The Best Ways to Use Renewable Energy

Hydrogen Fuel Cells (8/13)

Water vapor is emitted from a hydrogen-powered fuel cell bus in central London in January 2004. London is one of several cities to experiment with zero-emissions hydrogen fuel cell buses.

Hydrogen, the world's most abundant element has high energy content and low pollution. The typical byproduct of hydrogen fuel cells is water. Many companies experiment with such technology, but widespread application could be years or even decades away. (Photo: Reuters)