11.   It would run on fuel cells, a promising technology that uses hydrogen to generate electricity to power motors without producing emissions.

12.   Later, liquid hydrogen will be used to improve the range.

13.   Often, the cells use hydrogen to produce electricity, a relatively clean process.

14.   Recent research demonstrates that the shape of the combustion chamber in a rotary engine is particularly well suited to using pure hydrogen as a fuel.

15.   Several other inventors have won patents using hydrogen to power small engines.

16.   The fuel cells use this hydrogen to produce the electricity that runs the vehicle.

17.   The hydrogen is used to start the process over again by pumping more carbon dioxide out of the atmosphere.

18.   BMW has introduced cars with fuel cells that power air conditioning and electrical equipment using hydrogen extracted from gasoline.

19.   Fuel cells using pure hydrogen creates only water vapor as an exhaust gas, but several technological challenges remain before they can be mass-produced.

20.   General Motors unveiled a fuel cell generator in August that could provide electricity for an average-size home using hydrogen extracted from natural gas, methane or gasoline.