Natural gas powers about 116,000 vehicles in the United States and roughly 14.8 million vehicles worldwide as of 2010. There are two types of natural gas used for transportation fuel: compressed natural gas (CNG) and liquefied natural gas (LNG). Because it is a liquid, the energy density of LNG is greater than for CNG, so more fuel can be stored onboard the vehicle. This makes LNG well-suited for large trucks requiring a greater range. The gaseous form, CNG, is a good choice for high-mileage, centrally fueled fleets that operate within a limited area.
The driving range of natural gas vehicles (NGVs) generally is less than that of comparable gasoline- and diesel-fueled vehicles because of the lower energy content of natural gas. Extra storage tanks can increase range, but the additional weight may displace payload capacity. NGV horsepower, acceleration, and cruise speed are comparable with those of an equivalent gasoline or diesel vehicle.
Passenger, or light-duty, natural gas vehicles work much like gasoline-powered vehicles with spark-ignited engines. Vehicles can also have a bi-fuel system that can run on either natural gas or gasoline. Some heavy-duty vehicles use spark-ignited natural gas systems, but other systems exist as well. Heavy-duty vehicle engines can also use a dual-fuel system, where the system runs primarily on natural gas and diesel is used for ignition assistance.
The advantages of natural gas as a transportation fuel include its domestic availability, widespread distribution infrastructure, low cost, and inherently clean-burning qualities.
Visit the Alternative Fuels Data Center to learn more about natural gas vehicles.