This week it unveiled a prototype version of its 7-Series saloon car that has a hydrogen-powered engine.

ECONOMIST: Hydrogen-powered cars

It's powered by a hydrogen internal combustion engine that turns a 44-kilowatt electric generator that runs eight propellers and whatever communications equipment is loaded on board.

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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