A Natural gas vehicle or NGV is a alternative fuel vehicle that uses compressed natural gas (CNG) or, less commonly, liquefied natural gas (LNG) as a clean alternative to other automobile fuels. Worldwide, there are roughly 8 million NGVs as of 2008, with the largest number of NGVs in Argentina, Brazil, Iran, and Pakistan, with South America taking a global market share of 48%. The US has some 120,000, mostly buses. In OECD countries there are around 500,000 CNG vehicles, and they are popular in Germany and Italy.
NGV's can be refueled anywhere from existing natural gas lines. This makes home refuelling stations that tap into such lines possible. A company called FuelMaker has pioneered such a system known as "Phill", which they have developed in partnership with Honda.
Existing gasoline-powered vehicles may be converted to CNG. An increasing number of vehicles worldwide are being manufactured to run on CNG. GM do Brasil introduced the MultiPower engine in August 2004 which was capable of using CNG, alcohol and gasoline as fuel, and was used in the Chevrolet Astra, aimed at the taxi market. In 2006 the Brazilian subsidiary of FIAT introduced the Fiat Siena Tetra fuel, a four-fuel car developed under Magneti Marelli of Fiat Brazil. This automobile can run on 100% ethanol (Common ethanol fuel mixtures#E100), Common ethanol fuel mixtures#E20, E25 blend (Brazil's mandated gasoline blend), pure gasoline (not available in Brazil), and GNV.
Although a localized problem, NGV refill stations can be scarce in some places, with taxi drivers waiting in long queues to refill. This has led to suggestions that taxis should have their own options for fueling at taxi ranks - a model being tested in Casablanca, Morocco. Here, taxi drivers 'belong' to a base station where they operate from and have priority fuel rights including an account card.
The primary component of natural gas is methane (CH4), the shortest and lightest hydrocarbon molecule. It may also contain heavier gaseous hydrocarbons such as ethane (C2H6), propane (C3H8) and butane (C4H10), as well as other gases, in varying amounts. Hydrogen sulfide (H2S) is a common contaminant, which must be removed prior to most uses.
LNG (Liquefied Natural Gas) storage pressures are typically at or just above the local atmospheric pressure (0 to 30 lbf/in², or 0 to 2.1 bar). LNG is stored at temperatures as low as -260°F (-162°C). At these temperature and pressure conditions, natural gas is in a liquid state. Storage temperatures may vary due to varying composition and storage pressure. LNG is far denser than even the highly compressed state of CNG. As a consequence of the low temperatures, vacuum insulated storage tanks are used to hold LNG. These tanks are often referred to as dewars to credit the early cryogenic scientist Sir James Dewar.
Argentina has some 1.69 million NGV's as of 2008, with 1767 refuelling stations across the nation, or 15% of all vehicles. By July 2008 there were 1.56 million retrofitted vehicles in Brazil, or about 5% of the total light vehicle fleet, with 1585 refuelling stations, and a higher concentration in the cities of Rio de Janeiro and São Paulo.
Bolivia has increased its fleet from 30,000 in 2004 to 90,163 units in April 2008, Colombia has an NGV fleet of 257,468 vehicles, and 378 refueling stations as of June 2008. Peru has 41,411 NGV as of July 2008, but that number is expected to skyrocket as Peru sits on South America's largest gas reserves.
In 2006 the Brazilian subsidiary of FIAT introduced the Fiat Siena Tetra fuel, a four-fuel car developed under Magneti Marelli of Fiat Brazil. This automobile can run on 100% ethanol (Common ethanol fuel mixtures#E100), Common ethanol fuel mixtures#E20, E25 blend (Brazil's normal ethanol gasoline blend), pure gasoline (not available in Brazil), and natural gas, and switches from the gasoline-ethanol blend to CNG automatically, depending on the power required by road conditions.
Since 2003 and with the commercial success of flex cars in Brazil, another existing option is to retrofit an ethanol flexible-fuel vehicle to add a natural gas tank and the corresponding injection system. Some taxicabs in São Paulo and Rio de Janeiro, Brazil, run on this option, allowing the user to choose among three fuels (E25, E100 and CNG) according to current market prices at the pump. Vehicles with this adaptation are known in Brazil as tri-fuel cars.
In Malaysia, the use of compressed natural gas was originally introduced for taxicabs and airport limousines during the late-1990s, when new taxis were launched with CNG engines while taxicab operators were encouraged to send in existing taxis for full engine conversions, reducing their costs of operation. Any vehicle converted to use CNG is labelled with white rhombus "NGV" (Natural Gas Vehicle) tags, lending to the common use of "NGV" when referring to road vehicles with CNG engine. The practice of using CNG remained largely confined to taxicabs predominantly in the Klang Valley due to a lack of interest. No incentives were offered for those besides taxicab owners to use CNG engines, while government subsidies on petrol and diesel made conventional road vehicles cheaper to use in the eyes of the consumers. Petronas, Malaysia's state-owned oil company, also monopolises the provision of CNG to road users. As of July 2008, Petronas only operates about 150 CNG refueling stations, most of which are concentrated in the Klang Valley. At the same time, another 50 was expected by the end of 2008.
As fuel subsidies were gradually removed in Malaysia starting June 5, 2008, the subsequent 41% price hike on petrol and diesel led to a 500% increase in the number of new CNG tanks installed. National car maker Proton considered fitting its Waja, Saga and Persona models with CNG kits from Prins Autogassystemen by the end of 2008, while a local distributor of locally assembled Hyundai cars offers new models with CNG kits. Conversion centres, which also benefited from the rush for lower running costs, also perform partial conversions to existing road vehicles, allowing them to run on both petrol or diesel and CNG with a cost varying between RM3,500 to RM5,000 for passenger cars.
There were about 400 CNG-fueled vehicles in Singapore in mid-2007, of which about 110 are taxis operated by Smart Automobile. By February 2008, the number has risen 520 CNG vehicles, of which about half are taxies. All vehicles had to refuel at the sole CNG station operated by Sembcorp Gas and located on Jurong Island until the opening of the first publicly accessible CNG station at Mandai in 2008, operated by Smart Automobile. The company plans to build another four stations by 2011, by which time the company projects to operated 3,000 to 4,000 CNG taxies, and with 10,000 CNG public and commercial vehicles of other types on Singapore's roads. Sembcorp Gas opened its second CNG station a week after the Mandai station at Jalan Buroh.
Thailand has for over a decade run natural gas taxi cabs in Bangkok. However, conversion in earnest has begun since oil prices have risen, and now thousands of private automobiles and public buses have converted. Natural gas vehicles in Thailand have reached 98,000 in 2008.