Stan Meyer's Water Powered Dune Buggy
The water fuel cell is a device invented by American Stanley Meyer, which he claimed could convert water into its component elements, hydrogen and oxygen, using less energy than can be obtained by the subsequent combustion of those elements, a process that results the reconstitution of the water molecules. Thus, if the device operated as claimed, the combustion cycle would start and end in the same state while extracting usable energy, thereby violating the first law of thermodynamics and allowing operation as a perpetual motion machine. Meyer's claims about the Water Fuel Cell and the car that it powered were found to be fraudulent by an Ohio court in 1996.[1]
Similar devices have been promoted by others (see Water-fuelled car): there is no evidence that any of these devices operate as claimed.
Links
http://www.waterpoweredcar.com/stanmeyer.html
Stan Meyer with the original Water Fuel Cell, which he successfully demonstrated to the USPTO, in his Sec. 101 hearing, which resulted in the issuance of U.S. Patent 4,936,961, a fundamental "Methods" patent on the process. This patent, along with another on the device architecture, both expire on June 26th of 2007. As a result, this technology falls into the public domain, forever.