IAGS Glossary

Glossary

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

Activation. — Chemical. Treatment of a substance by heat, radiation, or other activating reagent to produce a more complete or rapid chemical or physical change. Electrical. The process of treating a cathode to increase its rate of reduction.

Alcohols — Organic compounds that are distinguished from hydrocarbons by the inclusion of a hydroxyl group. The two simplest alcohols are methanol and ethanol.

Aldehydes — A class of organic compounds derived by removing the hydrogen atoms from an alcohol. Aldehydes can be produced from the oxidation of an alcohol.

Alkaline Fuel Cell (AFC) — A type of hydrogen/oxygen fuel cell in which the electrolyte is concentrated KOH (35 - 50%, a liquid) and hydroxide ions (OH-) are transported from the cathode to the anode. Temperature of operation is typically in the range of 60 - 90ºC.

Alternating Current (AC) — An electric current that reverses its direction of flow from positive to negative at regular intervals, typically 60 times per second. The most efficient type of electric motor uses AC.

Alternative Fuel — As defined by the National Energy Policy Act (EPAct) the fuels are methanol, denatured alcohol and other alcohols, separately or in mixtures of 85 percent by volume or more (or other percentage not less than 70 percent as determined by U.S. Department of Energy rule) with gasoline or other fuels; Compressed Natural Gas (CNG); Liquefied Natural Gas (LNG); Liquefied Petroleum Gas LPG; hydrogen; "coal-derived liquid fuels; " fuels "other than alcohols" derived from "biological materials; " electricity, or any other fuel determined to be "substantially not petroleum" and yielding "substantial energy security benefits and substantial environment benefits."

Alternative Fuels Data Center (AFDC) — A program sponsored by the Department of Energy (DOE) and managed by the National Renewable Energy Laboratory (NREL) to collect emissions, operational and maintenance data on all types of alternative fuel vehicles across the country.

Ampere/Amperage (Amp) — Standard unit used to measure electric current; proportional to the quantity of electrons flowing through a conductor past a given point in one second. Amperage is calculated by dividing watts by volts.

Anion — Negative ion. Alkali, molten carbonate and solid oxide fuel cells are "anion-mobile" cells — anions migrate through the electrolyte toward the anode.

Anode — One of two electrodes in a fuel cell or battery. The anode, the negative post of the fuel cell, conducts the electrons that are freed from the hydrogen molecules so that they can be used in an external circuit. It has channels etched into it that disperse the hydrogen gas equally over the surface of the catalyst.

Aromatics — Hydrocarbons based on the ringed six-carbon benzene series of related organic groups. Benzene, Toluene and Xylene are the principal aromatics, commonly referred to as the BTX group. They represent one of the heaviest fractions of gasoline.

Auxiliary Power —Power from an independent source that functions as required to augment/support various performance criteria established for the prime power source.

Balance of Plant — Fuel cell power system supporting components, based on site-specific requirements and integrated into a comprehensive power system.

Battery — A battery is a container, or group of containers, holding electrodes and an electrolyte for producing electric current by chemical reaction and storing energy. The individual containers are called "cells". Batteries produce Direct Current (DC).

Battery Life — Number of miles an EV will travel on one battery pack before the pack must be replaced.

Benzene — A six-carbon aromatic; common gasoline component identified as being toxic. Benzene is a known carcinogen.

Biochemical Conversion — The use of enzymes and catalysts to change biological substances chemically to produce energy products. For example, the digestion of organic wastes or sewage by microorganisms to produce methane is a biochemical process.

Biodiesel — A biodegradable transportation fuel for use in diesel engines that is produced through the transesterfication of organically derived oils or fats. It may be used either as a replacement for or as a component of diesel fuel.

Biomass — Renewable organic matter such as agricultural crops, crop-waste residues, wood, animal and municipal waste, aquatic plants; and fungal growth, etc., used for the production of energy. More information about renewable energy sources.

Bipolar plates — Conductive plate in a fuel cell stack that acts as an anode for one cell and a cathode for the adjacent cell. The plate may be made of metal or a conductive polymer (which may be a carbon-filled composite). The plate usually incorporates flow channels for the fluid feeds and may also contain conduits for heat transfer.

British Thermal Unit (BTU)— The mean British Thermal Unit (BTU) is 1/180 of the heat required to raise the temperature of one pound (1 lb.) of water from 32ºF to 212ºF at a constant atmospheric pressure. It is about equal to the quantity of heat required to raise one pound (1 lb.) of water 1ºF.

Butane — A gas, easily liquefied, recovered from natural gas. Used as a low-volatility component of motor gasoline, processed further for a high-octane gasoline component, used in LPG for domestic and industrial applications and used as a raw material for petrochemical synthesis.

Butyl Alcohol — Alcohol derived from butane that is used in organic synthesis and as a solvent.

Capacity — Amount of electrical energy a cell or battery contains expressed in ampere-hours.

Carbon Dioxide (CO₂) — A product of combustion that has become an environmental concern in recent years. CO₂ does not directly impair human health but is a "greenhouse gas" that traps the earth's heat and contributes to the potential for global warming.

Carbon Monoxide (CO) — A colorless, odorless gas produced by the incomplete combustion of fuels with a limited oxygen supply as in automobile engines. CO is poisonous if inhaled, entering the bloodstream through the lungs and forming carboxyhemoglobin, a compound that inhibits the blood's capacity to carry oxygen to organs and tissues. CO can impair exercise capacity, visual perception, manual dexterity and learning functions.

Catalyst — A chemical substance that increases the rate of a reaction without being consumed, after the reaction it can potentially be recovered from the reaction mixture chemically unchanged. The catalyst lowers the activation energy required, allowing the reaction to proceed more quickly or at a lower temperature. In the context of fuel cells: a material that facilitates the reaction of oxygen and hydrogen without being affected itself. It is usually made of platinum powder very thinly coated onto carbon paper or cloth. The catalyst is rough and porous so that the maximum surface area of the platinum can be exposed to the hydrogen or oxygen. The platinum-coated side of the catalyst faces the membrane in the fuel cell.

Catalytic oxidation — Process of oxidizing unburned hydrocarbons and carbon monoxide by means of a catalytic reaction to reduce pollution..

Cathode — One of two electrodes in a fuel cell or battery. The cathode, the positive post of the fuel cell, has channels etched into it that distribute the oxygen to the surface of the catalyst. It also conducts the electrons back from the external circuit to the catalyst, where they can recombine with the hydrogen ions and oxygen to form water.

Cation — Positive ion. Phosphoric acid and PEM fuel cells are "cation-mobile" cells — the cation migrates through the electrolyte toward the cathode.

Cells — Basic unit used to store energy in a battery. A cell consists of an anode, cathode and the electrolyte.

Charge/Charging — Powering an EV battery to full capacity.

Charging Station — The physical device that provides a connection from a power source to an electric vehicle for charging.

Combustion —The rapid oxidation of fuel gases accompanied by flame and the production of heat, or heat and light.

Compressed Natural Gas (CNG) — Natural gas that has been condensed under high pressures, typically between 2,000 and 3,600 pounds per square inch, held in a container. The gas expands when released for use as a fuel.

Corrosion — Deteriorative loss of a metal as a result of environmental reactions.

Diesel Fuel — Petroleum products normally used as fuel for diesel engines are components of crude oil having heavy hydrocarbons containing at least 12 to 16 carbon atoms per molecule. These heavier fractions are taken from crude oil after the more volatile portions used in gasoline are removed.

Dimethyl Ether (DME) — A synthetic diesel fuel derived from natural gas, an excellent candidate for direct-injection engines. DME contains no sulfur and burns more cleanly than conventional diesel fuel, so it produces fewer particulates. It behaves much like propane, and its cetane number is 55-60, up to 20% better than modern diesel fuel. However, the viscosity of DME is 10 times less than that of diesel fuel, which makes it difficult to find pumps and valves that will not overheat or leak. Also, the entire fuel system must be kept under a pressure of at least 5 bars at room temperature to keep the DME liquid until it is injected.

Direct Internal Reforming —Production of a desired product (hydrogen) within a fuel cell from a hydrocarbon based fuel (methanol, gasoline, etc.) fed to the fuel cell or stack.

Direct Methanol Fuel Cell (DMFC) — A type of fuel cell in which the fuel is methanol (CH3OH), in gaseous or liquid form. The methanol is oxidized directly at the anode with no reformation to hydrogen. The electrolyte is typically a PEM.

Discharge Rate — The rate at which the battery expends its power.

Domestic Fuel — As defined by the Energy Policy Act, Section 301, domestic fuel is derived from resources within the United States, its possessions and commonwealths, and Canada and Mexico (the two nations in a free-trade agreement with the U.S.).

Direct Current (DC) — Electricity that flows continuously in one direction as contrasted with alternating current. Batteries produce direct current.

Driveline Efficiency — The measure of the amount of energy produced in an engine or motor that is used for propulsion (i.e. not wasted).

E85 — E85 is a blend of 85 percent ethanol and 15 percent gasoline. E85 runs clean, has good performance characteristics and is a domestic renewable energy.

Efficiency — A measure (usually a ratio) of the useful energy provided by a dynamic system versus the total energy supplied to it during a specific period of operation.

Electrical Efficiency —The ratio of useful electrical real power output to the total electrical power input.

Electric Vehicle (EV) — A vehicle that is propelled completely and exclusively by electric power.

Electrode — Electrical terminal that conducts an electric current into or out of a fuel cell.

Electrolyte — The medium of ion transfer, necessary to sustain the electrochemical process, between anode and cathode within the fuel cell. Usually liquid or paste which is either acidic or basic. Also insulates against electron transfer. In a PEM fuel cell, the electrolyte allows the transport of positively charged hydrogen ions (protons) from the anode, where they are produced, to the cathode where they react with oxygen molecules and electrons to produce water.

Electron — The negatively charged component of an atom and the unit of negative electrical charge.

Emissions standards —Regulatory standards that govern the amount of a given substance that can be discharged into the air.

Endothermic — Chemical reaction that absorbs heat.

Emissions — Exhaust emissions are the pollutants emitted by the engine through the tailpipe, high exhaust emissions leads to smog, poor air quality, and global warming.

Energy Density — A battery’s rated energy per unit of volume. Measured in units of watt-hours per liter (Wh/l).

Energy/Fuel Diversity — Policy that encourages the development of energy technologies to diversify energy supply sources, thus reducing reliance on conventional (petroleum) fuels; applies to all energy sources.

External Reforming — The production of hydrogen from a hydrocarbon fuel (methanol, gasoline, etc.) prior to entry to the fuel cell or stack.

Ethanol (also know as Ethyl Alcohol or Grain Alcohol, CH₃CH₂⁰H) — Can be produced chemically from ethylene or biologically from the fermentation of various sugars from carbohydrates found in agricultural crops and cellulosic residues from crops or wood. Used in the United States as a gasoline octane enhancer and oxygenate, it increases octane 2.5 to 3.0 numbers at 10% concentration. Ethanol can also be used in higher concentration in alternative-fuel vehicles optimized for its use.

Ethyl Tertiary Butly Ether (ETBE) — An aliphatic ether similar to MTBE. This fuel oxygenate is manufactured by reacting isobutylene with ethanol having high octane and low volatility characteristics ETBE can be added to gasoline up to a level of approximately 17 percent by volume. ETBE is used as an oxygenate in some reformulated gasolines.

EV (Electric Vehicle) — A vehicle powered by electricity, usually provided by batteries but may also be provided by photovoltaic (solar) cells or a fuel cell.

Flexible Fuel Vehicle (FFV) — A vehicle that can operate on any blend of gasoline and alcohol fuel (methanol or ethanol.)

Flue gases —Products of combustion plus excess air in appliance flues or heat exchangers.

Fuel Cell — An electrochemical engine (no moving parts) that converts the chemical energy of a fuel, such as hydrogen, and an oxidant, such as oxygen, directly to electricity. The principal components of a fuel cell are catalytically activated electrodes for the fuel (anode) and the oxidant (cathode) and an electrolyte to conduct ions between the two electrodes. The byproducts of fuel cells are pure water and useful heat. View a diagram of a fuel cell. Learn how a fuel cell works. Additional information about Fuel Cells.

Fuel processor — Device used to remove the hydrogen from fuels like methanol and ethanol, natural gas, propane, and gasoline, and convert it to hydrogen for use in fuel cell vehicles.

Gas— Fuel gas, such as natural gas, undiluted liquefied petroleum gases (vapor phase only), liquefied petroleum gas-air mixtures, or mixtures of these gases.

Gasification — A process that produces mixtures of Hydrogen and Carbon Monoxide - Synthesis Gas (Syn-Gas) - from carbonaceous materials. Additional information.

Gas Turbine — A turbine rotated by expanding gases.

Graphite — Mineral consisting of a form of carbon; it is soft, black, and lustrous and has a greasy feeling; used in pencils, crucibles, lubricants, paints, and polishes.

Hybrid Vehicle — Vehicles that have two or more sources of energy. There are two types of hybrid electric vehicles (HEVs), series and parallel. In a series hybrid, all of the vehicle power is provided from one source. For example, with an IC/electric series hybrid, the electric motor drives the vehicle from the battery pack and the internal combustion engine powers a generator that charges the battery. In a parallel hybrid, power is delivered through both paths. In an IC/electric parallel hybrid, both the electric motor and the internal combustion engine power the vehicle.

Hydrocarbons (HC) — The hydrogen and carbon residue that are left over after gasoline combustion. Hydrocarbon emissions are regulated by Federal law.

Hydrogen Fuel Cell — A fuel cell powered by hydrogen

Impurities — Undesirable foreign material(s) in a pure substance or mixture.

Indirect Internal Reforming — The reformer section is separated, but adjacent to, the fuel cell anode. This cell takes advantage of the close coupled thermal benefit where the exothermic heat of the cell reaction can be used for endothermic reforming reaction.

Internal combustion engine (ICE) — Engine does that converts the energy contained in the fuel inside the engine into motion. Combustion engines use the pressure created by the expansion of the gases to do mechanical work.

Ion — An electrically charged particle or molecule.

Kilowatt (kW) — The standard unit of measurement for electric power capacity. One kilowatt equals 1000 watts.

Kilowatt-Hour (kWh) — The standard unit for measuring large quantities of energy that are consumed over time. Specifically, it is one kilowatt supplied for one hour.

Liquefied Natural Gas (LNG) — Natural gas (primarily methane) that has been condensed to a liquid by reducing its temperature to -260 degrees Fahrenheit at atmospheric pressure.

Liquefied Petroleum Gas (LPG) — A mixture of hydrocarbons found in natural gas and produced from crude oil, used principally as a feedstock for the chemical industry, home heating fuel, and motor vehicle fuel.

Lithium-Ion Battery — A battery in which lithium is used as an electrochemically active material and the electrolyte is a liquid which conducts lithium ions.

Lithium Polymer Battery — A battery in which lithium is used as an electrochemically active material and the electrolyte is a polymer or polymer-like material which conducts lithium ions.

Low Emission Vehicle (LEV) — Refers to those light duty passenger vehicles that meet LEV emission control standards. California’s Air Resources Board and the Federal EPA set standards for tailpipe emissions and air emissions related to the volatility of fuel used in passenger cars and light trucks. California has established several categories of vehicles, based on the maximum permitted emissions of several pollutants. California has also established a fleet-wide emission control requirement.

Membrane — A thin sheet of natural or synthetic material that is permeable to substances in solution.

Membrane Electrode Assembly — The core of a fuel cell, consisting of two electrodes and the proton exchange membrane electrolyte bonded to form a single structure.

Metal Hydride Storage — A device that uses a metal alloy to store hydrogen. The hydrogen is soaked into the alloy like into a sponge filling spaces in the crystal lattice of the alloy. The storage is filled at moderate pressure (less than 1,000 pounds per square inch, psi) and is generally operated in the temperature range of 20 - 80°C.

Methanol (also known as Methyl Alcohol, Wood Alcohol, CH₃0H) — A liquid fuel formed by catalytically combining CO with hydrogen in a 1:2 ratio under high temperature and pressure. Methanol is a hydrogen carrier fuel. Info from the EPA: Methanol Basics. Also see Methanol Institute and Methanol and Fuel Cell vehicles.

Methyl Tertiary Butyl Ether (MTBE) — An ether manufactured by reacting methanol and isobutylene. The resulting ether has high octane and low volatility. MTBE is a fuel oxygenate and is permitted in unleaded gasoline up to a level of 15% by volume.

Miles Per Gallon Gasoline Equivalent (MPGGE) — The gasoline equivalent value is calculated based on the lower heating value of gasoline (42.6 kJ/g) and the density of gasoline (749 g/l) for all vehicles.

Mobile Source Emissions — Emissions resulting from the operations of any type of motor vehicle.

Natural Gas — A mixture of gaseous hydrocarbons, primarily methane, occurring naturally in the earth and used as a fuel.

Nitrogen Oxide (NO_x) — One of the exhaust emissions of an internal combustion engine. NO_x is produced by the combination of nitrogen and oxygen due to the high temperatures in the internal combustion process. NO_x emissions are regulated by Federal law.

Ohms — The unit of resistance (and of impedance) in the international system of units. One ohm is the resistance of a conductor such that a constant current of one ampere in it produces a voltage of one volt between its ends.

Oil sand — Mud-like material composed of sand, water and clay wrapped in thick hydrocarbon called bitumen. Once the bitumen is separated from the sand and the water it can be refined into synthetic crude.

Open-Loop Fuel Control — System in which the air/fuel mixture is preset by design with no feedback correction signal to optimize fuel metering.

Oxidation — Loss of one or more electrons by an atom, molecule, or ion. Oxidation is accompanied by an increase in oxidation number on the atoms, molecules, or ions that lose electrons.

Oxides of Nitrogen (NO_x) — Regulated air pollutants, primarily NO and NO₂ but including other substances in minute concentrations. Under the high pressure and temperature conditions in an engine, nitrogen and oxygen atoms in the air react to form various NO_x. Like hydrocarbons, NO_x are precursors to the formation of smog.

Oxygenate — A term used in the petroleum industry to denote fuel additives containing hydrogen, carbon and oxygen in their molecular structure. Includes ethers such as MTBE and ETBE and alcohols such as ethanol and methanol.

Oxygenated Fuels — Fuels blended with an additive, usually methyl tertiary butyl ether (MTBE) or ethanol to increase oxygen content, allowing more thorough combustion for reduced carbon monoxide emissions.

Partial Oxidation — Fuel reforming reaction where the fuel is partially oxidized to carbon monoxide and hydrogen rather than fully oxidized to carbon dioxide and water. This is accomplished by injecting air with the fuel stream prior to the reformer. The advantage of partial oxidation over steam reforming of the fuel is that it is an exothermic reaction rather than an endothermic reaction and therefore generates its own heat.

Particulate Matter (PM) — Unburned fuel particles that form smoke or soot and stock to lung tissue when inhaled. A chief component of exhaust emissions from heavy-duty diesel engines.

Particulate Trap — Diesel vehicle emission control device that traps and incinerates diesel particulate emissions after they are exhausted from the engine but before they are expelled into the atmosphere.

Photovoltaics — Also called "Solar Cells", these are cells that convert solar energy to electrical energy.

Polymer electrolyte membrane (PEM) — See Proton exchange membrane

Portable Fueling Systems — A System designed to deliver natural gas to fueling stations. Such systems are usually configured as tube trailers and are mobile. Fuel delivery usually occurs via over-the-roads vehicles.

Power — The rate at which energy is released, which is a measure of acceleration capability. Power is measured in kilowatts for an electric vehicle.

Powertrain — The elements of a propulsion system that convert electrical energy from a battery to mechanical energy at the wheels of a vehicle. It includes all drivetrain components plus an electrical power inverter and/or controller, but not the battery system.

Power Density —A batteries rated power per unit volume. Measured in units of watts per liter (w/l).

Private Fleet — A fleet of vehicles owned by a non-government entity.

Propane — A fuel comprised primarily of propane which is a gas at atmospheric pressures and is a liquid at the moderate pressures used for storage, propane fuel quality varies dramatically depending on the source of the fuel. See also LPG (Liquefied Petroleum Gas).

Proton exchange membrane (PEM) — Also called polymer electrolyte membrane. Specially treated material that looks something like ordinary kitchen plastic wrap but conducts only positively charged ions. It blocks electrons. The separating layer in a PEM fuel cell that acts as an electrolyte (which is proton conducting) as well as a barrier film separating the hydrogen-rich feed in the cathode compartment of the cell from the oxygen-rich anode side.

Proton Exchange Membrane Fuel Cell (PEMFC or PEFC)— Also called polymer electrolyte membrane fuel cell. A type of fuel cell in which the exchange of protons (H+) from the anode to the cathode via a membrane is involved in the chemical reaction producing electricity. The electrolyte is a called proton exchange membrane (PEM). The fuel cells typically run at low temperatures (<100ºC) and pressures (< 5 atm). Click here to see how it works.

Prototype — Functionally representative rendition of a device or system that is fabricated late in the development cycle, before production; an original model on which later improved models are based; an original piece of hardware that serves as the basis for evaluation, demonstration, and further development.

Reactor — Device or process vessel in which chemical reactions (e.g., catalysis in fuel cells) take place.

Reformer — Device that extracts pure hydrogen from hydrocarbon fuels.

Reforming — The thermal or catalytic conversion of petroleum naphtha into more volatile products with higher BTU ratings.

Reformulated gasoline — Gasoline that is blended so that, on average, it significantly reduces volatile organic compounds and air toxics emissions relative to conventional gasolines.

Reformulated Gasoline (RFG) — Gasolines that have had their compositions and/or characteristics altered to reduce vehicular emissions of pollutants, particularly pursuant to the EPA regulations under the CAA.

Refueling Emissions — VOC vapors that escape from the vehicle fuel tank during refueling. Storage II pump controls and onboard refueling vapor recovery systems (ORVR) are intended to control these emissions.

Retrofit — To change a vehicle or engine after its original purchase, usually by adding equipment such as conversion systems.

Resistance — The ability of an electrical conductor to resist the flow of current. The smaller the cross-section of the conductor, the greater the resistance. The higher the temperature, the greater the resistance. Thus, the higher the current, the larger the cable must be to carry the current effectively. Resistance is measured in ohms.

Solid Oxide —A hard ceramic compound of oxygen. In the context of fuel cells, the term refers to the electrolyte material, typically ZrO₂, the compound of zirconium metal and oxygen.

Solid Oxide Fuel Cell — A type of fuel cell that typically uses a hard ceramic material instead of a liquid electrolyte. SOFCs operate at very high temperatures (between 650 and 1000°C.) Click here for more detail (you'll need to scroll about half way down the page.)

Stack — Individual fuel cells connected in series.

Steam Reforming —A process for separating hydrogen from a hydrocarbon fuel, typically natural gas, in the presence of steam.

Sulfur Dioxide (SO₂) — An EPA criteria pollutant.

Syn-gas (Synthesis gas) — A gaseous mixture composed of carbon monoxide and hydrogen.

Tailpipe Emissions — EPA-regulated vehicle exhaust emissions released through the vehicle tailpipe. Tailpipe emissions do not include evaporative and refueling emissions, which are also regulated by EPA. EPA publishes allowable emission levels and vehicle certification standards in the Code of Federal Regulations.

TAME (Tiertiary Amyl Methyl Ether) — Another oxygenate that can be used in reformulated gasoline. It is another based on reactive C5 olefins and methanol.

Therm — A unit of heating value equivalent to 100,000 British Thermal Units (BTUs).

Torque — The amount of twisting force exerted at the crankshaft by the motor. The force that makes the wheel turn. Measured in foot-pounds.

Toxic Emission — Any pollutant emitted from a source that can negatively affect human health or the environment.

Toxic Substance — A generic term referring to a harmful substance or group of substances. Typically, these substances are especially harmful to health, such as those considered under EPA’s hazardous substance program. Technically, any compound that has the potential to produce adverse health effects is considered a toxic substance.

Turbine — Machine for generating rotary mechanical power from the energy in a stream of fluid. The energy, originally in the form of head or pressure energy, is converted to velocity energy by passing through a system of stationary and moving blades in the turbine.

U.S. Department of Energy (DOE) — A department of the Federal government established by Congress in 1977 to consolidate energy-oriented programs and agencies. The DOE mission includes the coordination and management of energy conservation, supply, information dissemination, regulation, research, development and demonstration. The Department includes the Office of Transportation Technologies, the umbrella of the Office of Alternative Fuels and others.

U.S. Department of Transportation (DOT) — A department of the Federal government established in 1967 that is responsible for transportation safety improvements and enforcement, international transportation agreements and the continuity of transportation services in the public interest. DOT consists of seven Administrations representing various transportation modes as well as the U.S. Coast Guard and the St. Lawrence Seaway Development Corporation. In addition, the department facilitates and coordinates various research, development and technology transfer activities to promote and advance technology innovation in the transportation sector.

U.S. Environmental Protection Agency (EPA) — A government agency, established in 1970, responsible for the protection of the environment and public health. EPA seeks to reduce air, water, and land pollution and pollution from solid waste, radiation, pesticides, and toxic substances. EPA also controls emissions from motor vehicles, fuels and fuel additives.

Variable Fuel Vehicle (VFV) — A vehicle that has the capacity of burning any combination of gasoline and an alternative fuel. Also known as a flexible fuel vehicle .

Vehicle Conversion — Retrofitting a vehicle engine to run on an alternative fuel.

Volatile Organic Compound (VOC) — Reactive gases released during combustion or evaporation of fuel and regulated by EPA. VOCs react with NO_x in the presence of sunlight and form ozone.

Volt — Unit of measurement expressing electromotive force. Watts divided by volts equals amps.

Watt — The unit of electrical power.

Xylene — An aromatic hydrocarbon derived from petroleum and used to increase octane. Highly valued as a petrochemical feedstock. Xylene is highly photochemically reactive and, as a constituent of tailpipe emissions, is a contributor to smog formation .

Zero Emission Vehicle(ZEV)— A vehicle that produces no air emissions from its fueling or operation. California regulations require in 2003, 10% of the vehicles sold in California by major auto makers be ZEV or ZEV equivalent. California has established a comprehensive program for determining this equivalency. See also LEV.