NGV ... What is it?

What is natural gas?
Natural gas is a mixture of hydrocarbons found in the ground independently or together with crude oil. Its composition varies (depending on where it is found), but its main component is "Methane"(CH4}. The rest of the gas is made up of varying amounts of other gases like ethane, propane, butane, and heavier hydrocarbons, plus Carbon Dioxide, Nitrogen, water and traces of other substances. Natural gas is a by product of decaying vegetable matter in underground strata. Natural gas is the cleanest burning fossil fuel; it can help improve the quality of air and water; especially when used in place of other; more polluting energy sources.

Malaysia is blessed with abundant natural gas reserves. At 82.5 trillion cubic feet, these reserves are two times the amount of oil, thus there is opportunity to promote and diversify the use of the natural gas not just as a power source in the industrial and utilities sector; but also as an alternative fuel for vehicles. PETRONAS, through its wholly, owned subsidiary, PETRONAS NGV Sdn Bhd , have been making NGV available to Malaysian motorists through its expanding chain of NGV outlets in the Klang Valley and other major urban areas in the country.

What is NGV?
Natural gas can make a significant contribution towards improved air quality in the transportation industry. Natural gas used in vehicles as fuel is commonly known as Natural Gas for Vehicles or NGV There are three types of natural gas vehicles available.

Bi-Fuel NGV Vehicles
Bi-fuel vehicles are vehicles equipped with two fuel systems i.e. one for petrol and one for NGV of which only one is used at anyone time. Most natural gas bi-fuel vehicles are produced by converting petrol (spark ignition engine) vehicles. In this process, an NGV kit is retrofitted as an addition to the existing petrol system. It is a relatively simple operation and can be done within one day by a certified installer.

Dual-Fuel NGV Vehicles
Diesel vehicles cannot be converted to natural gas bi-fuel operation, but it can be converted to dual-fuel operation or converted to 100% dedicated (monogas) natural gas engine. Converting from diesel to dedicated natural gas operation requires major modifications such as adding spark plugs and altering the compression ratio. These changes preclude the engine from running on diesel fuel. In dual-fuel vehicles, two fuel systems are fitted. The difference with bi-fuel vehicles is that in a dual-fuel vehicle both fuel are used simultaneously instead of one at a time. The dual-fuel system is to convert diesel (compression ignition) vehicle to run on a mixture of NGV and diesel. The diesel fuel is used as a pilot ignition to initiate combustion of the NGV in the engine combustion chambers.

Monogas (Dedicated) NGV Vehicles
When a vehicle is designed by the manufacturers to only use natural gas as fuel, the resulting chassis and engine units are better optimized for NGV than is the case for a converted vehicle. The engine will be able to achieve minimal exhaust emissions, low fuel consumption and adequate mechanical power.

In Malaysia, there are about 8,000 natural gas vehicles currently on the road mainly in the Klang Valley and Johor Bahru. Of this, retrofitted bi-fuel vehicles dominate the natural gas vehicle population in Malaysia with majority of the users being city taxis. The number of monogas vehicles available from original equipment manufacturers is still quite small. Transit buses and some other heavy-duty vehicles make up the greater portion of natural gas vehicles produced by the manufacturers. Until manufacturers build more natural gas vehicles on their assembly lines, most will be in the form of conventional vehicles that have been retrofitted with an NGV kit.

How does a Hi-Fuel vehicle operate?
Natural gas is compressed at the refueling station and dispensed into the vehicle through the natural gas filling valve. It then flows into the NGV cylinder located in the boot of the vehicle. When natural gas is selected, gas from the NGV cylinder goes through the NGV supply line and into the regulator. The regulator reduces the gas storage pressure from up to 3,000 pounds per square inch (psi) to approximately atmospheric pressure.

Next the gas goes through the NGV solenoid valve and into the mixer or fuel injectors. Natural gas mixed with air will then flow through the carburetor or fuel injection system and enters the engines combustion chambers. When petrol is selected, the NGV solenoid valve will shut off the NGV system enabling the vehicle to run on petrol. The diagram below shows the various components for the conversion of a petrol car to bi-fuel operation.