Solar Basics

Solar Glossary T - Z

Temperature Coefficient (of a solar photovoltaic cell)
The amount that the voltage, current, and/or power output of a solar cell changes due to a change in the cell temperature.

 

Thermal Envelope Houses
An architectural design (also known as the double envelope house), sometimes called a "house-within-a-house," that employs a double envelope with a continuous airspace of at least 6 to 12 inches on the north wall, south wall, roof, and floor, achieved by building inner and outer walls, a crawl space or sub-basement below the floor, and a shallow attic space below the weather roof. The east and west walls are single, conventional walls. A buffer zone of solar-heated, circulating air warms the inner envelope of the house. The south-facing airspace may double as a sunspace or greenhouse.
Thermal Storage Walls (Masonry or Water)
A thermal storage wall is a south-facing wall that is glazed on the outside. Solar heat strikes the glazing and is absorbed into the wall, which conducts the heat into the room over time. The walls are at least 8 in thick. Generally, the thicker the wall, the less the indoor temperature fluctuates.
Thermosiphon System
This passive solar hot water system consists relies on warm water rising, a phenomenon known as natural convection, to circulate water through the collectors and to the tank. In this type of installation, the tank must be above the collector. As water in the collector heats, it becomes lighter and rises naturally into the tank above. Meanwhile, cooler water in the tank flows down pipes to the bottom of the collector, causing circulation throughout the system. The storage tank is attached to the top of the collector so that thermosiphoning can occur.
Thermosiphon
The natural, convective movement of air or water due to differences in temperature. In solar passive design a thermosyphon collector can be constructed and attached to a house to deliver heat to the home by the continuous pattern of the convective loop (or thermosyphon).
Thin-Film
A layer of semiconductor material, such as copper indium diselenide or gallium arsenide, a few microns or less in thickness, used to make solar photovoltaic cells.
Tilt Angle (of a Solar Collector or Module)
The angle at which a solar collector or module is set to face the sun relative to a horizontal position. The tilt angle can be set or adjusted to maximize seasonal or annual energy collection.
Tracking Solar Array
A solar energy array that follows the path of the sun to maximize the solar radiation incident on the PV surface. The two most common orientations are (1) one axis where the array tracks the sun east to west and (2) two-axis tracking where the array points directly at the sun at all times. Tracking arrays use both the direct and diffuse sunlight. Two-axis tracking arrays capture the maximum possible daily energy.
Trickle (Solar) Collector
A 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 and into a tray at the bottom where it drains to a storage tank.
Trombe Wall
A wall with high thermal mass used to store solar energy passively in a solar home. The wall absorbs solar energy and transfers it to the space behind the wall by means of radiation and by convection currents moving through spaces under, in front of, and on top of the wall.
True South
The direction, at any point on the earth that is geographically in the northern hemisphere, facing toward the South Pole of the earth. Essentially a line extending from the point on the horizon to the highest point that the sun reaches on any day (solar noon) in the sky.
Tube-In-Plate-Absorber
A type of solar thermal collector where the heat transfer fluid flows through tubes formed in the absorber plate.
Tube-Type Collector
A type of solar thermal collector that has tubes (pipes) that the heat transfer fluid flows through that are connected to a flat absorber plate.
Two-Tank Solar System
A solar thermal system that has one tank for storing solar heated water to preheat the water in a conventional water heater.
Two-Axis Tracking
A solar array tracking system capable of rotating independently about two axes (e.g., vertical and horizontal).
Unglazed Solar Collector
A solar thermal collector that has an absorber that does not have a glazed covering. Solar swimming pool heater systems usually use unglazed collectors because they circulate relatively large volumes of water through the collector and capture nearly 80 percent of the solar energy available.
Useful Heat
Heat stored above room temperature (in a solar heating system).
Water Wall
An interior wall made of water filled containers for absorbing and storing solar energy.

About the list of terms on this page.

The U.S. Department of Energy Efficiency and Renewable Energy Home Page is a great starting point for learning about renewable energy methods and sources. To assist in educating consumers, the website provides calculators and guides of all kinds to assist the consumer in saving money, saving energy and making the most of the renewable energy sources available. The solar energy terms and definitions on our glossary pages were extracted from the extensive DOE EERE glossary of terms about all aspects and forms of energy.