From the platform it looked like any other British commuter train. But as several hundred passengers climbed on board the steel-bodied carriages at Long Marston, they were met with an unusual sight. In one of its cars, passengers were encouraged to perch around four hydrogen fuel tanks, a fuel cell and two lithium batteries.

The train’s hydrogen power system produces sufficient power to take the train 50 to 75 miles. The train, called Hydroflex, is the UK’s first to be powered by hydrogen. It was being shown off to the public in June 2019 for the first time on the tracks at the Quinton Rail Technology Centre, a test facility at Long Marston, near Stratford-upon-Avon, in England.

Engineers who developed the new train, from the University of Birmingham and British rail company Porterbrook, wanted passengers to sit alongside the train’s hydrogen fuel cells. The sooner they would become familiar with the technology, the sooner they would feel safe, they reasoned.

Some apprehension around hydrogen as a fuel source is perhaps understandable considering the unfortunate history of hydrogen-filled dirigibles, namely airships such as the ill-fated British R101 and the German Hindenburg. But hydrogen-powered trains have been emerging as a viable – and much safer – means of transport. How close are we to fleets of trains that release only water as a waste product?

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The way hydrogen powers a train like the Hydroflex is quite simple. The fuel cell is made up of an anode, a cathode and an electrolyte membrane. The stored hydrogen passes through the anode, where it is split into electrons and protons. The electrons are then forced through a circuit that generates an electric charge that can be stored in lithium batteries or sent directly to the train’s electric motor. The leftover part of the hydrogen molecule reacts with oxygen at the cathode and becomes the waste product – water.

The Hydroflex’s hydrogen tanks, fuel cell and batteries currently sit inside a passenger car, but the ultimate plan is to store them underneath the train in order to fit in more passengers. Hydrogen is of course extremely flammable, but on the Hydroflex it is stored in four secured high-pressure tanks, one of a range of measures to ensure passengers’ safety.