What Is a Fuel Cell?

Instructor: Michael Quist

Michael has taught college-level mathematics and sociology; high school math, history, science, and speech/drama; and has a doctorate in education.

In the desire to stop polluting our atmosphere and find inexpensive energy, fuel cells seem to make a lot of sense. In this lesson, we'll discuss what they are and how they work.

What is a Fuel Cell?

Next door, your neighbor is starting up his car. Loud revving, smoke, and exhaust fumes fill the air. Your car is a little different. You flip the switch and your car quietly hums into action, making no smoke, no smells, and little noise as you back out and head out to the highway.

Fuel cells are special electrical generators that make electricity by chemically converting fuels into byproducts while they strip away electrons and heat to use as power. Their fuels are usually much simpler than the hydrocarbons, such as gas, oil, and coal, that internal combustion systems (like the engine in a typical car) use. Often, the chemical process is merely the combination of hydrogen and oxygen into water, using a special electrolyte to control the chemical reaction. The smaller ones look like a big battery, while the larger ones can look like a huge generator or a large building transformer.

Fuel cell under the hood of a car
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How Fuel Cells Work

There are many versions of fuel cells, using many process variations, but they act sort of like a battery that uses fuel instead of a recharge to get its power. These features are common to most designs.


Solid oxide fuel cell
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  1. Generally, the hydrogen fuel comes in on the negative side of the cell (anode) and reacts in the electrolyte to split up into electrons (which make electricity for the circuit) and positively charged hydrogen ions. Excess hydrogen is either vented off or reused.
  2. On the other side of the cell, oxygen is coming in from the air. In the positive side (cathode), it picks up the electrons returning from the electrical circuit and forms negatively-charged oxygen ions.
  3. The hydrogen ions and oxygen ions react together, forming water and giving off energy that keeps the reaction going.
  4. The water and unused gases are drained/vented off.
  5. The electrolyte in the plates (anode and cathode) and in the area between regulates the reaction.

So long as there's fuel available to the cell, this process will go on indefinitely. The system is quiet, efficient, and non-polluting. Unfortunately, fuel cells are currently expensive, difficult to build, and only efficient at very high temperatures.

Common Design Features

The typical fuel cell design, like a battery, has a layer of electrolyte between two oppositely-charged plates. Unlike a battery, however, the plates on a fuel cell are porous, allowing gases to pass through them and providing a large surface area for reactions. These plates, called electrodes, do most of the work.

  1. They provide a place for the ionization and de-ionization process.
  2. They conduct ions to and from the reaction area.
  3. They separate the fuels from the electrolyte in the center of the cell.

Types of Fuel Cells

Since the fuel cell directly produces electricity, the power is readily available for use in power systems in cars, homes, industries, etc. The application determines which type of fuel cell is appropriate. The type of electrolyte used in the cell dictates how the cell must be built and the conditions under which it has to operate. Some of them operate at extremely high temperatures, so you might not want them under the hood of your car!

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