Hydrogen has long been a tantalizing alternative to petroleum fuel, and for good reason. It's abundant -- the gaseous element combines with oxygen to make water -- and carries a tremendous amount of energy. For years, scientists have worked on producing a hydrogen-powered internal combustion engine, in the hopes that this power source could become a clean-burning alternative to gasoline.
But hydrogen has some serious drawbacks that have slowed its adoption as an automotive fuel. It's not naturally occurring -- it must be extracted from water or other sources -- and the processes to obtain it require a lot of energy. Likewise, the light gas is difficult to store in large enough quantities to be useful for transportation. And the very energy density of hydrogen that makes it so attractive as a fuel also makes it dangerous if not handled properly [source: Alternative Energy News].
But that hasn't stopped a long string of inventors from offering mileage-boosting devices that claim to create hydrogen and add it to a car's fuel, boosting mileage with this high-energy wonder gas. Many of the so-called hydrogen generators work in the same fashion: An onboard electrolysis device pulls water from a storage tank, and, using electricity generated by the car's alternator, splits the hydrogen and oxygen. These are then injected into the engine, supposedly giving the car a power boost and saving fuel [source: Allen].
The problem with these onboard generators is one of capacity. Remember, it takes a great deal of electricity to split the strong bond between water's hydrogen and oxygen atoms. That energy has to come from somewhere, and in a car, that means a significant additional load is placed on the alternator. The car may be producing hydrogen fuel, but it's burning more energy than it creates.
As a result, hydrogen generators typically produce miniscule amounts of the gas. And while this gas may indeed make it into the car's fuel system (some sloppier generators could contain enough leaks to vent any hydrogen before it reaches the engine), it simply isn't enough to produce the claimed power or mileage boosts [source: Tony's Guide to Fuel Saving Gadgets].