A vehicle powered by hydrogen derived from water (salt or otherwise) cannot truly be said to be powered by water however because more energy will be consumed in the process of converting the water to fuel. That energy can be provided by some other energy source.
Exact. In fact these cars are powered by hydrogen. But when the convertion device is included in the car, it's fair to say that it uses water.
I pretty sure that the EROI for water craking/hydrogen burning, is positive because I have read and heard on several independant experiments where an engine could turn several minutes on water only. If the EROI was negative, their vehicles would have ran out of battery power very quickely.
With this new discovery, it takes less energy to crack water molecules so the EROI is certainly positive.
Like a microwave oven take less energy to heat a dish than a gaz stove.
One of the reason is that hydrogen is extremely explosive. It explodes extremely fast, so the engine is much more efficient because all the enrgy is used at the same time.
The biggest difficulty with gasoline is to optimize the explosion and most of the energy is lost because it's dispersed before and after the critical moment. Hydrogen takes only a fraction of what gas takes to burn.
But they faced other problems:
-Engines are not optimized for hydrogen and it's very difficult to regulate the hydrogen flow. The engine would eventualy cough and stop.
-Oxydation and lack of lubrification: The engine would rust and degrades quickely.
-Still dangerous as hydrogen is produced: If hydrogen is not burnt and accumulates somewhere, it can explode.
-Low budget
By "energy ratio" being negative I meant the energy spent in the whole process from exploration and drilling to the pump at the gas station. I may be wrong thought, but I'v read somewhere in a scientific publication that this ratio was negative (or inferior to 1).
Maybe they talked about tar sand. But the point was that even a negative "EROI" energy can be used provided it's refined outside the vehicle. It also doesn't mean it's more expensive if the souce of energy is virtualy free.