Renewable Energy Vocabulary: T-Z

A-C • D-F • G-I • J-M • N-P • R-S • T-Z

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 down or sideways to swing the rotor 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.

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 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.

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
A PV manufacturing technique where silicon is vapor deposited, a few molecules thick, onto another material.

TILT ANGLE
A fixed angle measured from the horizontal to which a solar array is tilted. The tilt angle is chosen to maximize the array output. Depending upon latitude, season, and time of day, the optimum angle will vary.

TILT-UP TOWER
A nonclimbable wind generator tower that tilts up and down to allow installation and servicing of the turbine on the ground. Normally these employ a gin pole—a horizontal lever arm that helps raise and lower the tower.

TOP-OF-POLE MOUNT
See POLE MOUNT.

TRACKER
A mounting rack for a PV array that automatically tilts to follow the daily path of the sun through the sky. A “tracking array” will produce more energy through the course of the day than a “fixed array” (nontracking), particularly during the long days of summer. Some trackers are single-axis while others are dual-axis.

TRANSFORMER
An electrical device that steps up voltage and steps down current proportionally (or vice-versa). Transformers work with AC only.

TRASH RACK
A large strainer at the input to a hydro system. Used to remove debris from the water before it enters the pipe.

TURBINE
An engine that produces rotary motion through reaction or impulse, or both, with moving fluid or gas. The resultant rotary motion is usually used to drive an alternator generator.

TURGO
In hydroelectric systems, a type of impact hydro runner optimized for lower heads and higher volumes than a Pelton runner.

UNINTERRUPTIBLE POWER SUPPLY (UPS)
A power supply providing continuous, uninterruptible service—commonly used in telecommunications and computer networks.

UPWIND
In relation to a wind turbine, toward the wind. An upwind turbine has its blades on the upwind side of the tower.

UTILITY GRID
Commercial electrical energy distribution system. Synonyms: Mains, Grid.

UTILITY-INTERTIE (UI) SYSTEM
See GRID-TIE SYSTEM.

VOLT (V)
The volt is the unit used in the measurement of electromotive force (electrical “pressure”). A standard electrical definition of the volt is: an electromotive force of 1 volt is necessary to move a current of 1 ampere through a 1 Ω resistor. It is often also referred to as electrical potential difference or potential difference.

VOLTAGE
A measure of the force or “push” given the electrons in an electrical circuit; a measure of electrical potential. Analogy: pressure in a water pipe. AKA Potential.

VOLTAGE DROP
Loss of voltage (electrical pressure) caused by the resistance in wire and electrical devices. Proper wire sizing will minimize voltage drop, particularly over long distances. Voltage drop is determined by four factors: wire size, current (amps), voltage, and length of wire. Water analogy: friction loss in pipe.

VOLTAGE, NOMINAL
A way of naming a range of voltage to a standard. Example: A “12 volt nominal” system may operate in the range of 10 to 20 Volts. We call it “12 volts” for simplicity.

VOLTAGE, OPEN CIRCUIT
See OPEN CIRCUIT VOLTAGE

VOLTAGE, PEAK POWER POINT (Vpp)
The voltage at which a photovoltaic module or array generates at the highest power (watts). A “12 volt nominal” PV module will typically have a peak power voltage of around 17 volts. A PV array-direct solar pump should reach this voltage in full sun conditions. In a higher voltage array, it will be a multiple of this voltage.

VOLTMETER
A device for measuring the voltage difference between any two points in an electrical circuit.

WATT
Unit of power. Power is the rate of generating or using energy. One watt is the power developed or dissipated in a one volt circuit in which there is a current of one ampere (6.28 million million electrons per second). Watts = amps X volts.

WATT-HOUR
A unit of measurement quantifying an amount of energy used or generated. A load that consumes 1 watt for 10 hours uses 10 watt-hours.