Fuel efficiency is a form of
thermal efficiency
In thermodynamics, the thermal efficiency (\eta_) is a dimensionless performance measure of a device that uses thermal energy, such as an internal combustion engine, steam turbine, steam engine, boiler, furnace, refrigerator, ACs etc.
For a ...
, meaning the
ratio
In mathematics, a ratio shows how many times one number contains another. For example, if there are eight oranges and six lemons in a bowl of fruit, then the ratio of oranges to lemons is eight to six (that is, 8:6, which is equivalent to the ...
of effort to result of a process that converts
chemical
A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be separated into its constituent elements by physical separation methods, i.e., w ...
potential energy contained in a carrier (
fuel) into kinetic energy or
work
Work may refer to:
* Work (human activity), intentional activity people perform to support themselves, others, or the community
** Manual labour, physical work done by humans
** House work, housework, or homemaking
** Working animal, an animal t ...
. Overall fuel efficiency may vary per device, which in turn may vary per application, and this spectrum of variance is often illustrated as a continuous
energy profile. Non-transportation applications, such as
industry
Industry may refer to:
Economics
* Industry (economics), a generally categorized branch of economic activity
* Industry (manufacturing), a specific branch of economic activity, typically in factories with machinery
* The wider industrial sector ...
, benefit from increased fuel efficiency, especially
fossil fuel power plant
A fossil fuel power station is a thermal power station which burns a fossil fuel, such as coal or natural gas, to produce electricity. Fossil fuel power stations have machinery to convert the heat energy of combustion into mechanical energy, wh ...
s or industries dealing with
combustion
Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combus ...
, such as
ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...
production during the
Haber process
The Haber process, also called the Haber–Bosch process, is an artificial nitrogen fixation process and is the main industrial procedure for the production of ammonia today. It is named after its inventors, the German chemists Fritz Haber and ...
.
In the context of
transport
Transport (in British English), or transportation (in American English), is the intentional movement of humans, animals, and goods from one location to another. Modes of transport include air, land ( rail and road), water, cable, pipelin ...
, fuel economy is the
energy efficiency
Energy efficiency may refer to:
* Energy efficiency (physics), the ratio between the useful output and input of an energy conversion process
** Electrical efficiency, useful power output per electrical power consumed
** Mechanical efficiency, a ra ...
of a particular vehicle, given as a
ratio
In mathematics, a ratio shows how many times one number contains another. For example, if there are eight oranges and six lemons in a bowl of fruit, then the ratio of oranges to lemons is eight to six (that is, 8:6, which is equivalent to the ...
of distance traveled per unit of
fuel consumed. It is dependent on several factors including
engine efficiency
Engine efficiency of thermal engines is the relationship between the total energy contained in the fuel, and the amount of energy used to perform useful work. There are two classifications of thermal engines-
#Internal combustion (gasoline, diesel ...
,
transmission design, and
tire
A tire (American English) or tyre (British English) is a ring-shaped component that surrounds a wheel's rim to transfer a vehicle's load from the axle through the wheel to the ground and to provide traction on the surface over which t ...
design. In most countries, using the
metric system
The metric system is a system of measurement that succeeded the decimalised system based on the metre that had been introduced in France in the 1790s. The historical development of these systems culminated in the definition of the Interna ...
, fuel economy is stated as "fuel consumption" in
liters per 100
kilometers
The kilometre ( SI symbol: km; or ), spelt kilometer in American English, is a unit of length in the International System of Units (SI), equal to one thousand metres (kilo- being the SI prefix for ). It is now the measurement unit used for ex ...
(L/100 km) or kilometers per liter (km/L or kmpl). In a number of countries still using other systems, fuel economy is expressed in
miles per
gallon
The gallon is a unit of volume in imperial units and United States customary units. Three different versions are in current use:
*the imperial gallon (imp gal), defined as , which is or was used in the United Kingdom, Ireland, Canada, Austr ...
(mpg), for example in the US and usually also in the UK (
imperial gallon); there is sometimes confusion as the imperial gallon is 20% larger than the US gallon so that mpg values are not directly comparable. Traditionally, litres per
mil were used in
Norway
Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and the ...
and
Sweden, but both have aligned to the EU standard of L/100 km.
Fuel consumption is a more accurate measure of a vehicle's performance because it is a linear relationship while fuel economy leads to distortions in efficiency improvements.
H
Weight-specific efficiency (efficiency per unit weight) may be stated for
freight
Cargo consists of bulk goods conveyed by water, air, or land. In economics, freight is cargo that is transported at a freight rate for commercial gain. ''Cargo'' was originally a shipload but now covers all types of freight, including tran ...
, and passenger-
specific efficiency (vehicle efficiency per passenger) for passenger vehicles.
Vehicle design
Fuel efficiency is dependent on many parameters of a vehicle, including its
engine
An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy.
Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power ...
parameters,
aerodynamic drag, weight, AC usage, fuel and
rolling resistance. There have been advances in all areas of vehicle design in recent decades. Fuel efficiency of vehicles can also be improved by careful maintenance and driving habits.
Hybrid vehicles
A hybrid vehicle is one that uses two or more distinct types of power, such as submarines that use diesel when surfaced and batteries when submerged. Other means to store energy include pressurized fluid in hydraulic hybrids.
The basic princip ...
use two or more power sources for propulsion. In many designs, a small combustion engine is combined with electric motors. Kinetic energy which would otherwise be lost to heat during braking is recaptured as electrical power to improve fuel efficiency. Engines automatically shut off when vehicles come to a stop and start again when the accelerator is pressed preventing wasted energy from idling.
Fleet efficiency
Fleet efficiency describes the average efficiency of a population of vehicles. Technological advances in efficiency may be offset by a change in buying habits with a propensity to heavier vehicles, which are less efficient, all else being equal.
Energy efficiency terminology
Energy efficiency
Energy efficiency may refer to:
* Energy efficiency (physics), the ratio between the useful output and input of an energy conversion process
** Electrical efficiency, useful power output per electrical power consumed
** Mechanical efficiency, a ra ...
is similar to fuel efficiency but the input is usually in units of energy such as
megajoules (MJ),
kilowatt-hours
A kilowatt-hour ( unit symbol: kW⋅h or kW h; commonly written as kWh) is a unit of energy: one kilowatt of power for one hour. In terms of SI derived units with special names, it equals 3.6 megajoules (MJ). Kilowatt-hours are a common bi ...
(kW·h), kilocalories (kcal) or
British thermal units (BTU). The inverse of "energy efficiency" is "
energy intensity", or the amount of input energy required for a unit of output such as MJ/passenger-km (of passenger transport), BTU/ton-mile or kJ/t-km (of freight transport), GJ/t (for production of steel and other materials), BTU/(kW·h) (for electricity generation), or litres/100 km (of vehicle travel). Litres per 100 km is also a measure of "energy intensity" where the input is measured by the amount of fuel and the output is measured by the
distance
Distance is a numerical or occasionally qualitative measurement of how far apart objects or points are. In physics or everyday usage, distance may refer to a physical length or an estimation based on other criteria (e.g. "two counties over"). ...
travelled. For example:
Fuel economy in automobiles.
Given a heat value of a fuel, it would be trivial to convert from fuel units (such as litres of gasoline) to energy units (such as MJ) and conversely. But there are two problems with comparisons made using energy units:
* There are two different heat values for any hydrogen-containing fuel which can differ by several percent (see below).
* When comparing transportation energy costs, it must be remembered that a
kilowatt hour of electric energy may require an amount of fuel with heating value of 2 or 3 kilowatt hours to produce it.
Energy content of fuel
The specific
energy content
In physics, energy density is the amount of energy stored in a given system or region of space per unit volume. It is sometimes confused with energy per unit mass which is properly called specific energy or .
Often only the ''useful'' or extrac ...
of a fuel is the heat energy obtained when a certain quantity is burned (such as a gallon, litre, kilogram). It is sometimes called the
heat of combustion. There exists two different values of
specific heat
In thermodynamics, the specific heat capacity (symbol ) of a substance is the heat capacity of a sample of the substance divided by the mass of the sample, also sometimes referred to as massic heat capacity. Informally, it is the amount of heat t ...
energy for the same batch of fuel. One is the high (or gross) heat of combustion and the other is the low (or net) heat of combustion. The high value is obtained when, after the combustion, the water in the exhaust is in liquid form. For the low value, the exhaust has all the water in vapor form (steam). Since water vapor gives up heat energy when it changes from vapor to liquid, the liquid water value is larger since it includes the
latent heat
Latent heat (also known as latent energy or heat of transformation) is energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process — usually a first-order phase transition.
Latent heat can be underst ...
of vaporization of water. The difference between the high and low values is significant, about 8 or 9%. This accounts for most of the apparent discrepancy in the heat value of gasoline. In the U.S. (and the table) the high heat values have traditionally been used, but in many other countries, the low heat values are commonly used.
[Appendix B, Transportation Energy Data Book]
from the Center for Transportation Analysis
Oak Ridge National Laboratory (ORNL) is a U.S. multiprogram science and technology United States Department of Energy national laboratories, national laboratory sponsored by the United States Department of Energy, U.S. Department of Energy (DOE) ...
of the Oak Ridge National Laboratory
Oak Ridge National Laboratory (ORNL) is a U.S. multiprogram science and technology national laboratory sponsored by the U.S. Department of Energy (DOE) and administered, managed, and operated by UT–Battelle as a federally funded research an ...
Neither the gross heat of combustion nor the net heat of combustion gives the theoretical amount of mechanical energy (work) that can be obtained from the reaction. (This is given by the change in
Gibbs free energy
In thermodynamics, the Gibbs free energy (or Gibbs energy; symbol G) is a thermodynamic potential that can be used to calculate the maximum amount of work that may be performed by a thermodynamically closed system at constant temperature and ...
, and is around 45.7 MJ/kg for gasoline.) The actual amount of mechanical work obtained from fuel (the inverse of the
specific fuel consumption) depends on the engine. A figure of 17.6 MJ/kg is possible with a gasoline engine, and 19.1 MJ/kg for a diesel engine. See
Brake specific fuel consumption
Brake-specific fuel consumption (BSFC) is a measure of the fuel efficiency of any prime mover that burns fuel and produces rotational, or shaft power. It is typically used for comparing the efficiency of internal combustion engines with a shaft out ...
for more information.
Fuel efficiency of motor vehicles
Measurement
The fuel efficiency of motor vehicles can be expressed in more ways:
* Fuel consumption is the amount of fuel used per unit distance; for example,
litre
The litre (international spelling) or liter (American English spelling) (SI symbols L and l, other symbol used: ℓ) is a metric unit of volume. It is equal to 1 cubic decimetre (dm3), 1000 cubic centimetres (cm3) or 0.001 cubic metre (m3 ...
s per 100
kilometres (L/100 km). The lower the value, the more economic a vehicle is (the less fuel it needs to travel a certain distance); this is the measure generally used across Europe (except the UK, Denmark and The Netherlands - see below), New Zealand, Australia and Canada. Also in Uruguay, Paraguay, Guatemala, Colombia, China, and Madagascar., as also in post-Soviet space.
* Fuel economy is the distance travelled per unit volume of fuel used; for example, kilometres per litre (km/L) or
miles per
gallon
The gallon is a unit of volume in imperial units and United States customary units. Three different versions are in current use:
*the imperial gallon (imp gal), defined as , which is or was used in the United Kingdom, Ireland, Canada, Austr ...
(MPG), where 1 MPG (imperial) ≈ 0.354006 km/L. The higher the value, the more economic a vehicle is (the more distance it can travel with a certain volume of fuel). This measure is popular in the US and the UK (mpg), but in Europe, India, Japan, South Korea and Latin America the metric unit ''km/L'' is used instead.
The formula for converting to miles per US gallon (3.7854 L) from L/100 km is
, where
is value of L/100 km. For miles per Imperial gallon (4.5461 L) the formula is
.
In parts of Europe, the two standard measuring cycles for "litre/100 km" value are "urban" traffic with speeds up to 50 km/h from a cold start, and then "extra urban" travel at various speeds up to 120 km/h which follows the urban test. A combined figure is also quoted showing the total fuel consumed in divided by the total distance traveled in both tests.
Statistics
A reasonably modern European
supermini and many mid-size cars, including station wagons, may manage
motorway
A controlled-access highway is a type of highway that has been designed for high-speed vehicular traffic, with all traffic flow—ingress and egress—regulated. Common English terms are freeway, motorway and expressway. Other similar terms i ...
travel at 5 L/100 km (47 mpg US/56 mpg imp) or 6.5 L/100 km in city traffic (36 mpg US/43 mpg imp), with
carbon dioxide
Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...
emissions of around 140 g/km.
An average
North American
mid-size car travels 21 mpg (US) (11 L/100 km) city, 27 mpg (US) (9 L/100 km) highway; a
full-size
Full-size car—also known as large car—is a vehicle size class which originated in the United States and is used for cars larger than mid-size cars, it is the largest size class for cars. In Europe, it is known as E-segment or F-segment.
...
SUV
A sport utility vehicle (SUV) is a car classification that combines elements of road-going passenger cars with features from off-road vehicles, such as raised ground clearance and four-wheel drive.
There is no commonly agreed-upon definiti ...
usually travels 13 mpg (US) (18 L/100 km) city and 16 mpg (US) (15 L/100 km) highway.
Pickup trucks vary considerably; whereas a 4 cylinder-engined light pickup can achieve 28 mpg (8 L/100 km), a
V8 full-size pickup with extended cabin only travels 13 mpg (US) (18 L/100 km) city and 15 mpg (US) (15 L/100 km) highway.
The average fuel economy for all vehicles on the road is higher in Europe than the United States because the higher cost of fuel changes consumer behaviour. In the UK, a gallon of gas without tax would cost US$1.97, but with taxes cost US$6.06 in 2005. The average cost in the United States was US$2.61.
European-built cars are generally more fuel-efficient than US vehicles. While Europe has many higher efficiency diesel cars, European gasoline vehicles are on average also more efficient than gasoline-powered vehicles in the USA. Most European vehicles cited in the CSI study run on diesel engines, which tend to achieve greater fuel efficiency than gas engines. Selling those cars in the United States is difficult because of emission standards, notes Walter McManus, a fuel economy expert at the University of Michigan Transportation Research Institute. "For the most part, European diesels don’t meet U.S. emission standards", McManus said in 2007. Another reason why many European models are not marketed in the United States is that labor unions object to having the big 3 import any new foreign built models regardless of fuel economy while laying off workers at home.
An example of European cars' capabilities of fuel economy is the
microcar
Microcar is a term often used for the smallest size of cars, with three or four wheels and often an engine smaller than . Specific types of microcars include bubble cars, cycle cars, invacar, quadricycles and voiturettes. Microcars are oft ...
''
Smart Fortwo'' cdi, which can achieve up to 3.4 L/100 km (69.2 mpg US) using a
turbocharged three-cylinder 41 bhp (30 kW) Diesel engine. The Fortwo is produced by
Daimler AG
The Mercedes-Benz Group AG (previously named Daimler-Benz, DaimlerChrysler and Daimler) is a German multinational automotive corporation headquartered in Stuttgart, Baden-Württemberg, Germany. It is one of the world's leading car manufactu ...
and is only sold by one company in the United States. Furthermore, the world record in fuel economy of production cars is held by the
Volkswagen Group
Volkswagen AG (), known internationally as the Volkswagen Group, is a German multinational automotive manufacturer headquartered in Wolfsburg, Lower Saxony, Germany. The company designs, manufactures and distributes passenger and commercial ...
, with special production models (labeled "3L") of the
Volkswagen Lupo
The Volkswagen Lupo (''Typ'' 6X) is a city car that was produced by the German car manufacturer Volkswagen, from 1998 to 2005. It shares most of its aspects with the Volkswagen Group's SEAT Arosa, both derived from the Volkswagen Polo Mk3 platfor ...
and the
Audi A2
The Audi A2 (internally designated ''Typ'' 8Z) is a compact MPV-styled supermini car, with a five-door hatchback body style and four or five seats,ETKA official factory data produced by the German manufacturer Audi from November 1999 (for the 200 ...
, consuming as little as .
Diesel engine
The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is a so-ca ...
s generally achieve greater fuel efficiency than petrol (gasoline) engines. Passenger car diesel engines have
energy efficiency
Energy efficiency may refer to:
* Energy efficiency (physics), the ratio between the useful output and input of an energy conversion process
** Electrical efficiency, useful power output per electrical power consumed
** Mechanical efficiency, a ra ...
of up to 41% but more typically 30%, and petrol engines of up to 37.3%, but more typically 20%. A common margin is 25% more miles per gallon for an efficient turbodiesel.
For example, the current model Skoda Octavia, using Volkswagen engines, has a combined European fuel efficiency of for the petrol engine and for the — and heavier — diesel engine. The higher compression ratio is helpful in raising the energy efficiency, but diesel fuel also contains approximately 10% more energy per unit volume than gasoline which contributes to the reduced fuel consumption for a given power output.
In 2002, the United States had 85,174,776 trucks, and averaged . Large trucks, over , averaged .
The average economy of automobiles in the United States in 2002 was . By 2010 this had increased to . Average fuel economy in the United States gradually declined until 1973, when it reached a low of and gradually has increased since, as a result of higher fuel cost. A study indicates that a 10% increase in gas prices will eventually produce a 2.04% increase in fuel economy. One method by car makers to increase fuel efficiency is
lightweighting in which lighter-weight materials are substituted in for improved engine performance and handling.
[Dee-Ann Durbin of the Associated Press, June 17, 2014, Mercury News]
Auto industry gets serious about lighter materials
, Retrieved April 11, 2015, "...Automakers have been experimenting for decades with lightweighting... the effort is gaining urgency with the adoption of tougher gas mileage standards. ..."
Fuel efficiency in microgravity
How fuel combusts affects how much energy is produced. The
National Aeronautics and Space Administration (NASA) has investigated fuel consumption in
microgravity.
The common distribution of a flame under normal gravity conditions depends on
convection
Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the conve ...
, because soot tends to rise to the top of a flame, such as in a candle, making the flame yellow. In microgravity or
zero gravity
Weightlessness is the complete or near-complete absence of the sensation of weight. It is also termed zero gravity, zero G-force, or zero-G.
Weight is a measurement of the force on an object at rest in a relatively strong gravitational f ...
, such as an environment in
outer space
Outer space, commonly shortened to space, is the expanse that exists beyond Earth and its atmosphere and between celestial bodies. Outer space is not completely empty—it is a near-perfect vacuum containing a low density of particles, pred ...
, convection no longer occurs, and the flame becomes
spherical
A sphere () is a geometrical object that is a three-dimensional analogue to a two-dimensional circle. A sphere is the set of points that are all at the same distance from a given point in three-dimensional space.. That given point is the ce ...
, with a tendency to become more blue and more efficient. There are several possible explanations for this difference, of which the most likely one given is the hypothesis that the temperature is evenly distributed enough that soot is not formed and complete combustion occurs., National Aeronautics and Space Administration, April 2005. Experiments by NASA in microgravity reveal that
diffusion flame
In combustion, a diffusion flame is a flame in which the oxidizer and fuel are separated before burning. Contrary to its name, a diffusion flame involves both diffusion and convection processes. The name diffusion flame was first suggested by S. ...
s in microgravity allow more soot to be completely oxidised after they are produced than diffusion flames on Earth, because of a series of mechanisms that behaved differently in microgravity when compared to normal gravity condition
LSP-1 experiment results National Aeronautics and Space Administration, April 2005.
Premixed flame
A premixed flame is a flame formed under certain conditions during the combustion of a premixed charge (also called pre-mixture) of fuel and oxidiser. Since the fuel and oxidiser—the key chemical reactants of combustion—are available througho ...
s in microgravity burn at a much slower rate and more efficiently than even a candle on Earth, and last much longer.
Transportation
Fuel efficiency in transportation
Vehicle efficiency and transportation pollution
Fuel efficiency directly affects emissions causing pollution by affecting the amount of fuel used. However, it also depends on the fuel source used to drive the vehicle concerned. Cars for example, can run on a number of fuel types other than gasoline, such as
natural gas
Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbo ...
,
LPG or
biofuel or electricity which creates various quantities of atmospheric pollution.
A kilogram of carbon, whether contained in petrol, diesel, kerosene, or any other hydrocarbon fuel in a vehicle, leads to approximately 3.6 kg of
CO2 emissions.
Due to the carbon content of gasoline, its combustion emits 2.3 kg/L (19.4 lb/US gal) of
CO2; since diesel fuel is more energy dense per unit volume, diesel emits 2.6 kg/L (22.2 lb/US gal).
This figure is only the CO
2 emissions of the final fuel product and does not include additional CO
2 emissions created during the drilling, pumping, transportation and refining steps required to produce the fuel. Additional measures to reduce overall emission includes improvements to the efficiency of
air conditioners, lights and tires.
Driving technique
Many drivers have the potential to improve their fuel efficiency significantly.
Thes
five basic fuel-efficient driving techniquescan be effective. Simple things such as keeping tires properly inflated, having a vehicle well-maintained and avoiding idling can dramatically improve fuel efficiency.
There is a growing community of enthusiasts known as hypermilers who develop and practice driving techniques to increase fuel efficiency and reduce consumption. Hypermilers have broken records of fuel efficiency, for example, achieving 109 miles per gallon in a
Prius
The is a car built by Toyota which has a hybrid drivetrain, combining an internal combustion engine with an electric motor. Initially offered as a four-door sedan, it has been produced only as a five-door liftback since 2003.
In 2007, th ...
. In non-hybrid vehicles these techniques are also beneficial, with fuel efficiencies of up to in a
Honda Accord
The , also known as the in Japan and China for certain generations, is a series of cars manufactured by Honda since 1976, best known for its four-door sedan variant, which has been one of the best-selling cars in the United States since 1989. ...
or in an
Acura MDX
The Acura MDX is a mid-size luxury crossover SUV with three-row seating produced by the Japanese automaker Honda under its luxury Acura division since 2000. The alphanumeric moniker stands for "Multi-Dimensional" luxury. It has ranked as the seco ...
.
Advanced technology improvements to improve fuel efficiency
The most efficient machines for converting energy to rotary motion are electric motors, as used in
electric vehicles. However, electricity is not a primary energy source so the efficiency of the electricity production has also to be taken into account.
Railway
Rail transport (also known as train transport) is a means of transport that transfers passengers and goods on wheeled vehicles running on rails, which are incorporated in tracks. In contrast to road transport, where the vehicles run on a pre ...
trains can be powered using electricity, delivered through an additional running rail, overhead
catenary
In physics and geometry, a catenary (, ) is the curve that an idealized hanging chain or cable assumes under its own weight when supported only at its ends in a uniform gravitational field.
The catenary curve has a U-like shape, superfici ...
system or by on-board generators used in
diesel-electric locomotives as common on the US and UK rail networks. Pollution produced from centralised generation of electricity is emitted at a distant power station, rather than "on site". Pollution can be reduced by using more railway electrification and
low carbon power
Low-carbon power is electricity produced with substantially lower greenhouse gas emissions than conventional fossil fuel power generation. The energy transition to low-carbon power is one of the most important actions required to limit clima ...
for electricity. Some railways, such as the French SNCF and Swiss federal railways derive most, if not 100% of their power, from hydroelectric or nuclear power stations, therefore atmospheric pollution from their rail networks is very low. This was reflected in a study by AEA Technology between a
Eurostar
Eurostar is an international high-speed rail service connecting the United Kingdom with France, Belgium and the Netherlands. Most Eurostar trains travel through the Channel Tunnel between the United Kingdom and France, owned and operate ...
train and airline journeys between London and Paris, which showed the trains on average emitting 10 times less CO
2, per passenger, than planes, helped in part by French nuclear generation.
Hydrogen fuel cells
In the future,
hydrogen cars may be commercially available. Toyota is test-marketing vehicles powered by hydrogen fuel cells in southern California, where a series of hydrogen fueling stations has been established. Powered either through chemical reactions in a
fuel cell that create electricity to drive very efficient electrical motors or by directly burning hydrogen in a combustion engine (near identically to a
natural gas vehicle
A natural gas vehicle (NGV) is an alternative fuel vehicle that uses compressed natural gas (CNG) or liquefied natural gas (LNG). Natural gas vehicles should not be confused with autogas vehicles powered by liquefied petroleum gas (LPG), ma ...
, and similarly compatible with both natural gas and gasoline); these vehicles promise to have near-zero pollution from the tailpipe (exhaust pipe). Potentially the atmospheric pollution could be minimal, provided the hydrogen is made by
electrolysis using electricity from non-polluting sources such as solar, wind or
hydroelectricity
Hydroelectricity, or hydroelectric power, is electricity generated from hydropower (water power). Hydropower supplies one sixth of the world's electricity, almost 4500 TWh in 2020, which is more than all other renewable sources combined an ...
or nuclear. Commercial
hydrogen production
Hydrogen production is the family of industrial methods for generating hydrogen gas. As of 2020, the majority of hydrogen (∼95%) is produced from fossil fuels by steam reforming of natural gas and other light hydrocarbons, partial oxidation of ...
uses fossil fuels and produces more carbon dioxide than hydrogen.
Because there are pollutants involved in the manufacture and destruction of a car and the production, transmission and storage of electricity and hydrogen, the label "zero pollution" applies only to the car's conversion of stored energy into movement.
In 2004, a consortium of major auto-makers —
BMW,
General Motors,
Honda
is a Japanese public multinational conglomerate manufacturer of automobiles, motorcycles, and power equipment, headquartered in Minato, Tokyo, Japan.
Honda has been the world's largest motorcycle manufacturer since 1959, reaching a producti ...
,
Toyota
is a Japanese multinational automotive manufacturer headquartered in Toyota City, Aichi, Japan. It was founded by Kiichiro Toyoda and incorporated on . Toyota is one of the largest automobile manufacturers in the world, producing about 10 ...
and
Volkswagen
Volkswagen (),English: , . abbreviated as VW (), is a German motor vehicle manufacturer headquartered in Wolfsburg, Lower Saxony, Germany. Founded in 1937 by the German Labour Front under the Nazi Party and revived into a global brand post-W ...
/
Audi
Audi AG () is a German automotive manufacturer of luxury vehicles headquartered in Ingolstadt, Bavaria, Germany. As a subsidiary of its parent company, the Volkswagen Group, Audi produces vehicles in nine production facilities worldwide.
Th ...
— came up with ''"Top Tier Detergent Gasoline Standard"'' to
gasoline
Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignited internal combustion engines (also known as petrol engines). It consists mostly of organi ...
brands in the US and Canada that meet their minimum standards for
detergent content
[Top Tier Gasoline](_blank)
and do not contain metallic additives. Top Tier gasoline contains higher levels of detergent additives in order to prevent the build-up of deposits (typically, on
fuel injector
Fuel injection is the introduction of fuel in an internal combustion engine, most commonly automotive engines, by the means of an injector. This article focuses on fuel injection in reciprocating piston and Wankel rotary engines.
All comp ...
and
intake valve
A poppet valve (also called mushroom valve) is a valve typically used to control the timing and quantity of gas or vapor flow into an engine.
It consists of a hole or open-ended chamber, usually round or oval in cross-section, and a plug, usual ...
) known to reduce fuel economy and engine performance.
See also
References
External links
US Government website on fuel economyUK DfT comparisons on road and railNASA Offers a $1.5 Million Prize for a Fast and Fuel-Efficient Aircraft
Car Fuel Consumption Official Figures(cf.
Spritmonitor)
*
ttp://fueleconomy.carconsumption.com/ Searchable fuel economy data from the EPA - United States Environmental Protection Agencypenghemat bbm - Alat penghemat bbm
{{DEFAULTSORT:Fuel Efficiency
Energy economics
Physical quantities
Energy efficiency
Transport economics