Compressed natural gas
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Compressed Natural Gas (CNG) is a substitute for gasoline (petrol) or diesel fuel. It is considered to be an environmentally "clean" alternative to those fuels. It is made by compressing purified natural gas, and is typically stored and distributed in hard containers.
Argentina and Brazil, in the Southern Cone of Latin America, are the two countries with the largest fleets of CNG vehicles. Conversion has been facilitated by a substantial price differential with liquid fuels, locally-produced conversion equipment and a growing CNG-delivery infrastructure. A 'Blue-network' of CNG stations is being developed on the major highways of the Southern Cone (including Chile and Bolivia) to allow for long-haul transportation fuelled by CNG.
In response to high fuel prices and environmental concerns, compressed natural gas is starting to be used in light-duty passenger vehicles and pickup trucks, medium-duty delivery trucks, and in transit and school buses.
CNG has grown into one of the major fuel sources used in car engines in Pakistan, Bangladesh and India. The use of CNG is mandated for the public transport system of New Delhi, India's capital city. The Delhi Transport Corporation operates the world's largest fleet of CNG buses. The government of Punjab, Pakistan, the most populous province of that country, has mandated that all public-transport vehicles will use CNG by 2007. Pakistan is the largest user of CNG in Asia, and third largest in the world. As of 2005, Pakistan has the third-largest number of natural gas vehicles, according to the [International Association for Natural Gas Vehicles].
During the 1970s and 1980s, CNG was commonly used in New Zealand in the wake of the oil crises, but fell into decline after petrol prices receded.
Brisbane Transport and Transperth in Australia have both adopted a policy of only purchasing CNG buses in future; the former purchasing 216 Scania L94UB and 180 MAN 18.310 models, with the latter purchasing 451 Mercedes-Benz OC500LE buses, including 58 articulated buses. Brisbane Transport has also ordered up to 30 articulated CNG buses on either a MAN or Scania chassis, the successful tendering company yet to be determined.
CNG buses are not completely compatible with existing transport infrastructure; the MBTA in Massachusetts, for instance, does not permit its CNG buses to enter its underground bus tunnels or enclosed stations. (See the "No CNG buses" sign in this [image.])
CNG is often measured and sold in Gasoline Gallon Equivalent GGE to help American consumers when comparing to gasoline.
In emerging countries, the cost of financing a conversion may represent a significant barrier, thus requiring promotional schemes by the government or private sector. A scheme allowing the owner to recover up to 60% of the conversion cost through 'free-CNG' vouchers was implemented in the city of Santa Cruz, Bolivia, duplicating the total number of CNG vehicles in less than one year.
Technology
CNG can be used in Otto (gasoline) and Diesel cycle engines.
CNG may be refueled from low-pressure or high-pressure systems. The difference lies in the cost of the station vs. the refueling time. There are also some implementations to refuel out of a residential gas line during the night.
A new CNG tank design utilizes aluminum sheets with fiberglass enforcements. Since CNG is lighter than air, leakages should not be risky if enough air exchange is provided. If the gas ignites, a metal or ceramic mesh prevents the gas tank from exploding.
External links
- [International Natural Gas Vehicle Statistics]
- [News and information provided by the International Association for Natural Gas Vehicles]News and information provided by the International Association for Natural Gas Vehicles
- [Alternative Fuel Vehicle Training] From the National Alternative Fuels Training Consortium.
- [European Natural Gas Vehicle Association]
See also
- Liquefied natural gas (LNG)
- Compressed Gas Association (Compressed Gas Association)
External pages
[Info about Sustainable green fleets]
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