T

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 non-climbable 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” (non-tracking), 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.