Glossary – Energy and Electrical Terms
Air-Conditioning – Cooling and dehumidifying the air in a building by a refrigeration unit by a refrigeration unit powered by electricity or natural gas. This definition excludes fans, blowers, or evaporative cooling systems (swamp coolers) that are not connected to a refrigeration unit. (See this word used in context.)
Air-Conditioning Equipment – Either a central system, window or wall units that cool the air in a housing unit by a refrigeration unit powered by electricity or natural gas. This definition excludes fans, blowers, or evaporative cooling systems (swamp coolers) that are not connected to a refrigeration unit.
Alternating Current – An electric current that reverses its direction at regular intervals or cycles; In the U.S. the standard is 120 reversals or 60 cycles per second; typically abbreviated as AC. (See this word used in context.)
Alternative-Fuel Vehicle (AFV) – A vehicle designed to operate on an alternative fuel (e.g., compressed natural gas, methane blend, electricity). The vehicle could be either a vehicle designed to operate exclusively on alternative fuel or a vehicle designed to operate on alternative fuel and/or a traditional fuel.
Anthropogenic – Made or generated by a human or caused by human activity. The term is used in the context of global climate change to refer to gaseous emissions that are the result of human activities, as well as other potentially climate-altering activities, such as deforestation.
Appliance – A piece of equipment, commonly powered by electricity, used to perform a particular energy-driven function. Examples of common appliances are refrigerators, clothes washers and dishwashers, conventional ranges/ovens and microwave ovens, humidifiers and dehumidifiers, toasters, radios, and televisions. (See this word used in context.)
Atomic Structure – The conceptualized concept of an atom, regarded as consisting of a central positively charged nucleus (protons and neutrons) and a number of negatively charged electrons revolving about in various orbits.
Average – The simple arithmetic average for a population; that is, the sum of all the values in a population divided by the size of the population. Population means are estimated by computing the weighted sum of the sample values, then dividing by the sum of the sample weights.
Avoided Cost – A renewable or cogeneration facility that qualifies for PURPA benefits is called a Qualifying Facility (QF). Utility companies buy the electricity from QFs at the “avoided cost.” This is the cost it would take for the utility company to generate the amount of electricity the QF produces.
Barrel: A unit of volume equal to 42 U.S. gallons. One barrel weights 306 pounds or 5.80 million Btu of crude oil. Barrel is abbreviated as bbl.
Also, see a brief list of Barrels, and convert barrels into other units using the energy calculator.
Biodiesel – An alternative fuel that can be made from any fat or vegetable oil. It can be used in any diesel engine with few or no modifications. Although biodiesel does not contain petroleum, it can be blended with diesel at any level or used in its pure form.
Biogenic waste – Waste made from materials that were produced by living organisms or biological processes. Note: EIA uses the term “biogenic” to refer only to organic nonfossil material of biological origin, such as paper or cotton.
Biomass – Any organic (plant or animal) material which is available on a renewable basis, including agricultural crops and agricultural wastes and residues, wood and wood wastes and residues, animal wastes, municipal wastes, and aquatic plants.
See our brief sections on: Biomass Energy and Biomass Energy Milestones.
British thermal unit (Btu) – The amount of heat required to raise the temperature of one pound of water one degree Fahrenheit; equal to 252 calories. British thermal unit is abbreviated as Btu. See our section on using Btu to compare energy.
Carbon Dioxide – A colorless, odorless noncombustible gas with the formula CO2 that is present in the atmosphere. It is formed by the combustion of carbon and carbon compounds (such as fossil fuels and biomass) and by respiration, which is a slow combustion in animals and plants, and by the gradual oxidation of organic matter in the soil.
Chain Reaction – A self-sustaining nuclear reaction which takes place during fission. A fissionable substance (i.e., uranium) absorbs a neutron and divides, releasing additional neutrons that are absorbed by other fissionable nuclei, releasing still more neutrons.
Climate Change – A term used to refer to all forms of climatic inconsistency, but especially to significant change from one prevailing climatic condition to another. In some cases, “climate change” has been used synonymously with the term “global warming”; scientists, however, tend to use the term in a wider sense inclusive of natural changes in climate, including climatic cooling.
Conversion Factors – A number that translates units of one measurement system into corresponding values of another measurement system. See our Energy Calculator.
Diesel Fuel – A fuel composed of distillates obtained in petroleum refining operation or blends of such distillates with residual oil used in motor vehicles. The boiling point and specific gravity are higher for diesel fuels than for gasoline.
Distillate Fuel Oil – A general classification for one of the petroleum fractions produced in conventional distillation operations. It includes diesel fuels and fuel oils. Products known as No. 1, No. 2, and No. 4 diesel fuel are used in on-highway diesel engines, such as those in trucks and automobiles, as well as off-highway engines, such as those in railroad locomotives and agricultural machinery. Products known as No. 1, No. 2, and No. 4 fuel oils are used primarily for space heating and electric power generation.
Distillation Unit (atmospheric) – The primary distillation unit that processes crude oil (including mixtures of other hydrocarbons) at approximately atmospheric conditions. It includes a pipe still for vaporizing the crude oil and a fractionation tower for separating the vaporized hydrocarbon components in the crude oil into fractions with different boiling ranges. This is done by continuously vaporizing and condensing the components to separate higher oiling point material.
Drilling – The act of boring a hole (1) to determine whether minerals are present in commercially recoverable quantities and (2) to accomplish production of the minerals (including drilling to inject fluids). There are three types of drilling : exploratory – drilling to locate probable mineral deposits or to establish the nature of geological structures; such wells may not be capable of production if minerals are discovered; developmental – drilling to delineate the boundaries of a known mineral deposit to enhance the productive capacity of the producing mineral property; and directional – drilling that is deliberately made to depart significantly from the vertical.
Electricity – A form of energy characterized by the presence and motion of elementary charged particles generated by friction, induction, or chemical change.
See our brief sections on: Electricity and Electricity Milestones.
Electricity Generation – The process of producing electric energy or the amount of electric energy produced by transforming other forms of energy, commonly expressed in kilowatthours (kWh) or megawatthours (MWh).
Emission – A discharge or something that is given off; generally used in regard to discharges into the air. Or, releases of gases to the atmosphere from some type of human activity (cooking, driving a car, etc). In the context of global climate change, they consist of greenhouse gases (e.g., the release of carbon dioxide during fuel combustion). Learn more about Greenhouse Gas Emissions on EIA’s main website (for grown-ups).
Energy – The ability to do work or the ability to move an object. Electrical energy is usually measured in kilowatthours (kWh), while heat energy is usually measured in British thermal units (Btu).
See our brief sections on What’s Energy? and General Energy Milestones,
Energy Efficiency – Refers to activities that are aimed at reducing the energy used by substituting technically more advanced equipment, typically without affecting the services provided. Examples include high-efficiency appliances, efficient lighting programs, high-efficiency heating, ventilating and air conditioning (HVAC) systems or control modifications, efficient building design, advanced electric motor drives, and heat recovery systems.
Ethanol – A colorless liquid that burns to produce water and carbon dioxide. The vapor forms an explosive mixture with air and may be used as a fuel in internal combustion engines.
See our brief sections on: Ethanol and Ethanol Milestones.
Fission – The splitting apart of atoms. This splitting releases large amounts of energy and one or more neutrons. Nuclear power plants split the nuclei of uranium atoms in a process called fission. See our section on Nuclear Energy.
- Oil and Oil Milestones,
- Coal and Coal Milestones,
- Natural Gas and Natural Gas Milestones, and
- Uranium and Nuclear Fuel Milestones.
Fusion – When the nuclei of atoms are combined or “fused” together. The sun combines the nuclei of hydrogen atoms into helium atoms in a process called fusion. Energy from the nuclei of atoms, called “nuclear energy” is released from fusion. See the Scientific Forms of Energy.
Gas – (1) A non-solid, non-liquid (as hydrogen or air) substance that has no fixed shape and tends to expand without limit. (2) A state of matter in which the matter concerned occupies the whole of its container irrespective of its quantity. Includes natural gas, coke-oven gas, blast furnace gas, and refinery gas.
Gasoline – A complex mixture of relatively volatile hydrocarbons with or without small quantities of additives, blended to form a fuel suitable for use in spark-ignition engines.
See our brief section on: Transportation Milestones.
Gas Turbine Plant – A plant in which the prime mover is a gas turbine. A gas turbine consists typically of an axial-flow air compressor and one or more combustion chambers where liquid or gaseous fuel is burned and the hot gases are passed to the turbine and where the hot gases expand drive the generator and are then used to run the compressor.
Geothermal Energy – The heat energy that is produced by natural processes inside the earth. It can be taken from hot springs, reservoirs of hot water deep below the ground, or by breaking open the rock itself.
See our brief sections on: Geothermal Energy and Geothermal Energy Milestones.
Global Warming – An increase in the near surface temperature of the Earth. Global warming has occurred in the distant past as the result of natural influences, but the term is today most often used to refer to the warming some scientists predict will occur as a result of increased anthropogenic emissions of greenhouse gases.
Greenhouse Effect – The effect of the Earth’s atmosphere, due to certain gases, in trapping heat from the sun; the atmosphere acts like a greenhouse. Learn more about the Greenhouse Effect on EIA’s main website (for grown-ups).
Greenhouse Emissions – Waste gases given off by industrial and power plants, automobiles and other processes. Learn more about Greenhouse Gas Emissions on EIA’s main website (for grown-ups).
Greenhouse Gases – Gases that trap the heat of the sun in the Earth’s atmosphere, producing the greenhouse effect. The two major greenhouse gases are water vapor and carbon dioxide. Lesser greenhouse gases include methane, ozone, chlorofluorocarbons, and nitrogen oxides. Learn more aboutGreenhouse Gas Emissions on EIA’s main website (for grown-ups).
Green Pricing – In the case of renewable electricity, green pricing represents a market solution to the various problems associated with regulatory valuation of the nonmarket benefits of renewables. Green pricing programs allow electricity customers to express their willingness to pay for renewable energy development through direct payments on their monthly utility bills.
Heat Content – The gross heat content is the number of British thermal units (Btu) produced by the combustion, of a volume of gas under certain with air of the same temperature and pressure as the gas, when the products of combustion are cooled to the initial temperature of gas and air and when the water formed by combustion is condensed to the liquid state.
Heating Equipment – Any equipment designed and/or specifically used for heating ambient air in an enclosed space. Common types of heating equipment include: central warm air furnace, heat pump, plug-in or built-in room heater, boiler for steam or hot water heating system, heating stove, and fireplace.
Hydrogen – A colorless, odorless, highly flammable gaseous element. It is the lightest of all gases and the most abundant element in the universe, occurring chiefly in combination with oxygen in water and also in acids, bases, alcohols, petroleum, and other hydrocarbons.
Hydropower – Energy that comes from moving water.
See our brief sections on: Water Energy.
Incandescent Light Bulb – An incandescent bulb is a type of electric light in which light is produced by a filament heated by electric current. The most common example is the type you find in most table and floor lamps. In commercial buildings, incandescent lights are used for display lights in retail stores, hotels and motels. This includes the very small, high-intensity track lights used to display merchandise or provide spot illumination in restaurants.
Joule – A metric unit for measuring work and energy, named after James Joule. It is equal to the work done when a one ampere current is passed through a resistance of one ohm for one second. See ourEnergy Calculator.
Kilowatthour(kWh) – A measure of electricity defined as a unit of work or energy, measured as 1 kilowatt (1,000 watts) of power expended for 1 hour. One kWh is equivalent to 3,412 Btu or 3.6 million joules.
Kinetic Theory of Gases – The theory that physical properties of a gas are due to the rapid motion in a straight line of its molecules, to their impacts against each other and the walls of the container, and to weak attraction forces between the molecules.
Liquefied Petroleum Gas (LPG) -A group of hydrocarbon-based gases derived from crude oil refining or natural gas fractionation. They include ethane, ethylene, propane, propylene, normal butane, butylene, isobutane, and isobutylene. For convenience of transportation, these gases are liquefied through pressurization.
Longwall Mining – An automated form of underground coal mining characterized by high recovery and extraction rates, feasible only in relatively flat-lying, thick, and uniform coalbeds. A high-powered cutting machine is passed across the exposed face of coal, shearing away broken coal, which is continuously hauled away by a floor-level conveyor system. Longwall mining extracts all machine-minable coal between the floor and ceiling within a contiguous block of coal, known as a panel, leaving no support pillars within the panel area. Panel dimensions vary over time and with mining conditions but currently average about 900 feet wide (coal face width) and more than 8,000 feet long (the minable extent of the panel, measured in direction of mining). Longwall mining is done under movable roof supports that are advanced as the bed is cut. The roof in the mined-out area is allowed to fall as the mining advances.
Megawatt – A unit of electrical power equal to 1000 kilowatts or one million watts. See our Energy Calculator.
Mercaptan – An organic chemical compound that has a sulfur like odor that is added to natural gas before distribution to the consumer, to give it a distinct, unpleasant odor (smells like rotten eggs). This serves as a safety device by allowing it to be detected in the atmosphere, in cases where leaks occur.
Methane -A colorless, flammable, odorless hydrocarbon gas (CH4) which is the major component of natural gas. It is also an important source of hydrogen in various industrial processes. Methane is a greenhouse gas.
Miles Per Gallon (MPG) – A measure of vehicle fuel efficiency. MPG is computed as the ratio of the total number of miles traveled by a vehicle to the total number of gallons consumed.
Also see our Energy Calculator.
Natural Gas – An odorless, colorless, tasteless, non-toxic clean-burning fossil fuel. It is usually found in fossil fuel deposits and used as a fuel.
See our brief sections on: Natural Gas and Natural Gas Milestones.
Natural Gas Hydrates – Solid, crystalline, wax-like substances composed of water, methane, and usually a small amount of other gases, with the gases being trapped in the interstices of a water-ice lattice. They form beneath permafrost and on the ocean floor under conditions of moderately high pressure and at temperatures near the freezing point of water.
Nonrenewable – Fuels that cannot be easily made or “renewed.” We can use up nonrenewable fuels. Oil, natural gas, and coal are nonrenewable fuels.
See our brief sections on Nonrenewable Energy.
Offshore – The geographic area that lies seaward of the coastline. In general, the coastline is the line of ordinary low water along with that portion of the coast that is in direct contact with the open sea or the line marking the seaward limit of inland water.
Oil – The raw material that petroleum products are made from. A black liquid fossil fuel found deep in the Earth. Gasoline and most plastics are made from oil.
See our brief sections on: Oil and Oil Milestones.
OPEC – The Organization of Petroleum Exporting Countries organized for the purpose of negotiating with oil companies on matters of oil production, prices, and future concession rights. Current members (as of the date of writing this definition) are Algeria, Indonesia, Iran, Iraq, Kuwait, Libya, Nigeria, Qatar, Saudi Arabia, the United Arab Emirates, and Venezuela. See OPEC’s site at http://www.opec.org for more information.
Petrochemicals – Organic and inorganic petroleum compounds and mixtures that include but are not limited to organic chemicals, cyclic intermediates, plastics and resins, synthetic fibers, elastomers, organic dyes, organic pigments, detergents, surface active agents, carbon black, and ammonia.
Periodic Table – Table of all known elements in a meaningful pattern. See Periodic Table.
Petroleum – Generally refers to crude oil or the refined products obtained from the processing of crude oil (gasoline, diesel fuel, heating oil, etc.) Petroleum also includes lease condensate, unfinished oils, and natural gas plant liquids.
See our brief sections on: Petroleum and Petroleum Milestones.
Photovoltaic Cells – A device, usually made from silicon, which converts some of the energy from light (radiant energy) into electrical energy. Another name for a solar cell.
See our brief sections on: Photovoltaics and Photovoltaic Milestones.
Prime Mover – The engine, turbine, water wheel, or similar machine that drives an electric generator; or, for reporting purposes, a device that converts energy to electricity directly (i.e. photovoltaic solar and fuel cells).
Propane (C3H8) – A normally gaseous straight-chain hydrocarbon. It is a colorless paraffinic gas that boils at a temperature of -43.67 degrees Fahrenheit. It is extracted from natural gas or refinery gas streams.
See our brief sections on Propane.
Public Utility Regulatory Policies Act (PURPA) – A law passed by Congress in 1978 to promote more efficient use of fossil fuels and greater use of renewable energy for generating electricity. A renewable or cogeneration facility that qualifies for PURPA benefits is called a Qualifying Facility (QF). Utility companies buy the electricity from QFs at the “avoided cost.” This is the cost it would take for the utility company to generate the amount of electricity the QF produces.
Refined Petroleum Products – Refined petroleum products include but are not limited to gasoline, kerosene, distillates (including No. 2 fuel oil), liquefied petroleum gas, asphalt, lubricating oils, diesel fuels, and residual fuels.
Semiconductor – Any material that has a limited capacity for conducting an electric current. Semiconductors are crystalline solids, such as silicon, that have an electrical conductivity between that of a conductor and an insulator.
Short ton – A unit of weight equal to 2,000 pounds, often used to measure coal. See our Energy Calculator.
Solar Power Tower – The conceptual method of producing electrical energy from solar rays. It involved the focusing of a large number of solar rays on a single source (boiler), usually located on an elevated tower, to produce high temperatures. A fluid located in or passed through the source changes into steam and used in a turbine generator to produce electrical energy.
Space Heating – The use of energy to generate heat for warmth in housing units using space-heating equipment. The equipment could be the main space-heating equipment or secondary space-heating equipment.
Spectrum of Electromagnetic Radiation – The name that scientists give to a bunch of types of radiation when they want to talk about them as a group. The types of radiation include the full range of frequencies, from radio waves to gamma waves, which characterize light.
Spent Fuel – Irradiated fuel that is permanently discharged from a nuclear reactor. Except for possible reprocessing, this fuel must eventually be removed from its temporary storage location at the reactor site and placed in a permanent repository. Spent fuel is typically measured either in metric tons of heavy metal (i.e., only the heavy metal content of the spent fuel is considered) or in metric tons of initial heavy metal (essentially, the initial mass of the fuel before irradiation). The difference between these two quantities is the weight of the fission products.
See our brief sections on: Nuclear Energy, Nuclear Power Milestones and Electricity Milestones.
Surface Mine – A coal-producing mine that is usually within a few hundred feet of the surface. Earth above or around the coal (overburden) is removed to expose the coal bed, which is then mined with surface excavation equipment, such as draglines, power shovels, bulldozers, loaders, and augers. It may also be known as an area, contour, open-pit, strip, or auger mine.
Transmission (Electric) – The movement or transfer of electric energy over an interconnected group of lines and associated equipment between points of supply and points at which it is transformed for delivery to consumers or is delivered to other electric systems. Transmission is considered to end when the energy is transformed for distribution to the consumer.
Transmission Line – A set of conductors, insulators, supporting structures, and associated equipment used to move large quantities of power at high voltage, usually over long distances between a generating or receiving point and major substations or delivery points.
Transmission System (Electric) – An interconnected group of electric transmission lines and associated equipment for moving or transferring electric energy in bulk between points of supply and points at which it is transformed for delivery over the distribution system lines to consumers or is delivered to other electric systems.
Turbine – A device which blades, which is turned by a force, e.g. that of wind, water , or high pressure steam. The mechanical energy of the spinning turbine is converted into electricity by a generator.
)Transportation Sector (of the Economy – The part of the economy having to do with the how people and goods are transported (moved) from place to place.. The transportation sector is made up of automobiles, airplanes, trucks, and ships. trains, etc.
See our brief section on: Transportation and Transportation Milestones.
Underground Mine – A mine where coal is produced by tunneling into the earth to the coal bed, which is then mined with underground mining equipment such as cutting machines and continuous, long wall, and short wall mining machines. Underground mines are classified according to the type of opening used to reach the coal, i.e., drift (level tunnel), slope (inclined tunnel), or shaft (vertical tunnel).
Uranium Fuel Cycle – The series of steps involved in supplying fuel for nuclear power reactors. It includes mining, refining, the making of fuel elements, their use in a reactor, chemical processing to recover spent (used) fuel, re-enrichment of the fuel material, and remaking into new fuel elements.
Vehicle Fuel Consumption – Vehicle fuel consumption is computed as the vehicle miles traveled divided by the fuel efficiency reported in miles per gallon (MPG). Vehicle fuel consumption is derived from the actual vehicle mileage collected and the assigned MPGs obtained from EPA certification files adjusted for on-road driving. The quantity of fuel used by vehicles.
Volt (V) – The volt is the International System of Units (SI) measure of electric potential or electromotive force. A potential of one volt appears across a resistance of one ohm when a current of one ampere flows through that resistance. Reduced to SI base units, 1 V = 1 kg times m2 times s-3 times A-1 (kilogram meter squared per second cubed per ampere).
Voltage – The difference in electrical potential between any two conductors or between a conductor and ground. It is a measure of the electric energy per electron that electrons can acquire and/or give up as they move between the two conductors.
Waste – Municipal solid waste, landfill gas, methane, digester gas, liquid acetonitrile waste, tall oil, waste alcohol, medical waste, paper pellets, sludge waste, solid byproducts, tires, agricultural byproducts, closed loop biomass, fish oil, and straw.
Waste Energy – Municipal solid waste, landfill gas, methane, digester gas, liquid acetonitrile waste, tall oil, waste alcohol, medical waste, paper pellets, sludge waste, solid byproducts, tires, agricultural byproducts, closed loop biomass, fish oil, and straw used as fuel.
See our brief sections on: Waste Energy , Waste Energy Milestones, and Waste-to-Energy Plant Visit.
Water Cycle – Water constantly moves through a vast global cycle, in which it evaporates from lakes and oceans, forms clouds, precipitates as rain or snow, then flows back to the ocean. The energy of this water cycle, which is driven by the sun, is tapped most efficiently with hydropower.
Watt – A metric unit of power, usually used in electric measurements, which gives the rate at which work is done or energy used. See our section on Measuring Electricity.
Wind – The term given to any natural movement of air in the atmosphere. A renewable source of energy used to turn turbines to generate electricity.
See our brief sections on: Wind Energy and Wind Energy Milestones.
Wood and Waste (as used at electric utilities) – Wood energy, garbage, bagasse (sugarcane residue), sewerage gas, and other industrial, agricultural, and urban refuse used to generate electricity for distribution.
Yellowcake: A natural uranium concentrate that takes its name from its color and texture. Yellowcake typically contains 70 to 90 percent U3O8 (uranium oxide) by weight. It is used as feedstock for uranium fuel enrichment and fuel pellet fabrication.