ABSTRACT
Gasoline and diesel are not only very convenient fuels for ground transportation, but also have a high energy density that permits storage in a relatively small volume-an important asset for automobiles. For example, these liquid fuels have a volumetric specic energy content of about 10,000 kWh/m3, compared to hydrogen compressed to 100 bar at about 300 kWh/m3. But known petroleum resources worldwide are being consumed rapidly, and future availability of these resources is bound to decline. At present, more than 97% of the fuel used for ground transportation in the United States is petroleum-based, more than half of it is imported, and the percentage of imported petroleum is continuously increasing. Moreover, the increase in cost of gas and oil has become of growing concern to average citizens, and the emission from current transportation systems is a major component of CO2 pollution that produces global warming.
