HYDROGEN FUEL CELLS

Hydrogen, the simplest element, is composed of one proton and one electron. It makes up more than 90% of the composition of the universe. It is the third most abundant element in the earth's surface, and is found mostly in water. Under ordinary (earthly) conditions, hydrogen is a colourless, odourless, tasteless, and non-poisonous gas composed of diatomic molecules (H₂).

The use of hydrogen:

• Offers an elegant way to store and regenerate electricity

• Does not produce carbon dioxide or any other greenhouse gas

• Avoids all the costs of producing and using fossil fuels

• Is clean: in the cycle of storing and releasing energy, water is both the source and end-product

• Fits with our existing electrical grid infrastructure, and is an excellent way to power a vehicle or a house

• Could solve our electrical grid's load management issues

• Addresses the finite nature of the earth's fossil fuel reserves

• Avoids the hidden ecological, health, aesthetic, and property damage costs of fossil fuel use

• Does not produce acid rain nor does it deplete the ozone layer

Hydrogen's potential use in fuel and energy applications includes powering vehicles, running turbines or fuel cells to produce electricity, and generating heat and electricity for buildings. The current focus is on hydrogen's use in fuel cells.

A fuel cell works like a battery but does not run down or need recharging. It will produce electricity and heat as long as fuel (hydrogen) is supplied and consists of two electrodes - a negative electrode (or anode) and a positive electrode (or cathode) - sandwiched around an electrolyte. Hydrogen is fed to the anode, and oxygen is fed to the cathode. When activated by a catalyst, hydrogen atoms separate into protons and electrons which take different paths to the cathode. The electrons go through an external circuit, creating a flow of electricity. The protons migrate through the electrolyte to the cathode, where they reunite with oxygen and the electrons to produce water and heat.

Fuel cells can be used to power vehicles or to provide electricity and heat to buildings, and the primary fuel cell technologies under development are:

• Phosphoric Acid Fuel Cells (PAFC) which consist of an anode and a cathode made of a finely dispersed platinum catalyst on carbon paper, and a silicon carbide matrix that holds the phosphoric acid electrolyte. This is the most commercially developed type of fuel cell and is being used in hotels, hospitals, and office buildings. The phosphoric acid fuel cell can also be used in large vehicles, such as buses.

• Proton-Exchange Membrane Fuel Cells (PEM) which use a fluorocarbon ion exchange with a polymeric membrane as the electrolyte. The PEM cell appears to be more adaptable to automobile use than the PAFC type of cell. These cells operate at relatively low temperatures and can vary their output to meet shifting power demands. These cells are the best candidates for light-duty vehicles, for buildings, and much smaller applications.

• Solid Oxide Fuel Cells (SOFC) which are currently under development and use a thin layer of zirconium oxide as a solid ceramic electrolyte, and include a lanthanum manganate cathode and a nickel-zirconia anode. This is a promising option for high-powered applications, such as industrial uses or central electricity generating stations.

• Alkaline Fuel Cells which use an alkaline electrolyte such as potassium hydroxide and were originally used by NASA on space missions. It is now finding applications in hydrogen-powered vehicles.