Transportation accounts for more than a quarter of total global energy consumption. For fuelling road transportation there has been much speculation about the use of hydrogen as an energy carrier, which proponents claim would usher in the “Hydrogen Economy”. The concept of the “complete energy conversion chain” has been used to compare the overall energy consumption and CO2 emissions from vehicles powered by hydrogen fuel cells with those from vehicles using a battery and electric drive. The analysis shows that if a sustainable source of electricity is used to produce hydrogen, then the hydrogen and fuel cell system is just equivalent to a battery. The efficiency of these two different approaches has been compared, and shows that the hydrogen system would consume nearly three times the primary energy required by a battery storage system. Conventional batteries do not, however, have a sufficiently high energy storage density to provide the range needed for most drivers. A new generation of plug-in hybrid vehicles is being developed which take advantage of the best attributes of both electric vehicles and conventional fossilfuelled vehicles. These vehicles show promise to dramatically reduce the quantity of greenhouse gases produced each year by the transportation sector.

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