Natural gas vehicle
A natural gas vehicle utilizes compressed natural gas or liquefied natural gas as an alternative fuel source. Distinguished from autogas vehicles fueled by liquefied petroleum gas, NGVs rely on methane combustion, resulting in cleaner emissions due to the removal of contaminants from the natural gas source.
Conversion of existing gasoline or diesel vehicles to NGVs is feasible, offering both dedicated and bi-fuel options. Heavy-duty vehicles such as trucks and buses can also undergo conversion, utilizing spark ignition systems or hybrid electric motor configurations.
Challenges in NGV adoption include the storage and refueling of natural gas, given its pressurized or liquefied state. While advancements in compression and liquefaction mitigate energy density differences, trade-offs regarding storage container size, complexity, and weight continue to affect vehicle range. Despite these challenges, the safety and cost advantages of methane over hydrogen fuel contribute to its viability.
Obstacles to widespread NGV adoption for private vehicles include concerns over additional weight, technological unfamiliarity, and limited refueling infrastructure in some regions. Nevertheless, global NGV numbers reached nearly 28 million by 2019, with significant market presence in countries such as China, Iran, India, Pakistan, Argentina, Brazil, and Italy.
Advantages
CNG may be generated and used for bulk storage and pipeline transport of renewable energy and also be mixed with biomethane, itself derived from biogas from landfills or anaerobic digestion. This enables the use of CNG in mobility, resulting in significantly lower carbon emissions compared to regular diesel-powered vehicles It would also allow the continued use of CNG vehicles currently powered by non-renewable fossil fuels so that those vehicles do not become obsolete if stricter emissions regulations are mandated to combat climate change.A key advantage of using natural gas is the existence, in principle, of most of the infrastructure and supply chain, which is non-interchangeable with hydrogen. Methane today mostly comes from non-renewable sources but can be supplied or produced from renewable sources, offering net carbon-neutral mobility. In many markets, especially the Americas, natural gas may trade at a discount to other fossil fuel products such as petrol, diesel or coal, or indeed be a less valuable by-product associated with their production that has to be disposed of. Many countries also provide tax incentives for natural gas-powered vehicles due to the environmental benefits to society. Lower operating costs and government incentives to reduce pollution from heavy vehicles in urban areas have driven the adoption of NGV for commercial and public uses, i.e. trucks and buses.
Challenges
Despite its advantages, the use of natural gas vehicles faces several limitations, including fuel storage and infrastructure available for delivery and distribution at fueling stations. CNG must be stored in high-pressure cylinders, and LNG must be stored in cryogenic cylinders. These cylinders take up more space than gasoline or diesel tanks that can be molded in intricate shapes to store more fuel and use less on-vehicle space. CNG tanks are sometimes located in the vehicle's trunk or pickup bed, reducing the space for other cargo. This problem is sometimes mitigated by installing the tanks under the vehicle's body or on the roof, leaving cargo areas free. As with alternative fuels, other barriers to the widespread use of NGVs are natural gas distribution and the lower number of CNG and LNG stations then liquid fuels.Other challenges include relatively expensive and environmentally insensitive but convenience-seeking private individuals; good profits and taxes extractable from small-batch sales of value-added, branded petrol and diesel fuels via established trade channels and oil refiners; resistance and safety concerns to increasing gas inventories in urban areas; dual-use of utility distribution networks originally built for home gas supply and allocation of network expansion costs; reluctance, effort and costs associated with switching; prestige and nostalgia associated with petroleum vehicles; fear of redundancy and disruption. A particular challenge may be that refiners are currently set up to produce a certain fuel mix from crude oil. Aviation fuel is likely to remain the fuel of choice for aircraft due to its weight sensitivity for the foreseeable future
Infrastructure
NGV filling stations can be located anywhere natural gas lines exist. Compressors or liquefaction plants are usually built on a large scale, but small home CNG refueling stations are possible. A company called Fuel Maker pioneered a system called Phil Home Refueling Appliance, which they developed in partnership with Honda for the American GX model. Phil is now manufactured and sold by BRC Fuel Maker, a division of Fuel Systems Solutions, Inc.Deployment
The Asia-Pacific region leads the world with 6.8 million vehicles, followed by Latin America with 4.2 million. In Latin America, almost 90% of NGVs have bi-fuel engines, allowing these vehicles to run on either gasoline or CNG. In Pakistan, almost every vehicle converted to alternative fuel use typically retains the capability of running on gasoline.As of 2016, the U.S. had a fleet of 160,000 NG vehicles, including 3,176 LNG vehicles. Other countries where natural gas-powered buses are popular include India, Australia, Argentina, Germany, and Greece. In OECD countries, there are around 500,000 CNG vehicles. Pakistan's market share of NGVs was 61.1% in 2010, followed by Armenia with more than 77%, and Bolivia with 20%. The number of NGV refueling stations has also increased to 18,202 worldwide as of 2010, up 10.2% from the previous year.
CNG/LNG as fuel for automobiles
An increasing number of vehicles worldwide are being manufactured to run on CNG by major carmakers. Until recently, the Honda Civic GX was the only NGV commercially available in the US market. More recently, Ford, General Motors and Ram Trucks have bi-fuel offerings in their vehicle lineup. In 2006, the Brazilian subsidiary of FIAT introduced the Fiat Siena Tetra fuel, a four-fuel car that can run on natural gas.CNG-powered vehicles are considered safer than gasoline-powered ones.
Available production cars
Existing gasoline-powered vehicles may be converted to run on CNG or LNG, and can be dedicated or bi-fuel. However, an increasing number of vehicles worldwide are being manufactured to run on CNG. Until recently, the now-discontinued Honda Civic GX was the only NGV commercially available in the US market. More recently, Ford, General Motors and Ram Trucks have bi-fuel offerings in their vehicle lineup. Ford's approach is to offer a bi-fuel prep kit as a factory option and then have the customer choose an authorized partner to install the natural gas equipment. Choosing GM's bi-fuel option sends the HD pickups with the 6.0L gasoline engine to IMPCO in Indiana to upfit the vehicle to run on CNG. Ram currently is the only pickup truck manufacturer with a truly CNG factory-installed bi-fuel system available in the U.S. market.Outside the U.S. GM do Brasil introduced the Multipower engine in 2004, which was capable of using CNG, alcohol, and gasoline as fuel. It was used in the Chevrolet Astra 2.0 model 2005, 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 natural gas ; 100% ethanol ; E20 to E25 gasoline blend, Brazil's mandatory gasoline; and pure gasoline. However, it is no longer available in Brazil but is used in other neighboring countries.
In 2015, Honda announced its decision to phase out the commercialization of natural-gas-powered vehicles to focus on the development of a new generation of electrified vehicles such as hybrids, plug-in electric cars and hydrogen-powered fuel cell vehicles. Since 2008, Honda sold about 16,000 natural gas vehicles, mainly to taxi and commercial fleets.
Differences between LNG and CNG fuels
Though LNG and CNG are both considered NGVs, the technologies are vastly different. Refueling equipment, fuel cost, pumps, tanks, hazards, and capital costs are different.One thing they share is that due to engines made for gasoline, computer-controlled valves to control fuel mixtures are required for both of them, often being proprietary and specific to the manufacturer. The on-engine technology for fuel metering is the same for LNG and CNG.
CNG as an auto fuel
CNG, or compressed natural gas, is stored at high pressure,. The required tank is more massive and costly than a conventional fuel tank. Commercial on-demand refueling stations are more expensive to operate than LNG stations because of the energy required for compression; the compressor requires 100 times more electrical power. However, slow-fill can be cost-effective with LNG stations . The time to fill a CNG tank varies greatly depending on the station. Home refuels typically fill at about 1 kg/h. At gas stations, where the pressure is greatly higher, it is possible to refill a 25 kg tank in 5–10 minutes. Also, because of the lower energy density, the CNG range is lower compared to LNG. Gas composition and throughput allowing, it should be feasible to connect commercial CNG fueling stations to city gas networks or enable home fueling of CNG vehicles directly using a gas compressor. Similar to a car battery, the CNG tank of a car could double as a home energy storage device, and the compressor could be powered at times when there is excess / free renewable electrical energy.LNG as an auto fuel
LNG, or liquified natural gas, is natural gas that has been cooled to the point that it is a cryogenic liquid. Its liquid state is still more than twice as dense as CNG. LNG is either dispensed from bulk storage tanks or made locally from utility pipes at LNG fuel stations. Because of its cryogenic nature, it is stored in specially designed insulated tanks. Generally speaking, these tanks operate at fairly low pressures when compared to CNG. A vaporizer is mounted in the fuel system, turning the LNG into a gas. When comparing a commercial LNG station with a CNG station, utility infrastructure, capital cost, and electricity heavily favor LNG over CNG, but the availability of piped gas is more common than LNG delivery by tanker. There are existing LCNG stations, where fuel is stored as LNG, then vaporized to CNG on demand. LCNG stations require less capital cost than fast-fill CNG stations alone but more than LNG stations.Aside from different fuel tanks, fuel metering, and computer modules, the engines in NG vehicles could be run by CNG or LNG without requiring any modification because both are forms of natural gas.