May/June 2002
Volume Two - Issue Three

FUEL CELLS

A fuel cell is an electrochemical energy conversion device that converts hydrogen and oxygen into electricity and heat. Fuel cells are similar to batteries in that they can be recharged while you are drawing power from it. Unlike batteries, fuel cells are more environmentally friendly and can be engineered to provide weight, size and performance benefits that batteries can not. It is expected that fuel cells will compete with other energy conversion devices, including the gas turbine, the gasoline engine and the battery as our need for electricity continues to increase. There are several different types of fuel cells that are generally classified by the type of electrolyte they use. Some types of fuel cells show promise for use in power generation plants. Others may be useful for small portable applications or for powering cars.

The proton exchange membrane (PEM) fuel cell is one of the most promising technologies. PEM fuel cells operate at relatively low temperatures (80°C), which means that they warm up quickly and don't require expensive containment structures. Constant improvements in engineering and in the materials used in these cells have increased the power density to a level where a device about the size of a small piece of luggage can power a car.

There are other types of fuel cell technologies being developed for possible commercial uses. These include:

  • Alkaline Fuel Cells (AFCs): AFCs have been used in the U.S. space program since the 1960s. The AFC is very susceptible to contamination and is very expensive, making commercialization unlikely.
  • 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 PEM fuel cells making it unsuitable for some uses. Phosphoric acid-based cells tend to be heavy, however, which makes them less than ideal for use in some applications.
  • 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 relatively high temperatures (around 1,000°C). This high temperature makes reliability a problem, but it has the advantage of producing steam that can be channeled into turbines to generate more electricity. This improves the overall efficiency of the system.
  • Molten Carbonate Fuel Cell (MCFC): These fuel cells are also best suited for large stationary power generators. They operate at approximately 600°C, so they also generate steam that can be used to generate additional power. Because they operate at lower temperatures than SOFCs, they are somewhat less expensive to produce.

Fuel cell makers are looking to capitalize on "distributed generation". For environmental and political reasons, the construction of new electric power plants and transmission lines has become very difficult. As the demand for electric power grows and with electricity deregulation taking shape in many states, analysts argue that small power plants located near the point of demand may provide cost effective ways to augment the existing electric infrastructure. Wind turbines, photovoltaics, and fuel cells are all being viewed as good candidates for distributed generation. However, economic analyst Peter Schwartz, author of "Future of the Global Economy-Towards a Long Boom," recently noted that, "most likely the fuel cell will be the power source of the next half century".
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