Learning to use water as fuel is an age-old fantasy. But for physicists Peter and Neal Graneau, it could be a dream that's about to come true.
They believe they have found a way to tap the energy associated with the forces that bind water molecules together in their liquid form. If on-going experiments confirm this possibility, the research could unlock a valuable new source of renewable energy.
Dr. Graneau, at Northeastern University in Boston, and his son Neal, at Oxford University in England, have taken a new view of a well-known phenomenon - the extraordinary force of water explosions induced by relatively small electric arcs.
It has been a marvel for half a century. Small amounts of water accelerated by such explosions reach speeds in excess of 2,000 miles per hour and can punch holes in quarter-inch-thick aluminum plates. Experimenters have measured water pressures of more than 20,000 atmospheres.
In the 1960s, engineers adapted the phenomenon for metal-shaping technology. Yet no one has explained how such enormous pressure and energy could arise in the first place. Some physicists speculated it might be due to a new kind of electrodynamic force.
Graneau explains that he and his son gave up on that theory in 1994 when they realized such a force would be too puny to do the job. It looked to them as though some form of chemical energy was being released from the water itself. They found the clue to what that energy could be by looking carefully at what happens in the cold-water explosions.
In a typical experiment, an electric arc is struck within a small pool of water. About a third of the water converts to fog and mist. But only the very smallest droplets actually explode. These shoot into the air at supersonic speeds.
The Graneaus, working in their own laboratories, have collaborated with George Hathaway, of Hathaway Consulting Services in Toronto, and Richard Hull, with the TCBOR Laboratories in Richmond, Va., in making detailed studies on such events. They confirm that the total energy output in the experiments far exceeds the energy used to strike the arc, Peter Graneau says. Their studies also rule out such exotic energy sources as nuclear reactions.
That leaves the molecular bonding energy of the water as the prime candidate. This is just the familiar "latent heat" of evaporation and condensation. When you boil water, you have to add 540 calories of heat to turn a gram of water into vapor. Conversely, water vapor gives up this energy when it condenses.
The Graneaus note that no one has measured the latent heat, or bonding energy, of small fog droplets. That is hard to do. They suggest that it may be less than the 540 calories per gram of bulk water.
Thus, when an electric arc suddenly transforms bulk water into tiny droplets, the difference between the bonding energies of the two different forms of water must be released. That could account for the excess energy in the water explosions. This energy creates the repulsive forces between the droplets, causing the explosion. The arc itself produces the drops but lacks the energy to set up the forces.
Peter Graneau notes that small clusters of matter often have quite different properties than do their bulk forms. He says, also, that their experiments provide strong - albeit not yet conclusive - support for their latent heat hypothesis. The Graneaus report the details of their theory and early results in their newly published treatise on electrodynamics, "Newtonian Electrodynamics," (World Scientific Publishing Co. Singapore and River Edge, N.J.) Peter Graneau plans to give more details this June at the fourth World Renewable Energy Congress in Denver.
Meanwhile, he says, experiments are under way to find ways to convert the energy of water explosions to electricity. If this proves practical, it could be a powerful way to use the solar energy which constantly recycles water between its liquid and vapor phases on our planet.