Hydrogen fuel cells are a greener way to power vehicles. But they have also been cost-prohibitive. Now that's starting to change - last week, German passengers boarded the world's first hydrogen-powered trains.
"Sure, buying a hydrogen train is somewhat more expensive than a diesel train," said Stefan Schrank, a project manager at locomotive company Alstom, which built the trains, in an interview with Agence France-Presse, "but it is cheaper to run."
Chemistry recap: Hydrogen fuel cells generate electricity by combining hydrogen with oxygen, and their only byproduct is water. That makes the cells a promising energy source that produces zero emissions and very little noise.
Though they remain pricey, hydrogen fuel cells have advantages over batteries.
Instead of recharging, for instance, you can just refuel them like you would a gas or diesel engine. And because train schedules are highly predictable, it's easier to build refueling infrastructure.
Trains are much heavier, though, so powering them with hydrogen instead of diesel could do much more to cut carbon emissions.
If all goes well with these first two trains, Alstom hopes to add another 12 to its Lower Saxony fleet. So while they might be the world's first hydrogen-powered trains, they're unlikely to be the last.