Definitions - t

Tail Boom

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

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Rock and other waste materials removed as impurities when minerals are mined and mineral deposits are processed. These materials are usually dumped on the ground or into ponds.

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A substance capable of causing birth defects.

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Thermal Break

A material of low heat conductance used to reduce the flow of heat. For example, the vinyl separating the interior and exterior frames in some metal windows.

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Thermal Comfort

The appropriate combination of temperatures, warm or cool, combined with air flow and humidity, which allows one to be comfortable within the confines of a building. This comfort is not usually achieved by the fixed setting of thermostats but through careful design and planning.

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Thermal Conduction

Thermal conduction is the transfer of heat (internal energy) by microscopic collisions of particles and movement of electrons within a body. In the building context this action is most often encountered when assessing how well a building can maintain its internal temperature in relation to the external temperature.

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Thermal Diffusivity

In heat transfer analysis, thermal diffusivity is the ratio of thermal conductivity to volumetric heat capacity.

Original Wikipedia entry

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Thermal Lag

Thermal lag describes a material's thermal mass in terms of time. A material with high thermal mass (high heat capacity and low conductivity) will have a high thermal lag. In effect the addition of (or removal of) energy from one side of the mass 'lags' with respect to the other side.

Thermal lag can be a useful feature, as for instance an outer brick wall on the Sunny Sunset side of a house in Winter would radiate its heat into the property in the evening, aiding with heating.

Thermal lag effects are often incorporated into good passive solar design for buildings.

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Thermal Mass

A thermal mass is a material that absorbs heat from a heat source, and then releases it slowly. This can be used to help regulate the heat in a space by increasing the amount of energy required to change its temperature. Concrete and bricks are often employed as thermal masses in a structure.

This is often used as part of a passive solar designed building.

Note: In order for a thermal mass to work it needs to interact with the air in the space, so cannot be covered.

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Thermal Performance

Thermal Performance refers to how well a structure responds to changes in external temperature during the daily and seasonal cycles. Typically this is in relation to the thermal conductivity of materials or the assemblies of materials.

You want a property to maintain a steady comfortable temperature inside whilst incurring as little energy costs as possible; this is often best achieved by first improving the thermal performance of the property by providing high levels of insulation (high R-Value, low U-Value) on all surfaces and adopting passive solar techniques.

The thermal behavior of a structure is also affected by conditions such as:
  • seasonal and temperature changes,
  • daily diurnals (the difference between highest & lowest temperatures in a day),
  • the amount of solar gain and structural shading,
  • incoming and outgoing heat radiation,
  • water and moisture absorption,
  • air movement,
  • infiltration,
  • pressure differences, etc

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Thermal Pollution
Thermal pollution is the degradation of the water quality by any process that changes the ambient water temperature. A common cause of thermal pollution is the use of water as a coolant by power plants and industrial manufacturers. When water used as a coolant is returned to the natural environment at a higher temperature, the change in temperature can impact organisms by:
  •  decreasing the oxygen supply, and,
  •  affecting the ecosystem composition.

Also by increasing the temperature of water that is normally cold it can increase the likelihood of water born diseases.

Urban runoff, such as storm water discharged to surface waters from roads and parking lots, can also be a source of elevated water temperatures.

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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.

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Thermal Storage

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Thermohaline Circulation

Large-scale density-driven circulation in the ocean, caused by differences in temperature and salinity. In the North Atlantic the thermohaline circulation consists of warm surface water flowing northward and cold deep water flowing southward, resulting in a net poleward transport of heat. The surface water sinks in highly restricted sinking regions located in high latitudes.

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Thermosiphon (alt. thermosyphon) refers to a method of passive heat exchange based on natural convection which circulates liquid without the necessity of a mechanical pump. This circulation can either be open-loop, as when liquid in a holding tank is passed in one direction via a heated transfer tube mounted at the bottom of the tank to a distribution point - even one mounted above the originating tank - or it can be a vertical closed-loop circuit with return to the original vessel. Its intended purpose is to simplify the pumping of liquid and/or heat transfer, by avoiding the cost and complexity of a conventional liquid pump.

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Local storm resulting from warm humid air rising in an unstable environment. Air may start moving upward because of unequal surface heating, the lifting of warm air along a frontal zone, or diverging upper-level winds (these diverging winds draw air up beneath them). The scattered thunderstorms that develop in the summer are called airmass thunderstorms because they form in warm, maritime tropical air masses away from other weather fronts. More violent severe thunderstorms form in areas with a strong vertical wind shear that forces the updraft into the mature stage, the most intense stage of the thunderstorm. Severe thunderstorms can produce large hail, forceful winds, flash floods, and tornadoes.

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Tip Speed Ratio

The ratio of how much faster than the wind speed that the blade tips are moving. Abbreviation TSR.

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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.

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A twisting, spinning funnel of low pressure air. The most unpredictable weather event, tornadoes are created during powerful thunderstorms. As a column of warm air rises, air rushes in at ground level and begins to spin. If the storm gathers energy a twisting, spinning funnel develops. Because of the funnel's cloud and rain composition and the dust, soil, and debris it draws up, the funnel appears blackish in color. The most energetic storms result in the funnel touching the ground. In these tornadoes, the roaring winds in the funnel can reach 300 mph, the strongest winds on Earth. Funnels usually travel at 20 to 40 mph, moving toward the northeast. When tornadoes form over lakes or oceans they suck water into the funnel cloud and are called waterspouts.

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Chemical that causes adverse health effects in domestic water supplies and is toxic to fresh water and marine aquatic life.

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Toxicity is the degree to which a substance can harm humans or animals.

Toxicity can be acute, subchronic, or chronic:

  • Acute toxicity involves harmful effects in an organism through a single or short-term exposure.
  • Subchronic toxicity is the ability of a toxic substance to cause effects for more than one year but less than the lifetime of the exposed organism.
  • Chronic toxicity is the ability of a substance or mixture of substances to cause harmful effects over an extended period, usually upon repeated or continuous exposure, sometimes lasting for the entire life of the exposed organism.
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Trade Winds

Surface air from the horse latitudes that moves back toward the equator and is deflected by the Coriolis Force, causing the winds to blow from the Northeast in the Northern Hemisphere and from the Southeast in the Southern Hemisphere. These steady winds are called trade winds because they provided trade ships with an ocean route to the New World.

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Treated Wastewater

Wastewater that has been subjected to one or more physical, chemical, and biological processes to reduce its potential of being health hazard.

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Tree Free

Papers made from sources other than trees; such as flax, eucalyptus, hemp, java, bananas, cotton and more.

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Trickle Irrigation

Method in which water drips to the soil from perforated tubes or emitters.

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Triple Bottom Line

A calculation of financial, environmental, and social performance. Often referred to as “profits, planet, and people.” This calculation method contrasts with the traditional business bottom line, which only considers profits.

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Trisodium Nitrilotriacetate

Trisodium Nitrilotriacetate (NTA) can be found in laundry detergents, stain removers and soap scum removers. Prolonged inhalation may cause respiratory irritation. Ingestion may cause nausea, vomiting, and diarrhea. NTA also causes irritation of skin and eyes. Major US detergent manufacturers voluntarily agreed in 1970 to discontinue the use and manufacture of NTA.

NTA is listed as a possible human carcinogen (IARC 2B) by the International Agency for Research on Cancer. It can disrupt the elimination of metals in wastewater treatment facilities.

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Trombe Wall

A Trombe wall is a very thick, south-facing wall, which is painted black and made of a material that absorbs a lot of heat (such as brick or concrete). A pane of glass or plastic glazing, installed a few inches in front of the wall, helps hold in the heat. The wall heats up slowly during the day. Then as it cools gradually during the night, it gives off its heat inside the building.

A Trombe wall is typically used in passive solar design to help improve energy efficiency of the building.

This article goes into more detail on how to use a Trombe wall and heat your home for free.

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Tropic Levels

A functional classification of species that is based on feeding relationships. The number of steps an organism is from the start of the food chain is a measure of its trophic level. Food chains start at trophic level 1 with primary producers such as plants, move to herbivores at level 2, predators at level 3 and usually finish with carnivores or apex predators at level 4 or 5.

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The tropicalzone lies between 23.5 degrees north and south of the equator, has small seasonal changes in temperature and large seasonal changes in precipitation.

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Tropical Storm Formation

Tropical storms generally form in the eastern portion of tropical oceans and track westward. Hurricanes and typhoons all start out as weak low pressure areas that form over warm tropical waters (e.g., surface water temperature of at least 80 oF). Initially winds and cloud formations over the warm tropical waters are minimal. Both intensify with time. Formation of tropical storms also requires a significant Coriolis effect to induce proper spin in the wind formation. As the storm begins to organize itself into a coherent pattern, it will experience increased activity and intensity.

When a storm develops a clearly recognizable pattern, it is referred to as a tropical depression. When wind speeds reach 35 knots (40.3 mph), it is called a tropical storm and is given a name. When wind speed equals or exceeds 74 mph, the storm is called a hurricane. In the western Pacific, a hurricane is referred to as a typhoon. In waters around Australia it is called a cyclone or willy-willy.

Hurricanes intensify when moving over areas of increased water temperatures, and weaken over colder water surfaces. Upper atmosphere wind shear (different wind direction and speeds at different elevations) will frequently prevent or slow intensification of tropical storms by "spreading out" the storm horizontally and preventing the formation of strong updrafts of warm, humid air. Movement over a land-mass will weaken hurricane winds but will result in large-scale rain that can result in serious flooding. When encountering a strong frontal system (such as a polar front) the hurricane will curve and track along the leading edge of the front or become implanted in it.

Satellite infrared imagery can identify surface water temperatures that will cause tropical storm development.

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The lowest layer of the atmosphere and contains about 95 percent of the mass of air in the Earth's atmosphere. The troposphere extends from the Earth's surface up to about 10 to 15 kilometers. All weather processes take place in the troposphere. Ozone that is formed in the troposphere plays a significant role in both the greenhouse gas effect and urban smog.

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Development or formation of small mounds of corrosion products on the inside of iron pipe. These tubercules roughen the inside of the pipe, increasing its resistance to water flow.

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Cloudiness caused by the presence of suspended solids in water; an indicator of water quality.

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The visible transmittance is the fraction of visible light transmitted through a window.

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Two-Axis Tracking

A photovoltaic array tracking system capable of rotating independently about two axes (e.g., vertical and horizontal).

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