SOLAR ENERGY TERMS:

Absorber - The blackened surface in a collector that absorbs the solar radiation and converts it to heat energy.

Absorptance - The ratio of solar energy absorbed by a surface to the solar energy striking it.

Active System - A solar heating or cooling system that requires external mechanical power to move the collected heat.

Air-Type Collector - A collector that uses air as the heat transfer fluid.

Auxiliary Heat - The extra heat provided by a conventional heating system for periods of cloudiness or intense cold when a solar heating system cannot provide enough. Azimuth The angular distance between true south and the point on the horizon directly below the sun.

British Thermal Unit (BTU) - The quantity of heat needed to raise the temperature of one pound of water one degree Fahrenheit.

Calorie - The quantity of heat needed to raise the temperature of one gram of water one degree Celsius.

Coefficient of Heat Transmission - The rate of heat loss in BTU per hour through a square foot wall or other building surface when the difference between indoor and outdoor air temperatures is one degree Fahrenheit.

Collector - A device that collects solar radiation and converts it to heat.

Collector Efficiency - The ratio of usable heat energy extracted from a collector to the solar energy striking the cover.

Concentrating Collector - A device which concentrates the sun's rays on an absorber surface which is significantly smaller than the overall collector area.

Conductance - The rate of heat flow (in BTUs per hour) through an object when a 1° F. temperature difference is maintained between the sides of the object.

Conduction - The flow of heat due to temperature variations within a material.

Conductivity - A measure of the ability of a material to permit conduction of heat flow through it.

Convection - The motion of fluid such as gas or liquid by which heat may be transported.

Degree Day - A unit that represents a 1 degree F. deviation from some fixed reference point (usually 65°F.) in the mean daily outdoor temperature.

Design Heat Load - The total heat loss from a house under the most severe winter conditions likely to occur.

Design Temperature - The temperature close to the lowest expected for a location, used to determine the design heat load.

Diffuse Radiation - Indirect sunlight that is scattered from air molecules, dust and water vapor.

Direct Radiation - Solar radiation that comes straight from the sun, casting shadows on a clear day.

Drain down System - Freeze protection is provided by solenoid valves opening and dumping the water in the system to drain at a preset low temperature. Collectors and piping must be pitched or sloped so that the system can drain down using gravity.

Drain back System - The solar heat transfer fluid automatically drains into a tank by gravity. Drain back systems are available in one or two tank configurations. A heat exchanger is necessary, because the city inlet pressure would prevent draining.

Emittance - A measure of the propensity of a material to emit thermal radiation.

Eutectic Salts - A group of materials that melt at low temperatures, absorbing large quantities of heat.

Flat Plate Collector - A solar collection device in which sunlight is converted into heat on a plane surface without the aid of reflecting surfaces to concentrate the rays.

Galvanic Corrosion - A condition caused as a result of a conducting liquid making contact with two different metal which are not properly isolated physically and/or electrically.

Gravity Convection - The natural movement of heat that occurs when a warm fluid rises and a cool fluid sinks under the influence of gravity.

Headers - The pipe that runs across the edge of an array of solar collectors, gathering or distributing the heat transfer fluid from, or to the risers in the individual collectors. This insures that equal flow rates and pressure are maintained.

Heat Capacity - A property of a material denoting its ability to absorb heat.

Heat Exchanger - A device, such as a coiled copper tube immersed in a tank of water, that is used to transfer heat from one fluid to another through a separating wall.

Heat Storage - A device or medium that absorbs collected solar heat and stores it for use during periods of inclement or cold weather.

Heat Storage Capacity - The amount of heat which can be stored by a material.

Heat Pump - A mechanical device that transfers heat from one medium to another, thereby cooling the first and warming the second.

Heat Sink - A medium or container to which heat flows.

Heat Source - A medium or container from which heat flows.

Hybrid Solar Energy System - A system that uses both active and passive methods in its operation.

Indirect System - A solar heating or cooling system in which the solar heat is collected exterior to the building and transferred inside using ducts or piping and, usually fans or ducts.

Infrared Radiation - Electromagnetic radiation from the sun that has wavelengths slightly longer than visible light.

Insolation - The total amount of solar radiation direct, diffused and reflected-striking a surface exposed to the sky.

Insulation - A material with high resistance (R-value) to heat flow.

Langley - A measure of solar radiation; equal to one calorie per square centimeter.

Liquid Type Collector - A collector using a liquid as the heat transfer fluid.

Nocturnal Cooling - The cooling of a building or heat storage device by the radiation of excess heat into the night sky.

Open System - Some part of the System is open to the atmosphere, or system contains fresh or changeable water.

Passive System - A solar heating or cooling system that uses no external mechanical power to move the collected solar heat.

Percentage of Possible Sunshine - The percentage of daytime hours during which there is enough direct solar radiation to cast a shadow.

Photovoltaic Cells - Semi conductor devices that convert solar energy into electricity.

Pyranometer - An instrument for measuring solar radiation.

Radiant Panels - Panels with integral passages for the flow of warm fluids, either air or liquids. Heat from the fluid is conducted through the metal and transferred to the rooms by thermal radiation.

Radiation - The flow of energy through open space via electromagnetic waves, such as visible light.

Reflected Radiation - Sunlight that is reflected from surrounding trees, terrain or buildings onto a surface exposed to the sky.

Refrigerant - A liquid such as Freon that is use in cooling devices to absorb heat from surrounding air or liquids as it evaporates.

Resistance, or R Value - The tendency of a material to retard the flow of heat.

Risers - The flow channels or pipes that distribute the heat transfer liquid across the face of an absorber.

Seasonal Efficiency - The ratio, over an entire heating season, of solar energy collected and used to the solar energy striking the collector.

Selective Surface - A surface that absorbs radiation of one wavelength (for example, sunlight) but emits little radiation of another wavelength (for example, infrared); used as a coating for absorber plates.

Shading Coefficient - The ratio of the solar heat gain through a specific glazing system to the total solar heat gain through a single layer of clear double-strength glass.

Solar Constant - The average intensity of solar radiation reaching the earth outside the atmosphere; accounting to two langleys or 1.94 gram-calories per square centimeter, equal to 442.4 BTU/hr/ft.², or 1395 watts/m².

Solar Radiation - Electromagnetic radiation emitted by the sun.

Solar Rights - A legal issue concerning the right of access to sunlight.

Specific Heat - The quantity of heat, in BTU, needed to raise the temperature of one pound of a material 1°F.

Standby Heat Loss - Heat lost though storage tank and piping walls.

Sun Path Diagram - A circular projection of the sky vault, similar to a map, that can be used to determine solar positions and to calculate shading.

Thermal Capacity - The quantity of heat needed to warm a collector up to its operating temperature.

Thermal Mass  - The tendency of a building with large quantities of heavy materials to remain at the same temperature or to fluctuate only very slowly; also the overall heat storage capacity of the building.

Thermal Radiation - Electromagnetic radiation emitted by a warm body.

Thermistor - Sensing device which changes its electrical resistance according to temperature. Used in the control system to generate input data on collector and storage temperatures.

Thermosyphoning - The process that makes water circulate automatically between a warm collector and a cooler storage tank above it.

Tilt Angle - The angle that a flat plate collector surface forms with the horizontal plane.

Trickle Type Collector - A collector in which the heat transfer liquid flows through metal tubes which are fastened to the absorber plate by solder, clamps or other means. (See Collector).

Tube-in-Plate-Absorber - A metal absorber plate in which the heat transfer fluid flows through passages formed in the plate itself.

Tube-Type Collector - A collector in which the heat transfer fluid flows through metal tubes that are fastened to the absorber plate with solder, clamps or other means. (See Collector).

WIND ENERGY TERMS:

AC - See Alternating Current

Airfoil - The cross section profile of the leeward side of a wind generator blade. Designed to give low drag and good lift. Also found on an airplane wing.

Air Gap - In a permanent magnet alternator, the distance between the magnets and the laminates.

Alternating Current - Electricity that changes direction periodically. The period is measured in Cycles per Second (Hertz, Hz).

Alternator - A device that produces Alternating Current from the rotation of a shaft.

Amperage - A unit of electrical current, equal to Coulombs per second. This is the flow rate of electrons moving through a circuit, very roughly analogous to gallons per minute flowing from a faucet.

Ampere-Hour - A measure of energy quantity, equal to amperes times hours. Also used to measure battery capacity.

Anemometer - A device that measures wind speed.

Angle of Attack - The angle of relative air flow to the blade chord.

Annealing - A heat treatment process that makes Cold-rolled steel more suitable for forming and bending.

Area of a Circle - Pi multiplied by the Radius squared.

Armature - The moving part of an alternator, generator or motor. In many PM alternator designs, it carries the magnets and is attached to the blades and hub. Also called a Rotor.

Axial Alternator - An alternator design where a flat disc carrying magnets on the face (the Armature) rotates near a flat disc carrying coils (the Stator).

Axis - The centerline of a rotating object's movement.

Balancing - With wind turbine blades, adjusting their weight and weight distribution through 2 axes so that all blades are the same. Unbalanced blades create damaging vibration.

Battery - An electrochemical device for storing energy.

Battery Bank - An array of Batteries connected in series, parallel, or both.

Bearing - A device that transfers a force to structural supports. In a wind generator, bearings allow the Shaft to rotate freely, and allow the machine to Yaw into and out of the wind.

Belt - A device for transferring power from a rotating shaft to a generator. Allows the use of Pulleys to change the ratio of shaft speed to and from the generator.

Betz Coefficient - 59.3 percent. This is the theoretical maximum efficiency at which a wind generator can operate, by slowing the wind down. If the wind generator slows the wind down too much, air piles up in front of the blades and is not used for extracting energy.

Blade - The part of a wind generator rotor that catches the wind.

Braking System - A device to slow a wind turbine's shaft speed down to safe levels electrically or mechanically.

Bridge Rectifier - An array of diodes used to convert Alternating Current to Direct Current. Single-phase bridge rectifiers use 4 diodes, 3-phase bridge rectifiers use 6 diodes.

Brushes - Devices for transferring power to or from a rotating object. Usually made of carbon-graphite.

Chord - The width of a wind turbine blade at a given location along the length.

Coercivity - The amount of power needed to magnetize or demagnetize a permanent magnet. Measured in MegaGauss Oersted (mGO)

Cogging - The cyclic physical resistance felt in some alternator designs from magnets passing the coils and gaps in the laminates. Detrimental to Start-up.

Coil - A length of wire wound around a form in multiple turns.

Cold-Rolled Steel - Steel processed by working at room temperatures. More expensive than hot-rolled steel.

Commutator - The rotating part of a DC generator.

Concave - A surface curved like the interior of a circle or sphere.

Convex - A surface curved like the exterior of a circle or sphere.

Cut-In - The rotational speed at which an alternator or generator starts pushing electricity hard enough (has a high enough voltage) to make electricity flow in a circuit.

Cycles per Second - Measured in Hertz. In electricity, it is the number of times an AC circuit reaches both minimum and maximum values in one second.

Darrieus - A Vertical Axis Wind Turbine design from the 1920s and 1930s by F.M. Darrieus, a French wind turbine designer.

Delta - A 3-phase alternator wiring configuration in which all phases are connected in Series.

Diameter - A straight line passing through the center of a circle, and ending on both edges. Equal to 2 times the Radius.

Diode - A solid-state device that allows electricity to flow in only one direction.

Downwind - Refers to a Horizontal Axis Wind Turbine in which the hub and blades point away from the wind direction, the opposite of an Upwind turbine.

Drag - In a wind generator, the force exerted on an object by moving air. Also refers to a type of wind generator or anemometer design that uses cups instead of a blades with airfoils.

Dump Load - A device to which wind generator power flows when the system batteries are too full to accept more power, usually an electric heating element. This diversion is performed by a Shunt Regulator, and allows a Load to be kept on the Alternator or Generator.

Duty Cycle - In a circuit, the ratio of off time to on time.

Dynamo - A device that produces Direct Current from a rotating shaft. See Generator.

Eddy Currents - Currents that flow in a substance from variations in magnetic induction. See also Lenz Effect. Laminates are used to prevent eddy currents, which cause physical and electrical resistance in an alternator or transformer, therefore wasting power.

Efficiency - The ratio of energy output to energy input in a device.

Electromagnet - A device made of wire coils that produces a magnetic field when electricity flows through the coils.

Excitation - Using an electric current to create a magnetic field. See Electromagnet.

Fatigue - Stress that causes material failure from repeated, cyclic vibration or stress.

Ferrite Magnets - Also called Ceramic Magnets. Made of Strontium Ferrite. High Coercivity and Curie Temperature, low cost, but brittle and 4-5 times weaker than NdFeB magnets.

Freewheeling - a wind generator that is NOT connected to a Load is freewheeling, and in danger of self-destruction from overspeeding.

Furling - The act of a wind generator Yawing out of the wind either horizontally or vertically to protect itself from high wind speeds.

Furling Tail - A wind generator protection mechanism where the rotor shaft axis is offset horizontally from the yaw axis, and the tail boom is both offset horizontally and hinged diagonally, thus allowing the tail to fold up and in during high winds. This causes the blades to turn out of the wind, protecting the machine.

Gauss - A unit of magnetic induction, equal to 1 Maxwell per square centimeter. Higher Gauss measurements mean more power can be induced to flow in an alternator. Gauss readings can be increased by putting steel behind magnets, stacking magnets, or using larger or higher-grade magnets.

Gearing - Using a mechanical system of gears or belts and pulleys to increase or decrease shaft speed. Power losses from friction are inherent in any gearing system.

Generator - A device that produces Direct Current from a rotating shaft.

Governor - A device that regulates the speed of a rotating shaft, either electrically or mechanically.

Guy Anchor - Attaches tower guy wires securely to the earth.

Guy Radius - The distance between a wind turbine tower and the guy anchors.

Guy Wire - Attaches a tower to a Guy Anchor and the ground.

H-Rotor - A Vertical Axis Wind Turbine design.

Horizontal Axis Wind Turbine - A "normal" wind turbine design, in which the shaft is parallel to the ground, and the blades are perpendicular to the ground.

Hub - The center of a wind generator rotor, which holds the blades in place and attaches to the shaft.

Impedance - See Resistance.

Induction - The production of a magnetic field by the proximity of a electric charge or the production of a magnetic field by proximity of an electric charge.

Induction Motor - An AC motor in which the rotating armature has no electrical connections to it (ie no slip rings), and consists of alternating plates of aluminum and steel.

Kilowatt - 1000 Watts (see Watt)

Laminations - Electrical circuit core parts, found in motors, generators, alternators and transformers. When core parts are subjected to alternating electrical or magnetic fields, the buildup of Eddy Currents causes physical and electrical power loss. Laminations are made of thin strips of materials that make good temporary magnets and poor permanent magnets, and each strip is insulated electrically from the next.

Leading Edge - The edge of a blade that faces toward the direction of rotation.

Leeward - Away from the direction from which the wind blows.

Lenz Effect - See also Eddy Currents. From H.F.E Lenz in 1833. Electromotive force is induced with variations in magnetic flux. It can be demonstrated physically in many different ways - for example dragging a strong magnet over an aluminum or copper plate, or shorting the terminals of a PM alternator and rotating the shaft by hand. Laminates are used to reduce power losses from this effect.

Lift - The force exerted by moving air on asymmetrically-shaped wind generator blades at right angles to the direction of relative movement. Ideally, wind generator blades should produce high Lift and low Drag.

Live - A circuit that is carrying electricity. When live, it can shock you.

Load - Something physical or electrical that absorbs energy. A wind generator that is connected to a battery bank is loaded. A disconnected wind generator is NOT loaded, so the blades are free to spin at very high speed without absorbing any energy from the wind, and it is in danger of destruction from overspeeding.

Losses - Power that is harvested by a wind generator but is not transferred to a usable form. Losses can be from friction, electrical resistance, or other causes.

Magnet - A body that attracts ferromagnetic materials. Can be a Permanent magnet, Temporary Magnet, or Electromagnet.

Magnetite - A common Iron-containing mineral with ferromagnetic properties.

Magnet Wire - The kind of wire always used in making electromagnets, alternators, generators and motors. Uses very thin enamel insulation to minimize thickness and maximize resistance to heat.

Magnetic Circuit - The path in which magnetic flux flows from one magnet pole to the other.

Magnetic Field - Magnetic fields are historically described in terms of their effect on electric charges. A moving electric charge, such as an electron, will accelerate in the presence of a magnetic field, causing it to change velocity and its direction of travel. An electrically charged particle moving in a magnetic field will experience a force (known as the Lorentz force) pushing it in a direction perpendicular to the magnetic field and the direction of motion. Also called magnetic flux.

Maximum Energy Product - Determines how good a magnet that different materials can make. Technically, the amount of energy that a material can supply to an external magnetic circuit when operating within its demagnetization curve.

MegaGauss Oersted - Magnetic force measurement, see Maximum Energy Product.

Moment - A force attempting to produce motion around an axis.

Nacelle - The protective covering over a generator or motor.

Neodymium-Iron-Boron Magnet - The composition of the most powerful Permanent Magnets known to man. The materials are mined, processed, and sintered into shape. Then, they are subjected to an extremely strong magnetic field and become Permanent Magnets.

Ohm's Law - The basic math needed for nearly all electrical calculations. Please see a dictionary or Pocket Ref for all of the variations on Ohm's Law! E=I*R (voltage(E)=amperage(I)*resistance(R)), and all of the algebraic variations of this (I=E/R, R=E/I). Also, for DC circuits, Watts=Volts*Amps. For AC circuits, Watts=Amps * Volts * Cosine of phase angle theta.

Open-Circuit Voltage - The voltage that a alternator or generator produces when it is NOT connected to a Load.

Parallel - In DC electrical circuits such as a battery bank or solar panel array, this is a connection where all negative terminals are connected to each other, and all positive terminals are connected to each other. Voltage stays the same, but amperage is increased. In AC circuits such as a wind generator alternator, each parallel coil is connected to common supply wires, again increasing amperage but leaving voltage the same. Opposite of Series. See also Star.

Permanent Magnet - A material that retains its magnetic properties after an external magnetic field is removed.

Permanent Magnet Alternator - An Alternator that uses moving permanent magnets instead of Electromagnets to induce current in coils of wire.

Phase - The timing of AC current cycles in different wires. 3-phase alternators produce current that is cyclically timed between 3 different wires and a common wire, while single phase produces it in only 1 wire and a common.

Pillow Blocks - Bearings that support a horizontal shaft.

Poles - A way of picturing magnetic phenomena. All magnets are considered to be "dipoles", having both a North pole (which would point North if used in a compass) and a South pole (which would point South if used in a compass. In an alternator, generator, or motor the number of Poles is a measure of how many coils, permanent magnets or electromagnets are in the armature or stator.

Propeller - The spinning thing that makes an airplane move forward. Often incorrectly used (by Otherpower.com also!) to describe a wind turbine Rotor.

Pulley - A device for transferring power when using Belts as Gearing. Changing to smaller or larger Pulleys changes the gear ratio, and can be used to make a shaft turn faster or slower than the shaft that is providing its power.

Pulse Width Modulation - (abbrev. PWM) A regulation method based on Duty Cycle. At full power, a pulse-width-modulated circuit provides electricity 100 percent of the time. At half power, the PWM is on half the time and off half the time. The speed of this alternation is generally very fast. Used in both solar wind regulators to efficiently provide regulation.

Radius - The distance between the center of a circle and the outside.

Rare-Earth Magnets - See Neodymium-Iron-Boron magnets.

Rated Power Output - Used by wind generator manufacturers to provide a baseline for measuring performance. Rated output may vary by manufacturer. For example, one manufacturer's 1500 watt turbine may produce that amount of power at a 30 mph windspeed, while another brand of 1500 watt turbine may not make 1500 Watts until it gets a 40 mph windspeed! So read manufacturer's ratings statements very carefully.

Radial - An alternator design in which the armature magnets are attached to the outside circumference of a disc, with the stator coils mounted around the outside.

Regulator - A device to adjust incoming power so as to avoid overcharging a battery bank. In solar power, the regulator generally just turns the solar array off when the batteries are full. With a wind generator, the regulator generally diverts all or part of the incoming power to a Dump Load when the batteries fill, thus keeping a Load on the wind generator so it will not Freewheel.

Relay - An electromechanical switch that uses a small amount of incoming electricity to charge an electromagnet, which physically pulls down a connecting switch to complete a circuit. This allows a low-power circuit to divert the electricity in a high-power circuit.

Resistance - The voltage per amp needed to make electricity flow through a wire. See Ohm's Law.

Root - The area of a blade nearest to the hub. Generally the thickest and widest part of the blade.

Rotor - 1) The blade and hub assembly of a wind generator. 2) The disc part of a vehicle disc brake. 3) The armature of a permanent magnet alternator, which spins and contains permanent magnets.

RPM - Revolutions Per Minute. The number of times a shaft completes a full revolution in one minute.

Savonius - A vertical-axis wind turbine design by S.J. Savonius of Finland from the 1920s and 30s. Shaped like a barrel split from end to end and offset along the cut. They are drag machines, and thus give very low rpm but lots of torque.

Series - In DC electrical circuits such as a battery bank or solar panel array, this is a connection where all the negative terminals are connected to the neighboring positive terminals. Voltage increases, but amperage stays the same. In AC circuits such as a wind generator alternator, each coil is connected to the one next to it, and so on, again increasing voltage but leaving amperage the same. Opposite of Parallel. See also Delta.

Servo Motor - A motor used for motion control in robots, hard disc drives, etc. Generally designed more like an alternator than a standard motor, most Servos need special control circuitry to make them rotate electrically. Some can be used in reverse to generate alternating current.

Setting Angle - The angle between the blade Chord and the plane of the blade's rotation. Also called Pitch or blade angle. A blade carved with a Twist has a different setting angle at the Tip than at the Root.

Shaft - The rotating part in the center of a wind generator or motor that transfers power.

Short Circuit - 1) Parts of a circuit connected together with only the impedance of the leads between them. 2) In wind generators, connecting the output leads directly together so as to heavily load a generator in high winds. This creates a "short" circuit path back to the generator, bypassing all other loads.

Shunt - An electrical bypass circuit that proportionally divides current flow between the shunt and the shunted equipment. It also allows high current measurements with low-current equipment.

Shunt Regulator - A bypass device for power not needed for charging batteries. When batteries are full, the regulator shunts all or part of the excess power to a Dump Load to protect the batteries from overcharging damage.

Slip Ring - Devices used to transfer electricity to or from rotating parts. Used in wound-field alternators, motors, and in some wind generator yaw assemblies.

Star - A coil connection scheme for 3 phase alternators and generators in which all 3 coil phases are connected in parallel - they all share a common connection.

Start-Up - The windspeed at which a wind turbine rotor starts to rotate. It does not necessarily produce any power until it reaches cut-in speed.

Stationary - With wind generator towers, a tower that does not tilt up and down. The tower must be climbed or accessed with a crane to install or service equipment at the top.

Stator - The part of a motor, generator or alternator that does not rotate. In permanent magnet alternators it holds the coils and laminates.

Tail Boom - A strut that holds the tail (Vane) to the wind generator frame.

Tape Drive Motor - A type of permanent magnet DC motor often used as a generator in small wind generator systems.

Taper - The change in wind turbine blade width (chord) along the length.

Temporary Magnet - A material that shows magnetic properties only while exposed to an external magnetic field.

Thrust - In a wind generator, wind forces pushing back against the rotor. Wind generator bearings must be designed to handle thrust or else they will fail.

Thrust Bearing - A bearing that is designed to handle axial forces along the centerline of the shaft - in a wind generator, this is the force of the wind pushing back against the blades.

Tilt-Up - A tower that is hinged at the base and tilted up into position using a gin pole and winch or vehicle. Wind turbines on tilt-up towers can be serviced on the ground, with no climbing required.

Tip - The end of a wind generator blade farthest from the hub.

Tip Speed Ratio - The ratio of how much faster than the windspeed that the blade tips are moving. Abbreviation TSR.

Torque - Turning force, equal to force times radius.

Tower - A structure that supports a wind generator, usually high in the air.

Trailing Edge - The edge of a blade that faces away from the direction of rotation.

Transformer - Multiple individual coils of wire wound on a laminate core. Transfers power from one circuit to another using magnetic induction. Usually used to step voltage up or down. Works only with AC current.

TSR - See Tip Speed Ratio.

Turn - In winding stator coils, this is one loop of wire around a form. A coil will often be referred to by how many turns of a certain gauge wire are in each coil.

Twist - In a wind generator blade, the difference in Pitch between the blade root and the blade tip. Generally, the twist allows more Pitch at the blade root for easier Startup, and less Pitch at the tip for better high-speed performance.

Vane - A large, flat piece of material used to align a wind turbine rotor correctly into the wind. Usually mounted vertically on the tail boom. Sometimes called a Tail.

Variable Pitch - A type of wind turbine rotor where the attack angle of the blades can be adjusted either automatically or manually.

Vertical Axis Wind Turbine - A wind generator design where the rotating shaft is perpendicular to the ground, and the cups or blades rotate parallel to the ground.

Voltage - A measure of electrical potential difference. One volt is the potential difference needed in a circuit to make one Ampere flow, dissipating one Watt of heat.

Volt-Amp - In an AC circuit, this is Volts * Amps, without factoring in the power factor, derived from the phase angle. See also Watt.

Watt - One Joule of electrical energy per second. In DC circuits, Watts=Volts * Amps. In AC circuits, Watts=Volts * Amps * the cosine of the phase angle. See also Volt-Amp.

Wild AC - Alternating Current that varies in Frequency.

Wind Generator - A device that captures the force of the wind to provide rotational motion to produce power with an alternator or generator.

Windmill - A device that uses wind power to mill grain into flour. But informally used as a synonym for wind generator or wind turbine, and to describe machines that pump water with wind power.

Wind Turbine - A machine that captures the force of the wind. Called a Wind Generator when used to produce electricity. Called a Windmill when used to crush grain or pump water.

Windward - Toward the direction from which the wind blows.

Yaw - Rotation parallel to the ground. A wind generator Yaws to face winds coming from different directions.

Yaw Axis - Vertical axis through the center of gravity.

ALTERNATIVE FUELS AND VEHICLES:

Aftermarket Conversion - A standard, conventionally fueled, factory-produced vehicle to which equipment has been added that enables the vehicle to operate on an alternative fuel.

Alcohols (CH₃-(CH₂)_n-OH) - The family name of a group of organic chemical compounds composed of carbon, hydrogen, and oxygen. The series of molecules vary in chain length and are composed of a hydrocarbon, plus a hydroxyl group (for example, methanol, ethanol, and tertiary butyl alcohol).

Aldehydes - One of several families of compounds formed as products of incomplete combustion in engines using gasoline, methanol, ethanol, propane, or natural gas as fuels. As a general rule of thumb, the presence of methanol or methyl ethers in the fuel will lead to formaldehyde as the primary aldehyde in the exhaust, while ethanol or ethyl ethers will lead to acetaldehyde as the primary aldehyde in the exhaust. In both cases, other aldehydes are present, but in much smaller quantities. Formaldehyde and acetaldehyde are toxic and possibly carcinogenic.

Alternative Fuel - As defined pursuant to the EPACT, methanol, denatured ethanol, and other alcohols, separately or in mixtures of 85 percent by volume or more (or other percentage not less than 70 as determined by DOE rule) with gasoline or other fuels, CNG, LNG, 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 environmental benefits.

Alternative-Fueled Vehicle (AFV) - A vehicle either designed and manufactured by an original equipment manufacturer or a converted vehicle designed to operate in either dual-fuel, flexible-fuel, or dedicated modes on fuels other than gasoline or diesel. This does not include a conventional vehicle that is limited to operation on blended or reformulated gasoline fuels.

Alternative-Fueled Vehicle Converter - An organization (including companies, government agencies, and utilities), or an individual who performs conversions involving alternative fueled vehicles. An AFV converter can convert (1) conventionally fueled vehicles to AFV's, (2) AFV's to conventionally fueled vehicles, or (3) AFV's to another alternative fuel.

Barrel - A volumetric unit of measure for crude oil and petroleum products equivalent to 42 U.S. gallons.

Bi-Fuel Vehicle - A vehicle with two separate fuel systems designed to run on either an alternative fuel or conventional fuel using only one fuel at a time.

Biodiesel - Any liquid biofuel suitable as a diesel fuel substitute or diesel fuel additive or extender. A diesel substitute made from transesterification of oils of vegetables such as soybeans, rapeseed, or sunflowers (end product known as methyl ester) or from animal tallow (end product known as methyl tallowate). Biodiesel can also be made by transesterification of hydrocarbons produced by the Fisher-Tropsch process from agricultural byproducts such as rice hulls.

British Thermal Unit (Btu) - A standard unit for measuring the quantity of heat energy equal to the quantity of heat required to raise the temperature of 1 pound of water by 1 degree Fahrenheit.

California Air Resources Board (CARB) - A State regulatory agency charged with regulating the air quality in California. Air quality regulations established by the Board and often stricter than those set by the Federal Government.

Carbon Cycle - All reservoirs and fluxes of carbon; usually thought of as a series of the four main reservoirs of carbon interconnected by pathways of exchange. The four reservoirs, regions of the Earth in which carbon behaves in a systematic manner, are the atmosphere, terrestrial biosphere (usually includes freshwater systems), oceans, and sediments (includes fossil fuels). Each of these global reservoirs may be subdivided into smaller pools ranging in size from individual communities or ecosystems to the total of all living organisms (biota). Carbon exchanges from reservoir to reservoir by various chemical, physical, geological, and biological processes.

Carbon Dioxide (CO₂) - A colorless, odorless, nonpoisonous gas that is a normal part of the ambient air. Carbon dioxide is a product of fossil fuel combustion.

Carbon Monoxide (CO) - A colorless, odorless gas slightly lighter than air. It is poisonous if inhaled, in that it combines with blood hemoglobin to prevent oxygen transfer. It is produced by the incomplete combustion of fossil fuels with a limited oxygen supply (as in automobiles). It is a major component of urban air pollution, which can be reduced by the blending of an oxygen-bearing compound such as alcohols and ethers into hydrocarbon fuels.

Chlorofluorocarbons (CFC's) - A family of inert, nontoxic, and easily liquified chemicals used in refrigeration, air conditioning, packaging, and insulation, or as solvents or aerosol propellants. Because they are not destroyed in the lower atmosphere, they drift into the upper atmosphere where their chlorine components destroy ozone.

Clean Alternative Fuel - Any fuel (including methanol, ethanol, or other alcohols (including any mixture thereof containing 85 percent or more by volume of such alcohol with gasoline or other fuels), reformulated gasoline, diesel, natural gas, liquefied petroleum gases, and hydrogen) or power source (including electricity) used in a clean fuel vehicle that complies with the standards and requirements of the Clean Air Act Amendments of 1990.

Compressed Natural Gas (CNG) - Natural gas compressed to a volume and density that is practical as a portable fuel supply (even when compressed, natural gas is not a liquid).

Carbon Monoxide Nonattainment Area - Areas with carbon monoxide design values of 9.5 parts per million or more (generally based on data for 1988 and 1989).

Converted Vehicle - A vehicle originally designed to operate on gasoline that has been modified or altered to operate on an alternative fuel.

Criteria Pollutant - A pollutant determined to be hazardous to human health and regulated under the Environmental Protection Agency's National Ambient Air Quality Standards. The 1970 amendments to the Clean Air Act require the Environmental Protection Agency to describe the health and welfare impacts of a pollutant as the criteria for inclusion in the regulatory regime.

Dedicated Vehicle - A vehicle designed to operate solely on one alternative fuel.

Diesel Fuel - A complex mixture of hydrocarbons with a boiling range between approximately 350 and 650 degrees Fahrenheit. Diesel fuel (simply referred to as "diesel") is composed primarily of paraffins and naphthenic compounds that auto-ignite from the heat of compression in a diesel engine. Diesel is used mainly by heavy-duty road vehicles, construction equipment, locomotives, and by marine and stationary engines.

Dual-Fuel Vehicle - A vehicle designed to operate on a combination of alternative fuel, such as CNG or LPG, and conventional fuel, such as gasoline or diesel. These vehicles have two separate fuel systems which inject both fuels simultaneously into the engine combustion chamber.

E85 - A fuel containing a mixture of 85 percent ethanol and 15 percent gasoline.

E95 - A fuel containing a mixture of 95 percent ethanol and 5 percent gasoline.

Energy Efficiency - The inverse of energy intensiveness - the ratio of energy outputs from a process to the energy inputs (for example, miles traveled per gallon of fuel).

Environmental Protection Agency (EPA) - A government agency, established in 1970. Its responsibilities include the regulation of fuels and fuel additives.

Ethyl Tertiary Butyl Ether (ETBE), (CH₃)₃COC₂H_{5 -} A colorless, flammable, oxygenated hydrocarbon blend stock formed by the catalytic etherification of isobutylene with ethanol.

Ethanol (C₂H₅OH) - Otherwise known as ethyl alcohol, alcohol, or grain-spirit. A clear, colorless, flammable oxygenated hydrocarbon with a boiling point of 78.5 degrees Celsius in the anhydrous state. However, it forms a binary azeotrope with water, with a boiling point of 78.15 degrees Celsius at a composition of 95.57 percent by weight ethanol. It is used in the United States as a gasoline octane enhancer and oxygenate (10 percent concentration). Ethanol can also be used in high concentrations in vehicles optimized for its use.

Ether - The family name applied to a group of organic chemical compounds composed of carbon, hydrogen, and oxygen, and which are characterized by an oxygen atom attached to two carbon atoms (for example, methyl tertiary butyl ether).

Flexible-Fuel Vehicle - A vehicle with the ability to operate on alternative fuels (such as M85 or E85), 100 percent traditional fuels, or a mixture of alternative fuel and traditional fuels.

Global Warming - The theoretical escalation of global temperatures caused by the greenhouse effect.

Greenhouse Effect - A popular term used to describe the roles of water vapor, carbon dioxide, and other trace gases in keeping the Earth's surface warmer than it would be otherwise. These radiatively active gases are relatively transparent to incoming shortwave radiation, but are relatively opaque to outgoing long wave radiation. The latter radiation, which would otherwise escape to space, is trapped by these gases within the lower levels of the atmosphere. The subsequent reradiation of some of the energy back to the Earth maintains the surface at temperatures higher than they would be if the gases were absent.

Greenhouse Gases - Those gases, such as water vapor, carbon dioxide, tropospheric ozone, nitrous oxide, and methane, that are transparent to solar radiation but opaque to long wave radiation. Their action is similar to that of increased humidity in a greenhouse.

Gross Vehicle Weight Rating - The weight of the empty vehicle plus the maximum anticipated load weight.

Heavy Duty Vehicles - Pursuant to the EPACT, trucks and buses having a gross vehicle weight rating of 8,500 pounds or more.

Hydrogen (H₂) - The lightest of all gases, the element (hydrogen) occurs chiefly in combination with oxygen in water. It also exists in acids, bases, alcohols, petroleum, and other hydrocarbons.

Light Duty Vehicles - Automobiles and trucks having a gross vehicle weight rating of less than 8,500 pounds.

Liquefied Natural Gas (LNG) - Natural gas that has been refrigerated to temperatures at which it exists in a liquid state.

Liquefied Petroleum Gases (LPG) - Propane, propylene, normal butane, butylene, isobutane, and isobutylene produced at refineries or natural gas processing plants (includes plants that fractionate raw natural gas plant liquids).

Lower Heating Value (LHV) - The Btu content per unit of fuel excluding the heat from the condensation of water vapor in the fuel.

M85 - A fuel containing a mixture of 85 percent methanol and 15 percent gasoline.

M100 - 100 percent (neat) methanol.

Methane (CH₄) - The simplest of the hydrocarbons and the chief constituent of natural gas. Methane, a gas at normal temperatures and pressures, boils at -263 degrees Fahrenheit.

Methanol (CH₃OH) - A colorless liquid with essentially no odor and very little taste. The simplest alcohol, it boils at 64.7 degrees Celsius. It is miscible with water and most organic liquids (including gasoline) and is extremely flammable, burning with a nearly invisible blue flame. Methanol is produced commercially by the catalyzed reaction of hydrogen and carbon monoxide. It was formerly derived from the destructive distillation of wood, which caused it to be known as wood alcohol.

Methyl Tertiary Butyl Ether (MTBE), (CH₃)₃COCH₃ - A colorless, flammable, liquid oxygenated hydrocarbon that contains 18.15 percent oxygen and has a boiling point of 55.2 degrees Celsius. It is a fuel oxygenate produced by reacting methanol with isobutylene.

Midwest Census Region - This region includes the following States - Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio, South Dakota, and Wisconsin.

Mcf - Million cubic feet.

Motor Gasoline Blending of Oxygenates - Blending of gasoline and oxygenates under the Environmental Protection Agency's "Substantially Similar" Interpretive Rule (56 FR [February 11, 1991]).

Natural Gas - A mixture of hydrocarbon compounds and small quantities of various nonhydrocarbons existing in the gaseous phase or in solution with crude oil in natural underground reservoirs at reservoir conditions. The primary constituent compound is CH₄. Gas coming from wells also can contain significant amounts of ethane, propane, butanes, and pentanes, and widely varying amounts of carbon dioxide and nitrogen. Pipeline-quality natural gas has had most, but not all natural gas liquids and other contaminants removed. On board a vehicle, it is stored under high pressure at 2,500 to 3,600 pounds per square inch (psi). A gallon of natural gas at 2,000 psi contains about 20,000 Btu; at 3,600 psi, a gallon contains about 30,000 Btu.

Neat Alcohol Fuels - Straight alcohol (not blended with gasoline) that may be either in the form of ethanol or methanol. Ethanol, as a neat alcohol fuel, does not need to be at 200 proof; therefore, it is often used at 180 to 190 proof (90 to 95 percent). Most methanol fuels are not strictly "neat," since 5 to 10 percent gasoline is usually blended in to improve its operational efficiency.

Nitrogen Oxides (NO_x) - Air-polluting gases contained in automobile emissions, which are regulated by the Environmental Protection Agency. They comprise colorless nitrous oxide (N₂O) (otherwise known as dinitrogen monoxide, or as the anaesthetic "laughing gas"), colorless nitric oxide (NO), and the reddish-brown-colored nitrogen dioxide (NO₂). Nitric oxide is very unstable, and on exposure to air it is readily converted to nitrogen dioxide, which has an irritating odor and is very poisonous. Nitrogen dioxide contributes to the brownish layer in the atmospheric pollution over some metropolitan areas. Other nitrogen oxides of less significance are nitrogen tetroxide (N₂O₄) and nitrogen pentoxide (N₂O₅). Nitrogen oxides are sometimes collectively referred to as "NO_x" where "x" represents any proportion of oxygen to nitrogen.

Nonattainment Area - A region that exceeds minimum acceptable National Ambient Air Quality Standards (NAAQS) for one or more criteria pollutants, in high population density areas, in accordance with the U.S. Census Bureau population statistics. Such regions (areas) are required to seek modifications to their State Implementation Plans, setting forth a reasonable timetable using means (approved by the Environmental Protection Agency) to achieve attainment of NAAQS by a certain date. Under the Clean Air Act, if a nonattainment area fails to attain NAAQS, the Environmental Protection Agency may superimpose a Federal Implementation Plan with stricter requirements or impose fines, construction bans, or cutoffs in Federal grant revenues until the area achieves applicable NAAQS.

Northeast Census Region - This region includes the following States - Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, and Vermont.

Original Equipment Manufacturers (OEM's) - Vehicle manufacturers that provide the original design and materials for assembly and manufacture of their product. They are directly responsible for manufacturing and modifying vehicles, making the vehicles commercially available, and providing a warranty for the finished product.

Oxygenated Fuel - Any fuel substance containing oxygen (includes oxygen-bearing compounds such as ethanol and methanol). Oxygenated fuel tends to give a more complete combustion of its carbon into carbon dioxide (rather than monoxide), thereby reducing air pollution from exhaust emissions.

Oxygenated Gasoline - Gasoline with an oxygen content of 1.8 percent or higher, by weight, that has been formulated for use in motor vehicles.

Ozone (O₃) - An oxygen molecule with 3 oxygen atoms that occurs as a blue, harmful, pungent-smelling gas at room temperature. The stratospheric ozone layer, which is a concentration of ozone molecules located at 6 to 30 miles above sea level, is in a state of dynamic equilibrium. Ultraviolet radiation forms the ozone from oxygen, but can also reduce the ozone back to oxygen. The process absorbs most of the ultraviolet radiation from the sun, shielding life from the harmful effects of radiation. Tropospheric ozone is normally present at the ground level in low concentrations. In cities where high levels of air pollutants are present, the action of the sun's ultraviolet light can, through a complex series of reactions, produce a harmful concentration of ozone in the air. The resulting air pollution is known as photochemical smog. Certain air pollutants (e.g., chlorofluorocarbons) can drift up into the atmosphere and damage the balance between ozone production and destruction, resulting in a reduced concentration of ozone in the layer.

Ozone Precursor - A chemical compound (such as nitrogen oxides, methane, nonmethane hydrocarbons and hydroxyl radicals) that, in the presence of solar radiation, reacts with other chemical compounds to form ozone.

Petroleum - A generic term applied to oil and oil products in all forms (such as crude oil, lease condensate, unfinished oil, refined petroleum products, natural gas plant liquids, and finished petroleum products).

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.

Reformulated Gasoline (RFG) - Gasoline whose composition has been changed (from that of gasolines sold in 1990) to 1) include oxygenates, 2) reduce the content of olefins and aromatics and volatile components, and 3) reduce the content of heavy hydrocarbons to meet performance specifications for ozone-forming tendency and for release of toxic substances (benzene, formaldehyde, acetaldehyde, 1,3-butadiene, and polycyclic organic matter) into the air from both evaporation and tailpipe emissions.

Replacement Fuel - The portion of any motor fuel that is methanol, ethanol, or other alcohols, natural gas, liquefied petroleum gases, hydrogen, coal derived liquid fuels, electricity (including electricity from solar energy), ethers, or any other fuel the Secretary of Energy determines, by rule, is substantially not petroleum and would yield substantial energy security benefits and substantial environmental benefits.

South Census Region - This U.S. Census Bureau region consists of the following States - Alabama, Arkansas, Delaware, District of Columbia, Florida, Georgia, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, Virginia, and West Virginia.

Tax Incentives - In general, a means of employing the tax code to stimulate investment in or development of a socially desirable economic objective without the direct expenditure from the budget of a given unit of government. Such incentives can take the form of tax exemptions or credits.

Tertiary Amyl Methyl Ether (TAME) (CH₃)₂(C₂H₅)COCH₃ - An oxygenate blend stock formed by the catalytic etherification of isoamylene with methanol.

BIOENERGY TERMS:

Anaerobic digestion - Decomposition of biological wastes by micro-organisms, usually under wet conditions, in the absence of air (oxygen), to produce a gas comprising mostly methane and carbon dioxide.

Barrel of oil equivalent - (boe) The amount of energy contained in a barrel of crude oil, i.e. approximately 6.1 GJ (5.8 million Btu), equivalent to 1,700 kWh. A "petroleum barrel" is a liquid measure equal to 42 U.S. gallons (35 Imperial gallons or 159 liters); about 7.2 barrels are equivalent to one tonne of oil (metric).

Biochemical conversion - The use of fermentation or anaerobic digestion to produce fuels and chemicals from organic sources.

Bioenergy - Useful, renewable energy produced from organic matter. The conversion of the complex carbohydrates in organic matter to energy. Organic matter may either be used directly as a fuel or processed into liquids and gases.

Biogas - A combustible gas derived from decomposing biological waste under anaerobic conditions. Biogas normally consists of 50 to 60 percent methane. See also landfill gas.

Biomass - Organic matter available on a renewable basis. Biomass includes forest and mill residues, agricultural crops and wastes, wood and wood wastes, animal wastes, livestock operation residues, aquatic plants, fast-growing trees and plants, and municipal and industrial wastes.

Biomass fuel - Liquid, solid, or gaseous fuel produced by conversion of biomass. Examples include bioethanol from sugar cane or corn, charcoal or woodchips, and biogas from anaerobic decomposition of wastes.

Bone dry - Having zero percent moisture content. Wood heated in an oven at a constant temperature of 100°C (212°F) or above until its weight stabilizes is considered bone dry or oven dry.

Bottoming cycle - A cogeneration system in which steam is used first for process heat and then for electric power production.

British thermal unit - (Btu) A non-metric unit of heat, still widely used by engineers. One Btu is the heat energy needed to raise the temperature of one pound of water from 60°F to 61°F at one atmosphere pressure. 1 Btu = 1055 joules (1.055 kJ).

Capacity - The maximum power that a machine or system can produce or carry safely. The maximum instantaneous output of a resource under specified conditions. The capacity of generating equipment is generally expressed in kilowatts or megawatts.

Capital cost - The total investment needed to complete a project and bring it to a commercially operable status. The cost of construction of a new plant. The expenditures for the purchase or acquisition of existing facilities.

cfm - Cubic feet per minute (1000 cfm = 0.472 cubic meters per second, m3/s)

Cellulose - The principal chemical constituent of cell walls of plants - a long chain of simple sugar molecules.

Char - The remains of solid biomass that has been incompletely combusted, such as charcoal if wood is incompletely burned.

Chipper - A machine that produces wood chips by knife action.

Chips - Woody material cut into short, thin wafers. Chips are used as a raw material for pulping and fiberboard or as biomass fuel.

Cogeneration - The sequential production of electricity and useful thermal energy from a common fuel source. Reject heat from industrial processes can be used to power an electric generator (bottoming cycle). Conversely, surplus heat from an electric generating plant can be used for industrial processes, or space and water heating purposes (topping cycle).

Combined cycle - Two or more generation processes in series or in parallel, configured to optimize the energy output of the system.

Combined-cycle power plant - The combination of a gas turbine and a steam turbine in an electric generation plant. The waste heat from the gas turbine provides the heat energy for the steam turbine.

Combined heat and power - (CHP) See Cogeneration.

Combustion - Burning. The transformation of biomass fuel into heat, chemicals, and gases through chemical combination of hydrogen and carbon in the fuel with oxygen in the air.

Combustion air - The air fed to a fire to provide oxygen for combustion of fuel. It may be preheated before injection into a furnace.

Combustion efficiency - (actual heat produced by combustion) divided by (total heat potential of the fuel consumed)

Commercial forest land - Forested land which is capable of producing new growth at a minimum rate of 20 cubic feet per acre/per year, excluding lands withdrawn from timber production by statute or administrative regulation.

Coppice regeneration - The ability of certain hardwood species to regenerate by producing multiple new shoots from a stump left after harvest.

Cord - A stack of wood consisting of 128 cubic feet (3.62 cubic meters). A cord has standard dimensions of 4 x 4 x 8 feet, including air space and bark. One cord contains about 1.2 U.S. tons (oven-dry), i.e. 2400 pounds or 1089 kg.

Diameter at breast height - (DBH) The diameter of a tree measured 4 feet 6 inches above the ground.

Digester - An airtight vessel or enclosure in which bacteria decomposes biomass in water to produce biogas.

Discount rate - A rate used to convert future costs or benefits to their present value.

Downdraft gasifier - A gasifier in which the product gases pass through a combustion zone at the bottom of the gasifier.

Dutch oven furnace - One of the earliest types of furnaces, having a large, rectangular box lined with firebrick (refractory) on the sides and top. Commonly used for burning wood. Heat is stored in the refractory and radiated to a conical fuel pile in the center of the furnace.

Effluent - The liquid or gas discharged from a process or chemical reactor, usually containing residues from that process.

Emissions - Waste substances released into the air or water. See also Effluent.

Energy crops - Crops grown specifically for their fuel value. These include food crops such as corn and sugarcane, and nonfood crops such as poplar trees and switchgrass. Currently, two energy crops are under development - short-rotation woody crops, which are fast-growing hardwood trees harvested in 5 to 8 years, and herbaceous energy crops, such as perennial grasses, which are harvested annually after taking 2 to 3 years to reach full productivity.

Externality - A cost or benefit not accounted for in the price of goods or services. Often "externality" refers to the cost of pollution and other environmental impacts.

Feedstock - Any material which is converted to another form or product.

Feller-buncher - A self-propelled machine that cuts trees with giant shears near ground level and then stacks the trees into piles to await skidding.

Fermentation - Conversion of carbon-containing compounds by micro-organisms for production of fuels and checmicals such as alcohols, acids or energy-rich gases.

Firm power - (firm energy) Power which is guaranteed by the supplier to be available at all times during a period covered by a commitment. That portion of a customer's energy load for which service is assured by the utility provider.

Fluidized-bed boiler - A large, refractory-lined vessel with an air distribution member or plate in the bottom, a hot gas outlet in or near the top, and some provisions for introducing fuel. The fluidized bed is formed by blowing air up through a layer of inert particles (such as sand or limestone) at a rate that causes the particles to go into suspension and continuous motion. The super-hot bed material increased combustion efficiency by its direct contact with the fuel.

Fly ash - Small ash particles carried in suspension in combustion products.

Forest residues - Material not harvested or removed from logging sites in commercial hardwood and softwood stands as well as material resulting from forest management operations such as precommercial thinnings and removal of dead and dying trees.

Forest health - A condition of ecosystem sustainability and attainment of management objectives for a given forest area. Usually considered to include green trees, snags, resilient stands growing at a moderate rate, and endemic levels of insects and disease. Natural processes still function or are duplicated through management intervention.

Fossil fuel - Solid, liquid, or gaseous fuels formed in the ground after millions of years by chemical and physical changes in plant and animal residues under high temperature and pressure. Oil, natural gas, and coal are fossil fuels.

Fuel cell - A device that converts the energy of a fuel directly to electricity and heat, without combustion.

Fuel cycle - The series of steps required to produce electricity. The fuel cycle includes mining or otherwise acquiring the raw fuel source, processing and cleaning the fuel, transport, electricity generation, waste management and plant decommissioning.

Fuel handling system - A system for unloading wood fuel from vans or trucks, transporting the fuel to a storage pile or bin, and conveying the fuel from storage to the boiler or other energy conversion equipment.

Furnace - An enclosed chamber or container used to burn biomass in a controlled manner to produce heat for space or process heating.

Gas turbine - (combustion turbine) A turbine that converts the energy of hot compressed gases (produced by burning fuel in compressed air) into mechanical power. Often fired by natural gas or fuel oil.

Gasification - A chemical or heat process to convert a solid fuel to a gaseous form.

Gasifier - A device for converting solid fuel into gaseous fuel. In biomass systems, the process is referred to as pyrolitic distillation. See Pyrolysis.

Genetic selection - Application of science to systematic improvement of a population, e.g. through selective breeding.

Gigawatt - (GW) A measure of electrical power equal to one billion watts (1,000,000 kW). A large coal or nuclear power station typically has a capacity of about 1 GW.

Greenhouse effect - The effect of certain gases in the Earth's atmosphere in trapping heat from the sun.

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. Other greenhouse gases include methane, ozone, chlorofluorocarbons, and nitrous oxide.

Grid - An electric utility company's system for distributing power.

Habitat - The area where a plant or animal lives and grows under natural conditions. Habitat includes living and non-living attributes and provides all requirements for food and shelter.

Hardwoods - Usually broad-leaved and deciduous trees.

Heat Rate - The amount of fuel energy required by a power plant to produce one kilowatt-hour of electrical output. A measure of generating station thermal efficiency, generally expressed in Btu per net kWh. It is computed by dividing the total Btu content of fuel burned for electric generation by the resulting net kWh generation.

Heat transfer efficiency - useful heat output released / actual heat produced in the firebox

Heating value - The maximum amount of energy that is available from burning a substance.

Hectare - Common metric unit of area, equal to 2.47 acres. 100 hectares = 1 square kilometer.

Herbaceous - Non-woody type of vegetation, usually lacking permanent strong stems, such as grasses, cereals and canola (rape).

Higher heating value - (HHV) The maximum potential energy in dry fuel. For wood, the range is from 7,600 to 9,600 Btu/lb (17.7 to 22.3 GJ/t).

Horsepower - (electrical horsepower; hp) A unit for measuring the rate of mechanical energy output, usually used to describe the maximum output of engines or electric motors. 1 hp = 550 foot-pounds per second = 2,545 Btu per hour = 745.7 watts = 0.746 kW

Hydrocarbon - Any chemical compound containing hydrogen, oxygen, and carbon.

Incinerator - Any device used to burn solid or liquid residues or wastes as a method of disposal. In some incinerators, provisions are made for recovering the heat produced.

Inclined grate - A type of furnace in which fuel enters at the top part of a grate in a continuous ribbon, passes over the upper drying section where moisture is removed, and descends into the lower burning section. Ash is removed at the lower part of the grate.

Incremental energy costs - The cost of producing and transporting the next available unit of electrical energy. Short run incremental costs (SRIC) include only incremental operating costs. Long run incremental costs (LRIC) include the capital cost of new resources or capital equipment.

Independent power producer - A power production facility that is not part of a regulated utility.

Indirect liquefaction - Conversion of biomass to a liquid fuel through a synthesis gas intermediate step.

Joule - Metric unit of energy, equivalent to the work done by a force of one Newton applied over a distance of one meter (= 1 kg m2/s2). One joule (J) = 0.239 calories (1 calorie = 4.187 J).

Kilowatt - (kW) A measure of electrical power equal to 1,000 watts. 1 kW = 3,413 Btu/hr = 1.341 horsepower. See also watt..

Kilowatt hour - (kWh) A measure of energy equivalent to the expenditure of one kilowatt for one hour. For example, 1 kWh will light a 100-watt light bulb for 10 hours. 1 kWh = 3,413 Btu.

Landfill gas - A type of biogas that is generated by decomposition of organic material at landfill disposal sites. Landfill gas is approximately 50 percent methane. See also biogas.

Levelized life-cycle cost - The present value of the cost of a resource, including capital, financing and operating costs, expressed as a stream of equal annual payments. This stream of payments can be converted to a unit cost of energy by dividing the annual payment amount by the annual kilowatt-hours produced or saved. By levelizing costs, resources with different lifetimes and generating capabilities can be compared.

Lignin - Structural constituent of wood and (to a lesser extent) other plant tissues, which encrusts the cell walls and cements the cells together.

Megawatt - (MW) A measure of electrical power equal to one million watts (1,000 kW). See also watt.

Mill/kWh - A common method of pricing electricity in the U.S. Tenths of a U.S. cent per kilowatt hour.

Mill residue - Wood and bark residues produced in processing logs into lumber, plywood, and paper.

MMBtu - One million British thermal units.

Moisture content - (MC) The weight of the water contained in wood, usually expressed as a percentage of weight, either oven-dry or as received.

Moisture content, dry basis - Moisture content expressed as a percentage of the weight of oven-dry wood, i.e. - [(weight of wet sample - weight of dry sample) / weight of dry sample ] x 100

Moisture content, wet basis - Moisture content expressed as a percentage of the weight of wood as-received, i.e. - [(weight of wet sample - weight of dry sample) / weight of wet sample ] x 100

Monoculture - The cultivation of a single species crop.

Net present value - The sum of the costs and benefits of a project or activity. Future benefits and costs are discounted to account for interest costs.

Nitrogen fixation - The transformation of atmospheric nitrogen into nitrogen compounds that can be used by growing plants.

Noncondensing, controlled extraction turbine - A turbine that bleeds part of the main steam flow at one (single extraction) or two (double extraction) points.

Organic compounds - Chemical compounds based on carbon chains or rings and also containing hydrogen, with or without oxygen, nitrogen, and other elements.

Particulate - A small, discrete mass of solid or liquid matter that remains individually dispersed in gas or liquid emissions. Particulates take the form of aerosol, dust, fume, mist, smoke, or spray. Each of these forms has different properties.

Photosynthesis - Process by which chlorophyll-containing cells in green plants concert incident light to chemical energy, capturing carbon dioxide in the form of carbohydrates.

Pilot scale - The size of a system between the small laboratory model size (bench scale) and a full-size system.

Present value - The worth of future receipts or costs expressed in current value. To obtain present value, an interest rate is used to discount future receipts or costs.

Process heat - Heat used in an industrial process rather than for space heating or other housekeeping purposes.

Producer gas - Fuel gas high in carbon monoxide (CO) and hydrogen (H2), produced by burning a solid fuel with insufficient air or by passing a mixture of air and steam through a burning bed of solid fuel.

Pyrolysis - The thermal decomposition of biomass at high temperatures (greater than 400° F, or 200° C) in the absence of air. The end product of pyrolysis is a mixture of solids (char), liquids (oxygenated oils), and gases (methane, carbon monoxide, and carbon dioxide) with proportions determined by operating temperature, pressure, oxygen content, and other conditions.

Quad - One quadrillion Btu (10^15 Btu) = 1.055 exajoules (EJ), or approximately 172 million barrels of oil equivalent.

Recovery boiler - A pulp mill boiler in which lignin and spent cooking liquor (black liquor) is burned to generate steam.

Refractory Lining - A lining, usually of ceramic, capable of resisting and maintaining high temperatures.

Refuse-derived fuel - (RDF) Fuel prepared from municipal solid waste. Noncombustible materials such as rocks, glass, and metals are removed, and the remaining combustible portion of the solid waste is chopped or shredded. RDF facilities process typically between 100 and 3,000 tons of MSW per day.

Reserve Margin - The amount by which the utility's total electric power capacity exceeds maximum electric demand.

Return on investment - (ROI) The interest rate at which the net present value of a project is zero. Multiple values are possible.

Rotation - Period of years between establishment of a stand of timber and the time when it is considered ready for final harvest and regeneration.

Saturated steam - Steam at boiling temperature for a given pressure.

Shaft horsepower - A measure of the actual mechanical energy per unit time delivered to a turning shaft. See also horsepower.

Silviculture - Theory and practice of controlling the establishment, composition, structure and growth of forests and woodlands.

SRIC - Short rotation intensive culture - the growing of tree crops for bioenergy or fiber, characterized by detailed site preparation, usually less than 10 years between harvests, usually fast-growing hybrid trees and intensive management (some fertilization, weed and pest control, and possibly irrigation).

Stand - (of trees) A tree community that possesses sufficient uniformity in composition, constitution, age, spatial arrangement, or condition to be distinguishable from adjacent communities.

Steam turbine - A device for converting energy of high-pressure steam (produced in a boiler) into mechanical power which can then be used to generate electricity.

Superheated steam - Steam which is hotter than boiling temperature for a given pressure.

Surplus electricity - Electricity produced by cogeneration equipment in excess of the needs of an associated factory or business.

Sustainable - An ecosystem condition in which biodiversity, renewability, and resource productivity are maintained over time.

Therm - A unit of energy equal to 100,000 Btus (= 105.5 MJ); used primarily for natural gas.

Thermochemical conversion - Use of heat to chemically change substances from one state to another, e.g. to make useful energy products.

Tipping fee - A fee for disposal of waste.

Ton, tonne - One U.S. ton (short ton) = 2,000 pounds. One Imperial ton (long ton or shipping ton) = 2,240 pounds. One metric tonne (tonne) = 1,000 kilograms (2,205 pounds). One oven-dry ton or tonne (ODT, sometimes termed bone-dry ton/tonne) is the amount of wood that weighs one ton/tonne at 0% moisture content. One green ton/tonne refers to the weight of undried (fresh) biomass material - moisture content must be specified if green weight is used as a fuel measure.

Topping cycle - A cogeneration system in which electric power is produced first. The reject heat from power production is then used to produce useful process heat.

Topping and back pressure turbines - Turbines which operate at exhaust pressure considerably higher than atmospheric (noncondensing turbines). These turbines are often multistage types with relatively high efficiency.

Transmission - The process of long-distance transport of electrical energy, generally accomplished by raising the electric current to high voltages.

Traveling grate - A type of furnace in which assembled links of grates are joined together in a perpetual belt arrangement. Fuel is fed in at one end and ash is discharged at the other.

Turbine - A machine for converting the heat energy in steam or high temperature gas into mechanical energy. In a turbine, a high velocity flow of steam or gas passes through successive rows of radial blades fastened to a central shaft.

Turn down ratio - The lowest load at which a boiler will operate efficiently as compared to the boiler's maximum design load.

Waste streams - Unused solid or liquid by-products of a process.

Water-cooled vibrating grate - A boiler grate made up of a tuyere grate surface mounted on a grid of water tubes interconnected with the boiler circulation system for positive cooling. The structure is supported by flexing plates allowing the grid and grate to move in a vibrating action. Ashes are automatically discharged.

Watershed - The drainage basin contributing water, organic matter, dissolved nutrients, and sediments to a stream or lake.

Watt - The common base unit of power in the metric system. One watt equals one joule per second, or the power developed in a circuit by a current of one ampere flowing through a potential difference of one volt. One Watt = 3.413 Btu/hr. See also kilowatt.

Wheeling - The process of transferring electrical energy between buyer and seller by way of an intermediate utility or utilities.

Whole-tree harvesting - A harvesting method in which the whole tree (above the stump) is removed.

Yarding - The initial movement of logs from the point of felling to a central loading area or landing.