MUNICH, GERMANY – The BMW Hydrogen 7 is one of only 20 hydrogen-powered cars in the world. The car runs on a dual-fuel system and can process both regular gasoline and hydrogen. A button on the steering wheel allows a driver to choose, or the engine switches automatically when one tank is empty, according to

The engineering process involved adapting the regular 760Li’s 12-cylinder engine to work with both fuel sources and to make room in the car for the hydrogen tank, which holds 17.5 lbs of liquid hydrogen. The tank sits in the trunk, halving the luggage space of a regular 7 Series.

Five sensors are distributed throughout the car to detect escaping hydrogen. If that happens, the windows automatically open in order to let the gas out into the atmosphere, and the fuel supply is cut.