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In page Fossil fuel phase-out:

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The use of hydrogen fuel is another alternative under development in various countries, alongside, hydrogen vehicles[1] though hydrogen is actually an energy storage medium, not a primary energy source, and consequently the use of a non-petroleum source would be required to extract the hydrogen for use. Though hydrogen is currently outperformed in terms of cost and efficiency by battery powered vehicles[2][citation needed], there are applications where it would come in useful. Short haul ferries and very cold climates are two examples. Hydrogen fuel cells are about a third as efficient as batteries and double the efficiency of petrol vehicles.