Renewable Energy Glossary

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Tail

The part of a wind generator that makes the rotor face into the wind. Often the tail is also involved in governing the machine, by folding to allow the rotor to swing sideways out of the wind.

Tailrace

The pipe, flume, or channel in a hydroelectric system that carries the water from the turbine runner back to the stream or river.

Temperature and Pressure Relief Valve

A safety valve on used on all pressure-rated tanks that will reduce system pressure on excessive temperature or pressure.

Temperature Coefficients

The measured variance of module specifications (current, voltage, and power) due to changes in temperature (relative to 25ÂșC).

Temperature Sensor

A device that changes resistance with temperature.

Tempered Glass

Safety glass that breaks into small pieces; used in patio and shower doors, automobiles, photovoltaic modules, and solar collectors.

Thermal Break

A material of low thermal conductivity placed in such a way as to reduce the flow of heat between two materials of high thermal conductivity.

Thermal Bridge

An area in an otherwise-insulated system where a more conductive component exists, therefore compromising the energy performance of the overall system.

Thermal Mass

A material that has the ability to absorb, store, and release heat energy. The more heat energy that is required to change the temperature of high-density materials (concrete, bricks, tiles), the more thermal mass the materials have.

Thermal Storage Wall

A thick mass wall built on the solar side of the house directly behind glazing with a small airspace. The glazing traps the heat, which is absorbed and stored by the solid masonry wall. At night, the wall re-radiates the stored heat into the cooler house.

Thermal Zoning

Coordinating the placement of living spaces based on the building's natural susceptibility to heat gain.

Thermistor

A device that changes resistance with temperature. Used on most U.S.-made controls.

Thermosyphon

Passive solar hot water systems that rely on the natural convection of liquids to collect energy. Designed with the tank above the collection surface.

Thin-Film Modules

Modules created by depositing multiple thin layers of photovoltaic material on a substrate; they use significantly less semiconductor material than crystalline cells and so can be less expensive to manufacture.

Three-Port Valve

A valve with three ports that allows flow in two paths, one direction at a time; may be manual or motorized as is typical in a solar pool-heating system.

Tiered-Rate System

Allows for the utility to charge different prices based on parameters such as the time of year, time of day, or overall amount of energy consumption.

Tilt-and-Roll Tracker

Active trackers that have a primary support running north to south; the array pivots over the bar in an east to west direction throughout the day.

Tilt-Up Tower

A wind generator tower that can be lowered to a horizontal position to allow installation and servicing of the turbine. Some free-standing towers are erected using hydraulic rams. Common tilt-ups include tubular towers (which are not climbable) and lattice towers (which may be).

Tip Speed Ratio

The relative speed of the blade tips compared to the wind speed at the same instant. Turbines that are designed for high tip speed ratio will be able to run at higher rpm. Higher rotational speed is beneficial for producing electricity but high tip speed can create more noise, and more wear and tear.

Top-Down Rail Mounting

A type of mounting system where mid and end clips clamp modules to the rack instead of using bolts through the back of module frames.

Top-Fastened Roof

Roofs that use screws or nails to attach the stamped, crimped, or corrugated metal to the roof system.

Torque

The measure of force applied to an object such as a bolt or screw, which causes the object to rotate; measured in inch-pounds, foot-pounds, or newton-meters.

Tracker

A type of pole or ground mount system that adjusts an array's orientation to follow the sun throughout the day.

Trash Rack

A rack of widely spaced bars at the intake to a hydro system. Used to prevent larger debris, for example tree branches, from reaching the intake screen. A well-designed trash rack will have its bars aligned with the passing flow so that the flood water removes the debris.

Trombe Wall

A specific type of thermal storage wall--a thick mass wall built on the solar side of the house directly behind glazing with a small airspace. The glazing traps the heat, which is absorbed and stored by the solid masonry wall. At night, the wall re-radiates the stored heat into the cooler house.

Tubular Skylight

Tubular skylights have three components: a round, domed plastic skylight that mounts on the roof; a cylindrical metal tube with a highly reflective interior surface; and a diffuser that mounts on the ceiling. Sunlight enters the skylight dome and reflects downward through the reflective tube to the diffuser, which delivers the light below.

Turbine

In relation to wind, synonymous with "wind generator."

Turgo

A type of impulse hydro turbine runner that can accept larger flows than a similar sized Pelton. The turgo can therefore operate at lower head for the same power output.

1 A B C D E F G H I J K L M N O P Q R S T U V W Y

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