. Hydrogen is also used in fuel cells to produce electricity and do not require to be recharged with electricity.

Hydrogen fuel cells are vital to the well being of the environment. New projects for creating infrastructures of this technology are becoming widespread across the world. Countries in Western Europe, North America, and Asia are embracing the path of a clean air environment. Many automobile companies like DaimlerChrysler, BMW and General Motors have already brought out models of hydrogen cars that will sold to the general public within the near future.

How do hydrogen fuel cells work?

Photo courtesy of U.S. Department of Energy
PEM Fuel cell is one of many types of different fuel cells

The most common type of hydrogen fuel cells is the PEM (Polymer Electrolyte Membrane) fuel cell. In the fuel cell,

1. Hydrogen is fueled into the anode, where oxidation occurs.
2. Oxygen is fed to the cathode, where reduction occurs.
3. Activated by a catalyst, hydrogen atoms are oxidized, separating into protons and electrons, which take different paths to the cathode.
4. The electrons go through an external circuit, creating an electric current.
5. The protons (hydrogen ions) migrate through the electrolyte to the cathode, where they reunite with oxygen and the electrons to produce water and heat.

As shown in the diagram, the only products are electricity, water, and heat. There is no air pollutants produced.

For better understanding of how hydrogen fuel cells work, fuel cell animation can be viewed at http://www.eere.energy.gov/hydrogenandfuelcells/fuelcells/basics.html

Different types of hydrogen fuel cells

Different types of fuel cells include:

Polymer Electrolyte Membrane(PEM) Fuel Cells	Direct Methanol Fuel Cells
Alkaline Fuel Cells	Phosphoric Acid Fuel Cells
Molten Carbonate Fuel Cells	Solid Oxide Fuel Cells
Regenerative Fuel Cells

Each of the fuel cells has its own type of chemical reaction, optimum temperature range, and type of electrolyte. Therefore each has a different application and differnt advantages over other types of fuel cells.

Comparison chart of different types of fuel cells


Type of Fuel Cell	Applications	Advantages	Disadvantages

Polymer Electrolyte membrane (PEM)	• electric utility • portable power • transportation	• Solid electrolyte reduces corrosion & management problems • Low temperature • Quick start-up	• Low temperature requires expensive catalysts • High sensitivity to fuel impurities

Alkaline (AFC)	• military • space	• Cathode reaction faster in alkaline electrolyte so high performance	• Expensive removal of CO2 from fuel and air streams required

Phosphoric Acid (PAFC)	• electric utility • transportation	• Up to 85% efficiency in cogeneration of electricity and heat • Can use impure H2 as fuel	• Requires platinum catalyst • Low current and power • Large size/weight

Molten Carbonate (MCFC)	• electric utility	• High efficiency • Fuel flexibility • Can use a variety of catalysts	• High temperature enhances corrosion and breakdown of cell components

Solid Oxide (SOFC)	• electric utility	• High efficiency • Fuel flexibility • Can use a variety of catalysts • Solid electrolyte reduces corrosion & management problems • Low temperature • Quick start-up	• High temperature enhances breakdown of cell components source:U.S. Department of Energy