gen know: fuel

Compressed natural gas

Compressed natural gas vehicles require a greater amount of space for fuel storage than conventional gasoline powered vehicles. Since it is a compressed gas, rather than a liquid like gasoline, CNG takes up more space for each gasoline gallon equivalent (GGE). Therefore, the tanks used to store the CNG usually take up additional space in the trunk of a car or bed of a pickup truck which runs on CNG. This problem is solved in factory-built CNG vehicles that install the tanks under the body of the vehicle, leaving the trunk free (e.g. Fiat Multipla, New Fiat Panda, Volkswagen Touran Ecofuel,Volkswagen Caddy Ecofuel, Chevy Taxi - which sold in countries such as Peru). Another option is installation on roof (typical on buses), requiring, however, solution of structural strength issues. CNG-powered vehicles are considered to be safer than gasoline-powered vehicles.^[11]^[12]^[13]

[edit]Codes and Standards

The lack of harmonized codes and standards across international jurisdictions is an additional barrier to NGV market penetration.^[14] The International Organization for Standards has an active technical committee working on a standard for natural gas fuelling stations for vehicles.^[15]

Despite the lack of harmonized international codes, Natural Gas vehicles have an excellent global safety record. Existing international standards include ISO 14469-2:2007 which applies to compressed natural gas (CNG) vehicle nozzles and receptacle^[16] and ISO 15500-9:2012 specifies tests and requirements for the pressure regulator^[17]

NFPA-52 covers natural gas vehicle safety standards in the US.

[edit]CNG compared to LNG

Compressed Natural Gas is often confused with liquefied natural gas (LNG). While both are stored forms of natural gas, the key difference is that CNG is gas that is stored (as a gas) at high pressure, while LNG is stored at very low temperature, becoming liquid in the process. CNG has a lower cost of production and storage compared to LNG as it does not require an expensive cooling process and cryogenic tanks. CNG requires a much larger volume to store the same mass of gasoline or petrol and the use of very high pressures (3000 to 4000 psi, or 205 to 275 bar). As a consequence of this, LNG is often used for transporting natural gas over large distances, in ships, trains or pipelines, and the gas is then converted into CNG before distribution to the end user.

CNG can also be confused with LPG, which is liquified propane. Unlike natural gas (mostly methane), propane can be compressed to a liquid without continual refrigeration. LPG is commonly used to fuel vehicles in Australia.

CNG can be stored at lower pressure in a form known as an ANG (Adsorbed Natural Gas) tank, at 35 bar (500 psi, the pressure of gas in natural gas pipelines) in various sponge like materials, such as activated carbon^[18] and metal-organic frameworks (MOFs).^[19] The fuel is stored at similar or greater energy density than CNG. This means that vehicles can be refuelled from the natural gas network without extra gas compression, the fuel tanks can be slimmed down and made of lighter, weaker materials.

Iran, Pakistan, Argentina, Brazil and India have the highest number of CNG run vehicles in the world.^[5]