Natural gas vehicles (NGV) are the vehicles run by alternative fuels such as compressed natural gas. Natural gas engines are suitable for a wide range of applications including aircraft, rail locomotives marine vessels, buses, heavy-duty trucks, light commercial vehicles, sedans and forklifts. According to the 2011 statistics, there are 14.8 million NGVs worldwide and 112,000 vehicles in the United States. There are different types of natural gas vehicles. We will discuss them briefly.

  • Dedicated engines: If the vehicle runs only by the natural gas, it is known as a dedicated vehicle. It can be a re-power engine or new vehicle engine. Normally in both the cases old fuel tank is concern supportive cylinders. This means they want to change for CNG, CNG cylinders are replaced for old cylinders. Sometimes these engines are also referred to as spark ignited. Dedicated engines provide optimum emissions and maximum efficiency.
  • Bi-fuel engines: Bi-fuel or switchable system or bivalent vehicles can run either spark ignited fuel or natural gas. The spark ignited fuels may be gasoline or ethanol. These are available either as an ex-showroom original equipment manufacturer (OEM) vehicle or aftermarket conversion. Generally, bi-fuel vehicles rely on the gasoline for ignition to turn on. These can either run on natural gas or gasoline. If the natural gas tank is empty, most vehicles switch automatically to gasoline.
  • Dual fuel engines: A mixture of diesel and natural gas is used in duel-fuel engines. A diesel pilot ignites the air-gas mixture. While the gas is introduced into the air intake by gas injection or by carburetion, diesel directly gets injected into the combustion chamber. The diesel and the natural gas mixture varies as per the duty cycle and the load of the engine. It can be anywhere from zero percent to eighty percent.

Diesel usage is higher at lower engine loads and gas usage is higher when the load on the engine is higher. These engines are generally conversion of a diesel engine. Therefore, the advantage with them is for fuel supply, we don’t need to completely depend upon natural gas. If the natural gas tank becomes empty and you are away from the source where it is available, you can go with diesel on your vehicle.

  • Tri-fuel engines: Tri-fuel is a recent technological development. These vehicles combine a natural gas vehicle and a flex fuel vehicle. A tri-fuel vehicle can run on natural gas, ethanol or gasoline or both because these vehicle engines use ethanol and gasoline either blended or exclusively.

NGVs are usually run on compressed natural gas (CNG) or liquefied natural gas (LNG). LNG is good for the vehicles that need to travel for long distances. For high mileage, CNG is a good choice.