1.   Two sources, side by side, emit water into the uniform flow in a water channel.

2.   Fuel-cell-powered vehicles, ideally, emit only water.

3.   Promoters say fuel cells create no polluting particles or gases, and emit only water as exhaust.

4.   Fuel cells produce electricity through a reaction between hydrogen and oxygen, and emit only water.

5.   The fuel cell emits only water as a byproduct of the electro-chemical reaction.

6.   They emit only water and heat as exhaust and have become the focal point of research in an industry seeking cleaner alternatives to the internal-combustion engine.