It is powered by a hydrogen fuel-cell engine, which converts hydrogen gas into energy.

NPR: On the Road with GM's Newest Hydrogen Car

The technology isn't new-a patent for a hydrogen internal combustion engine was issued in 1928, and a 20hp fuel-cell tractor was demonstrated in the late 1950s.

FORBES: Magazine Article

Hundreds of millions of dollars were invested in hydrogen-engine experiments. gm and Ford argued about which would have the greatest increases in fuel mileage.

FORBES: Magazine Article