Use this comprehensive glossary to define terms commonly used in the alternative fuels and advanced vehicles industry. If you have questions about specific technologies or fuels, contact the Technical Response Service at 1-800-254-6735.
Click on the appropriate letter.· A · B · C · D · E · F · G · H · I · J · K · L · M · N · O · P · Q · R · S · T · U · V · W · X · Y · Z ·
· A ·
A nonprofit organization that develops and delivers international standards. ASTM standards, test methods, specifications, and procedures are recognized as definitive guidelines for fuel quality.
Advanced Technology Vehicles
A vehicle that combines new engine, power, or drivetrain systems to significantly improve fuel economy. This includes hybrid power systems and fuel cells, as well as some specialized electric vehicles.
Alternative Fuel Vehicles
A dedicated, flexible fuel, or dual-fuel vehicle designed to operate on at least one alternative fuel.
The Energy Policy Act of 1992 defines an alternative fuel as:
Anaerobic digestion is series of processes in which microorganisms break down biodegradable material in the absence of oxygen.
· B ·
The lowest temperature at which a flammable gas vapor will ignite spontaneously, without a source of ignition, after several minutes of exposure to sources of heat.
Chemical reactions in living organisms.
Using enzymes and catalysts to change biological substances chemically to produce energy products. An example is digestion of organic wastes or sewage by microorganisms to produce methane.
Plant matter such as trees, grasses, agricultural residue, algae, and other biological material.
· C ·
A fuel dispenser that draws fuel from two separate storage tanks and can dispense preprogrammed blends of those two fuels.
Cetane number relates to the fuels susceptibility to self-ignite. The higher the cetane number, the greater the fuel's tendency to self-ignite.
· E ·
Clean Air Act Amendments of 1990
Amendments to the Clean Air Act of 1970 creating two gasoline standards to reduce vehicle emissions in highly polluted cities by requiring gasoline to contain cleaner-burning additives, such as ethanol.
A high-level gasoline-ethanol blend containing 51% to 83% ethanol, depending on geography and season.
An interconnected system that maintains an instantaneous balance between supply and demand (generation and load) while moving electricity from generation source to customer.
Electric current used as a power source. Electricity can be produced from a variety of feedstocks, including oil, coal, nuclear, hydro, natural gas, wind, and solar.
Electrolysis is a method by which an electric current splits water into hydrogen and oxygen. If the electricity used is from renewable sources, such as solar or wind, the resulting hydrogen will be considered renewable as well.
Emission Control Technologies
Equipment used in diesel-powered vehicles to reduce exhaust emissions, such as particulate matter and nitrogen oxides. New engines and vehicles can be designed with these technologies, and used engines can be retrofitted to use this equipment.
· F ·
Energy Policy Act of 1992
Passed by Congress to enhance U.S. energy security by requiring federal, state, and alternative fuel provider fleets to implement petroleum-reduction measures. Learn more about EPAct Transportation Regulatory Activities.
Any material converted to another form of fuel or energy product. An example is using cornstarch to produce ethanol.
The minimum temperature at which a liquid gives off vapor within a test vessel in sufficient concentration to form an ignitable mixture with air near the surface of the liquid.
· G ·
A chemical used in fuel to reduce friction and increase performance.
Gasoline Gallon Equivalent
The amount of fuel it takes to equal the energy content of one liquid gallon of gasoline where one gasoline gallon equivalent (GGE) equals 120,167 British thermal units (BTUs).
· H ·
Gross Vehicle Weight Rating
The maximum weight of a vehicle, including curb weight (the weight of the vehicle on its own) and payload (the weight of cargo).
Higher Heating Value
The heating value is the amount of heat released during the combustion of a specific substance, usually a fuel or food. The higher heating value is determined by bringing all the products of combustion back to the original pre-combustion temperature, condensing any water vapor generated. This value assumes the entire water component is liquid in the products of combustion and that heat can be used.
· I ·
The ability to reduce friction—usually in fuel pumps and fuel injectors.
The additional price of an alternative fuel vehicle over a similar conventional vehicle.
Internal Combustion Engine
A conventional vehicle motor that burns fossil fuel in a chamber in the presence of air.
· K ·
Two or more compounds with the same formula but a different arrangement of atoms in the molecule and different properties.
· L ·
A measurement for electricity use.
Legacy electric charging systems such as inductive paddles. Learn more about types of chargers.
A large group or block (aggregate) of consumers joined together to leverage their combined purchasing power when negotiating rates for energy services.
· N ·
Lower Heating Value
The heating value is the amount of heat released during the combustion of a specific substance, usually a fuel or food. The lower heating value is determined by subtracting the heat of vaporization of water from the higher heating value for a particular substance, treating any water as a vapor.
· O ·
Negative Energy Balance
When producing a fuel takes more energy than the amount of energy the fuel provides.
A cleaner-burning additive in a fuel—usually containing hydrogen, carbon, and oxygen. Examples are ethers and alchohols, such as ethanol and methanol.
· P ·
Fuels blended with an additive—usually ether or ethanol—to increase oxygen content, allowing more-thorough combustion for reduced carbon monoxide emissions.
Passenger-Miles per Gallon
Pmpg is the vehicle miles per gallon multiplied by the number of passengers traveling in the vehicle.
Petroleum Administration for Defense Districts
The Petroleum Administration for Defense Districts (PADD) are groupings of U.S. states and the District of Columbia. These districts are defined by the U.S. Energy Information Administration and used to report fuel prices.
Positive Energy Balance
When producing a fuel takes less energy than the amount of energy the fuel provides.
· R ·
Pump Octane Number
This number represents the ability of a fuel to resist knocking when ignited in the cylinder of an internal-combustion engine. The number here is the average of the research octane number and motor octane number.
A feature of hybrid and plug-in electric vehicles that captures energy normally lost during braking by using the electric motor as a generator and storing the captured energy in the battery.
· S ·
Renewable Fuels Standard
A regulation created under the Energy Policy Act of 2005 and implemented by the U.S. Environmental Protection Agency to ensure transportation fuel sold in the United States contains a minimum volume of renewable fuel.
· T ·
Selective Catalytic Reduction
Selective catalytic reduction (SCR) is a means of converting nitrogen oxides (NOx) into nitrogen (N2) and water (H20). This is done using a reductant, such as urea or ammonia, and a catalyst.
Emissions produced through fuel combustion during a vehicle's operation.
Animal fat that can be used to produce biodiesel.
Technical Response Service
For assistance with technical questions about alternative fuels and advanced vehicles, email the Technical Response Service at firstname.lastname@example.org or call 1-800-254-6735.
Heat and pressure-based chemical reactions that produce energy. Through gasification (heating biomass by partial oxidation to produce synthesis gas) and pyrolysis (heating biomass in the absence of oxygen to produce liquid oil), biomass feedstocks can be converted to alcohol and hydrocarbon fuels, chemicals, and power.
In this process, the feedstock chemically reacts with an alcohol (usually methanol) in the presence of a catalyst, like lye. The products are glycerin and the biodiesel fuel or FAME (fatty acid methyl esters).
· V ·
An energy-consuming sector that consists of all vehicles whose primary purpose is transporting people and/or goods from one physical location to another. Included are automobiles; trucks; buses; recreational vehicles; motorcycles; trains, subways, and other rail vehicles; aircraft; ships, barges, and other waterborne vehicles; and pipelines. Vehicles whose primary purpose is not transportation (e.g., construction cranes and bulldozers, farming vehicles, and warehouse tractors and forklifts) are not included.
Vapor pressure is the pressure of the vapor resulting from evaporation of a fuel above a sample of the liquid in a closed container. It is used to measure volatility, an important property of transportation fuels.
A system of classifying vehicles (e.g., passenger cars, commercial vehicles, trailers, off-road vehicles, and special-purpose vehicles).
· Y ·
Vehicle Weight Class
The size of vehicles. Includes light-duty, medium-duty, and heavy-duty vehicles based on their gross vehicle weight rating (the weight of a vehicle on its own plus the weight of cargo).
· w ·
Second-hand cooking oil that can be used to produce biodiesel.
Analysis of energy use and emissions from the primary energy source through vehicle operation.