# Using Water as Fuel in Automobiles

What about using water as fuel in Automobiles, recently I've seen in local TV channel of our country, Genepax Co Ltd of Japan built a new car that uses water as fuel. The system produces Hydrogen from water. For more detail, I used this link,

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Q_Goest
Homework Helper
Gold Member
So many uninformed threads on this...

If water goes in, then what comes out? Water, right? So why don't these brilliant inventors just put the water right back in again? Conservation of mass says all the water that goes in has to come back out again.

So water goes in, miraculously creates energy and violates the principal of conservation of energy (which no one has ever found a way to avoid, by the way) and then this water, having created all this new energy, comes right back out again.

Let's put it back in! Yes, that's the ticket. Stop wasting it. No need. Just recycle it. Better than green. SuperGreen fuel! A car that runs forever by cycling water around in a circle! Charged up by the manufacturer with all the water it will ever need. Never put water into your tank again! :!!)

~ reality check ~

Water isn't fuel. If it was, something would happen to it. Like it would disassociate into something and remain in this lower energy state. If these inventors haven't rewritten the physics books, then they must be trying to defraud people. :grumpy:

Actually water is a fuel. If the humidity is less than 100%, water will evaporate all by itself. Therefore, by converting water to water vapor in a reversible way, you can extract work.

Averagesupernova
Gold Member
So would you say that water is a fuel in a steam engine? I mean really, there is an awful lot of evaporation going on there right? Rethink what you are claiming Count.

Q_Goest
Homework Helper
Gold Member
Actually water is a fuel. If the humidity is less than 100%, water will evaporate all by itself. Therefore, by converting water to water vapor in a reversible way, you can extract work.

Water is not a fuel.

Any material will change phase given sufficient energy. Alchohol will evaporate. Liquid nitrogen will boil, iron will melt. Per that logic, everything is a fuel.

You don't need to supply the energy for evaporation. It can be extracted from the environment. If you have a glas of water then without adding any energy, you can extract a lot of work by letting it evaporate reversibly into the atmosphere

Similarly, if you have salt and fresh water, you can extract work by letting the salt dissolve in the water in a reversible way (which involves using filters that lets through only the water or the salt so that osmotic pressure builds up). Note that when salt disolves into water that process actually costs energy.

Suppose you have some stuff in a system that is kept at constant pressure and temperature. It can be coal, or just plain water, water and salt, or whatever. Assume that the system is in (metastable) thermodynamical equilibrium. If the system then changes into some other form and the sytem is again in thermodynamical equilibrium, then the total amount of work that you can extract from that change is the drop in the Gibbs energy.

So, suppose we start with water and air and no water vapor at 1 bar pressure. This sytem has a certain Gibbs energy. If the water evaporates a bit until the partial pressure of the water vapor equals the thermal equilibrium value at the temperature the system is kept at, then the Gibbs energy will have reached its minimal value.

So, we can clearly extract work from such a system as long as the relative humidity is not 100%. To do this in practice will involve using filters that only let through air molecules or only let through water molecules.

russ_watters
Mentor
We've gotten a rash of these lately, probably due to a combination of the Genepax hoax and wishful thinking due to high oil prices.

Count Iblis, it doesn't matter where the energy comes from. What you are describing is a steam cycle and water isn't the fuel, it is the working fluid. Heck, reread your own first two sentences: you say explicitly that the energy isn't coming from the water.

There are several threads discussing the specific story and the general concept. The short of it is that chemistry dictates that a chemical reaction has the same energy output as you have to input to reverse it. So there is no extra energy available.