Sir William Grove invented the first fuel cell in 1839. Grove knew that water could be split into hydrogen and oxygen by sending an electric current through it
(a process called electrolysis). He hypothesized that by reversing the procedure you could produce electricity and water. He created a primitive fuel cell and called it a
gas voltaic battery. After experimenting with his new invention, Grove proved his hypothesis. Fifty years later, scientists Ludwig Mond and Charles Langer coined the
term fuel cell while attempting to build a practical model to produce electricity.
A fuel cell converts the chemicals hydrogen and oxygen into water, and in the process it produces electricity. The other electrochemical device that we are all familiar with is
the battery. A battery has all of its chemicals stored inside, and it converts those chemicals into electricity too. This means that a battery eventually "goes dead" and you
either throw it away or recharge it.
With a fuel cell, chemicals constantly flow into the cell so it never goes dead -- as long as there is a flow of chemicals into the cell, the electricity flows out of the cell. Most
fuel cells in use today use hydrogen and oxygen as the chemicals.
A fuel cell provides a DC (direct current) voltage that can be used to power motors, lights or any number of electrical appliances.
There are several different types of fuel cells, each using a different chemistry. Fuel cells are usually classified by their operating temperature and the type of electrolyte
they use. Some types of fuel cells work well for use in stationary power generation plants. Others may be useful for small portable applications or for powering cars.
The
main types of fuel cells include:
Polymer exchange membrane fuel cell (PEMFC)
The Department of Energy (DOE), USA is focusing on the PEMFC as the most likely candidate for transportation applications. The Polymer exchange membrane fuel cell has a high power density and
a relatively low operating temperature (ranging from 60 to 80 degrees Celsius, or 140 to 176 degrees Fahrenheit). The low operating temperature means that it doesn't
take very long for the fuel cell to warm up and begin generating electricity.
Solid oxide fuel cell (SOFC)
These fuel cells are best suited for large-scale stationary power generators that could provide electricity for factories or towns. This type of fuel cell operates at very
high temperatures (between 700 and 1,000 degrees Celsius). This high temperature makes reliability a problem, because parts of the fuel cell can break down after
cycling on and off repeatedly. However, solid oxide fuel cells are very stable when in continuous use. In fact, the Solid oxide fuel cell has demonstrated the longest operating life of
any fuel cell under certain operating conditions. The high temperature also has an advantage: the steam produced by the fuel cell can be channeled into turbines to
generate more electricity. This process is called co-generation of heat and power (CHP) and it improves the overall efficiency of the system.
Alkaline fuel cell (AFC)
`This is one of the oldest designs for fuel cells. The Alkaline fuel cell is very susceptible to contamination, so it requires pure hydrogen and oxygen. It is also very expensive, so this
type of fuel cell is unlikely to be commercialized.
Molten-carbonate fuel cell (MCFC)
Like the Solid oxide fuel cell , these fuel cells are also best suited for large stationary power generators. They operate at 600 degrees Celsius, so they can generate steam that can
be used to generate more power. They have a lower operating temperature than solid oxide fuel cells, which means they don't need such exotic materials. This makes
the design a little less expensive.
Phosphoric-acid fuel cell (PAFC)
The phosphoric-acid fuel cell has potential for use in small stationary power-generation systems. It operates at a higher temperature than polymer exchange membrane
fuel cells, so it has a longer warm-up time. This makes it unsuitable for use in cars.
Direct-methanol fuel cell (DMFC)
Methanol fuel cells are comparable to a Polymer exchange membrane fuel cell in regards to operating temperature, but are not as efficient. Also, the Direct-methanol fuel cell requires a relatively large amount of
platinum to act as a catalyst, which makes these fuel cells expensive.
