Most hydrogen cars on the market today are hydrogen-electric hybrids. They combine hydrogen fuel-cell technology with rechargeable batteries. Currently, the spread of hydrogen cars is limited by the number of hydrogen fueling stations that exist.
A gallon of gasoline has roughly the same energy content as a kilogram of hydrogen, but the greater efficiency of fuel cells means that hydrogen cars get two to three times better mileage than gasoline-powered counterparts.
Some companies are offering name-brand car models that have been converted to use hydrogen fuel. Intergalactic Hydrogen, for example, sells converted Hummers, Nissan Frontier pickup trucks and Shelby Cobras.
Honda recently began producing the FCX Clarity, a hydrogen car that gets the equivalent of 74 miles to the gallon without emitting greenhouse gases. As of 2010, the car is only being leased to a handful of customers. A British company, Horizon Fuel Cell Technologies, unveiled a prototype two-seater car that gets the equivalent of 360 miles per gallon. The car is powered by a 6-kilowatt fuel cell that runs four electric motors. It has a range of 240 miles on just one tank of hydrogen weighing 2.2 pounds. As of 2010, it is not yet available to consumers.
