Thorn forestA type of forest formation, mostly tropical and subtropical, intermediate between desert and steppe, dominated by small trees and shrubs.
Threatened speciesAny species that is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range.
Three-phase CurrentAlternating current in which three separate pulses are present, identical in frequency and voltage, but separated 120 degrees in phase.
Tidal PowerThe power available from the rise and fall of ocean tides. A tidal power plant works on the principal of a dam or barrage that captures water in a basin…
Timber stand improvementIntermediate pruning, weeding, and thinning of a stand of timber prior to its reaching mature rotation age to improve growing conditions and control stand…
TimberlandForest land capable of producing 20 cubic feet of wood per acre per year.
Time-of-Use (TOU) RatesThe pricing of electricity based on the estimated cost of electricity during a particular time block.
Time-of-use pricingA rate design imposing higher charges to customers during periods of the day when higher demand is experienced.
TimerA device that can be set to automatically turn appliances (lights) off and on at set times.
Timer (Water Heater)This device can automatically turn the heater off at night and on in the morning.
Tip Speed RatioIn reference to a wind energy conversion device's blades, the difference between the rotational speed of the tip of the blade and the actual velocity of…
TopographyThe shape of the Earth's surface; the relative position and elevations of natural and human-made features of an area.
Topping and back pressure turbinesTurbines which operate at exhaust pressure considerably higher than atmospheric (noncondensing turbines).
Topping cycleA means to increase the thermal efficiency of a steam electric generating system by increasing temperatures and interposing a device, such as a gas…
Torque (Motor)The turning or twisting force generated by an electrical motor in order for it to operate.
Total dissolved solids (TDS)(TDS)The dry weight of dissolved material, organic and inorganic, contained in water. The term is used to reflect salinity.
Total Harmonic DistortionThe measure of closeness in shape between a waveform and it's fundamental component.
Total HeatThe sum of the sensible and latent heat in a substance or fluid above a base point, usually 32 degrees Fahrenheit.
Total Incident RadiationThe total radiation incident on a specific surface area over a time interval.
Total Internal ReflectionThe trapping of light by refraction and reflection at critical angles inside a semiconductor device so that it cannot escape the device and must be…
total ligninThe sum of the acid soluble lignin and acid insoluble lignin fractions.
total solidsThe amount of solids remaining after all volatile matter has been removed from a biomass sample by heating at 105°C to constant weight.
Total suspended particulates (TSP)(TSP)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…
Toxic substancesA chemical or mixture of chemicals that presents a high risk of injury to human health or to the environment.
Toxic Substances Control Act (TSCA)(TSCA)The Toxic Substances Control Act (TSCA), passed in 1976, requires tests of chemicals that may harm human health or the environment; reviews of new…
toxicity(tok-SIH-sih-tee) The extent to which something is poisonous or harmful.
toxicsAs defined in the 1990 Clean Air Act Amendments, toxics include benzene, 1,3 butadiene, formaldehyde, acetaldehyde, and polycyclic organic matter.
Tracking arrayA PV panel array that follows the path of the sun to maximize the solar radiation incident on the PV surface.
Tracking Solar ArrayA solar energy array that follows the path of the sun to maximize the solar radiation incident on the PV surface.
Traditional cultural propertyA property that is eligible for inclusion in the National Register of Historic Places because of its association with cultural practices or beliefs of a…
Traditional NeighborhoodsTraditional neighborhood development emphasizes two broad goals: to reduce the destruction of habitat and natural resources, and to reduce dependency on…
Trailing EdgeThe part of a wind energy conversion device blade, or airfoil, that is the last to contact the wind.
Transaction costsCosts, such as commissions and spreads, incurred when buying or selling assets. Large bid-ask spreads are an indication of high transaction costs.
transesterificationA chemical process which reacts an alcohol with the triglycerides contained in vegetable oils and animal fats to produce biodiesel and glycerin.
Transfer of Development Rights (TDR)(TDR)A system that assigns development rights to parcels of land and gives landowners the option of using those rights to develop or to sell their land.
TransformerAn electromagnetic device that changes the voltage of alternating current electricity.
Transit NodesStops along a public transportation route where people board and disembark, often where one or more routes intersect with each other.
Transit-Oriented Development (TOD)(TOD)The development of housing, commercial space, services, and job opportunities in close proximity to public transportation.
Translocation(TRANZ-loh-KAY-shun) A genetic change in which a piece of one chromosome breaks off and attaches to another chromosome.
Transmission and Distribution LossesThe losses that result from inherent resistance in electrical conductors and transformation inefficiencies in distribution transformers in a transmission…
Transmission corridorAn electric or pipeline transmission corridor is a route approved on public lands, in a BLM or other federal agency land use plan, as a location that may…
Transmission lineA set of electrical current conductors, insulators, supporting structures, and associated equipment used to move large quantities of power at high…
Transmission LinesTransmit high-voltage electricity from the transformer to the electric distribution system.
Transmission loading relief (TLR)(TLR)A NERC procedure that allows reliability coordinators to curtail transactions (among other actions) to mitigate potential or actual operating security…
TransmissivityThe rate at which water of the prevailing kinematic viscosity is transmitted through a unit width of the aquifer under a unit hydraulic gradient.
TransparencyTransparency is a measure of how much information you have about the markets where you invest, the corporations whose stocks or bonds you buy, or the…
Traveling GrateA furnace grate that moves fuel through the combustion chamber.
TravertineA sedimentary rock formed by the precipitation of carbonate minerals from solution in ground and surface waters, and/or geothermal hot-springs.
Tree measurement saleA type of timber sale contract in which the buyer and seller agree upon the volume at the time of the sale.
TrellisAn architectural feature used to shade exterior walls; usually made of a lattice of metal or wood; often covered by vines to provide additional summertime…
Tribal landIn NAGPRA, tribal land is defined as: (a) all lands within the exterior boundaries of any Indian reservation; (b) all dependent Indian communities; (c)…
TribeTerm used to designate a federally recognized group of American Indians and their governing body. Tribes may be composed of more than one band.
TributaryA creek, stream, or river that feeds a larger stream or river, or lake.
Trickle (Solar) CollectorA type of solar thermal collector in which a heat transfer fluid drips out of header pipe at the top of the collector, runs down the collector absorber…
triglycerideA triglyceride is an ester of glycerol and three fatty acids. Most animal fats are composed primarily of triglycerides.
Triple Pane (Window)This represents three layers of glazing in a window with an airspace between the middle glass and the exterior and interior panes.
Trombe WallA wall with high thermal mass used to store solar energy passively in a solar home.
TroposphereThe layer of the atmosphere closest to the Earth's surface.
True PowerThe actual power rating that is developed by a motor before losses occur.
True SouthThe direction, at any point on the earth that is geographically in the northern hemisphere, facing toward the South Pole of the earth.
TsunamiOcean wave produced by earthquakes or underwater landslides.
Tube-In-Plate-AbsorberA type of solar thermal collector where the heat transfer fluid flows through tubes formed in the absorber plate.
Tube-Type CollectorA type of solar thermal collector that has tubes (pipes) that the heat transfer fluid flows through that are connected to a flat absorber plate.
TuffVolcanic rock made up of rock and mineral fragments in volcanic ash matrix. Tuffs commonly are composed of much shattered volcanic rock glass—chilled…
Tungsten Halogen LampA type of incandescent lamp that contains a halogen gas in the bulb, which reduces the filament evaporation rate increasing the lamp life.
TurbidityThe relative clarity of water, which may be affected by material in suspension in the water.
TurbineA device for converting the flow of a fluid (air, steam, water, or hot gases) into mechanical motion.
Turn Down RatioThe ratio of a boiler's or gasifier's maximum output to its minimum output.
Turn of logsA group of logs yarded at the same time by the same machine.
Turnkey systemA system which is built, engineered, and installed to the point of readiness for operation by the owner.
Two-Axis TrackingA solar array tracking system capable of rotating independently about two axes (e.g., vertical and horizontal).
Two-settlement systemA system under which the price for electricity on any given day is established and settled both on a day-ahead and a real-time basis.
Two-Tank Solar SystemA solar thermal system that has one tank for storing solar heated water to preheat the water in a conventional water heater.
U.S. Environmental Protection AgencyThe independent federal agency, established in 1970, that regulates federal environmental matters and oversees the implementation of federal environmental…
Ultimate AnalysisA procedure for determining the primary elements in a substance (carbon, hydrogen, oxygen, nitrogen, sulfur, and ash).
UltravioletElectromagnetic radiation at wavelengths shorter than 400 nm.
Unconsolidated shore wetlandsIncludes all wetland habitats having three characteristics: (1) unconsolidated substrates with less than 75% areal cover of stones, boulders, or bedrock…
Unconventional natural gasA term applied to natural gas that is difficult and expensive to find and produce; if found, it often is bypassed in favor of more easily obtainable…
UnderflowThe movement of groundwater through the soil or a subsurface stratum, or under a structure; specifically, the water flowing beneath the bed of a stream…
Underground HomeA house built into the ground or slope of a hill, or which has most or all exterior surfaces covered with earth.
UnderstoryThe trees and other woody species growing under a relatively continuous cover of branches and foliage formed by the overstory trees.
Unglazed Solar CollectorA solar thermal collector that has an absorber that does not have a glazed covering.
Uniform Building Code (UBC)(UBC)A building code published by the International Conference of Building Officials, adopted and amended by Oregon Department of Commerce.