Well this really Is Eco Diesel,

Exciting stuff. With solar getting cheaper all the time, storing the energy for later use is the gap. If this can beat batteries in cost per mile then it's got potential.
And perhaps even at higher cost for some applications. You can't carry enough batteries to drive hundreds of miles. At least not yet.

The water will return to where it came from in the combustion process.

That's pretty cool but I wonder how many gallons of water it takes to make 1 gallon of fuel.

It's a great idea and kudos to Audi for the development work. But it's going to take a INCREDIBLE amount of solar/wind generation to power the electrolysis step on a large scale.

Don't these people know how much it costs to change oil in a diesel :h