Can a car run on just water? Actually, yes.

Glenn Reynolds links to AutoblogGreen's post about the Geneplex car, whose makers say it can be fueled only with water. Sam Abuelsamid writes that the claim is "highly unlikely."

Well, not so fast. Sam does point out that the car's electric drive is powered by a fuel cell, a well-proven technology that is the feature of the new Honda Clarity, which uses a fuel-cell stack to power the drivetrain. It uses no gasoline (see my post, "Buy a Honda, kill a polar bear.")

So the fuel call is no big deal for the Geneplex. Sam explains,

They have devised a system that consists of a fuel cell and a so called energy generator. The energy generator is claimed to consume water and breaks it down to hydrogen and oxygen which is fed to the fuel cell. While fuel cells are well understood and are known to work, the hydrogen generator is the issue.

Hydrogen can actually be separated from water quite easily with no energy input. Just put a piece of aluminum in into some water and hydrogen will be release as the surface of the aluminum oxidizes. The problem is that such processes are not sustainable. Once the surface of the aluminum is fully oxidized, the reaction stops. After this, the material needs to be reprocessed so it can be used again. This part requires significant energy input. Genepax has not revealed details of their process, however it is believed to be something along these lines.

But there is an efficient process to generate hydrogen gas on demand (H2) using aluminum. It was discovered by a Purdue University engineer. Basically, he produced hydrogen by adding water to an alloy of aluminum and gallium. The aluminum oxidizes, freeing the H2. "The gallium is critical to the process because it hinders the formation of a skin normally created on aluminum's surface after oxidation" and makes the solid aluminum of the alloy reactive with water, which plain solid aluminum is not. Gallium, however, is very expensive. Fortunately, the gallium is not consumed in the process and can be reused. The only other product of the process besides H2 is alumina (aluminum oxide), which can be recycled back into aluminum.

So is a purely water-powered car actually "highly unlikely"? Well, no. But it remains to be seen whether the Geneplex will be both efficient and economical to drive.