Size and Weight

• Since hydrogen has the lightest atomic mass of any element, it has advantages and disadvantages compared to gasoline. Hydrogen stores 2.6 times the energy per unit mass then gasoline; however it needs four times the volume. For example, a 15-gallon tank holds 90 lbs. of gasoline while a hydrogen tank would hold 60 gallons and weigh approximately 35 lbs.
  
  

Function

• Typical hydrogen fueled vehicles have a hydrogen tank to store hydrogen, fuel cells that convert hydrogen and oxygen into electricity, a battery to store electricity and an electric motor. This design is meant to propel the vehicle more efficiently than an internal combustion gasoline engine. Furthermore, hydrogen fueled cars release only water, whereas gasoline releases water, carbon dioxide and pollutants.
  
  

Benefits

• According to the U.S. Department of Energy, the 2011 fuel cell powered Honda FCX Clarity averages around 60 miles per kilogram (roughly 1 gallon). Although this car is not available for sale in the United States, small fleets are being released for evaluation.