Hydrogen generator
Q I’ve seen quite a bit of advertising lately regarding a hydrogen generator for cars, which claims to reduce emissions and fuel consumption. Apparently, it is going to be rolled out across some MOT centres. Your opinion on this subject would be appreciated. Ray Bradford
A With the green emphasis on everything motoring nowadays, these fuel-from-water solutions can seem quite attractive. The point to remember is that current hydrogen vehicles do not run on hydrogen, but use hydrogen to power an electric motor, resulting in the byproduct of water. Although they require refuelling with hydrogen, they are considered electric vehicles. The vehicles which do run on hydrogen using an internal combustion engine do not produce the hydrogen gas on-board.
The concept of running motor vehicles on water goes back to 1935 when Henry ‘Dad’ Garrett of Dallas in the US patented an invention that he claimed substituted water for fuel. Garrett is also credited with inventing the traffic light.
In the May 2009 issue of CM, there was a feature on free fuel from water. Rob Hawkins looked at what was involved in fitting the water boost kit.
The HHO or hydrogen producing units do work, but the amount of energy that is required to generate the hydrogen gas is more than the gas can produce to run the engine and alternator. If this was not the case, then you would effectively have a machine that was self-propelling and would enjoy perpetual motion. A running engine uses around 500 litres of air per minute at 1000rpm. The hydrogen generators available tend to average about 50 litres per hour of HHO, a hydrogen and oxygen mix. While this tiny amount may add a small boost to the engine, the effect will be negative because of the power taken to generate it. Even if the hydrogen generator did work as promised, there is another problem: embrittlement. When hydrogen burns within an internal combustion engine, the cylinder walls and pistons become saturated in hydrogen ions, causing the metal to lose its ductility due to the chemical reaction and resulting in cracks beginning to form.
Having said that, vehicles have been built to run on hydrogen, but this is using the hydrogen as fuel and not trying to produce it by filling up with water. Such vehicles include the 2002 BMW 750hl and the 2007 Hydrogen 7, which was a dual-fuel vehicle. In 1991 and 1993, Mazda produced a Wankel rotary engine which ran on hydrogen, and in 2003, there was the RX-8. These engines have, of course, been specially designed to compensate for the effect of the hydrogen ions.