Glossary of Renewable Energy Terms

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Abiotic: Having an absence of life or living organisms.

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.

Accumulating shear: A feller-buncher shearhead that is capable of accumulating and holding 2 or more cut stems.

AC: See Alternating Current

ACFM: Actual cubic feet per minute. The actual cubic feet per minute of gas flowing in a process at the temperature and pressure of the process at that point.

Acid hydrolysis: A chemical process in which acid is used to convert cellulose or starch to sugar.

Activated sludge process: A biological wastewater treatment process in which a mixture of waste water and activated sludge is agitated and aerated. The activated sludge is then separated from the treated wastewater by sedimentation and disposed of or returned to the process as needed.

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

Active solar energy: Solar radiation used by special equipment to provide space heating, hot water or electricity.

Active solar energy system:- A system designed to convert solar radiation into usable energy for space, water heating, or other uses. It requires a mechanical device, usually a pump or fan, to collect the sun's energy.

Adaptive management: A continuing process of action-based planning, monitoring, researching, evaluating, and adjusting with the objective of improving implementation and achieving the goals of the selected alternative.

Adaptive management area: Landscape units designated for development and testing of technical and social approaches to achieving desired ecological, economic, and other social objectives.

Adverse Hydro: Water conditions limiting the production of hydroelectric power. In years having below-normal levels of rain and snow, and in seasons having less-than-usual runoff from mountain snow pack, there is then less water available for hydro energy production.

Aeration Basin: A basin where oxygen is supplied by mechanical agitation or pneumatic means to enhance the breakdown of wastes held in suspension.

After Market: broad term that applies to any change after the original purchase, such as adding equipment not a part of the original purchase. As applied to alternative fuel vehicles, it refers to conversion devices or kits for conventional fuel vehicles.

Air Change: The replacement of a quantity of air in a space within a given period of time, typically expressed as air changes per hour. If a building has one air change per hour, this is equivalent to all of the air in the building being replaced in a one-hour period.

Air Conditioner: An assembly of equipment for air treatment consisting of a means for ventilation, air circulation, air cleaning, and heat transfer (either heating or cooling). The unit usually consists of an evaporator or cooling coil, and an electrically-driven compressor and condenser combination.

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

Air Quality Maintenance Area: Specific populated area where air quality is a problem for one or more pollutants.

Air to Air Heat Exchanger: A device with separate air chambers that transfers heat between the conditioned air being exhausted and the outside air being supplied to a building.

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

Alcohol: A general class of hydrocarbons that contain a hydroxyl group (OH). The term "alcohol" is often used interchangeably with the term "ethanol," even though there are many types of alcohol. (See Butanol, Ethanol, Methanol.)

Alcohol Fuels: A class of liquid chemicals that have certain combinations of hydrogen, carbon and oxygen, and that are capable of being used as fuel.

Alkali: A soluble mineral salt.

Alterating Current: (AC) Flow of electricity that constantly changes direction between positive and negative sides. Almost all power produced by electric utilities in the United States moves in current that shifts direction at a rate of 60 times per second.

Alternative fuel: As defined in the US Energy Policy Act of 1992 (EPACT):

          • Methanol, denatured ethanol and other alcohols, separately or in blends of at least 10 percent by volume with gasoline or other fuels
          • Compressed natural gas
          • Liquefied natural gas
          • Liquefied propane gas
          • Hydrogen
          • Coal derived liquid fuels
          • Fuels other than alcohols derived from biological materials
          • Electricity
          • Biodiesel
          • Any other fuel determed to be substantially not petroleum and yielding potential energy and environmental benefits.

Alternative Fuel Vehicle (AFV): Motor vehicles that run on fuels other than petroleum-based fuels. As defined by the National Energy Policy Act (EPAct), this excludes reformulated gasoline as an alternative fuel.

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

aMW: See average megawatt.

Ambient: The surrounding atmosphere; encompassing on all sides; the environment surrounding a body but undisturbed or unaffected by it.

Ampere: The unit of measure that tells how much electricity flows through a conductor. It is like using cubic feet per second to measure the flow of water. For example, a 1,200 watt, 120-volt hair dryer pulls 10 amperes of electric current (watts divided by volts).

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

Anaerobic: Life or biological processes that occur in the absence of oxygen.

Anemometer: A device that measures wind speed.

Angle of Attack: The angle of relative air flow to the blade chord of a wind turbine.

Anhydrous: A compound that does not contain water. For example, fuel ethanol is referred to as "anhydrous ethanol" because most of the water has been removed.

Angle of Incidence: The angle that the sun's rays make with a line perpendicular to a surface. The angle of incidence determines the percentage of direct sunshine intercepted by a surface.

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

Annual Maximum Demand: The greatest of all demands of the electrical load which occurred during a prescribed interval in a calendar year.

AFUE (Annual Fuel Utilization Efficiency) A measure of heating efficiency, in consistent units, determined by applying the federal test method for furnaces. This value is intended to represent the ratio of heat transferred to the conditioned space by the fuel energy supplied over one year.

Anthracite: Hard coal, found deep in the earth. It burns very hot, with little flame. It usually has a heating value of 12,000-15,000 British thermal units (Btus) per pound.

Appliance Saturation: A percentage telling what proportion of all households in a given geographical area have a certain appliance.

Area Load: The total amount of electricity being used at a given point in time by all consumers in a utility's service territory.

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

Armature (wind turbine): 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.

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.

Average megawatt: (MWa or aMW) One megawatt of capacity produced continuously over a period of one year. 1 aMW = 1 MW x 8760 hours/year = 8,760 MWh = 8,760,000 kWh.

Avoided costs: An investment guideline describing the value of a conservation or generation resource investment by the cost of more expensive resources that a utility would otherwise have to acquire.

Axial Alternator (wind turbine): 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.

Azimuth: The angular distance between true south and the point on the horizon directly below the sun. Typically used as an input for opaque surfaces and windows in computer programs for calculating the energy performance of buildings.

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Background level: The average amount of a substance present in the environment. Originally referring to naturally occurring phenomena. Used in toxic substance monitoring.

Backup rate: A utility charge for providing occasional electricity service to replace on-site generation.

Backup electricity, backup services: Power or services needed occasionally; for example, when on-site generation equipment fails.

BACT: See best available control technology.

Baffle chamber: In incinerator design, a chamber designed to settle fly ash and coarse particulate matter by changing the direction and reducing the velocity of the combustion gases.

Baghouse: A chamber containing fabric filter bags that remove particles from furnace stack exhaust gases. Used to eliminate particles greater than 20 microns in diameter.

Ballast: A device that provides starting voltage and limits the current during normal operation in electrical discharge lamps (such as fluorescent lamps).

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.

Bar screen: A screen made of parallel bars set 3/4" to 2" apart used to filter out large objects.

Barrel: In the petroleum industry, a barrel is 42 U.S. gallons. One barrel of oil has an energy content of 6 million British thermal units. It takes one barrel of oil to make enough gasoline to drive an average car from Los Angeles to San Francisco and back (at 18 miles per gallon over the 700-mile round trip).

Barrel of oil equivalent: A unit of energy equal to the amount of energy contained in a barrel of crude oil. Approximately 5.78 million Btu or 1,700 kWh. A barrel is a liquid measure equal to 42 gallons.

Baseload: The lowest level of power production needs during a season or year.

Baseload capacity: The power output that generating equipment can continuously produce.

Baseload demand: The minimum demand experienced by an electric utility, usually 30-40% of the utility´s peak demand.

Base Rate: That portion of the total electric or gas rate covering the general costs of doing business unrelated to fuel expenses.

Battery: A device that stores energy and produces electric current by chemical action.

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

BDU: See bone dry unit.

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 (wind turbine): 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.

Benzene: A toxic, six-carbon aromatic component of gasoline. A known carcinogen.

Best available control measures: The most effective measures for controlling small or dispersed particulates from sources such as soot and ash from woodstoves and open burning of brush, timber, grasslands, or trash.

Best available control technology: (BACT) That combination of production processes, methods, systems, and techniques that will result in the lowest achievable level of emissions of air pollutants from a given facility. BACT is an emission limitation that the permitting authority determines on a case-by-case basis, taking into account energy, environmental, economic and other costs of control. BACT may include fuel cleaning or treatment or innovative fuel combustion techniques. Applies in attainment areas.

Best management practices: A practice or combination of practices that a designated agency determines to be the most effective, practical means of reducing the amount of pollution generated by nonpoint sources to a level compatible with water quality goals.

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.

Bi-gas: A process being developed as a means of making synthetic gas from coal. The synthetic gas would be intended to substitute for natural gas in meeting industrial and home energy needs.

Bioaccumulants: Substances in contaminated air, water, or food that increase in concentration in living organisms exposed to them because the substances are very slowly metabolized or excreted.

Bioaccumulation: See bioconcentration.

Biochemical conversion process: The use of living organisms or their products to convert organic material to fuels, chemicals or other products.

Biochemical oxygen demand: (BOD) A standard means of estimating the degree of water pollution, especially of water bodies that receive contamination from sewage and industrial waste. BOD is the amount of oxygen needed by bacteria and other microorganisms to decompose organic matter in water. The greater the BOD, the greater the degree of pollution. Biochemical oxygen demand is a process that occurs over a period of time and is commonly measured for a five-day period, referred to as BOD5.

Bioconcentration: (Bioaccumulation) The accumulation of a chemical in tissues of an organism to levels greater than in the environment in which the organism lives.

Bioconversion: Processes that use plants or micro-organisms to change one form of energy into another. For example, an experimental process uses algae to convert solar energy into gas that could be used for fuel.

Biodegradable: Capable of decomposing rapidly under natural conditions.

Biodiesel: A biofuel produced through transesterification, a process in which organically-derived oils are combined with alcohol (ethanol or methanol) in the presence of a catalyst to form ethyl or methyl ester. The biomass-derived ethyl or methyl esters can be blended with conventional diesel fuel or used as a neat fuel (100% biodiesel). Biodiesel can be made from soybean or rapeseed oils, animal fats, waste vegetable oils or microalgae oils.

Biodiversity: The relative abundance and variety of plant and animal species and ecosystems within particular habitats.

Bioenergy: 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 or gases.

Biofuels: Fuels made from biomass. Biofuels include ethanol, biodiesel and methanol.

Biogas: A combustible gas derived from decomposing biological waste. Biogas normally consists of 50 to 60 percent methane.

Biological assessment: A specific process required as part of an environmental assessment. An evaluation of potential effects of a proposed project on proposed, endangered, threatened and sensitive animal and plant species and their habitats.

Biological magnification: The process by which substances such as pesticides or heavy metals become concentrated as they move up the food chain.

Biological oxidation: Decomposition of organic materials by microorganisms.

Biomass: Renewable organic matter such as agricultural crops and residue, wood and wood waste, animal waste, aquatic plants and organic components of municipal and industrial wastes.

Biomass fuel: Liquid, solid or gaseous fuel produced by conversion of biomass.

Biomass energy: See bioenergy.

Biome: The community of living organisms in a given area.

Bioremediation: The use of living organisms to clean up pollutants from soil or water.

Biosphere: The portion of the Earth and its atmosphere that can support life.

Biota: The animal and plant life of a region or period.

Biotechnology: Technology that use living organisms to produce products such as medicines, to improve plants or animals, or to produce microorganisms for bioremediation.

Biotic: Pertaining to life or living organisms.

Biotic community: A naturally occurring, interdependent community of plants and animals that live in the same environment.

Bituminous Coal: Soft coal containing large amounts of carbon. It has a luminous flame and produces a great deal of smoke.

Blackout: A power loss affecting many electricity consumers over a large geographical area for a significant period of time.

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

BMP: See best management practices.

Boiler horsepower: A measure of the maximum rate of heat energy output of a steam generator. One boiler horsepower equals 33,480 Btu/hr output in steam.

Boiler: Any device used to burn biomass fuel to heat water for generating steam.

Bone dry: Having zero percent moisture content. Wood heated in an oven at a constant temperature of 212 degrees F or above until its weight stabilizes is considered bone dry or oven dry.

Bone dry ton: (or "oven dry ton"). An amount of wood that weighs 2,000 pounds at zero percent moisture content.

Bone dry unit: (BDU) A quantity of wood residue which weighs 2,400 pounds at zero percent moisture content.

Bottom ash: Noncombustible ash that is left after solid fuel has been burned.

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

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

Bridge Rectifier (wind turbine): 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.

British thermal unit: (Btu) A unit of heat energy equal to the heat needed to raise the temperature of one pound of water one degree Fahrenheit at one atmosphere pressure (sea level).

Brownout: A controlled power reduction in which the utility decreases the voltage on the power lines, so customers receive weaker electric current. Brownouts can be used if total power demand exceeds the maximum available supply. The typical household does not notice the difference.

Brushes (wind turbine): Devices for transferring power to or from a rotating object. Usually made of carbon-graphite.

Btu: See British thermal unit

Bulk density: Weight per unit of volume, usually specified in pounds per cubic foot.

Bulk Power Supply: Often this term is used interchangeably with wholesale power supply. In broader terms, it refers to the aggregate of electric generating plants, transmission lines, and related-equipment. The term may refer to those facilities within one electric utility, or within a group of utilities in which the transmission lines are interconnected.

Busbar: In electric utility operations, a busbar is a conductor that serves as a common connection for two or more circuits. It may be in the form of metal bars or high-tension cables.

Butane: A gas derived from natural gas. Used as a component of gasoline. Used in liquefied petroleum gas (LPG) for domestic and industrial applications.

Butanol or butyl alcohol: An alcohol with the chemical formula CH3(CH2)3OH. It is formed during anaerobic fermentation using bacteria to convert the sugars to butanol and carbon dioxide.

Butt log: The log taken from the base of a tree; often slightly irregular.

Buy Through: An agreement between utility and customer to import power when the customer's service would otherwise be interrupted.

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calorie: (energy calorie - small "c" - as opposed to food Calorie - capital "C") Any of several approximately equal values of heat, each measured as the quantity of heat require to raise the temperature of 1 gram of water by 1 degree Celsius from a standard initial temperature, esp. from 3.98 degrees Celsius. 14.5 degrees Celsius, or 19.5 degrees Celsius, at 1 atmosphere pressure. A calorie is the unit of heat equal to 4.184 joules.

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.

Capacity factor: The amount of energy that a power plant actually generates compared to its maxumum rated output, expressed as a percentage.

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.

Carbohydrate: A chemical compound made up of carbon, hydrogen, and oxygen. Includes sugars, cellulose, and starches.

Carbon Dioxide: (CO2) A product of combustion. The most common greenhouse gas.

Carbon Monoxide: (CO) A colorless, odorless gas produced by incomplete combustion. Carbon monoxide is poisonous if inhaled.

Carbon Sequestration: The absorption and storage of carbon dioxide from the atmosphere. Naturally-occurring in plants.

Capacity: The amount of electric power for which a generating unit, generating station, or other electrical apparatus is rated either by the user or manufacturer. The term is also used for the total volume of natural gas that can flow through a pipeline over a given amount of time, considering such factors as compression and pipeline size.

There are various types of electricity capacity.:

Dependable Capacity: The systems's ability to carry the electric power for the time interval and period specific, when related to the characteristics of the load to be supplied. Dependable capacity is determined by such factors as capability, operating power factor, weather, and portion of the load the station is to supply.
-Installed (or Nameplate) Capacity: The total manufacturer-rated capacities of equipment such as turbines, generators, condensers, transformers, and other system components.
-Peaking Capacity: The capacity of generating equipment intended for operation during the hours of highest daily, weekly or seasonal loads.
-Purchased Capacity: The amount of energy and capacity available for purchase from outside the system.
-Reserve Capacity: Extra generating capacity available to meet peak or abnormally high demands for power and to generate power during scheduled or unscheduled outages. Units available for service, but not maintained at operating temperature, are termed "cold." those units ready and available for service, though not in actual operation, are termed "hot."

Capacity Factor: A percentage that tells how much of a power plant's capacity is used over time. For example, typical plant capacity factors range as high as 80 percent for geothermal and 70 percent for co-generation.

Capacity Release: A secondary market for capacity that is contracted by a customer which is not using all of its capacity.

Captive Customer: A customer who does not have realistic alternatives to buying power from the local utility, even if that customer had the legal right to buy from competitors.

Cascade aeration: Aeration of an effluent stream through the action of falling water.

Cetane: Ignition performance rating of diesel fuel.

cfm: Cubic feet per minute.

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

Chemical oxygen demand: (COD) The amount of dissolved oxygen required to combine with chemicals in wastewater. A measure of the oxygen equivalent of that portion of organic matter that is susceptible to oxidation by a strong chemical oxidizing agent.

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

Chlorofluorocarbon: A family of chemicals composed primarily of carbon, hydrogen, chlorine, and fluorine. Used principally as refrigerants and industrial cleansers. Chlorofluorocarbons have the tendency to destroy the Earth´s protective ozone layer.

Clarifier: A tank used to remove solids by gravity, to remove colloidal solids by coagulation, and to remove floating oil and scum through skimming.

Clean Air Act: (CAA) USNational law establishing ambient air quality emission standards to be implemented by participating states. Originally enacted in 1963, the CAA has been amended several times, most recently in 1990. The CAA includes vehicle emission standards regulating the emission of criteria pollutants (lead, ozone, carbon monoxide, sulfur dioxide, nitrogen oxides and particulate matter). The 1990 amendments added reformulated gasoline (RFG) requirements and oxygenated gasoline provisions.

COD: See chemical oxygen demand.

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.

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

Cogeneration: The sequential production of electricity and useful thermal energy from a common fuel source. Rejected 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).

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.

Coke: A porous solid left over after the incomplete burning of coal or of crude oil.

Coke Oven Gas: Gas given off by coke ovens. Coke oven gas is interchangeable with goal gas.

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.

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. The term is more commonly used in Europe and other foreign countries.

Combined Hydronic Space/Water Heating: a system in which both space heating and domestic water heating are provided by the same water heater(s)..

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 gases: The gases released from a combustion process.

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: The actual heat produced by combustion divided by the total heat potential of the fuel consumed.

Combustion turbine: See gas turbine.

Commutator: The rotating part of a DC generator.

Compressed natural gas: (CNG) Natural gas that has been compressed under high pressure (typically 2000 to 3600 psi).

Comfort Conditioning: The range of temperatures over which the majority of persons feel comfortable (neither too hot nor too cold

Comfort Zone: The process of treating air to simultaneously control its temperature, humidity, cleanliness, and distribution to meet the comfort requirements of the occupants of the conditioned space.

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

Condenser: A heat-transfer device that reduces a fluid from a vapor phase to a liquid phase.

Condensing, controlled extraction turbines: A controlled turbine that bleeds off (condenses) part of the main stream flow at one (single extraction) or two (double extraction) points. Used when process steam is required at pressures below the inlet pressure and above the exhaust pressure.

Condensing turbine: A turbine used for electrical power generation from a minimum amount of steam. To increase plant efficiency, these units can have multiple uncontrolled extraction openings for feed-water heating.

Condensing power: Power generated through a final steam turbine stage where the steam is exhausted into a condenser and cooled to a liquid to be recycled back into a boiler.

Conditioned Floor Area:The floor area of enclosed conditioned spaces on all floors measured from the interior surfaces of exterior partitions for nonresidential buildings and from the exterior surfaces of exterior partitions for residential buildings.

Conductance: The quantity of heat, in Btu's, that will flow through one square foot of material in one hour, when there is a 1 degree F temperature difference between both surfaces. Conductance values are given for a specific thickness of material, not per inch thickness.

Conduction: The transfer of heat energy through a material (solid, liquid or gas) by the motion of adjacent atoms and molecules without gross displacement of the particles.

Conductivity (k): The quantity of heat that will flow through one square foot of homogeneous material, one inch thick, in one hour, when there is a temperature difference of one degree Fahrenheit between its surfaces.

Conservation: Efficiency of energy use, production, transmission, or distribution that results in a decrease of energy consumption while providing the same level of service.

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

Conversion efficiency: A comparison of the useful energy output to the potential energy contained in the fuel. The efficiency calculation relates to the form of energy produced. A direct comparison of the efficiency of different conversion processes can be made only when the processes produce the same form of energy output.

Converter: Any technology that changes the potential energy in a fuel into a different from of energy such as heat or motion. The term also is used to mean an apparatus that changes the quantity or quality of electrical energy.

Cooling Capacity, Latent: Available refrigerating capacity of an air conditioning unit for removing latent heat from the space to be conditioned.

Cooling Capacity, Sensible: Available refrigerating capacity of an air conditioning unit for removing sensible heat from the space to be conditioned.

Cooling Capacity, Total: Available refrigerating capacity of an air conditioner for removing sensible heat and latent heat from the space to be conditioned.

Cooling Degree Day: A unit of measure that indicates how heavy the air conditioning needs are under certain weather conditions.

Cooling Load: The rate at which heat must be extracted from a space in order to maintain the desired temperature within the space.

Cooling Load Temperature Difference (CLTD): A value used in cooling load calculations for the effective temperature difference (delta T) across a wall or ceiling, which accounts for the effect of radiant heat as well as the temperature difference.

Cooling Tower: A device for evaporatively cooling water by contact with air.

Co-op: This is the commonly used term for a rural electric cooperative. Rural electric cooperatives generate and purchase wholesale power, arrange for the transmission of that power, and then distribute the power to serve the demand of rural customers. Co-ops typically become involved in ancillary services such as energy conservation, load management and other demand-side management programs in order to serve their customers at least cost.

Cooperative(Electric utility): A joint venture organized by consumers to make electric utility service available in their area.

Cord: A stack of wood consisting of 128 cubic feet. A cord has standard dimensions of 4´ x 4´ x 8´ including air space and bark. One cord contains about 1.2 bone dry tons.

Corn stover: Residue materials from harvesting corn consisting of the cob, leaves and stalk.

Corporate average fuel economy: (CAFE) Federal standards enacted in 1975 for fuel economy in motor vehicles. The average of city and highway fuel economy test results weighted by a manufacturer for its car or truck fleet.

Critical habitat: Under the Endangered Species Act, critical habitat is defined as "the specific areas within the geographic area occupied by a species on which are found those physical and biological features essential to the conservation of the species, and that may require special management considerations or protection; and specific areas outside the geographic area occupied by a species at the time it is listed, upon determination that such areas are essential for the conservation of the species."

Crude Oil: Petroleum as found in the earth, before it is refined into oil products. Also called "crude".

Cull trees: Live saw-timber and pole-timber size trees which do not contain a merchantable sawlog due to poor form, quality, or undesirable species.

Cull: Any item of production picked out for rejection because it does not meet certain specifications. Chip culls and utility culls are specifically defined for purposes of log grading by percentage of sound wood content.

Cumulative effects: Effects on the environment resulting from actions that are individually minor but that add up to a greater total effect as they take place over a period of time.

Curie: A measure of radioactivity.

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.

Cyclone separator: A device used to remove particulate matter suspended in exhaust gases.

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

Daylighting: The use of sunlight to supplement or replace electric lighting.

Daylighting Control: A control system that varies the light output of an electric lighting system in response to variations in available daylight.

Deaeration: Removal of gases from a liquid.

Decibels: (dBA) A scale to measure sound levels.

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.

Delta: (dBA) - A difference in temperature. Often used in the context of the difference between the design indoor temperature and the outdoor temperature.

Delta (wind turbine): A 3-phase alternator wiring configuration in which all phases are connected in Series.

Demand: The rate at which energy is delivered to loads and scheduling points by generation, transmission or distribution facilities.

Denatured: Ethanol that has had a substance added to make it unfit for human consumption.

Densification: A mechanical process to compress biomass (usually wood waste) into pellets, briquettes, cubes, or densified logs.

Depletable Energy Sources: 1) electricity purchased from a public utility 2) energy obtained from burning coal, oil, natural gas or liquefied petroleum gases. [See California Code of Regulations, Title 24, Section 2-5302]

Deregulation: The elimination of regulation from a previously regulated industry or sector of an industry.

Derivatives: A specialized security or contract that has no intrinsic overall value, but whose value is based on an underlying security or factor as an index. A generic term that, in the energy field, may include options, futures, forwards, etc.

Desired future condition: A vision of the desired future state of a specific area. A description of land and resource conditions expected to result if management goals and objectives are achieved.

Diesel engine: A compression-ignition piston engine in which fuel is ignited by injecting it into air that has been heated (unlike a spark-ignition engine).

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 Raditation: Solar radiation, scattered by water vapor, dust and other particles as it passes through the atmosphere, so that it appears to come from the entire sky. Diffuse radiation is higher on hazy or overcast days than on clear days.

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

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

Dioxin: A family of compounds, some of which are hazardous, that result from combustion of carbon materials. The most toxic of these compounds is 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin.

Direct Access: The ability of a retail customer to purchase commodity electricity directly from the wholesale market rather than through a local distribution utility. (See also Retail Competition)

Direct Current (DC): Electricity that flows continuously in the same direction.

Direct Energy Conversion: Production of electricity from an energy source without transferring the energy to a working fluid or steam. For example, photovoltaic cells transform light directly into electricity. Direct conversion systems have no moving parts and usually produce direct current.

Direct Expansion (refrigeration): Any system that, in operation between an environment where heat is absorbed (heat source), and an environment into which unwanted heat is directed (heat sink) at two different temperatures, is able to absorb heat from the heat source at the lower temperature and reject heat to the heat sink at the higher temperature. The cooling effect is obtained directly from a fluid called a refrigerant that absorbs heat at a low temperature and pressure, and transfers heat at a higher temperature and higher pressure.

Direct Radiation: Radiation that has traveled a straight path from the sun, as opposed to diffuse radiation.

Direct Solar Gain: Solar energy collected from the sun (as heat) in a building through windows, walls, skylights, etc.

Disaggregation: The functional separation of the vertically integrated utility into smaller, individually owned business units (i.e., generation, dispatch/control, transmission, distribution). The terms "deintegration," "disintegration" and "delamination" are sometimes used to mean the same thing. (See also "Divestiture.")

Distillate oil: Any distilled product of crude oil. A light petroleum product used for home heating and most machinery.

Distillation: The process to separate the components of a liquid mixture by boiling the liquid and then recondensing the resulting vapor.

Distillers´ dried grains: (DDG) The dried byproduct of the grain fermentation process. Typically used as a high-protein animal feed.

Distribution: The transfer of electricity from the transmission network to the consumer.

District heating or cooling: A system that involves the central production of hot water, steam, or chilled water and the distribution of these transfer media to heat or cool buildings.

Diversity: The distribution and abundance of different plants and animals within an area.

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

Double Glazing: Windows having two sheets of glass with an airspace between.

Downstream: A term used in the petroleum industry referring to the refining, transportation and marketing side of the business.

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.

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.

Drainage: See Watershed.

Dry Hole: A drilled well that does not yield gas and/or oil quantities or condition to support commercial production; also applied to gas that has been produced and from which liquid components have been removed.

Dry Steam: The conventional type of geothermal energy used for electricity production in California. Dry steam captured at the earth's surface is used to run electric turbines. The principal dry steam resource area is the Geysers in Northern California; one of only two known areas in the world for dry steam - the other being Larderello, Italy.

Dry Ton: 2,000 pounds of material dried to a constant weight.

Dual-Duct System: A central plant heating , ventilation and air conditioning (HVAC ) system that produces conditioned air at two temperatures and humidity levels. The air is then supplied through two independent duct systems to the points of usage where mixing occurs.

Dual-fuel or Bi-fuel Vehicle: refers to a vehicle capable of operating on two different fuels, in distinct fueling systems, such as compressed natural gas and gasoline.

Dual Paned (double-glazed): Two panes of glass or other transparent material, separated by a space.

Duct: A passageway made of sheet metal or other suitable material used for conveying air or other gas at relatively low pressures.

Dump: Excess hydropower that cannot be stored or conserved. Also know as "spill energy".

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.

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E85: A blend of 15 percent gasoline and 85 percent denatured ethanol by volume.

Ecology: The study of the interrelationships between organisms and their environment. From the Greek word oikos, meaning "house."

Ecosystem: The system of interactions between living organisms and their environment.

Eddy Currents (Wind Turbine): 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 the useful energy delivered by a dynamic system (such as a machine, engine, or motor) to the energy supplied to it over the same period or cycle of operation. The ratio is usually determined under specific test conditions.

Effluent: The treated waste water discharged by sewage treatment plants.

Electric Generator: A device that converts a heat, chemical or mechanical energy into electricity.

Electric Resistance Heater: A device that produces heat through electric resistance. For example, an electric current is run through a wire coil with a relatively high electric resistance, thereby converting the electric energy into heat which can be transferred to the space by fans.

Electric Radiant Heating: A heating system in which electric resistance is used to produce heat which radiates to nearby surfaces. There is no fan component to a radiant heating system.

Electricity: Electric current used as a power source. A property of the basic particles of matter. A form of energy having magnetic, radiant and chemical effects. Electric current is created by a flow of charged particles (electrons).

Electrolysis: Breaking a chemical compound down into its elements by passing a direct current through it. Electrolysis of water, for example, produces hydrogen and oxygen.

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

Electromagnetic Fields (EMF): Ordinary every day use of electricity produces magnetic and electric fields. These 60 Hertz fields (fields that go back and forth 60 times a second) are associated with electrical appliances, power lines and wiring in buildings.

Emission offset: A reduction in the air pollution emissions of existing sources to compensate for emissions from new sources.

Emissions: Waste substances released into the air or water.

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

Endangered species: See threatened, endangered, and sensitive species.

Endemic: Naturally existing at low levels in the environment.

Energy: The ability to do work.

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 in the United States: 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.

Energy Effeciency: Using less energy/electricity to perform the same function. Programs designed to use electricity more efficiently - doing the same with less. For the purpose of this paper, energy efficiency is distinguished from DSM programs in that the latter are utility-sponsored and -financed, while the former is a broader term not limited to any particular sponsor or funding source. "Energy conservation" is a term which has also been used but it has the connotation of doing without in order to save energy rather than using less energy to do the some thing and so is not used as much today. Many people use these terms interchangeably.

EER (Energy Efficiency Ratio): the ratio of cooling capacity of an air conditioning unit in Btus per hour to the total electrical input in watts under specified test conditions.

Environment: The external conditions that affect organisms and influence their development and survival.

Environmental assessment: (EA) A public document that analyzes a proposed federal action for the possibility of significant environmental impacts. The analysis is required by the National Environmental Policy Act. If the environmental impacts will be significant, the federal agency must then prepare an environmental impact statement.

Environmental impact statement: (EIS) A statement of the environmental effects of a proposed action and of alternative actions. Section 102 of the National Environmental Policy Act requires an EIS for all major federal actions.

Enzymatic hydrolysis: A process by which enzymes (biological catalysts) are used to break down starch or cellulose into sugar.

EPA - The Environmental Protection Agency. A federal agency charged with protecting the environment.

EP Toxicity: A test defined by the federal Environmental Protection Agency to check a substance for the presence of arsenic, barium, cadmium, chromium, lead, mercury, selenium, or silver. 40 CFR 261.24 defines the concentrations constituting hazardous waste and the test procedure.

ESCO: Efficiency Service Company - A company that offers to reduce a client's electricity consumption with the cost savings being split with the clien

Ethanol: Ethyl alcohol produced by fermentation and distillation. An alcohol compound with the chemical formula CH3CH20H formed during sugar fermentation by yeast. Grain alcohol.

Ethyl tertiary butyl ether: (ETBE) An ether similar to MTBE. ETBE is manufactured by reacting ethanol with isobutylene. ETBE has high octane and low volatility characteristics. Used as an oxygenate.

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

Evapotranspiration: The water released from plants as they grow. The evaporation of water from plant surfaces and adjacent soil.

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

Exhaust: Air removed deliberately from a space, by a fan or other means, usually to remove contaminants from a location near their source.

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.

Extra High Voltage (EHV): Voltage levels higher than those normally used on transmission lines. Generally EHV is considered to be 345,000 volts or higher.

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

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Fan Coil: A component of a heating, ventilation and air conditioning (HVAC) system containing a fan and heating or cooling coil, used to distribute heated or cooled air.

Fast pyrolysis: Thermal conversion of biomass by rapid heating to between 450ø to 600øC in the absence of oxygen.

Fenestration: Windows or glass doors. Technically fenestration is described as any transparent or translucent material plus any sash, frame, mullion or divider. This includes windows, sliding glass doors, French doors, skylights, curtain walls and garden windows.

Fermentation: The biological conversion of biomass by yeast or sugar. The products of fermentation are carbon dioxide and alcohol.

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.

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.

Fischer-Tropsch Fuels: Liquid hydrocarbon fuels produced by a process that combines carbon monoxide and hydrogen. The process is used to convert coal, natural gas and low-value refinery products into a high-value diesel substitute fuel.

Fission: A release of energy caused by the splitting of an atom's nucleus. This is the energy process used in conventional nuclear power plants to make the heat needed to run steam electric turbines.

Fissionable Material: A substance whose atoms can be split by slow neutrons. Uranium-235, plutonium-239 and uranium-233 are fissionable materials.

Flare Gas: Unwanted natural gas that is disposed of by burning as it is released from an oil field.

Flat Plate: A device used to collect solar energy. It is a piece of metal painted black on the side facing the sun, to absorb the sun's heat.

Flexible-fuel vehicle: A vehicle with a single fuel tank designed to run on varying blends of unleaded gasoline with either ethanol or methanol.

Floodplain: Relatively flat surfaces adjacent to active stream or river channels, formed by deposition of sediments during major floods. The floodplain may be covered by water during floods.

Flow rate: The amount of water that moves through an area (usually pipe) in a given period of time.

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.

Flue Gas: Gas that is left over after fuel is burned and which is disposed of through a pipe or stack to the outer air.

Fluidized Bed Combustion: A process for burning powdered coal that is poured in a liquid-like stream with air or gases. The process reduces sulfur dioxide emissions from coal combustion.

Fluorescent Lamp: A tubular electric lamp that is coated on its inner surface with a phosphor and that contains mercury vapor whose bombardment by electrons from the cathode provides ultraviolet light which causes the phosphor to emit visible light either of a selected color or closely approximating daylight.

Fluorocarbon Gases: Propellants used in aerosol products and refrigerants that are believed to be causing depletion of the earth's ozone shield. See CFCs.

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. A more fire-tolerant forest condition and the elimination of unnatural woody biomass accumulations that have resulted from past fire suppression.

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.

Footcandle: A unit of illuminance on a surface that is one foot from a uniform point source of light of one candle and is equal to one lumen per square foot.

Forced Air Unit (FAU): A central furnace equipped with a fan or blower that provides the primary means for circulation of air.

Fossil Fuel: Oil, coal, natural gas or their by-products. Fuel that was formed in the earth in prehistoric times from remains of living-cell organisms.

Fractional Distillation: the process of refining crude oil into various oil products. The various products are separated out in the order of their boiling points.

Framing Effects: The effect of framing (wood or metal studs, joists, beams, etc.) on the overall U-value of a wall, roof, floor, window or other building surface. Framing generally increases the U-Value and decreases the R-Value of insulated surfaces.

Framing Percentage: The area of actual framing in an envelope assembly divided by the overall area of the envelope assembly. This percentage is used to calculate the overall U-value of an assembly.

Francis turbine: A water-powered turbine used to transform water falling vertically to mechanical (rotating) energy.

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

Frequency: The number of cycles which an alternating current moves through in each second. Standard electric utility frequency in the United States is 60 cycles per second, or 60 Hertz.

Fuel: Any material that can be converted to energy.

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

Fuel-cell furnace: A variation of the Dutch oven design, that usually incorporates a primary and secondary combustion chamber (cell). The primary chamber is a vertical refractory-lined cylinder with a grate at the bottom in which combustion is partially completed. Combustion is completed in the secondary chamber.

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.

Fuel gas: Synthetic gas used for heating or cooling. It has less energy content than pipeline-quality gas.

Fuel oil: Petroleum products that are burned to produce heat or power.

Fuel Reprocessing (Nuclear): The means for obtaining usable, fissionable material from spent reactor fuel.

Fuel Rod (Nuclear):A long slender tube that holds fissionable material (fuel) for nuclear reactor use. Fuel rods are assembled into bundles called fuel elements or assemblies, which are loaded individually into the reactor core

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

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.

Fusion Energy: A power source, now under development, based on the release of energy that occurs when atoms are combined under the most extreme heat and pressure. It is the energy process of the sun and the stars.

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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.

Gas engine: A piston engine that uses gaseous fuel rather than gasoline. Fuel and air are mixed before they enter cylinders; ignition occurs with a spark.

Gas shift process: A process in which carbon monoxide and hydrogen react in the presence of a catalyst to form methane and water.

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 also referred to as pyrolitic distillation.

Gasohol: A motor vehicle fuel which is a blend of 90 percent unleaded gasoline with 10 percent ethanol (by volume). This term was used in the late 1970s.

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 in turbines. Power losses from friction are inherent in any gearing system.

Generator: A machine used for converting rotating mechanical energy to electrical energy.

Geomorphic: Pertaining to those processes that affect the form or shape of the surface of the earth.

Geothermal energy: Energy derived from the natural heat of the Earth contained in hot rocks, hot water, hot brines or steam.

Girdling: Killing a tree by removing a strip of bark from around its trunk.

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

gr/SCF: Grains of pollutant per standard cubic foot of gas. A measure of dust particles in a gas stream.

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

Green ton: 2,000 pounds of undried biomass material. Moisture content must be specified if green tons are used as a measure of fuel energy.

Green logging: The logging of timber that is still alive.

Greenhouse effect: A warming of the Earth and its atmosphere caused by greenhouse gases and water vapor 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´s system for distributing power.

Grid connection: Joining a plant that generates electric power to a utility system so that electricity can flow in either direction between the utility system and the plant.

Gross heating value: (GHV) The maximum potential energy in the fuel as received, considering moisture content (MC). It reflects the heat used to evaporate moisture. Compare higher heating value (HHV). Expressed as: GHV = HHV ((1 - MC) / 100)

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.

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H-Rotor: A Vertical Axis Wind Turbine design.

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.

Head: The vertical distance water drops from the highest level to the level of the receiving body of water.

Header: A pipe from which two or more tributary pipes run.

Header (solar): 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 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: The useful heat output released to a room divided by the actual heat produced in the firebox.

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.

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

Heterogeneity: The condition or state of being different in kind or nature.

HHV: See higher heating value.

Higher heating value: (HHV) The maximum potential energy in dry fuel. For wood, the range is 7,600 to 9,600 Btu/lb.

Hog fuel or hogged fuel: Wood residues processed through a chipper or mill to produce coarse chips normally used for fuel. Bark, sawdust, planer shavings, wood chunks, dirt, and fines may be included.

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.

Horsepower: (electrical horsepower; hp) A unit for measuring the rate of mechanical energy output. The term is usually applied to engines or electric motors to describe maximum output. 1 hp = 745.7 Watts = 0.746 kW = 2,545 Btu/hr.

hp: See horsepower.

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

Hybrid electric vehicle: A vehicle that is powered by two or more energy sources, one of which is electricity.

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

Hydraulic load: Amount of liquid going into a system.

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

Hydroelectric power: The generation of electricity using falling water.

Hydrolysis: A process of breaking chemical bonds of a compound by adding water to the bonds.

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Impedance: See Resistance.

Imhoff treatment system: In wastewater treatment, a tank without aeration or oxygenation where solids settle out. The solids are digested in a separate compartment in the bottom.

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.

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.

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 generator: A variable speed multi-pole electric generator.

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.

Infiltration: Leakage of ground water into a sewage collection system.

Inflow: Water (and pollutants) that enter sewage systems through street inlets, roof drains, and similar sources.

Influent: Wastewater going into the sewage treatment plant.

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

Inorganic compounds: Those compounds lacking carbon but including carbonates and cyanides. Compounds not having the organized anatomical structure of animal or vegetable life.

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.

Interconnection: A connection or link between power systems that enables them to draw on one another´s reserve in time of need.

Interruptible load: Loads that can be curtailed at the supplier´s discretion or in accordance with a contractual agreement.

Investor-owned utility: (IOU) A private power company owned by and responsible to its shareholders. The Public Utility Commission regulates IOUs in Oregon.

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No terms begin with "J ."


Kilowatt: (kW) A measure of electrical power equal to 1,000 Watts. 1 kW = 3,413 Btu/hr = 1.341 horsepower.

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.

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LAER: See lowest achievable emission rate.

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.

Landfill gas: Gas that is generated by decomposition of organic material at landfill disposal sites. Landfill gas is approximately 50 percent methane.

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

Leachates: Liquids percolated through waste piles. Leachate can include various minerals, organic matter, or other contaminants and can contaminate surface water or ground water.

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

Least cost planning: (integrated resource planning) A method of power planning that recognizes load uncertainty, embodies an emphasis on risk management, and reviews all available and reliable resources to meet future loads. It takes into consideration all costs of a resource, including capital, labor, fuel, maintenance, decommissioning, known environmental impacts, and the difficulty in quantifying the consequences of selecting one resource over another. Least cost planning seeks to minimize total energy costs.

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.

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.

LH2O: The heat (Btu) needed to vaporize and superheat one pound of water.

Life-cycle costing: A method of comparing costs of equipment or buildings based on original costs plus all operating and maintenance costs over the useful life of the equipment. Future costs are discounted.

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.

Liquefaction: The process of converting biomass from a solid to a liquid. The conversion process is a chemical change that takes place at elevated temperatures and pressures.

Liquid hydrocarbon: One of a very large group of chemical compounds composed only of carbon and hydrogen. The largest source of hydrocarbons is petroleum.

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

Liquefied natural gas: (LNG) Natural gas that has been condensed to a liquid by cooling the gas.

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

Load: (1) The amount of electrical power required at a given point on a system. (2) The average demand on electrical equipment or on an electric system.

Load factor: Load factor is the ratio of average demand to maximum demand or to capacity.

Load management: Any method or device that evens out electric power demand by eliminating uses during peak periods or shifting usage from peak time to off-peak time.

Long ton: (shipping ton) 2,240 pounds. Commonly used in Great Britain.

Lower heating value: (LHV) The potential energy in a fuel if the water vapor from combustion of hydrogen is not condensed.

Lowest achievable emissions rate: (LAER) Used to describe air emissions control technology. A rate of emissions defined by the permitting agency. LEAR sets emission limits for non-attainment areas.

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.

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

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.

Mass burn facility: A facility in which the pretreatment of MSW includes only inspection and simple separation to remove oversize, hazardous, or explosive materials. Large mass burn facilities have capacities of 3000 tons of MSW per day or more. Modular plants with capacities as low as 25 tons per day have been built. Mass burn technologies represent over 75% of all the MSW-to-energy facilities constructed in the United States to date. The major components of a mass burn facility include refuse receiving and handling, combustion and steam generation, flue gas cleaning, power generation, condenser cooling water, residue hauling, and storage.

Materials recovery facility: A recycling facility for municipal solid waste.

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.

Megawatt: (MW) The electrical unit of power that equals one million Watts (1,000 kW).

Methane: An odorless, colorless, flammable gas with the formula CH4 that is the primary constituent of natural gas.

Methanogen: A methane-producing organism.

Methanol: Methyl alcohol having the chemical formula CH30H. Methanol is usually produced by chemical conversion at high temperatures and pressures. Wood alcohol. Although usually produced from natural gas, methanol can be produced from gasified biomass (syngas).

Methyl tertiary butyl ether: (MTBE) An ether manufactured by reacting methanol and isobutylene. MTBE has high octane and low volatility. Used as a fuel oxygenate.

Metric ton: (or tonne) 1000 kilograms. 1 metric ton = 2,204.62 lb = 1.023 short tons.

mg/l: Milligrams per liter.

Million gallons per day.

Mill/kWh: A common method of pricing electricity. Tenths of a cent per kilowatt hour.

Mill: A tenth of a cent ($0.001).

Mitigation: Steps taken to avoid or minimize negative environmental impacts. Mitigation can include: avoiding the impact by not taking a certain action; minimizing impacts by limiting the degree or magnitude of the action; rectifying the impact by repairing or restoring the affected environment; reducing the impact by protective steps required with the action; and compensating for the impact by replacing or providing substitute resources.

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

MMBtu: One million British thermal units.

mscf: One thousand standard cubic feet.

Mscf: One million standard cubic feet.

MSW: See municipal solid waste.

Municipal solid waste: (MSW) Garbage. Refuse offering the potential for energy recovery; includes residential, commercial, and institutional wastes.

MWa: See average megawatt.

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NAAQS: See National Ambient Air Quality Standards.

Nacelle: The protective covering over a generator or motor.

National Ambient Air Quality Standards: (NAAQS) Federal standards established by the Clean Air Act.

National Environmental Policy Act: (NEPA) A US federal law enacted in 1969 that requires all federal agencies to consider and analyze the environmental impacts of any proposed action. NEPA requires an environmental impact statement for major federal actions significantly affecting the quality of the environment. NEPA requires federal agencies to inform and involve the public in the agency´s decision making process and to consider the environmental impacts of the agency´s decision.

National Pollution Discharge Elimination System:
(NPDES) The US federal water quality program administered in Oregon by the DEQ.

National Emissions Standards for Hazardous Pollutants: (NESHAPS) US Federal standards that control pollutants considered toxic to humans.

Natural gas: A mixture of gaseous hydrocarbons, primarily methane, occurring naturally in the earth. Used as fuel.

Neat fuel: Fuel that is free from admixture or dilution with other fuels.

NEPA: See National Environmental Policy Act.

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.

Nephelometric turbidity unit: A measurement unit of the clarity of water, dependent on the amount of suspended matter.

Net heating value:
(NHV) The potential energy available in the fuel as received, taking into account the energy loss in evaporating and superheating the water in the sample. Expressed as NVH = (HHV x (1- MC / 100)) - (LH(2)O x MC / 100)

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.

Nitrogen oxides: (NOx) Regulated air pollutants, primarily NO and NO2. Nitrogen oxides are precursors to the formation of smog and contribute to the formation of acid rain.

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

Nonattainment area: (NAA) A geographic area in which air quality is worse than that allowed by federal air pollution standards.

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

NTU: See nephelometric turbidity unit.

Null hypothesis: The assumption that any observed difference between two samples of a statistical population is purely accidental and not due to systematic causes.

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Octane enhancer: Any substance that is added to gasoline to increase octane.

OEM: Original equipment manufacturer.

Offset: See emission offset.

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.

Old growth: Timber stands with the following characteristics: large mature and over-mature trees in the overstory, snags, dead and decaying logs on the ground and a multi-layered canopy with trees of several age classes.

Opacity: The degree to which smoke or particles emitted into the air reduce the transmission of light and obscure the view of an object in the background.

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

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

Organic: Derived from living organisms.

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

Organic level: The amount of organic matter prescribed to be left after logging.

Oven dry: See bone dry.

Oven dry ton: (ODT) An amount of wood that weighs 2,000 pounds at zero percent moisture content.

Overnight capital cost: The capital cost of a project if it could be constructed overnight. This cost does not include the interest cost of funds used during construction.

Overstory: The portion of the trees forming the upper or uppermost canopy in a forest stand.

Oxygenate: A gasoline fuel additive containing hydrogen, carbon and oxygen. The oxygen content promotes more complete combustion of gasoline, which reduces tailpipe emissions of carbon monoxide.

Oxygenated gasoline: Gasoline containing an oxygenate.

Ozone: Tropospheric ozone (ground-level ozone), or smog, is formed when volatile organic compounds, oxygen and nitrogen oxides react in the presence of sunlight. Ground-level ozone is a pollutant and a respiratory irritant. Stratospheric ozone occurs in the upper atmosphere an protects the earth from the sun´s ultraviolet rays.

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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.

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.

Particulate emissions: Fine liquid or solid particles discharged with exhaust gases. Usually measured as grains per cubic foot or pounds per million Btu input.

Passive solar energy system: Solar heating or cooling that uses natural energy flows to transfer heat.

PCB´s: Polychlorinated biphenyls. A group of organic compounds. PCB´s are highly toxic to aquatic life. They persist in the environment for long periods of time, and they are bioaccumulants.

Peak flow: The highest flow of water attained during a particular flood for a given stream or river.

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

Percolation: The filtering of a liquid passed through a medium with many fine spaces.

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.

PETS: Proposed, endangered, threatened, or sensitive species.

pH: A measure of acidity or alkalinity. A pH of 7 represents neutrality. Acid substances have lower pH. Basic substances have higher pH.

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.

Photovoltaic: A system that converts direct sunlight to electricity using semi-conductor materials.

Pillow Blocks: Bearings that support a horizontal shaft.

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

PM2.5: Particulate that is less than 2.5 microns in diameter.

PM10: Particulate that is less than 10 microns in diameter. These particulates are present in the smoke created by burning wood.

Poles: A way of describing 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.

Polishing treatment: The final sewage treatment process to further reduce BOD5, suspended solids, and other pollutants.

Post-aeration: The introduction of oxygen into waste water to further reduce BOD and COD after secondary or advanced treatment.

Pound: Pound mass (sometimes abbreviated lb(m)). A unit of mass equal to 0.454 kilograms.

Pound of steam: One pound mass of water converted to steam.

Pound force: (sometimes abbreviated lb(f)) A force which will accelerate one pound mass at a rate of 32.2 ft/second(2).

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.

Productive machine hours: That portion of scheduled operating hours during which a machine performs its designated functions, excluding time to transport the machine and operational or mechanical delays.

Proof: A measure of ethanol content. 1-percent ethanol content equals 2 proof.

Proximate analysis: An analysis which reports volatile matter, fixed carbon, moisture content, and ash present in a fuel as a percentage of dry fuel weight.

psi: Pounds force of pressure per square inch.

psia: Pounds force of pressure per square inch absolute (including atmospheric pressure).

psig: Pounds force of pressure per square inch gauge (excluding atmospheric pressure).

Public utility district: (PUD) A publicly owned energy producer or distributor. PUDs operate as special government districts under the authority of elected commissions. They are not regulated by public utility commissions.

Public utility commissions: State agencies that regulate investor-owned utilities operating in the state.

Publicly Owned Treatment Works Permit: (POTW) A permit that regulates discharges to publicly owned sewage treatment plants.

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.

Pyranometer: An instrument for measuring solar radiation.

Pyrolysis: The thermal decomposition of biomass at high temperatures (greater than 400 degrees Fahrenheit, or 200 degrees Celcius) in the absence of air. Also called destructive distillation. 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.

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Quad: One quadrillion Btu (1015 Btu). An energy equivalent to approximately 172 million barrels of oil.

Quaternary: The present period, forming the latter part of the Cenozoic Era, originating about 1 million years ago and including the Recent and Pleistocene epochs.

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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.

Rate schedule: A price list showing how the electric bill of a particular type of customer will be calculated by an electric utility company.

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.

RDF: See refuse-derived fuel.

Recirculation: Returning a fraction of the effluent outflow to the inlet to dilute incoming wastewater.

Record of Decision: (ROD) The decision document for an environmental impact statement (EIS). Separate from the EIS itself, this document states the decision, states the reasons for the decision, identifies all alternatives and states compliance with applicable laws.

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

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

Reformulated gasoline: (RFG) Gasoline that has altered composition or characteristics to reduce emissions of pollutants from vehicles in accordance with the Clean Air Act.

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

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

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 between 100 and 3000 tons of MSW per day.

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.

Reid vapor pressure: (RVP) A standard measurement of a liquid´s vapor pressure at 100 degrees Fahrenheit. An indication of the propensity of the liquid to evaporate.

Reinjection: The feeding of unburned char and fly ash obtained from mechanical collectors into the furnace for further combustion.

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.

Renewable energy source: An energy source that is replenished continuously in nature or that is replaced after use through natural means. Sustainable energy source. Renewable energy sources include the sun, the winds, flowing water, biomass and geothermal energy.

Reserve margin: The amount by which the utility´s total electric power capacity exceeds maximum electric demand.

Resistance, or R Value: The voltage per amp needed to make electricity flow through a wire. The tendency of a material to retard the flow of heat.

Resource values: A resource, natural or social, that is found in an area. Resource values may have varying levels of significance.

Retrofitting: The application of conservation, efficiency, or renewable energy technologies to existing structures.

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

Riparian area: An area of land directly influenced by water. An ecosystem that is transitional between land and water ecosystems. Riparian areas usually have visible vegetative or physical characteristics reflecting the influence of water. River sides, lake borders, and marshes are typical riparian areas.

Riparian buffer: Riparian areas that are managed to protect the aquatic and riparian ecosystem. A riparian buffer protects water quality and temperature, habitat along the banks, upland habitat for aquatic and riparian species, and some or all of the floodplain.

Risers: The flow channels or pipes that distribute the heat transfer liquid across the face of a solar absorber.

ROI: See return on investment.

Root: The area of a wind turbine 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.

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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.

Saturated steam: Steam at the temperature that corresponds to its boiling temperature at the same pressure.

Scrubber: A device to clean combustible gas or stack gas by the spraying of water.

Sedimentation: A process in which material carried in suspension by water flows into streams and rivers, increasing turbidity and eventually settling to the bottom.

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.

Sensitive species: See Threatened, endangered, and sensitive species.

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.

Sewage: The waste water from domestic, commercial and industrial sources carried by sewers.

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.

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

Shaft horsepower: A measure of the actual mechanical energy per unit time delivered to a turning shaft. 1 shaft horsepower = 1 electric horsepower = 550 ft-lb/second.

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.

Short ton: 2000 pounds. A ton, as commonly used in the U.S. and Canada.

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.

Silviculture: The theory and practice of forest stand establishment and management.

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.

Slow pyrolysis: Thermal conversion of biomass to fuel by slow heating to less than 450°C in the absence of oxygen.

Sludge: The mixture of organic and inorganic substances separated from sewage.

Smog: A visible haze caused by particulate matter and ground-level ozone.

Socioeconomic: Relating to social or economic factors or to a combination of both social and economic factors.

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.

Solvent Extraction: A method of separation used to purify vegetable oils.

Source Emission Reduction Plan: (SERP) A contingency plan developed to reduce emissions during an air quality emergency.

Spreader stoker furnace: A furnace in which fuel is automatically or mechanically spread. Part of the fuel is burned in suspension. Large pieces fall on a grate.

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.

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.

Steam conversion factors: (approximations)
1 pound of steam = 1,000 Btu = .3 kW. 10,000 lbs/hr steam = 300 boiler horsepower.

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.

Stillage: The grains and liquid effluent remaining after distillation.

Stoichiometric condition: That condition at which the proportion of the air-to-fuel is such that all combustible products will be completely burned with no oxygen remaining in the combustion air.

Stumpage: (1) Standing live or dead uncut trees. (2) The value or rate paid to purchase standing trees for harvest.

Subdrainage: A land area (basin) bounded by ridges or similar topographic features, encompassing only part of a watershed.

Substrate: The material forming the underlying layer of streams. Substrates may be bedrock, gravel, boulders, sand, or clay.

Sunk cost: A cost already incurred and therefore not considered in making a current investment decision.

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.

Superheated steam: Steam at a given pressure which is above the temperature which corresponds to boiling temperature at that given pressure.

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

Suspended solids: Waste particles suspended in water. Suspended solids can harbor harmful microorganisms and toxic chemicals. Suspended solids cloud the water and make disinfection more difficult and costly.

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

Sustained yield: The maintenance in perpetuity of regular, periodic harvest of a crop without damaging the productivity of the land.

Syngas: A syntheses gas produced through gasification of biomass. Syngas is similar to natural gas and can be cleaned and conditioned to form a feedstock for production of methanol.

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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.

TE&S species: See threatened, endangered and sensitive species.

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

Therm: A unit of energy equal to 100,000 British thermal units; used primarily for natural gas.

Thermal Capacity: The quantity of heat needed to warm a solar 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.

Thermal resource: A facility that produces electricity by using a heat engine to power an electric generator. The heat may be supplied by the combustion of coal, oil, natural gas, biomass, or other fuels, including nuclear fission, solar, or geothermal resources.

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.

Thermal cover:
Vegetative condition, generally with greater than 70% canopy closure and 40 feet in height, that can significantly ameliorate weather effects such as wind, heat, cold, and snow. Used by wildlife in winter.

Thermochemical conversion process: Chemical reactions employing heat to produce fuels.

Threatened, endangered and sensitive species:
Formal classifications of species.
Sensitive: Species for which population viability is a concern. Sensitive species are not federally designated under the Endangered Species Act.

The U.S. Fish and Wildlife Service, after study, makes the following designations:

- Candidate: Species under consideration for listing as endangered or threatened but for which conclusive data on biological vulnerability are not currently available to support listing. Also known as Category 2 species.
- Endangered: A species in danger of becoming extinct throughout all or a significant portion of its range.
- Threatened: A species likely to become endangered in the foreseeable future.
- Proposed: Those species named in formal documents published in the Federal Register under the direction of the Endangered Species Act and 50 CFR 402.2 but which have not yet been listed as endangered or threatened.

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

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

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.

Tipping fee: A fee for disposal of waste.

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.

Torque: Turning force, equal to force times radius.

Total suspended particulates: The quantity of solid particles in a gas or exhaust stream. Any finely divided material (solid or liquid) that is airborne with a diameter smaller than a few hundred micrometers.

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

Toxic substances: A chemical or mixture of chemicals that presents a high risk of injury to human health or to the environment.

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.

Trickle Type Collector: A solar 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).

TSP: See total suspended particulates.

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).

Turbidity: The relative clarity of water, which may be affected by material in suspension in the water.

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: 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.

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

Turnkey system: A system which is built, engineered, and installed to the point of readiness for operation by the owner.

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.

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Ultimate analysis: A description of a fuel´s elemental composition as a percentage of the dry fuel weight.

Understory: The trees and other woody species growing under a relatively continuous cover of branches and foliage formed by the overstory trees.

Uniform Mechanical Code: (UMC) A code sponsored by the International Association of Plumbing and Mechanical Officials and the International Conference of Building Officials, adopted and amended by the Oregon Department of Commerce. The UMC contains requirements for the installation and maintenance of heating, ventilating, cooling, and refrigeration systems.

Uniform Building Code: (UBC) A building code published by the International Conference of Building Officials, adopted and amended by Oregon Department of Commerce. The UBC covers the fire, life and structural safety aspects of all buildings and related structures.

Unit (fuel or pulp): A bulk measure of hog fuel or pulp chips containing 200 cubic feet. A unit contains varying amounts of solid material depending on the amount of compaction. It is customary to weigh material, correct for moisture, and calculate the number of bone dry tons.

Urban growth boundary: A land use boundary surrounding a city within which urban land uses are allowed.

USFS: United States Department of Agriculture Forest Service.

USFWS: United States Fish and Wildlife Service.

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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.

VOC: see Volatile organic compounds.

Volatile organic compounds: (VOC) Non-methane hydrocarbon gases. Released during combustion or evaporation of fuel.

Volatiles: Substances that are readily vaporized.

Volatility: The tendency of a liquid to pass into the vapor state at a given temperature. Vapor pressure.

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.
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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.

Watermaster: In Oregon, an official of the Water Resources Department who allocates available surface or groundwater in the state.

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. It is 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.

Wetlands: Lands where saturation with water is the primary factor determining soil development and the kinds of plant and animal communities living on or under the surface.

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

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.

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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.

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