Wikipedia explains it best:
en.wikipedia.org
"Chemical energy content of water
The burning of conventional fuels such as petrol (gasoline), wood and coal releases energy, which converts the fuel into substances with less energy. In the case of most fossil fuels, one of the waste products is water. This is because water is at a lower energy state than the original fuel (see enthalpy of formation).
Chemical processes do not create energy, they merely store and release it in the form of bond energy between the atoms. Water is such an abundant chemical compound in part because it is already at a very low, stable, energy level. Where water takes part in a reaction that produces energy, the material it is reacting with contains the chemical energy that is being released. For example, mixing water with sodium produces a vigorous reaction which generates heat and generates hydrogen which can be burned in air. But in that case, sodium is being converted into a lower energy state, making sodium the source of the energy — not the water.
Nuclear energy content of water
It is theoretically possible to extract energy from water by nuclear fusion, and indeed, all naturally occurring water contains trace amounts of heavy water molecules in which one of the hydrogen atoms is deuterium (an isotope of hydrogen) which is useful in nuclear fusion reactions. However, this process is not claimed by water-fuelled car promoters, and there is no suggestion that any motor, small or large, has yet been proposed that can achieve this — indeed, practical nuclear fusion power plants of any kind are not yet technologically feasible. For further discussion, see Cold fusion." |
