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.