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Dacia at the Science Media Centre sent me this article regarding hydrogen-on-demand systems. Supposedly by attaching one of these systems to your car the hydrogen produced causes your car to run with greater fuel efficiency.

However, I suspect that the apparent fuel efficiency is most likely due to wishful thinking as the science just doesn’t measure up.

Claims of efficiency are based on the idea that these systems produce hydrogen which augments the petrol powering the car, therefore reducing the amount of petrol needed to drive the car. (Even if these devices do work as stated and I have yet to find reliable data that shows they do), they overlook an important fact – in order to produce the hydrogen gas electrical energy is required. The hidden cost of producing this energy (cost of charging the battery) is likely to negate any savings made by suggested reductions in fuel consumption.

With regards to the “test” described in the article – comparing the performance of a specific vehicle against a reported “average fuel consumption” has no value. The only way to test the hydrogen-on-demand system fairly is to use the same car, under the same conditions, first with the system connected and then with it disconnected, and to also take into account the energy provided by the battery (which doesn’t come free as the battery needs to be charged).

It is a pity a scientist or engineer wasn’t consulted for the story, it could have been used as a warning not to let wishful thinking replace thorough testing when it comes to such devices.