Glossary of Terms

A

Active Solar-Heating System: a system for using solar energy that requires equipment such as pumps and collectors.

Alternative Fuel Provider: A fuel provider (or any affiliate or business unit under its control) is an alternative fuel provider if its principal business is producing, storing, refining, processing, transporting, distributing, importing, or selling (at wholesale or retail) any alternative fuel (other than electricity); or generating, transmitting, importing, or selling (at wholesale and retail) electricity; or if that fuel provider produces, imports, or produces and imports (in combination), an average of 50,000 barrels per day of petroleum and 30% (a substantial portion) or more of its gross annual revenues are derived from producing alternative fuels.

Alternative Fuel: Methanol, denatured ethanol, and other alcohols; mixtures containing 85% or more by volume of methanol, denatured ethanol, and other alcohols with gasoline or other fuels; natural gas; liquefied petroleum gas; hydrogen; coal-derived liquid fuels; non-alcohol fuels (such as biodiesel) derived from biological material; and electricity. ‘P-Series’ fuels were added to this list since the original definition in EPAct.

Anaerobic: Not requiring oxygen to live; the micro-organisms used in manure biodigestion are anaerobic bacteria.

Anemometer: Measures the wind speed and transmits wind speed data to the controller.

B

B100: 100% (neat) biodiesel.

B20: blend of biodiesel fuel with petroleum-based diesel where 20% of the volume is biodiesel.

Biodiesel: A biodegradable transportation fuel for use in diesel engines that is produced through transesterification of organically derived vegetable and animal oils or fats. Currently, biodiesel is most often used as a component of diesel fuel. In the future it may be used as a replacement for diesel. The chemical name for biodiesel is fatty acid methyl (or ethyl) ester (FAME). Oils are mixed with sodium or potassium hydroxide (e.g., lye) and methanol (or ethanol) and the chemical reaction produces biodiesel (FAME) and glycerol. 1 part glycerol is produced for every 10 parts biodiesel.

Biofuels: Biofuels are any gaseous or liquid fuels produced from biomass that can be used as a fuel for engines. They are a renewable energy source. Biofuels refers to those biofuels which are used as a direct replacement for gasoline or diesel in gasoline or diesel engines, such as biodiesel and bioethanol.

Bioheat: Heat from vegetable- or animal-derived fuel, as opposed to a mineral source such as coal or petroleum oil, or the sun.

Biomass: Renewable organic matter such as agricultural crops; crop waste residues; wood, animal, and municipal waste, aquatic plants; fungal growth; etc., used for the production of energy.

Biomas-to-Liquid (BTL): Biomass to liquid (BTL) or BMTL is a (multi step) process to produce liquid biofuels from biomass: The process uses the whole plant to improve the CO2 balance and increase yield. 1) The Fischer Tropsch process is used to produce synfuels from gasified biomass. While biodiesel and bio-ethanol production so far only use parts of a plant, i.e. oil, sugar, starch or cellulose, BTL production uses the whole plant which is gasified by gasification. The result is that for BTL, less land area is required per unit of energy produced compared with biodiesel or bio-ethanol. 2) Flash Pyrolysis – producing bio-oil, char and gas at temperatures between 350-550°C and residence times < 1 second (also called anhydrous pyrolysis). 3) Catalytic depolymerization - using heat and catalysts to separate usable diesel fuel from hydrocarbon wastes.

Blades: Most turbines have either two or three blades. Wind blowing over the blades causes the blades to “lift” and rotate.

Btu: British thermal unit, the standard measure for the amount of heat produced. Technically, it’s the amount of heat required to raise one pound of water by one degree.

C

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 dioxide is compound of carbon and oxygen formed whenever carbon is burned. It is a colorless gas that absorbs infrared radiation, mostly at wavelengths between 12 and 18 microns. It behaves as a one-way filter, allowing incoming, visible light to pass through in one direction, while preventing outgoing infrared radiation from passing in the opposite direction. The one-way filtering effect of carbon dioxide causes an excess of the infrared radiation to be trapped in the atmosphere; thus it acts as a “greenhouse” and has the potential to increase the surface temperature of the planet (see Greenhouse Gasses).

Carbon Offset Credits: A marketable certification of renewable energy that doesn’t add CO2 to the atmosphere; now traded as a commodity on many world exchanges.

Carbon Sequestration: The absorption and storage of CO2 from the atmosphere by the roots and leaves of plants; the carbon builds up as organic matter in the soil.

Catalyst: A substance whose presence changes the rate of chemical reaction without itself undergoing permanent change in its composition. Catalysts may be accelerators or retarders. Most inorganic catalysts are powdered metals and metal oxides, chiefly used in the petroleum, vehicle, and heavy chemical industries. When making biodiesel for farm or home use, the most common catalysts are sodium hydroxide (NaOH), in the form of lye, and potassium hydroxide (KOH).

Clean Diesel: An evolving definition of diesel fuel with lower emission specifications, which strictly limit sulfur content to 0.05 weight %; in California, aromatics content is further limited to 10 volume % (for large refiners). In 2008, Clean Diesel passenger vehicles will become available in the entire U.S., passing emissions standards in all fifty states including California and New York.

Climate Change: A change attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which, in addition to natural climate variability, is observed over comparable time periods.

Co-gen: Short for co-generation, the creation and use of both electricity and heat (also called CHP, or combined heat and power). Co-gen/CHP systems are more efficient because less heat is released into the atmosphere.

Co-generation or Co-gen: The simultaneous production of electric power and another form of useful energy (such as heat or steam) from the same fuel source (also called CHP, or combined heat and power). Co-gen/CHP systems are more efficient because less heat is released into the atmosphere.

Compact Fluorescent Light (CFL): A direct energy efficient replacement for the traditional incandescent light bulb due to greatly improved color, long life and very good payback. CFLs are 75 per cent more efficient and last 7-10 times longer than incandescent bulbs.

Conversion Loss: The energy lost during the conversion from primary energy (petroleum, natural gas, coal, hydro, uranium, wind, biomass and solar energy) into electrical energy. Losses occur during generation, transmission and distribution of electricity, and include plant and unaccounted-for uses.

D

Demand-Side Management: Measures which aim to reduce either energy consumption or peaks in demand. Most often used in relation to electricity, the term includes energy efficiency demand-response measures (such as shifting load to other times or cutting load during periods of peak demand).

Demand-Side: The load that creates the demand for energy as opposed to supply side which refers to energy generation and supply systems. Demand-side is simply on the customer side of the meter.

Distributed Generation: Usually refers to electricity generation connected into either a distribution network or end-users system. Distributed generation can be effective in reducing transmission losses.

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 United States).

Drip Irrigation, also known as trickle irrigation or microirrigation: An irrigation method which minimizes the use of water and fertilizer by allowing water to drip slowly to the roots of plants, either onto the soil surface or directly onto the root zone, through a network of valves, pipes, tubing, and emitters. Modern drip irrigation has arguably become the most important innovation in agriculture since the invention of the impact sprinkler in the 1930s, which replaced wasteful flood irrigation.

E

E10 (Gasohol): Ethanol mixture that contains 10% ethanol, 90% unleaded gasoline.

E85: Ethanol/gasoline mixture that contains 85% denatured ethanol and 15% gasoline, by volume.

E93: Ethanol mixture that contains 93% ethanol, 5% methanol and 2% kerosene, by volume.

E95: Ethanol/gasoline mixture that contains 95% denatured ethanol and 5% gasoline, by volume.

End-use: Any specific activity that requires energy (e.g. refrigeration, space heating, water heating, manufacturing processes and feedstock).

End-use: Any specific activity that requires energy (such as refrigeration, space heating, water heating).

Energy Efficiency: A change to energy use that results in an increase in net benefits per unit of energy used.

ENERGY STAR®: ENERGY STAR® is the global mark of energy efficiency, identifying the energy used. For example, providing a similar (or better) level of service with less energy consumption on a per unit basis is considered an improvement in energy efficiency.

Environmental Sustainability: A movement towards redesigning the ways society’s needs and wants are met so that they can be accommodated within the long term carrying capacity of the environment.

Ester: An organic compound formed by reacting an acid with an alcohol, always resulting in the elimination of water.

Ethanol (also known as Ethyl Alcohol, Grain Alcohol, CH 3 CH 2 OH): 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 also can be used in higher concentration in alternative fuel vehicles optimized for its use.

Ethyl Ester: A fatty ester formed when organically derived oils are combined with ethanol in the presence of a catalyst. After water washing, vacuum drying, and filtration, the resulting ethyl ester has characteristics similar to petroleum-based diesel motor fuels.

F

Feedstock: Any biomass that is intended to be used for energy generation, including wood, cellulosic materials, corn, oilseeds and manure.

Fermentation: The enzymatic transformation by microorganisms of organic compounds such as sugar. It is usually accompanied by the evolution of gas as the fermentation of glucose into ethanol and CO2.

Fischer-Tropsch: A method discovered in 1923 by the German coal researchers Franz Fischer and Hans Tropsch, for the synthesis of hydrocarbons and other aliphatic compounds. A mixture of hydrogen and carbon monoxide is reacted in the presence of an iron or cobalt catalyst. Much heat is evolved and products such as methane, synthetic gasoline and waxes, and alcohols are made. Water or carbon dioxide is its by-product.

Flagging: The directional bend or uneven growth pattern on tree limbs, usually evidence of prevailing wind direction and degree of wind activity; suggests wind power generation potential.

Flexible-Fuel Vehicle (FFV): A Vehicle with a common fuel tank designed to run on varying blends of unleaded gasoline with either ethanol or methanol.

Fluorescent lighting: A lighting unit that emits ultraviolet (UV) radiation, which is converted to visible light by the fluorescent coating on the inside of the tube.

Fossil Fuel: A fuel such as coal, oil, and natural gas. Fossil fuels are the remains of ancient plants and animals.

Fuel Cell: An electrochemical engine with 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.

G

Gas to Liquid Technology: Gas-to-liquid conversion technologies use chemical or physical means to convert natural gas to a liquid form suitable for ready transport or direct use.

Gasohol: In the United States, gasohol (E10) refers to gasoline that contains 10% ethanol by volume. This term was used in the late 1970s and early 1980s but has been replaced in some areas of the country with E10, super unleaded plus ethanol, or unleaded plus.

Generator: Usually an off-the-shelf induction generator that produces 60-cycle AC electricity.

Geothermal system: A geothermal system is a heat exchanger that uses the earth or ground water or both as sources of building heat in the winter and as a “sink” for heat removed from a building in the summer. The system provides heat by removing it from the earth through a liquid such as ground water or an antifreeze solution, which is upgraded by the heat pump and transferred to indoor air. The system provides cooling by reversing the process.

Geothermal: Heat from the earth’s interior made available by extraction of geothermal hot water or steam.

Global Warming: The theoretical escalation of global temperatures caused by the increase of greenhouse gas emissions in the lower atmosphere.

Glycerin: A syrupy, colorless or yellowish liquid derived from oilseeds, separated from plant oils during biodiesel production; a saleable by-product used in solvents, antifreeze, dynamite, cosmetics, soaps and lubricants.

Green Building: Green, or sustainable, building is the practice of promoting healthier and more resource-efficient building construction, renovation, operation, maintenance and demolition.

Greenhouse Effect: A warming of the Earth and its atmosphere as a result of the thermal trapping of incoming solar radiation by CO2, water vapor, methane, nitrogen oxide, chlorofluorocarbons, and other gases, both natural and man-made.

Greenhouse Gasses: Often the by-products of power generation, greenhouse gases such as carbon dioxide and methane increase the atmosphere’s ability to trap heat and contribute to global warming. Reduction of greenhouse gas emissions is one of the main goals of renewable energy development and credit trading systems.

H

Hybrid Electric Vehicle (HEV): A hybrid car uses an internal combustion engine (such as petrol or diesel) alongside regenerative braking systems to provide power to the wheels while also charging a battery. An electric motor then uses the stored energy in the battery to move the vehicle at low speeds and while accelerating. This dual or hybrid drive train can use less fuel than a conventional car, sometimes only half as much.

Hydroelectric Power Plant: A power plant that produces electricity by the force of water falling through a hydro turbine that spins a generator.

I

Incandescent Light Bulb: A light source based on incandescence in which an electric current heats a metallic filament to create light.

Insulation Blanket: Insulation that covers a hot water tank in order to conserve energy.

J

Joule: An international unit of measure of energy, produced by the power of one watt flowing for a second. There are 3.6 million joules in one kilowatt-hour.

K

Kilowatt-Hour (kWh): The unit of electricity equivalent to one kilowatt (1000 watts) operating for one hour. The consumption of electrical energy by homes and small businesses is usually measured in kilowatt-hours. Larger businesses and institutions sometimes use the megawatt-hours (MWh), where 1 MWh = 1,000 kWh.

L

Light Emitting Diode (LED): Semi-conductors, that use a small LED chip mounted in a reflector cup on a lead-frame and when energized, photons are generated, some of which are emitted as light energy. LED lighting has been around since the 1960s, but is just now beginning to appear in the residential market for space lighting. The biggest limitation to LED for common residential use is the cost of manufacturing due to still-limited production runs. Manufacturers claim production will increase considerably in the near future, further lowering prices. LED lights are more rugged and damage-resistant than compact fluorescents and incandescent bulbs. LED lights don’t flicker. They are very heat sensitive; excessive heat or inappropriate applications dramatically reduce both light output and lifetime.

Low-E Coating: Low-E (low-emissivity) coatings are highly reflective, transparent coatings applied to windowpanes to slow heat loss.

M

Megawatt (MW): One million watts. It is a standard unit for electricity generation. One MW of capacity is enough to supply the electricity needs of about 240 to 300 households in the U.S.

Methane: An odorless flammable gas, CH4, derived from digestion of organic substances by anaerobic bacteria.

Methanol (also known as Methyl Alcohol, Wood Alcohol, CH3 OH): A liquid fuel formed by catalytically combining CO with hydrogen in a 1 to 2 ratio under high temperature and pressure. Commercially, it is typically manufactured by steam reforming natural gas. Also formed in the destructive distillation of wood.

Methanol: A colorless flammable liquid used in antifreeze, solvents, and fuels; toxic to humans.

Methyl Ester: A fatty ester formed when organically derived oils are combined with methanol in the presence of a catalyst. Methyl Ester has characteristics similar to petroleum-based diesel motor fuels.

Municipal Solid Waste (MSW): Any organic matter, including sewage, industrial, and commercial wastes, from municipal waste collection systems. Municipal waste does not include agricultural and wood wastes or residues.

N

Nacelle: The nacelle sits atop a wind turbine tower and contains the gear box, low- and high-speed shafts, generator, controller, and brake. Some nacelles are large enough for a helicopter to land on.

Net Metering: Electricity metering that measures both incoming (from the utility) and outgoing (from a local generating source) electricity. The customer pays the utility only the net- the amount bought that is in excess of the amount fed into the electricity grid. Net metering creates the potential to save money on power bills and to functionally “store” excess power on the grid.

Non-Renewable Energy: Energy that cannot be replaced once it is used or energy that is not being replaced as fast as it is being used.

Non-Renewable Resource: A non-renewable energy resource is one that cannot be replaced as it is used. Although fossil fuels, like coal and oil, are in fact fossilized biomass resources, they form at such a slow rate that, in practice, they are non-renewable.

O

Ocean Thermal Energy Conversion (OTEC): The process or technologies for producing energy by harnessing the temperature differences (thermal gradients) between ocean surface waters and that of ocean depths. Warm surface water is pumped through an evaporator containing a working fluid in a closed Rankine-cycle system. The vaporized fluid drives a turbine/generator. Cold water from deep below the surface is used to condense the working fluid. Open-Cycle OTEC technologies use ocean water itself as the working fluid. Closed-Cycle OTEC systems circulate a working fluid in a closed loop. A working 10 kilowatt, closed-cycle prototype was developed by the Pacific International Center for High Technology Research in Hawaii with U.s. Department of Energy funding, but was not commercialized.

Off-Road: Any non-stationary device, powered by an internal combustion engine or motor, used primarily off the highways to propel, move, or draw persons or property, and used in any of the following applications: marine vessels, construction/farm equipment, locomotives, utility and lawn and garden equipment, off-road motorcycles, and off-highway vehicles.

P

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.

Passive Solar Heating: Using solar energy to heat a building without special equipment such as pumps or collectors, usually through windows and skylights.

Petroleum Fuel: Gasoline or diesel fuel.

Photovoltaic: Also known as PV, this technology is made of layers of silicon that create electrical current from sunlight.

Pitch: Blades are turned, or pitched, out of the wind to control the rotor speed and keep the rotor from turning in winds that are too high or too low to produce electricity.

P-Series Fuels: Fuels designed by the Pure Fuel Corporation to run in E85/gasoline flexible fuel vehicles. Added by DOE after EPAct as an alternative fuel.

R

Renewable Diesel: is a broad class of fuels derived from biomass feed stocks, including oils or animal fats, but processed through other chemical processes and commonly referred to as non-esterified renewable diesel (NERD). The most advanced of these alternatives is produced through hydrotreating, a process which is being utilized in today’s petroleum refineries. A recent Internal Revenue Service decision broadens the definition of renewable diesel fuel to include processing vegetable oils and animal fats with oil refinery equipment, which means that major oil refineries can take advantage of a $1 per gallon tax credit on such fuel. Other methods under consideration for creating renewable diesel fuel include biomass-to-liquid (BTL) and thermal conversion process (TCP) technologies. The former converts biomass (predominantly cellulosic material such as certain grasses or other plants) through high-temperature gasification into synthetic gas or “syngas” and then uses a Fischer-Tropsch process to catalytically convert the syngas to liquid fuel. TCP processing converts biomass or other carboneous material into a “bio-oil” which is then refined into diesel-like fuel. Both BTL and TCP offer potential to convert cellulosic biomass into liquid fuels, but need further development and are might currently be less economical for large scale fuel production.

Renewable Energy Certificate: Also known as RECs, these credits represent the renewable attributes of energy. Furthermore, RECs can be sold by energy producers independently of the energy produced and can provide significant cost benefit to power producers.

Renewable Energy Resource: An energy resource that can be replaced as it is used.

Renewable Energy: Energy derived from resources that are regenerative or for all practical purposes cannot be depleted. Renewable energy utilizes natural resources such as sunlight, wind, tides and geothermal heat, which are naturally replenished. Renewable energy technologies range from solar power, wind power, marine energy and hydroelectricity to biomass and biofuels for transportation.

Renewable Portfolio Standard: A policy established by a state government by which the state mandates that power companies generate a certain percentage of their power from renewable sources. Power companies can comply by generating or buying renewable power, or can purchase renewable energy credits from other sources.

Retrofit: The improvement in the energy efficiency of existing energy-using equipment or the thermal characteristics of an existing building.

Return on Energy: Also known as ROE, this is the net energy gained after energy used to create it (plant, harvest, transport, process, etc.) has been deducted from the energy released.

Rotor: The blades and the hub together are called the rotor.

S

Second-Generation Biofuels: Generally refers to new methods of producing biofuels. Examples include the conversion of plant lignin and cellulose into fuels by enzymes and the gasification of biomass material followed by a gas-to-liquid Fischer-Tropsch process. Biomass that could be used in these processes includes all types of trees, grasses, agricultural plant wastes, straw and algae. Second-generation biofuels are not yet ready for commercial development but are the subject of extensive R&D.

Smog: A visible haze caused primarily by particulate matter and ozone. Ozone is formed by the reaction of hydrocarbons and NOx in the atmosphere.

Solar Cell: A device for changing light rays from the sun directly into electricity, also called photovoltaic cell.

Solar Collector: A device to collect the heat energy from the sun utilizing a circulating anti-freeze solution to provide space or hot water heating to a building.

Solar Thermal Electric Systems: Solar energy conversion technologies that convert solar energy to electricity, by heating a working fluid to power a turbine that drives a generator. Examples of these systems include central receiver systems, parabolic dish, and solar trough.

Solar Thermal Parabolic Dishes: A solar thermal technology that uses a modular mirror system that approximates a parabola and incorporates two-axis tracking to focus the sunlight onto receivers located at the focal point of each dish. The mirror system typically is made from a number of mirror facets, either glass or polymer mirror, or can consist of a single stretched membrane using a polymer mirror. The concentrated sunlight may be used directly by a Stirling, Rankine, or Brayton cycle heat engine at the focal point of the receiver or to heat a working fluid that is piped to a central engine. The primary applications include remote electrification, water pumping, and grid-connected generation.

Solar Thermal Systems: Solar energy systems that collect or absorb solar energy for useful purposes. Can be used to generate high temperature heat (for electricity production and/or process heat), medium temperature heat (for process and space/water heating and electricity generation), and low temperature heat (for water and space heating and cooling).

Solar Trough Systems (see also Parabolic Trough, above): A type of solar thermal system where sunlight is concentrated by a curved reflector onto a pipe containing a working fluid that can be used for process heat or to produce electricity. The world’s largest solar thermal electric power plants use solar trough technology. They are located in California, and have a combined electricity generating capacity of 240,000 kilowatts.

Sustainable development: Development that meets the needs of the present without compromising the ability of future generations to meet their own needs (Brundtland Commission definition). Sustainable development must be based on the efficient and environmentally responsible use of all of society’s scarce resources – natural, human and economic.

Sustainable Energy: Sustainable energy resource use and supply is an important area of emphasis contributing to sustainable development.

T

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.

Thermal Depolymerization Process (TDP): Thermal depolymerization (TDP) is a process using hydrous pyrolysis (thermal decomposition which takes place when organic compounds are heated to high temperatures in the presence of water) for the reduction of complex organic materials (usually waste products of various sorts, often known as biomass and plastic) into light crude oil. It mimics the natural geological processes thought to be involved in the production of fossil fuels. Under pressure and heat, long chain polymers of hydrogen, oxygen, and carbon decompose into short-chain petroleum hydrocarbons with a maximum length of around 18 carbons. The process only breaks long molecular chains into shorter ones, so small molecules such as carbon dioxide or methane cannot be converted to oil through this process. The fixed carbon solids produced by the TDP process have multiple uses as a filter, a fuel source and a fertilizer. It can be used as activated carbon in wastewater treatment, as a fertilizer, or as a fuel similar to coal. The process can break down organic poisons, due to breaking chemical bonds and destroying the molecular shape needed for the poison’s activity. It is highly effective at killing pathogens, including prions (e.g., BSE aka “mad cow disease”). It can also safely remove heavy metals from the samples by converting them from their ionized or organometallic forms to their stable oxides which can be safely separated from the other products. The United States Environmental Protection Agency estimates that in 2001 there were 229 million tons of municipal solid waste, or 4.4 pounds generated per day per person in the USA. Industrial facilities in the USA create 7.6 billion tons of industrial wastes each year, however 97% of that waste is water, which means only 228 million tons of potential feedstock remains. Furthermore, any agricultural and animal wastes could be processed, but many of these are already used as fertilizer, animal feed, and, in some cases, as feedstocks for paper mills or as boiler fuel.

Transesterification: A process in which organically derived oils or fats are combined with alcohol (ethanol or methanol) in the presence of a catalyst, to form esters (ethyl or methyl ester), commonly referred to as biodiesel.

Turbine: The power-generating apparatus that takes mechanical power- as from wind, water, combustion, etc., and converts that power into electricity.

W

Watt (W): A measure of power calculated by multiplying the voltage times the current. (see Kilowatt-hour).

Wind Direction: This is an “upwind” turbine, so-called because it operates facing into the wind. Other turbines are designed to run “downwind,” facing away from the wind.

Wind Energy Conversion System (WECS) or Device: An apparatus for converting the energy available in the wind to mechanical energy that can be used to power machinery (grain mills, water pumps) and to operate an electrical generator.

Wind Energy: Energy available from the movement of the wind across a landscape caused by the heating of the atmosphere, earth, and oceans by the sun.

Wind Generator: A WECS designed to produce electricity.

Wind Power Plant: A group of wind turbines interconnected to a common power provider system through a system of transformers, distribution lines, and (usually) one substation. Operation, control, and maintenance functions are often centralized through a network of computerized monitoring systems, supplemented by visual inspection. This is a term commonly used in the United States. In Europe, it is called a generating station.

Wind Resource Assessment: The process of characterizing the wind resource, and its energy potential, for a specific site or geographical area.

Wind Rose: A diagram that indicates the average percentage of time that the wind blows from different directions, on a monthly or annual basis.

Wind Speed Duration Curve: A graph that indicates the distribution of wind speeds as a function of the cumulative number of hours that the wind speed exceeds a given wind speed in a year.

Wind Speed Frequency Curve: A curve that indicates the number of hours per year that specific wind speeds occur.

Wind Speed Profile: A profile of how the wind speed changes with height above the surface of the ground or water.

Wind Speed: The rate of flow of the wind undisturbed by obstacles.

Wind Turbine Rated Capacity: The amount of power a wind turbine can produce at its rated wind speed, e.g., 100 kW at 20 mph. The rated wind speed generally corresponds to the point at which the conversion efficiency is near its maximum. Because of the variability of the wind, the amount of energy a wind turbine actually produces is a function of the capacity factor (e.g., a wind turbine produces 20% to 35% of its rated capacity over a year).

Wind Turbine: A term used for a wind energy conversion device that produces electricity; typically having one, two, or three blades.

Wind vane: Measures wind direction and communicates with the yaw drive to orient the turbine properly with respect to the wind.

Wind Velocity: The wind speed and direction in an undisturbed flow.

Windmill: A WECS that is used to grind grain, and that typically has a high-solidity rotor; commonly used to refer to all types of WECS.

Windpower Curve: A graph representing the relationship between the power available from the wind and the wind speed. The power from the wind increases proportionally with the cube of the wind speed.

Windpower Profile: The change in the power available in the wind due to changes in the wind speed or velocity profile; the windpower profile is proportional to the cube of the wind speed profile.