Natural Gas for Vehicles (NGV) or Compressed Natural Gas (CNG) is an automotive fuel derived from the compression of natural gas, the bulk of which is methane, to about 3,000 pounds/square inch (psi) and storage in containers of extreme strength and durability, including steel. NGV serves as an alternative automotive fuel to gasoline or diesel thanks to its cheaper prices and remarkable safety: NGV is lighter than air, so it rapidly dissipates upward.
Today biogas is derived from fermented waste or surplus, including agricultural produce, pig droppings, or cow dung. With their quality improvement and pressurization to resemble NGV in properties, they can also be used in vehicles, collectively called Compressed Bio-Methane Gas (CBG).
Properties
- Gaseous. Today natural gas can be liquefied by lowering its temperature to minus 160 Celsius, upon which the volume will shrink 600 times, thus enabling marine transport
- Colorless and no smell
- Lighter than air, with 0.6-0.8 specific gravity, thus tending to flow upward and rapidly dissipate
- Flammability limit at 5-15% of atmospheric volume and 537-540 Celsius in ignition temperature
- Completely clean-burning, leaving no soot, together with less nitrogen oxides and sulfur dioxide than other fuels.
Quality
Under its latest announcement on NGV quality specifications, effective since May 8, 2018, the Department of Energy Business (DOEB) specified:
- Regular NGV for vehicles with a Wobbe Index (WI) of 39-44 megajoules/cubic meter (MJ/m3); this NGV has evolved from that of the old days and is on sale at every NGV station
- NGV Plus for vehicles with a WI of 44-52 MJ/m3; this NGV improves driving performance through superior acceleration rates, distances traveled, and fuel consumption. Today NGV Plus is on sale at the following PTT NGV stations: Pannee Power in Pathum Thani, Sooksomkiat Transport (2004) in Sara Buri, and PTT Nam Phong in Khon Kaen. PTT has planned more such stations to fill more service areas.
Note: Investigations have shown that, with proper tune-ups, NGV-fueled vehicles consume 3% less NGV for each MJ/m3 rise in WI