Natural Gas Vehicles
Natural gas powers more than 150,000 vehicles in the United States and roughly 15.2 million vehicles worldwide. Natural gas vehicles (NGVs) are good choices for high-mileage, centrally fueled fleets. Compressed natural gas (CNG) tanks and safety are improving, and in many cases CNG can provide adequate range for the required vehicle application. For vehicles needing to travel long distances, liquefied natural gas (LNG) is a good choice. The advantages of natural gas as a transportation fuel include its domestic availability, widespread distribution infrastructure, and reduced greenhouse gas emissions compared to conventional gasoline and diesel fuels.
CNG and LNG are considered alternative fuels under the Energy Policy Act of 1992. The horsepower, acceleration, and cruise speed of NGVs are comparable with those of equivalent conventional vehicles. Also, compared with conventional diesel and gasoline vehicles, NGVs offer other air-quality benefits.
There are light-, medium-, and heavy-duty natural gas vehicles available from original equipment manufacturers, as well as medium- and heavy-duty vehicle options available through qualified system retrofitters. Qualified system retrofitters can also economically, safely, and reliably convert many vehicles for natural gas operation with aftermarket conversion systems.
Types of Natural Gas Vehicles
There are three types of NGVs:
- Dedicated: These vehicles are designed to run only on natural gas.
- Bi-fuel: These vehicles have two separate fueling systems that enable them to run on either natural gas or gasoline.
- Dual-fuel: These vehicles are traditionally limited to heavy-duty applications, have fuel systems that run on natural gas, and use diesel fuel for ignition assistance.
Light-duty vehicles are typically equipped with dedicated or bi-fuel systems, while heavy-duty vehicles use dedicated or dual-fuel systems. CNG vehicles, store natural gas in tanks and it remains in the gaseous state. More fuel can be stored onboard a vehicle using LNG because the fuel is stored as a liquid, therefore making its energy density greater than CNG. This makes LNG well-suited for Class 7 and 8 trucks requiring a greater range. Often, the fuel choice is determined by factors such as vehicle application needs and the required driving range.
The driving range of NGVs is generally less than that of comparable conventional vehicles because of the lower energy density of natural gas. Extra storage tanks can increase range, but the additional weight may displace cargo capacity.