January 10th, 2010 
Aaron Turpen 
One of the most promising alternative fuel options for future heavy transportation and commercial vehicle use is the of fuel cells to provide electricity. A hydrogen fuel-cell (the most common) is a two-part system, at its essence:
- Hydrogen gas, stored as a fuel (energy) source, and
- A fuel-cell, which combines hydrogen gas with oxygen (usually from the atmosphere) to make water and electricity.
Hydrogen (H2) is one of the most readily-available elements in the universe. Water (H2O) is two parts hydrogen and one part oxygen. Hydrogen can be obtained by splitting water through electrolysis, by burning natural gas, and from many other sources.
Fuel cells, however, are still a burgeoning technology and have yet to become mainstream in most applications. They are relatively expensive to build, but have so much potential that literally every major vehicle manufacturer in the world is either experimenting with them or working with someone who is.
The fuel cell itself is made up of an exchange system, or catalyst, which separates the electrons from the fuel (in this case hydrogen) to make electrical power. A fuel cell will usually work something like this:
Image Courtesy of Wikimedia
The proton-exchange cell (shown above) is the most common basic type of fuel-cell used for automotive applications, but there are many others. In fact, hydrogen isn’t the only available gas to be used in a fuel-cell, it is just the most common. Methane, zinc, and even carbon (petroleum) fuel cells are possible and are being experimented with.
Fuel Cell vs. Battery Power and the History of Fuel Cells
What we refer to as a “fuel cell” in a vehicle is actually several cells put together to create a desired voltage. This is similar to a battery. Fuel cells typically produce 0.6-0.7 volts per cell and can be combined in series or parallel circuits to create the desired output in total. Similar to a big truck having four to six batteries combined in series to make 24V out of 6 or 12V cells.
Experimentation with fuel cells began in 1838 with a Welsh scientist named Sir William Robert Grove publishing a rudimentary demonstration fuel-cell in 1839. It wasn’t until 1955 that a GE scientist improved that system with more modern technology and components to create the basis for most of our modern fuel-cells today.
Today’s Fuel Cells
Current innovations in fuel cell technology center around the electrolyte (or its equivalent) used to surround the cells and facilitate their operation, the temperature tolerances of the cells (with some operating in ambient temps as low as -6°C), and their overall efficiency.
Most automotive uses of hydrogen fuel-cells are taking ambient air (air from outside the vehicle, sent through a filter as with combustion engines) and using the oxygen in it to mix with hydrogen for the reaction. This means that while the fuel-cell is less efficient than it would be were it to use pure oxygen injection, no stored oxygen is required on the vehicle itself, increasing usability and lower the overall energy required to power the vehicle by reducing both weight and energy requirements to extract and store oxygen.
Hydrogen Fuel Cell Vehicles
Hydrogen is usually stored on the vehicle as a compressed gas, often replacing the vehicle’s gasoline or diesel storage tanks with cylinders in a series that hold compressed hydrogen. These cylinders have also been the focus of much of the development of fuel-cell systems, being seen as its largest safety concern. Cylinders today are typically capable of holding compressed hydrogen at 800-1,200psi and are built to such requirements that they are virtually impossible to puncture. Hydrogen gas is, of course, flammable, just as diesel and gasoline fumes are.
While hydrogen isn’t available at every gas or diesel pumping station, it is easy enough to get that there are many companies working on solutions to the “infrastructure problem.” In Europe, a “Hydrogen Highway” stretches through the Netherlands and is expected to go all the way to France in the next three to five years.
Other companies, such as Honda, are working towards a “Hydrogen Home” concept in which every home could use renewable electricity (wind, solar, or both) to provide the power to split water and store compressed hydrogen for use in fuel-cell cars. Similar ideas are being explored for large, commercial settings for hydrogen fuel-cell forklifts, machinery, and heavy vehicles.
For more information on fuel-cells, visit the Wikipedia entry on Fuel Cell technology.
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