[neilep (OP)]

Is it actually possible to run a car with water ?...can it really be done ?...or any engine ?

If it has been....I gather it must NOT be cost effective yes ?...do you know if there is ongoing research into this ?

where are are we up to ?

I don't H2O !!...Do eau ?

[Seany]

Well.. You cannot run an engine with the compound H2O, or as far as I am aware of.

However, you can run an engine with H, the Hydrogen. That means that you must split the compound H2O, into two parts, the Hydrogen and Oxygen. This means that you need energy to do this, which returns to square one, that you needing the fuel to supply this energy.

Thus, you need the fuel anyway! []

Also, even if we do later find a way of splitting H2O.. There may be that little problem of losing the water in our world. Yes, they would probably return to water again, but you never know.

[another_someone]

There are three ways you can obtain energy from water.

The first is not strictly from the water itself, but from the gravitational energy vested in the water, is to use a water wheel or water turbine (e.g. in a hydroelectric power station or a water mill).

The other way (although at present only theoretically possible) is by the nuclear fusion of the hydrogen in water.

The third way is to create a reaction between water and something that will react with it (e.g. sodium).  Again, as with the problem with extracting hydrogen, the ability to obtain such reactive substances will probably cost more energy than the energy you would obtain from the reaction.

[Seany]

George, is the third point you made, a displacement reaction to get the hydrogen out?

[JimBob]

There are three ways you can obtain energy from water.

The first is not strictly from the water itself, but from the gravitational energy vested in the water, is to use a water wheel or water turbine (e.g. in a hydroelectric power station or a water mill).

The other way (although at present only theoretically possible) is by the nuclear fusion of the hydrogen in water.

The third way is to create a reaction between water and something that will react with it (e.g. sodium).  Again, as with the problem with extracting hydrogen, the ability to obtain such reactive substances will probably cost more energy than the energy you would obtain from the reaction.

George,

If you are going to include kinetic energy, you also need to include steam energy. It necessitates the use of water - a consistent and stead source of added water even for turbines - to generate energy.

[another_someone]

George, is the third point you made, a displacement reaction to get the hydrogen out?

Yes, it would be.

[Batroost]

Being a bit imaginative...

(1) Let water out of a small hole in a spacecraft. Assuming that it doesn't freeze fast enough to block the nozzle you've got a crude rocket.

(2) Or, start with a cold block of metal on a warm day and watch it heat-up as condensation forms on the outside. In this instance you're taking energy (latent heat of evaporation) from the water molecules in the atmosphere.

Admittedly neither of these could really be a practical source of energy as in teh first instance you have to get to space with your water ( []) and in teh second you'll use more energy cooling down your block of metal ( []).