Toyota Prius, a hybrid vehicle. Museum of Toyota of Aichi Prefecture, Japan.

A Brazilian filling station with four alternative fuels for sale: biodiesel (B3), gasohol (E25), neat ethanol (E100), and compressed natural gas (CNG). Piracicaba, Brazil.

An alternative fuel vehicle is a vehicle that runs on a fuel other than "traditional" petroleum fuels (petrol or diesel); and also refers to any technology of powering an engine that does not involve solely petroleum (e.g. electric car, hybrid electric vehicles, solar powered). Because of a combination of factors, such as environmental concerns, high oil prices and the potential for peak oil, development of cleaner alternative fuels and advanced power systems for vehicles has become a high priority for many governments and vehicle manufacturers around the world.

Hybrid electric vehicles such as the Toyota Prius are not actually alternative fuel vehicles, but through advanced technologies in the electric battery and motor/generator, they make a more efficient use of petroleum fuel.^[1] Other research and development efforts in alternative forms of power focus on developing all-electric and fuel cell vehicles, and even the stored energy of compressed air.

As of 2011 there were more than one billion vehicles in use in the world,^[2][3] compared with around 70 million alternative fuel and advanced technology vehicles that had been sold or converted worldwide as of December 2011, and made up mainly of:

• 27.1 million flexible-fuel vehicles through December 2011, led by Brazil with 16.3 million,^[4][5] followed by the United States with almost 10 million,^[6] Canada (600,000),^[7] and Europe, led by Sweden (228,522).^[8] The Brazilian fleet includes 1.5 million flexible-fuel motorcycles sold since 2009.^{[9][10][11][9]}
• 17.5 million LPG powered vehicles by December 2010, led by Turkey with 2.39 million, Poland (2.32 million), and South Korea (2.3 million).^[12]
• 14.8 million natural gas vehicles by December 2011, led by Iran with 2.86 million, followed by Pakistan (2.85 million), Argentina (2.04 million), Brazil (1.7 million), and India (1.1 million).^[13]
• 5.7 million neat-ethanol only light-vehicles built in Brazil since 1979,^[4] with 2.4 to 3.0 million vehicles still in use by 2004.^[14][15]
• More than 4.5 million hybrid electric vehicles sold through December 2011, led by the United States with 2.16 million units,^[16][17] followed by Japan with more than 1.5 million hybrids.^{[18][19][20][21][22]} Toyota Motor Company is the market leader with more than 3.5 million Lexus and Toyota hybrids sold worldwide,^[23] followed by Honda Motor Co., Ltd. with cumulative sales of more than 800,000 hybrids,^[24] and Ford Motor Corporation with more than 185,000 hybrids sold in the United States by December 2011.^[16][17]
• More than 530,000 plug-in electric vehicles (PEVs) sold worldwide by December 2011. Most electric vehicles in the world roads are low-speed, low-range neighborhood electric vehicles (NEVs), with about 479,000 NEVs on the road by 2011.^[25] The world's top selling NEV is the GEM, with global sales of 45,000 units through December 2010.^[26] The world's best selling highway-capable plug-in electric car is the Nissan Leaf all-electric car, with more than 21,000 units sold worldwide through December 2011,^[27] followed by the Mitsubishi i-MiEV electric car, with global cumulative sales of more than 17,000 units through October 2011,^[28] and the Chevrolet Volt plug-in hybrid, with 8,272 units sold through December 2011 in the U.S. and Canada.^{[29][30][30][31]} The United States and Japan are the world's largest highway-capable plug-in electric car markets as of December 2011. Since December 2010, around 18,000 plug-in electric cars have been sold in the U.S. through December 2011, led by the Nissan Leaf (9,693 units) and the Chevrolet Volt (7,997 units).^[32] Since July 2009, more than 13,000 electric cars have been sold in Japan by November 2011, which includes more than 8,000 Leafs^[33] and 5,000 i-MiEVs.^[34]

An environmental analysis extends beyond just the operating efficiency and emissions. A life-cycle assessment of a vehicle involves production and post-use considerations. A cradle-to-cradle design is more important than a focus on a single factor such as the type of fuel.^[35][36]

Single fuel source[link]

Air engine[link]

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The air engine is an emission-free piston engine that uses compressed air as a source of energy. The first compressed air car was invented by a French engineer named Guy Nègre. The expansion of compressed air may be used to drive the pistons in a modified piston engine. Efficiency of operation is gained through the use of environmental heat at normal temperature to warm the otherwise cold expanded air from the storage tank. This non-adiabatic expansion has the potential to greatly increase the efficiency of the machine. The only exhaust is cold air (−15 °C), which could also be used to air condition the car. The source for air is a pressurized carbon-fiber tank. Air is delivered to the engine via a rather conventional injection system. Unique crank design within the engine increases the time during which the air charge is warmed from ambient sources and a two stage process allows improved heat transfer rates.

Battery-electric[link]

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General Motors EV1 electric car.

Battery electric vehicles (BEVs), also known as all-electric vehicles (AEVs), are electric vehicles whose main energy storage is in the chemical energy of batteries. BEVs are the most common form of what is defined by the California Air Resources Board (CARB) as zero emission vehicle (ZEV) because they produce no tailpipe emissions at the point of operation. The electrical energy carried onboard a BEV to power the motors is obtained from a variety of battery chemistries arranged into battery packs. For additional range genset trailers or pusher trailers are sometimes used, forming a type of hybrid vehicle. Batteries used in electric vehicles include "flooded" lead-acid, absorbed glass mat, NiCd, nickel metal hydride, Li-ion, Li-poly and zinc-air batteries.

Attempts at building viable, modern battery-powered electric vehicles began in the 1950s with the introduction of the first modern (transistor controlled) electric car - the Henney Kilowatt, even though the concept was out in the market since 1890. Despite the poor sales of the early battery-powered vehicles, development of various battery-powered vehicles continued through the mids 1990s, with such models as the General Motors EV1 and the Toyota RAV4 EV.

The 2011 Nissan Leaf was introduced in Japan and the U.S. in December 2010, and in several European countries in early 2011.

Battery powered cars have primarily used lead-acid batteries and NiMH batteries. Lead-acid batteries' recharge capacity is considerably reduced if they're discharged beyond 75% on a regular basis, making them a less-than-ideal solution. NiMH batteries are a better choice, but are considerably more expensive than lead-acid. Lithium-ion battery powered vehicles such as the Venturi Fetish and the Tesla Roadster have recently demonstrated excellent performance and range, but they remain expensive, nevertheless is used in most mass production models launched in the late 2000s.

As of May 2011, several neighborhood electric vehicles, city electric cars and highway-capable electric cars are available in several countries, including the Tesla Roadster, GEM cars, REVAi, Buddy, Th!nk City, Mitsubishi i MiEV, Nissan Leaf, Smart ED, and Wheego Whip LiFe. Due to the premium price of electric cars because of the high cost of the battery pack, several countries and local governments have established tax credits and other incentives for early buyers of electric vehicles. Other models expected to reach the market between 2011 and 2012 include the CODA Sedan, REVA NXR, Renault Fluence Z.E., Ford Focus Electric, Hyundai BlueOn, Tesla Model S, and BMW ActiveE. There are also several pre-production models and plug-in conversions of existing models that are currently undergoing field trials or are part of demonstration programs including the Mini E, BYD e6, Audi A1 e-tron and Volvo C30 DRIVe Electric.

Solar[link]

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Nuna team at a racecourse.

Nuna solar powered car, which has travelled up to 140km/h (84mph).

A solar car is an electric vehicle powered by solar energy obtained from solar panels on the car. Solar panels cannot currently be used to directly supply a car with a suitable amount of power at this time, but they can be used to extend the range of electric vehicles. They are raced in competitions such as the World Solar Challenge and the North American Solar Challenge. These events are often sponsored by Government agencies such as the United States Department of Energy keen to promote the development of alternative energy technology such as solar cells and electric vehicles. Such challenges are often entered by universities to develop their students engineering and technological skills as well as motor vehicle manufacturers such as GM and Honda.

Trev's battery lasts over 250,000 kilometres.

The North American Solar Challenge is a solar car race across North America. Originally called Sunrayce, organized and sponsored by General Motors in 1990, it was renamed American Solar Challenge in 2001, sponsored by the United States Department of Energy and the National Renewable Energy Laboratory. Teams from universities in the United States and Canada compete in a long distance test of endurance as well as efficiency, driving thousands of miles on regular highways.

Nuna is the name of a series of manned solar powered vehicles that won the World solar challenge in Australia three times in a row, in 2001 (Nuna 1 or just Nuna), 2003 (Nuna 2) and 2005 (Nuna 3). The Nunas are built by students of the Delft University of Technology.

The World solar challenge is a solar powered car race over 3,021 kilometres (1,877 mi) through central Australia from Darwin to Adelaide. The race attracts teams from around the world, most of which are fielded by universities or corporations although some are fielded by high schools.

Trev (two-seater renewable energy vehicle) was designed by the staff and students at the University of South Australia. Trev was first displayed at the 2005 World Solar Challenge as the concept of a low-mass, efficient commuter car. With 3 wheels and a mass of about 300 kg, the prototype car had maximum speed of 120 km/h and acceleration of 0–100 km/h in about 10 seconds. The running cost of Trev is projected to be less than 1/10 of the running cost of a small petrol car.

Dimethyl ether fuel[link]

Installation of BioDME synthesis towers at Chemrec's pilot facility

Dimethyl ether (DME) is a promising fuel in diesel engines,^[37] petrol engines (30% DME / 70% LPG), and gas turbines owing to its high cetane number, which is 55, compared to diesel's, which is 40–53.^[38][39] Only moderate modification are needed to convert a diesel engine to burn DME. The simplicity of this short carbon chain compound leads during combustion to very low emissions of particulate matter, NO_x, CO. For these reasons as well as being sulfur-free, DME meets even the most stringent emission regulations in Europe (EURO5), U.S. (U.S. 2010), and Japan (2009 Japan).^[40] Mobil is using DME in their methanol to gasoline process.

DME is being developed as a synthetic second generation biofuel (BioDME), which can be manufactured from lignocellulosic biomass.^[41] Currently the EU is considering BioDME in its potential biofuel mix in 2030;^[42] the Volvo Group is the coordinator for the European Community Seventh Framework Programme project BioDME^[43][44] where Chemrec's BioDME pilot plant based on black liquor gasification is nearing completion in Piteå, Sweden.^[45]

Ammonia fuelled vehicles[link]

Ammonia GreenNH3 is being used with success by developers in Canada, since it can run in spark ignited or diesel engines with minor modifications,also the only green fuel to power jet engines,and despite its toxicity is reckoned to be no more dangerous than petrol or LPG.^[46] It can be made from renewable electricity, and having half the density of petrol or diesel can be readily carried in sufficient quantities in vehicles. On combustion it has no emissions other than nitrogen and water vapour.^{[citation needed]}

Biofuels[link]

Bioalcohol / Ethanol[link]

The Ford Model T was the first commercial flex-fuel vehicle. The engine was capable of running on gasoline or ethanol, or a mix of both.

The 1996 Ford Taurus was the first flexible-fuel vehicle produced with versions capable of running with either ethanol (E85) or methanol (M85) blended with gasoline.

The 2003 VW Gol 1.6 Total Flex was the first commercial flexible-fuel vehicle in the Brazilian market, capable of running on any mixture of gasoline (E20 to E25 blend) and ethanol (E100).

The first commercial vehicle that used ethanol as a fuel was the Ford Model T, produced from 1908 through 1927. It was fitted with a carburetor with adjustable jetting, allowing use of gasoline or ethanol, or a combination of both.^[47][48][49] Other car manufactures also provided engines for ethanol fuel use.^[50] In the United States, alcohol fuel was produced in corn-alcohol stills until Prohibition criminalized the production of alcohol in 1919. The use of alcohol as a fuel for internal combustion engines, either alone or in combination with other fuels, lapsed until the oil price shocks of the 1970s. Furthermore, additional attention was gained because of its possible environmental and long-term economical advantages over fossil fuel.

Both ethanol and methanol have been used as an automotive fuel.^[51] While both can be obtained from petroleum or natural gas, ethanol has attracted more attention because it is considered a renewable resource, easily obtained from sugar or starch in crops and other agricultural produce such as grain, sugarcane, sugar beets or even lactose. Since ethanol occurs in nature whenever yeast happens to find a sugar solution such as overripe fruit, most organisms have evolved some tolerance to ethanol, whereas methanol is toxic. Other experiments involve butanol, which can also be produced by fermentation of plants. Support for ethanol comes from the fact that it is a biomass fuel, which addresses climate change and greenhouse gas emissions, though these benefits are now highly debated,^{[50][52][53][54]} including the heated 2008 food vs fuel debate.

Most modern cars are designed to run on gasoline are capable of running with a blend from 10% up to 15% ethanol mixed into gasoline (E10-E15). With a small amount of redesign, gasoline-powered vehicles can run on ethanol concentrations as high as 85% (E85), the maximum set in the United States and Europe due to cold weather during the winter,^[55] or up to 100% (E100) in Brazil, with a warmer climate. Ethanol has close to 34% less energy per volume than gasoline,^[56][57] consequently fuel economy ratings with ethanol blends are significantly lower than with pure gasoline, but this lower energy content does not translate directly into a 34% reduction in mileage, because there are many other variables that affect the performance of a particular fuel in a particular engine, and also because ethanol has a higher octane rating which is beneficial to high compression ratio engines.

For this reason, for pure or high ethanol blends to be attractive for users, its price must be lower than gasoline to offset the lower fuel economy. As a rule of thumb, Brazilian consumers are frequently advised by the local media to use more alcohol than gasoline in their mix only when ethanol prices are 30% lower or more than gasoline, as ethanol price fluctuates heavily depending on the results and seasonal harvests of sugar cane and by region.^[58][59] In the US, and based on EPA tests for all 2006 E85 models, the average fuel economy for E85 vehicles was found 25.56% lower than unleaded gasoline.^[50] The EPA-rated mileage of current American flex-fuel vehicles^[60] could be considered when making price comparisons, though E85 has octane rating of about 104 and could be used as a substitute for premium gasoline. Regional retail E85 prices vary widely across the US, with more favorable prices in the Midwest region, where most corn is grown and ethanol produced. In August 2008 the US average spread between the price of E85 and gasoline was 16.9%, while in Indiana was 35%, 30% in Minnesota and Wisconsin, 19% in Maryland, 12 to 15% in California, and just 3% in Utah.^[61] Depending of the vehicle capabilities, the break even price of E85 usually has to be between 25 to 30% lower than gasoline.^[50] (See price comparisons for most states at e85prices.com)

E85 fuel sold at a regular gasoline station in Washington, D.C..

Reacting to the high price of oil and its growing dependence on imports, in 1975 Brazil launched the Pro-alcool program, a huge government-subsidized effort to manufacture ethanol fuel (from its sugar cane crop) and ethanol-powered automobiles. These ethanol-only vehicles were very popular in the 1980s, but became economically impractical when oil prices fell - and sugar prices rose - late in that decade. In May 2003 Volkswagen built for the first time a commercial ethanol flexible fuel car, the Gol 1.6 Total Flex. These vehicles were a commercial success and by early 2009 other nine Brazilian manufacturers are producing flexible fuel vehicles: Chevrolet, Fiat, Ford, Peugeot, Renault, Honda, Mitsubishi, Toyota, Citroën, and Nissan.^[4][62] The adoption of the flex technology was so rapid, that flexible fuel cars reached 87.6% of new car sales in July 2008.^[63] As of August 2008, the fleet of "flex" automobiles and light commercial vehicles had reached 6 million new vehicles sold,^[64] representing almost 19% of all registered light vehicles.^[65] The rapid success of "flex" vehicles, as they are popularly known, was made possible by the existence of 33,000 filling stations with at least one ethanol pump available by 2006, a heritage of the Pro-alcool program.^[66][67]

In the United States, initial support to develop alternative fuels by the government was also a response to the 1973 oil crisis, and later on, as a goal to improve air quality. Also, liquid fuels were preferred over gaseous fuels not only because they have a better volumetric energy density but also because they were the most compatible fuels with existing distribution systems and engines, thus avoiding a big departure from the existing technologies and taking advantage of the vehicle and the refueling infrastructure.^[51] California led the search of sustainable alternatives with interest in methanol.^[51] In 1996, a new FFV Ford Taurus was developed, with models fully capable of running either methanol or ethanol blended with gasoline.^[51][68] This ethanol version of the Taurus was the first commercial production of a E85 FFV.^[69] The momentum of the FFV production programs at the American car companies continued, although by the end of the 90's, the emphasis was on the FFV E85 version, as it is today.^[51] Ethanol was preferred over methanol because there is a large support in the farming community and thanks to government's incentive programs and corn-based ethanol subsidies.^[70] Sweden also tested both the M85 and the E85 flexifuel vehicles, but due to agriculture policy, in the end emphasis was given to the ethanol flexifuel vehicles.^[71]

Biodiesel[link]

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Bus running on soybean biodiesel

Biodiesel (B20) pump in the U.S.

The main benefit of Diesel combustion engines is that they have a 44% fuel burn efficiency; compared with just 25-30% in the best gasoline engines.^[72] In addition diesel fuel has slightly higher Energy Density by volume than gasoline. This makes Diesel engines capable of achieving much better fuel economy than gasoline vehicles.

Biodiesel (Fatty acid methyl ester), is commercially available in most oilseed-producing states in the United States. As of 2005, it is somewhat more expensive than fossil diesel, though it is still commonly produced in relatively small quantities (in comparison to petroleum products and ethanol). Many farmers who raise oilseeds use a biodiesel blend in tractors and equipment as a matter of policy, to foster production of biodiesel and raise public awareness. It is sometimes easier to find biodiesel in rural areas than in cities. Biodiesel has lower Energy Density than fossil diesel fuel, so biodiesel vehicles are not quite able to keep up with the fuel economy of a fossil fuelled diesel vehicle, if the diesel injection system is not reset for the new fuel. If the injection timing is changed to take account of the higher Cetane value of biodiesel, the difference in economy is negligible. Because biodiesel contains more oxygen than diesel or vegetable oil fuel, it produces the lowest emissions from diesel engines, and is lower in most emissions than gasoline engines. Biodiesel has a higher lubricity than mineral diesel and is an additive in European pump diesel for lubricity and emissions reduction.

Some Diesel-powered cars can run with minor modifications on 100% pure vegetable oils. Vegetable oils tend to thicken (or solidify if it is waste cooking oil), in cold weather conditions so vehicle modifications (a two tank system with diesel start/stop tank), are essential in order to heat the fuel prior to use under most circumstances. Heating to the temperature of engine coolant reduces fuel viscosity, to the range cited by injection system manufacturers, for systems prior to 'common rail' or 'unit injection ( VW PD)' systems. Waste vegetable oil, especially if it has been used for a long time, may become hydrogenated and have increased acidity. This can cause the thickening of fuel, gumming in the engine and acid damage of the fuel system. Biodiesel does not have this problem, because it is chemically processed to be PH neutral and lower viscosity. Modern low emission diesels (most often Euro -3 and -4 compliant), typical of the current production in the European industry, would require extensive modification of injector system, pumps and seals etc. due to the higher operating pressures, that are designed thinner (heated) mineral diesel than ever before, for atomisation, if they were to use pure vegetable oil as fuel. Vegetable oil fuel is not suitable for these vehicles as they are currently produced. This reduces the market as increasing numbers of new vehicles are not able to use it. However, the German Elsbett company has successfully produced single tank vegetable oil fuel systems for several decades, and has worked with Volkswagen on their TDI engines. This shows that it is technologically possible to use vegetable oil as a fuel in high efficiency / low emission diesel engines.

Greasestock is an event held yearly in Yorktown Heights, New York, and is one of the largest showcases of vehicles using waste oil as a biofuel in the United States.^{[73][74][75][76]}

Biogas[link]

Compressed Biogas may be used for Internal Combustion Engines after purification of the raw gas. The removal of H2O, H2S and particles can be seen as standard producing a gas which has the same quality as Compressed Natural Gas. The use of biogas is particularly interesting for climates where the waste heat of a biogas powered power plant cannot be used during the summer.^[46][77]

Charcoal[link]

In the 1930s Tang Zhongming made an invention using abundant charcoal resources for Chinese auto market. The Charcoal-fuelled car was later used intensively in China, serving the army and conveyancer after the breakout of World War II.

CNG Compressed Natural Gas[link]

The Brazilian Fiat Siena Tetrafuel 1.4, the first multifuel car that runs as a flexible-fuel on pure gasoline, or E25, or E100; or runs as a bi-fuel with natural gas (CNG).

High pressure compressed natural gas, mainly composed of methane, that is used to fuel normal combustion engines instead of gasoline. Combustion of methane produces the least amount of CO₂ of all fossil fuels. Gasoline cars can be retrofitted to CNG and become bifuel Natural gas vehicles (NGVs) as the gasoline tank is kept. The driver can switch between CNG and gasoline during operation. Natural gas vehicles (NGVs) are popular in regions or countries where natural gas is abundant. Widespread use began in the Po River Valley of Italy, and later became very popular in New Zealand by the eighties, though its use has declined.^[78]

Buses powered with CNG are common in the United States.

As of December 2011, there were 14.8 million natural gas vehicles worldwide, led by Iran with 2.86 million, followed closely by Pakistan (2.85 million), Argentina (2.07 million), Brazil (1.70 million), and India (1.10 million).^[13] As of 2010, the Asia-Pacific region led the global market with a share of 54%.^[79] In Europe they are popular in Italy (730,000), Ukraine (200,000), Armenia (101,352), Russia (100,000) and Germany (91,500),^[79] and they are becoming more so as various manufacturers produce factory made cars, buses, vans and heavy vehicles.^[77] In the United States CNG powered buses are the favorite choice of several public transit agencies, with an estimated CNG bus fleet of some 130,000.^[80] Other countries where CNG-powered buses are popular include India, Australia, Argentina, and Germany.^[78]

CNG vehicles are common in South America, where these vehicles are mainly used as taxicabs in main cities of Argentina and Brazil. Normally, standard gasoline vehicles are retrofitted in specialized shops, which involve installing the gas cylinder in the trunk and the CNG injection system and electronics. The Brazilian GNV fleet is concentrated in the cities of Rio de Janeiro and São Paulo.^[81] Pike Research reports that almost 90% of NGVs in Latin America havebi-fuel engines, allowing these vehicles to run on either gasoline or CNG.^[82]

In 2006 the Brazilian subsidiary of FIAT introduced the Fiat Siena Tetra fuel, a four-fuel car developed under Magneti Marelli of Fiat Brazil.^[83][84] This automobile can run on 100% ethanol (E100), E25 (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.^[85] Other 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.^[86]

Hydrogen[link]

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The 2009 Honda FCX Clarity is an hydrogen fuel cell automobile launched to the market in 2008.

Hydrogen fueling station in California.

Sequel, a hydrogen fuel cell-powered vehicle from General Motors.

A hydrogen car is an automobile which uses hydrogen as its primary source of power for locomotion. These cars generally use the hydrogen in one of two methods: combustion or fuel-cell conversion. In combustion, the hydrogen is "burned" in engines in fundamentally the same method as traditional gasoline cars. In fuel-cell conversion, the hydrogen is turned into electricity through fuel cells which then powers electric motors. With either method, the only byproduct from the spent hydrogen is water.

Honda introduced its fuel cell vehicle in 1999 called the FCX and have since then introduced the second generation FCX Clarity. Limited marketing of the FCX Clarity, based on the 2007 concept model, began in June 2008 in the United States, and it was introduced in Japan in November 2008.^[87] The FCX Clarity is available in the U.S. only in Los Angeles Area, where 16 hydrogen filling stations are available, and until July 2009, only 10 drivers have leased the Clarity for US$600 a month.^[88] Honda stated that it could start mass producing vehicles based on the FCX concept by the year 2020.^[88]

A small number of prototype hydrogen cars currently exist, and a significant amount of research is underway to make the technology more viable. The common internal combustion engine, usually fueled with gasoline (petrol) or diesel liquids, can be converted to run on gaseous hydrogen. However, the most efficient use of hydrogen involves the use of fuel cells and electric motors instead of a traditional engine. Hydrogen reacts with oxygen inside the fuel cells, which produces electricity to power the motors. One primary area of research is hydrogen storage, to try to increase the range of hydrogen vehicles while reducing the weight, energy consumption, and complexity of the storage systems. Two primary methods of storage are metal hydrides and compression. Some believe that hydrogen cars will never be economically viable and that the emphasis on this technology is a diversion from the development and popularization of more efficient hybrid cars and other alternative technologies.^{[citation needed]}

High speed cars, buses, motorcycles, bicycles, submarines, and space rockets already run on hydrogen, in various forms. There is even a working toy model car that runs on solar power, using a reversible fuel cell to store energy in the form of hydrogen and oxygen gas. It can then convert the fuel back into water to release the solar energy.^{[citation needed]}

BMW's Clean Energy internal combustion hydrogen car has more power and is faster than hydrogen fuel cell electric cars. A limited series production of the 7 Series Saloon was announced as commencing at the end of 2006. A BMW hydrogen prototype (H2R) using the driveline of this model broke the speed record for hydrogen cars at 300 km/h (186 mi/h), making automotive history. Mazda has developed Wankel engines to burn hydrogen. The Wankel uses a rotary principle of operation, so the hydrogen burns in a different part of the engine from the intake. This reduces pre-detonation, a problem with hydrogen fueled piston engines.^{[citation needed]}

The other major car companies like Daimler, Chrysler, Honda, Toyota, Ford and General Motors, are investing in hydrogen fuel cells instead. VW, Nissan, and Hyundai/Kia also have fuel cell vehicle prototypes on the road. In addition, transit agencies across the globe are running prototype fuel cell buses. Fuel cell vehicles, such as the new Honda Clarity, can get up to 70 miles (110 km) on a kilogram of hydrogen.^{[citation needed]}

Liquid nitrogen car[link]

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Liquid nitrogen (LN2) is a method of storing energy. Energy is used to liquify air, and then LN2 is produced by evaporation, and distributed. LN2 is exposed to ambient heat in the car and the resulting nitrogen gas can be used to power a piston or turbine engine. The maximum amount of energy that can be extracted from 1 kg of LN2 is 213 W-hr or 173 W-hr per liter, in which a maximum of 70 W-hr can be utilized with an isothermal expansion process. Such a vehicle can achieve ranges similar to that of gasoline with a 350 liter (90 gallon) tank. Theoretical future engines, using cascading topping cycles, can improve this to around 110 W-hr/kg with a quasi-isothermal expansion process. The advantages are zero harmful emissions and superior energy densities compared to a Compressed-air vehicle, and a car powered by LN2 can be refilled in a matter of minutes.

LPG or Autogas[link]

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A propane-fueled school bus in the United States.

LPG or liquified petroleum gas is a low pressure liquified gas mixture composed mainly of propane and butane which burns in conventional gasoline combustion engines with less CO₂ than gasoline. Gasoline cars can be retrofitted to LPG aka Autogas and become bifuel vehicles as the gasoline tank stays. You can switch between LPG and gasoline during operation. Estimated 10 million vehicles running worldwide.

There are 17.473 million LPG powered vehicles worldwide as of December 2010, and the leading countries are Turkey (2.394 million vehicles), Poland (2.325 million), and South Korea (2.3 million).^[12] In the U.S., 190,000 on-road vehicles use propane,^[89] and 450,000 forklifts use it for power.

Hyundai Motor Company began sales of the Elantra LPI Hybrid in the South Korean domestic market in July 2009. The Elantra LPI (Liquefied Petroleum Injected) is the world's first hybrid electric vehicle to be powered by an internal combustion engine built to run on liquefied petroleum gas (LPG) as a fuel.^[90][91]

Steam[link]

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The Stanley Steam Car

A steam car is a car that has a steam engine. Wood, coal, ethanol, or others can be used as fuel. The fuel is burned in a boiler and the heat converts water into steam. When the water turns to steam, it expands. The expansion creates pressure. The pressure pushes the pistons back and forth. This turns the driveshaft to spin the wheels forward. It works like a coal-fueled steam train, or steam boat. The steam car was the next logical step in independent transport.

Steam cars take a long time to start, but some can reach speeds over 100 mph (161 km/h) eventually. the late model doble could be brought to operational condition in less than 30 seconds, and were fast, with high acceleration, but they were ridiculously expensive.

A steam engine uses external combustion, as opposed to internal combustion. Gasoline-powered cars are more efficient at about 25-28% efficiency. In theory, a combined cycle steam engine in which the burning material is first used to drive a gas turbine can produce 50% to 60% efficiency. However, practical examples of steam engined cars work at only around 5-8% efficiency.

The best known and best selling steam-powered car was the Stanley Steamer. It used a compact fire-tube boiler under the hood to power a simple two-piston engine which was connected directly to the rear axle. Before Henry Ford introduced monthly payment financing with great success, cars were typically purchased outright. This is why the Stanley was kept simple; to keep the purchase price affordable.

Steam produced in refrigeration also can be use by a turbine in other vehicle types to produce electricity, that can be employed in electric motors or stored in a battery.

Steam power can be combined with a standard oil-based engine to create a hybrid. Water is injected into the cylinder after the fuel is burned, when the piston is still superheated, often at temperatures of 1500 degrees or more. The water will instantly be vaporized into steam, taking advantage of the heat that would otherwise be wasted.

Wood gas[link]

Vehicle with a gasifier

Wood gas can be used to power cars with ordinary internal combustion engines if a wood gasifier is attached. This was quite popular during World War II in several European and Asian countries because the war prevented easy and cost-effective access to oil.

Multiple fuel source[link]

Flexible fuel[link]

Six typical Brazilian full flex-fuel models from several carmakers, popularly known as "flex" cars, that run on any blend of ethanol and gasoline(actually between E20-E25 to E100).

A flexible-fuel vehicle (FFV) or dual-fuel vehicle is an alternative fuel automobile or light duty truck with a multifuel engine that can use more than one fuel, usually mixed in the same tank, and the blend is burned in the combustion chamber together. These vehicles are colloquially called flex-fuel, or flexifuel in Europe, or just flex in Brazil. FFVs are distinguished from bi-fuel vehicles, where two fuels are stored in separate tanks. The most common commercially available FFV in the world market is the ethanol flexible-fuel vehicle, with the major markets concentrated in the United States, Brazil, Sweden, and some other European countries. In addition to flex-fuel vehicles running with ethanol, in the US and Europe there were successful test programs with methanol flex-fuel vehicles, known as M85 FFVs, and more recently there have been also successful tests using p-series fuels with E85 flex fuel vehicles, but as of June 2008, this fuel is not yet available to the general public.

Ethanol flexible-fuel vehicles have standard gasoline engines that are capable of running with ethanol and gasoline mixed in the same tank. These mixtures have "E" numbers which describe the percentage of ethanol in the mixture, for example, E85 is 85% ethanol and 15% gasoline. (See common ethanol fuel mixtures for more information.) Though technology exists to allow ethanol FFVs to run on any mixture up to E100,^[50][92] in the U.S. and Europe, flex-fuel vehicles are optimized to run on E85. This limit is set to avoid cold starting problems during very cold weather. The alcohol content might be reduced during the winter, to E70 in the U.S. or to E75 in Sweden. Brazil, with a warmer climate, developed vehicles that can run on any mix up to E100, though E20-E25 is the mandatory minimum blend, and no pure gasoline is sold in the country.

By December 2010 cumulative global sales of flexible-fuel vehicles have reached around 22.6 million units, led by Brazil with 12 million automobiles and light trucks, and 515,726 flexible-fuel motorcycles,^[4][10][11] followed by the United States with 9.3 million,^[93] Canada (600,000),^[7] and Europe, led by Sweden (216,975).^[8] In Brazil, 65% of flex-fuel owners use ethanol fuel regularly in 2009,^[94] while, the actual number of American FFVs being run on E85 is much lower; surveys conducted in the U.S. have found that 68% of American flex-fuel car owners were not aware they owned an E85 flex.^[50] This is thought to be due to a number of factors, including:

Typical labeling used in the US to identify E85 vehicles. Top left: a small sticker in the back of the fuel filler door. Bottom left: the bright yellow gas cap used in newer models. E85 Flexfuel badging used in newer models from Chrysler (top right), Ford (middle right) and GM (bottom right).

• The appearance of flex-fuel and non-flex-fuel vehicles is identical;

• There is no price difference between a pure-gasoline vehicle and its flex-fuel variant;

• The lack of consumer awareness of flex-fuel vehicles;

• The lack of promotion of flex-fuel vehicles by American automakers, who often do not label the cars or market them in the same way they do to hybrid cars

By contrast, automakers selling FFVs in Brazil commonly affix badges advertising the car as a flex-fuel vehicle. As of 2007, new FFV models sold in the U.S. were required to feature a yellow gas cap emblazoned with the label "E85/gasoline", in order to remind drivers of the cars' flex-fuel capabilities.^[95][96] Use of E85 in the U.S. is also affected by the relatively low number of E85 filling stations in operation across the country, with just over 1,750 in August 2008,^[97] most of which are concentrated in the Corn Belt states, led by Minnesota with 353 stations, followed by Illinois with 181, and Wisconsin with 114.^[98] By comparison, there are some 120,000 stations providing regular non-ethanol gasoline in the United States alone.^[99]

US E85FlexFuel Chevrolet Impala LT 2009.

There have been claims that American automakers are motivated to produce flex-fuel vehicles due to a loophole in the Corporate Average Fuel Economy (CAFE) requirements, which gives the automaker a "fuel economy credit" for every flex-fuel vehicle sold, whether or not the vehicle is actually fueled with E85 in regular use.^[67] This loophole allegedly allows the U.S. auto industry to meet CAFE fuel economy targets not by developing more, more fuel-efficient models, but by spending between $100 and $200 extra per vehicle to produce a certain number of flex-fuel models, enabling them to continue selling less fuel-efficient vehicles such as SUVs, which netted higher profit margins than smaller, more fuel-efficient cars.^[100][101]

In the United States, E85 FFVs are equipped with sensor that automatically detect the fuel mixture, signaling the ECU to tune spark timing and fuel injection so that fuel will burn cleanly in the vehicle's internal combustion engine. Originally, the sensors were mounted in the fuel line and exhaust system; more recent models do away with the fuel line sensor. Another feature of older flex-fuel cars is a small separate gasoline storage tank that was used for starting the car on cold days, when the ethanol mixture made ignition more difficult.

The Honda CG 150 Titan Mix was the first flex-fuel motorcycle launched to the market in the world.

Modern Brazilian flex-fuel technology enables FFVs to run an any blend between E20-E25 gasohol and E100 ethanol fuel, using a lambda probe to measure the quality of combustion, which informs the engine control unit as to the exact composition of the gasoline-alcohol mixture. This technology, developed by the Brazilian subsidiary of Bosch in 1994, and further improved and commercially implemented in 2003 by the Italian subsidiary of Magneti Marelli, is known as "Software Fuel Sensor". The Brazilian subsidiary of Delphi Automotive Systems developed a similar technology, known as "Multifuel", based on research conducted at its facility in Piracicaba, São Paulo.^[102] This technology allows the controller to regulate the amount of fuel injected and spark time, as fuel flow needs to be decreased to avoid detonation due to the high compression ratio (around 12:1) used by flex-fuel engines.

The first flex motorcycle was launched by Honda in March 2009. Produced by its Brazilian subsidiary Moto Honda da Amazônia, the CG 150 Titan Mix is sold for around US$2,700.^{[103][104][105][106]} Because the motorcycle does not have a secondary gas tank for a cold start like the Brazilian flex cars do, the tank must have at least 20% of gasoline to avoid start up problems at temperatures below 15°C (59°F). The motorcycle’s panel includes a gauge to warn the driver about the actual ethanol-gasoline mix in the storage tank.^[106][107]

Hybrid[link]

The Toyota Prius Plug-in Hybrid has an all-electric range of 15 miles (24 km).

The Chevrolet Volt is a plug-in hybrid able to run in all-electric mode for 35 miles (56 km)

The Sinclair C5 pedal-assisted battery vehicle.

A hybrid vehicle uses multiple propulsion systems to provide motive power. The most common type of hybrid vehicle is the gasoline-electric hybrid vehicles, which use gasoline (petrol) and electric batteries for the energy used to power internal-combustion engines (ICEs) and electric motors. These motors are usually relatively small and would be considered "underpowered" by themselves, but they can provide a normal driving experience when used in combination during acceleration and other maneuvers that require greater power.

The Toyota Prius first went on sale in Japan in 1997 and it is sold worldwide since 2000. By 2010 the Prius is sold in more than 70 countries and regions, with Japan and the United States as its largest markets.^[108] In May 2008, global cumulative Prius sales reached the 1 million units, and by September 2010, the Prius reached worldwide cumulative sales of 2 million units.^[108] The United States is the largest hybrid market in the world, with more than 2 million hybrid automobiles and SUVs sold through May 2011.^[109] The Prius is the top selling hybrid car in the U.S. with 1 million units sold by April 2011.^[110]

The Honda Insight is a two-seater hatchback hybrid automobile manufactured by Honda. It was the first mass-produced hybrid automobile sold in the United States, introduced in 1999, and produced until 2006.^[111][112] Honda introduced the second-generation Insight in Japan in February 2009, and the new Insight went on sale in the U.S. on April 22, 2009.^[113][114] Honda also offers the Honda Civic Hybrid since 2002.

Among others, the following are popular gasoline-electric hybrid models available in the market by 2009: Ford Escape Hybrid, Chevrolet Silverado/GMC Sierra Hybrid, Lexus RX 400h, Toyota Highlander Hybrid, Mercury Mariner Hybrid, Toyota Camry Hybrid, Saturn Vue Green Line, Lexus LS600hL, Mazda Tribute Hybrid, Nissan Altima Hybrid, Ford Fusion/Mercury Milan Hybrid, and Mercedes S400 BlueHybrid.

Several major carmakers are currently developing plug-in hybrid electric vehicles (PHEVs). Chinese battery manufacturer and automaker BYD Auto released the F3DM PHEV-68 (PHEV109km) hatchback to the Chinese fleet market on December 15, 2008.^[115][116] The 2011 Chevrolet Volt is the first mass produced PHEV launched in the United States, and it was introduced in November 2010.^[117][118] Other PHEVs undergoing field testing as of December 2010 include the Toyota Prius Plug-in Hybrid, Ford Escape Plug-in Hybrid, Volvo V70 Plug-in Hybrid, and Suzuki Swift Plug-in.

The Elantra LPI Hybrid, launched in the South Korean domestic market in July 2009, is a hybrid vehicle powered by an internal combustion engine built to run on liquefied petroleum gas (LPG) as a fuel. The Elantra PLI is a mild hybrid and the first hybrid to adopt advanced lithium polymer (Li–Poly) batteries.^[90][91]

Pedal-assisted electric hybrid vehicle[link]

In very small vehicles, the power demand decreases, so human power can be employed to make a significant improvement in battery life. Two such commercially made vehicles are the Sinclair C5 and the TWIKE.

See also[link]

Energy portal

• Alternative Fuels Training Consortium
• Alternatives to the automobile
• Clean Cities
• Future of the car
• Hydrogen vehicle
• List of 2007 Hybrid Vehicles
• Solar-charged vehicle
• The Hype about Hydrogen
• Water-fuelled car (urban legend)
• Jack Talbert (Vaporization)

References[link]

External links[link]

• EERE:
  • US Alternative Fueling Stations.
  • Alternative Fuel Price Report.
• Alternative Fuels for Road Vehicles - M.L. Poulton
• Sustainable Green Fleets EU-sponsored Dissemination project for alternative propelled cars and alternative fuels
• Popular Mechanics describes the pros and cons of various alternative fuels and what the future looks like for each.
• Green Car Guide
• Questions and Answers about Trev., UniSA, Division of Information Technology, Engineering and the Environment.

Typical Brazilian filling station with four alternative fuels for sale: biodiesel (B3), gasohol (E25), neat ethanol (E100), and compressed natural gas (CNG). Piracicaba, São Paulo, Brazil.

Alternative fuels, known as non-conventional or advanced fuels, are any materials or substances that can be used as fuels, other than conventional fuels. Conventional fuels include: fossil fuels (petroleum (oil), coal, propane, and natural gas), as well as nuclear materials such as uranium and thorium, as well as artificial radioisotope fuels that are made in nuclear reactors, and store their energy.

Some well-known alternative fuels include biodiesel, bioalcohol (methanol, ethanol, butanol), chemically stored electricity (batteries and fuel cells), hydrogen, non-fossil methane, non-fossil natural gas, vegetable oil, and other biomass sources.

Background[link]

The main purpose of fuel is to store energy, which should be in a stable form and can be easily transported to the place of production. Almost all fuels are chemical fuels. The user employs this fuel to generate heat or perform mechanical work, such as powering an engine. It may also be used to generate electricity, which is then used for heating, lighting or electronics purposes.

Biofuel[link]

Alternative fuel dispensers at a regular gasoline station in Arlington, Virginia. B20 biodiesel at the left and E85 ethanol at the right.

Biofuels are also considered a renewable source. Although renewable energy is used mostly to generate electricity, it is often assumed that some form of renewable energy or a percentage is used to create alternative fuels.

Biomass[link]

Biomass in the energy production industry is living and recently dead biological material which can be used as fuel or for industrial production.

Algae based fuels[link]

Algae based biofuels have been hyped in the media as a potential panacea to our Crude Oil based Transportation problems. Algae could yield more than 2000 gallons of fuel per acre per year of production.^[1] Algae based fuels are being successfully tested by the U.S. Navy^[2] Algae based plastics show potential to reduce waste and the cost per pound of algae plastic is expected to be cheaper than traditional plastic prices.^[3]

Biodiesel[link]

Biodiesel is made from animal fats or vegetable oils, renewable resources that come from plants such as, soybean, sunflowers, corn, olive, peanut, palm, coconut, safflower, canola, sesame, cottonseed, etc. Once these fats or oils are filtered from their hydrocarbons and then combined with alcohol like methanol, biodiesel is brought to life from this chemical reaction. These raw materials can either be mixed with pure diesel to make various proportions, or used alone. Despite one’s mixture preference, biodiesel will release a smaller number of its pollutants (carbon monoxide particulates and hydrocarbons) than conventional diesel, because biodiesel burns both cleaner and more efficiently. Even with regular diesel’s reduced quantity of sulfur from the ULSD (ultra-low sulfur diesel) invention, biodiesel exceeds those levels because it is sulfur-free. ^[4]

Alcohol fuels[link]

Methanol and Ethanol fuel are primary sources of energy; they are convenient fuels for storing and transporting energy. These alcohols can be used in "internal combustion engines as alternative fuels", with butanol also having known advantages, such as being the only alcohol-based motor fuel that can be transported readily by existing petroleum-product pipeline networks, instead of only by tanker trucks and railroad cars.

Ammonia[link]

Ammonia can be used as fuel. A small machine can be set up to create the fuel and it is used where it is made. Benefits of ammonia include, no need for oil, zero emissions, low cost,^[5] and distributed production reducing transport and related pollution.

Hydrogen[link]

Hydrogen is an emissionless fuel. The byproduct of hydrogen burning is water, although some mono-nitrogen oxides NOx are produced when hydrogen is burned with air.^[6][7]

HCNG[link]

HCNG (or H2CNG) is a mixture of compressed natural gas and 4-9 percent hydrogen by energy.^[8]

Liquid nitrogen[link]

Liquid nitrogen is another type of emissionless fuel.

Compressed air[link]

The air engine is an emission-free piston engine using compressed air as fuel. Unlike hydrogen, compressed air is about one-tenth as expensive as fossil oil, making it an economically attractive alternative fuel.

Alternative fossil fuels[link]

Compressed natural gas (CNG) is a cleaner burning alternative to conventional petroleum automobile fuels. The energy efficiency is generally equal to that of gasoline engines, but lower compared with modern diesel engines. CNG vehicles require a greater amount of space for fuel storage than conventional gasoline power vehicles because CNG takes up more space for each GGE (Gallon of Gas Equivalent). Almost any existing gasoline car can be turned into a bi-fuel (gasoline/CNG) car. However, natural gas is a finite resource like all fossil fuels, and production of natural gas is expected to peak soon after oil.^{[citation needed]}

Natural gas, like hydrogen, is another fuel that burns cleanly; cleaner than both gasoline and diesel engines. Also, none of the smog-forming contaminates are emitted, seen substantially by the latter. Around the world, this gas powers more than 5 million vehicles, and just over 150,000 of these are in the U.S. ^[9]

Nuclear power and radiothermal generators[link]

Nuclear reactors[link]

Nuclear power is any nuclear technology designed to extract usable energy from atomic nuclei via controlled nuclear reactions. The only controlled method now practical uses nuclear fission in a fissile fuel (with a small fraction of the power coming from subsequent radioactive decay). Use of the nuclear reaction nuclear fusion for controlled power generation is not yet practical, but is an active area of research.

Nuclear power is usually used by using a nuclear reactor to heat a working fluid such as water, which is then used to create steam pressure, which is converted into mechanical work for the purpose of generating electricity or propulsion in water. Today, more than 15% of the world's electricity comes from nuclear power, and over 150 nuclear-powered naval vessels have been built.

In theory, electricity from nuclear reactors could also be used for propulsion in space, but this has yet to be demonstrated in a space flight. Some smaller reactors, such as the TOPAZ nuclear reactor, are built to minimize moving parts, and use methods that convert nuclear energy to electricity more directly, making them useful for space missions, but this electricity has historically been used for other purposes. Power from nuclear fission has been used in a number of spacecraft, all of them unmanned. The Soviets up to 1988 orbited 33 nuclear reactors in RORSAT military radar satellites, where electric power generated was used to power a radar unit that located ships on the Earth's oceans. The U.S. also orbited one experimental nuclear reactor in 1965, in the SNAP-10A mission. No nuclear reactor has been sent into space since 1988.

Radiothermal generators[link]

In addition, radioisotopes have been used as alternative fuels, on both land and in space. Their use on land is declining due to the danger of theft of isotope and environmental damage if the unit is opened. The decay of radioisotopes generates both heat and electricity in many space probes, particularly probes to outer planets where sunlight is weak, and low temperatures is a problem. Radiothermal generators (RTGs) which use such radioisotopes as fuels do not sustain a nuclear chain reaction, but rather generate electricity from the decay of a radioisotope which has (in turn) been produced on Earth as a concentrated power source (fuel) using energy from an Earth-based nuclear reactor. ^[10]

See also[link]

Wikinews has news related to: Energy

	Sustainable development portal
	Energy portal

References[link]

External links[link]

• Alternative Fuels Data Center (U.S. DOE)
• Alternative Fuels Information Centre (Victorian Government)
• Alternative Fuel Vehicle Training National Alternative Fuels Training Consortium, West Virginia University
• Clean Cities Program U.S. DOE program encouraging alternative fuel use
• International Air Transport Association alternative aviation fuels
• ScienceDaily - Alternative Fuel News
• Student's Guide to Alternative Fuel (California Energy Commission)
• Sustainable Green Fleets, an EU-sponsored dissemination project for alternatively fuels for fleets
• Pop. Mechanics: Crunching the numbers on alternative fuels
• Global list of Alternative Fuels related Organizations on WiserEarth
• Alternative Fuels portal on WiserEarth
• Alternative Clean Transportation Expo

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