In the simplest terms, a fuel cell combines hydrogen and oxygen in a process that releases electricity, heat and water.

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Fuel cell electric vehicles generate their power from hydrogen and oxygen, and emit only water.

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"If you turn the experiment around and put the hydrogen and oxygen in and take the electricity off, you have a fuel cell, " Roan said.

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The fuel cell, which has been around for 50 years, generates electricity from hydrogen and oxygen.

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