In mid-2015 a Brazilian public servant named Ricardo Azevedo became briefly famous around the world. Working with his son Gabriel in São Paulo, he had built a prototype called the T Power H2O, a motorcycle he said could travel about 500 kilometres (310 miles) on a single litre of water. A video showed him drinking from a bottle, pouring the rest into the tank and then topping it up with polluted water from the Tietê River. Headlines did the rest.

Ricardo Azevedo working beside his T Power H2O motorcycle prototype in 2015
Ricardo Azevedo working beside the motorcycle featured in the 2015 report.

How the T Power H2O was said to work

According to the reports first published by Brazil's UOL in June 2015 and then repeated by outlets such as Oddity Central and Visordown, the bike carried an external car battery. Electricity from the battery split water into hydrogen and oxygen, and the hydrogen was then burned in the motorcycle's engine. Azevedo said the exhaust was simply water vapour.

The family made several further claims:

  • about 10 hours of running time on a litre of water;
  • chemical additives, tested over six months, that Gabriel Azevedo said made the electrolysis 350% more efficient;
  • a recovery system similar to the KERS used in Formula 1 that recharged the battery while riding, extending its life without removing the need for eventual recharging;
  • an original engine able to burn hydrogen without modification, a view supported in the reports by a University of São Paulo chemistry professor, Ernesto Gonzalez.

Azevedo also offered to take the bike to an official Honda dealer for testing. No independent test results were published.

Why water cannot be a fuel

The key detail is that battery. Water is what you get when hydrogen burns: it is, in effect, the ash of a fire that has already happened. To get hydrogen back out of it, you have to put energy in. The US Department of Energy describes electrolysis exactly this way: an electrolyser uses electricity to split water into hydrogen and oxygen across an anode and a cathode separated by an electrolyte.

When that hydrogen is burned again, it releases at most the same energy that went into splitting the water. The first law of thermodynamics says nothing extra can appear; the second law says some is always lost as heat along the way. In a system like the T Power H2O, the energy that turns the wheels starts in the battery. The water is a carrier that is split and remade, and a litre of it carries no energy of its own.

That is why the headline figure of "500 km per litre" tells you little. The useful number would be how much electrical energy the battery delivered over a measured distance, with the battery's charge checked before and after. Additives can change how easily water conducts electricity, but they cannot change the energy needed to break its chemical bonds.

A long history of water-powered vehicle claims

Azevedo's bike joined a long line of water-fuelled vehicles that made news without reaching the road:

  • Charles Garrett, 1935: reportedly ran a car for several minutes with an "electrolytic carburettor".
  • Stanley Meyer, 1980s–1990s: claimed a "water fuel cell" that ran a dune buggy. An Ohio court found him guilty of fraud in 1996.
  • Genepax, 2008: a Japanese company showed a car said to run on water and air; critics pointed to a metal hydride as the real energy source, and the company closed its website in early 2009.
  • "HHO" kits: sold online for years with promises of big fuel savings. Asked whether such devices improve mileage, a spokesman for the US motoring association AAA answered bluntly: "they don't".

There is also a legitimate idea behind some of these stories. "Hydrogen on demand" systems react water with metals such as aluminium or magnesium to release hydrogen. Here the energy comes from the metal, which is used up and has to be replaced, and refining that metal takes more energy than the reaction gives back.

Where hydrogen really fits in transport

Hydrogen is a serious energy carrier. It can be produced by electrolysis in large central plants or small distributed units, and the DOE notes that its environmental value depends on where the electricity comes from: renewable or nuclear power gives low-carbon hydrogen, fossil-fuelled grids do not. High-temperature solid oxide electrolysers can even use waste heat to reduce the electricity needed.

The hydrogen vehicles on sale today, such as fuel-cell cars, fill up with hydrogen produced elsewhere and stored under pressure. They are honest about where their energy comes from. For other transport ideas that drew big headlines, read about the Route 66 solar-road proposal and the Volkswagen ID. Buzz feature.

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