When the Hindenburg airship approached its dock in Lakehurst, N.J., on May 6, 1937, the blimp that held the passenger decks aloft was filled with hydrogen. This element, the simplest -- and most abundant -- in the universe, has one proton with a single electron revolving around it. Hydrogen also weighs the least of all the elements atomically. It can pack quite a punch, creating vast amounts of energy when oxygen and an ignition source are introduced. When the Hindenburg exploded, the world witnessed the power of hydrogen.
As the Hindenburg was docking that May evening, the blimp's outer skin was exposed to a static spark. In a matter of seconds, flames tore across the airship, reducing it to a ball of flames and twisted metal. Thirty-six people lost their lives in the disaster [source: National Archives]. And as fast as the Hindenburg burned, so, too, did the public's opinion of hydrogen. For many decades following the disaster, hydrogen was viewed with skepticism and even alarm. A "hydrogen fear factor" developed regarding the element [source: Edwards].
Today, as concerns grow about a possibly dwindling global supply of oil -- and increasing emissions of pollutants from that oil -- energy researchers are reconsidering hydrogen as a source of fuel. It certainly has a tremendous amount of promise: Hydrogen emits little or no greenhouse gases (GHGs). Its major byproducts are water vapor and heat. Hydrogen has the highest energy output by weight of any fuel [source: CECA]. And it's plentiful; hydrogen can be produced by a number of sources, from natural gas to water itself.
But the question still remains: Is hydrogen fuel a safe source of energy for our cars? How can hydrogen even be used as fuel? There's a quick primer on the next page.
Hydrogen Fuel Cell Challenges
Hydrogen isn't actually an energy source -- it's an energy carrier [source: CECA]. Hydrogen carries the energy that's created when it's produced. It's similar to electricity: We can't burn electricity (which is an energy carrier), but electricity can be produced by burning energy sources like natural gas or petroleum. Then electricity transports this energy to other places, like the outlets in your home.
This means that the energy carrier has to be given the energy to carry, crudely speaking. So we must create energy to make hydrogen. This is a lot easier than the conventional method of obtaining our primary fuel source, oil. Getting oil requires drilling into reserves, pumping it out of the ground, refining it, and sending it to the gas station. By using hydrogen as a fuel source, essentially we can produce our own fuel and eliminate all of these steps -- and maybe the geopolitical strife that oil causes.
Hydrogen is created through a process known as reforming. Certainly, we can generate hydrogen as a means of energy transfer by burning natural gas or some other carbon-based fuel source. In fact, methane reforming (separating hydrogen from hydrocarbons by burning natural gas) is currently the most viable method of producing hydrogen fuel. But through this method, we're right back at square one, as far as greenhouse gas (GHG) emissions go. While the process of transferring energy from hydrogen will be a clean one, the process of creating hydrogen will still burn fossil fuel and emit GHGs.
Just as there are cleaner ways to produce electricity (like hydroelectric power), hydrogen can also be created cleanly through wind or solar power -- even through microbes that eat algae and produce hydrogen as a waste product [source: NREL]. Researchers are evaluating these methods as reliable ways of producing hydrogen without burning fossil fuels. And others are figuring out the best way to use this produced hydrogen to power your car.
Auto engineers have devised hydrogen fuel cells. These fuel cells create electricity to power your car through electrochemical conversion. The pure chemical element hydrogen is split into its proton and electron, a process which generates electricity. When it mixes with oxygen, the byproduct of the process is water. Since a fuel cell can't produce enough electricity on its own to power a car, cells must be put together to create fuel cell stacks [source: Fuel Economy.gov]. Once you put a few stacks together, though, your car can zoom along.
A big issue remains, however: storing the hydrogen aboard your vehicle. Some methods are already in use. Hydrogen may be stored in the form of a highly pressurized gas or an extremely cold liquid, like cryogenic hydrogen. This works for storing hydrogen at the fuel pumps, but it's not practical for carrying around fuel in your car. Cryogenic hydrogen liquid would require an extra onboard system to keep the fuel cold. This would add weight, which affects the vehicle's energy efficiency.
Researchers are still investigating the optimal ways to store and exploit hydrogen as a fuel source. Part of that research includes dispelling the public's fears of hydrogen fuel. Science may be able to crack the hydrogen fuel puzzle, but if drivers still envision themselves being flash-burned alive in a ball of white-hot flame after a fender bender, then who would buy a hydrogen-fueled car anyway? Perhaps the next page will assuage your worries.
Hydrogen Fuel Safety
In many cases, hydrogen is safer than the fuel we currently use to power our cars. Carbon-based fuels tend to spread as liquids (as you well know if you've ever spilled gasoline on yourself at the pump). When it burns, conventional fuel produces hot ash, creating radiant heat. This isn't the case with hydrogen. In its pure form, hydrogen burns no carbon and produces no hot ash and very little radiant heat [source: RMI]. What's more, when hydrogen leaks, it ascends rapidly into the atmosphere, so it has less time to burn [source: Princeton].
So what about the Hindenburg? Both proponents and opponents of hydrogen fuel have latched onto the ill-fated blimp in their debate. While opponents point to it as a cautionary tale, proponents view it as exoneration for hydrogen.
Although the hydrogen aboard the Hindenburg certainly did burn with incredible force, it wasn't the hydrogen that created the disaster -- it was aluminum powder. To reflect sunlight, the skin of Hindenburg was covered in this powder, a form equivalent to rocket fuel [source: RMI]. And the cotton fabric that made up the blimp's skin was waterproofed with highly flammable acetate [source: ABC]. Hydrogen proponents also point out that the flames in the Hindenburg disaster burned upward rather than out because the element is so lightweight. This left the passengers in the carrier beneath relatively unmolested by the flames. Thirty-five of the 36 Hindenburg deaths were the result of passengers jumping from the airship; all of those who remained aboard survived [source: RMI].
The challenge presented by hydrogen fuel storage is to come up with ways to create storage tanks that won't prove to be a cautionary tale against hydrogen for future generations. In other words, what would make the best storage tank to prevent hydrogen from exploding in a car accident?
Steel tanks are one possibility. They're strong enough to serve as reliable carriers for hydrogen gas in automobiles. If an accident does occur, a steel tank will likely be able to withstand an impact without suffering a puncture or rupture. One problem with steel, however, is that hydrogen is so lightweight and therefore less dense than gasoline. Any tank that holds pressurized hydrogen fuel would have to be much bigger than the conventional gas tank on your car. A steel tank would be pretty heavy and reduce energy efficiency.
Composite materials seem to offer even more promise than steel. Tanks made of polyethylene are lightweight, can be shaped to fit a car and are designed to powder -- absorb the energy of an impact, reducing the tank to dust and ostensibly releasing the hydrogen safely into the atmosphere [source: Princeton].
Hydrogen may ultimately be stored in materials that can hold the element and release it when needed. Some types of metal, like metal hydride, can trap hydrogen molecules within their compositional structure. Here, the hydrogen is stored safely and released when the metal is heated. What makes this technology even more appealing is that the heat necessary for the release of hydrogen molecules from their metal tanks could come from the waste heat produced by a hydrogen fuel cell [source: DOE].
It doesn't seem the "hydrogen fear factor" is doing much to dissuade continued research into its viability as a fuel source. And if the world really is running out of oil, we may have to put aside those fears once and for all.
For more information on hydrogen fuel and other related topics, visit the next page.
Related HowStuffWorks Articles
More Great Links
- Edwards, Peter P. "Our fear of hydrogen fuel stations." The Times. April 21, 2008. http://www.timesonline.co.uk/tol/comment/letters/article3784369.ece
- Kruszelnicki, Karl S. "Hindenburg and hydrogen." Australian Broadcasting Company. 2004. http://www.abc.net.au/science/k2/moments/s1052864.htm
- Murphy, Christian. "Differentiating energy sources and carriers." Consumer Energy Council of America. July 30, 2003. http://www.cecarf.org/Programs/Fuels/SourcesCarriers.html
- "Fuel cell vehicles." California Energy Commission. http://www.consumerenergycenter.org/transportation/fuelcell/index.html
- "Fuel storage." Princton University. http://www.princeton.edu/~chm333/2002/spring/FuelCells/H_storage.shtml
- "How they work: PEM fuel cells." Fuel Economy.gov. http://www.fueleconomy.gov/feg/fcv_PEM.shtml
- "Hydrogen facts." Consumer Energy Council of America. 2003. http://www.cecarf.org/Programs/Fuels/Fuelfacts/HydrogenFacts.html
- "Hydrogen production and delivery." National Renewable Energy Laboratory. June 1, 2007. http://www.nrel.gov/hydrogen/proj_production_delivery.html
- "Is hydrogen dangerous?" Rocky Mountain Institute. http://www.rmi.org/sitepages/pid205.php
- "Metal hydrides." U.S. Department of Energy. November 6, 2006. http://www1.eere.energy.gov/hydrogenandfuelcells/storage/metal_hydrides.html
- "Scenes from hell: Herb Morrison - Hindenburg disaster, 1937." National Archives. http://www.archives.gov/exhibits/eyewitness/html.php?section=5