A term used for lighting appliances; the ratio of lumens received on a flat surface to the light output, in lumens, from a lamp; used to evaluate the effectiveness of luminaries in delivering light.

A federal government agency involved in rural development, marketing and regulatory programs, food safety, research, education and economics, food, nutrition and consumer service, farm and foreign agricultural services, and natural resources and environme ...

In reference to a wind energy conversion device, the area through which the rotor blades spin, as seen when directly facing the center of the rotor blades.

The voltage developed across a cell by the current flow through the resistance of the cell.

A popular term used for a length of wood or steel used in or for wall framing.

A type of insulation made from virgin basalt, an igneous rock, and spun into loose fill or a batt. It is fire resistant and helps with soundproofing.

A process for making inexpensive Galium Arsenide (GaAs)photovoltaic cells in which a thin film of GaAs is grown atop a thick, single-crystal GaAs (or other suitable material) substrate and then is cleaved from the substrate and incorporated into a cell, a ...

A window located high in a wall near the eaves that allows daylight into a building interior, and may be used for ventilation and solar heat gain.

Defects, such as dangling bonds, induced in an amorphous silicon semiconductor upon initial exposure to light.

The sum of the sensible and latent heat in a substance or fluid above a base point, usually 32 degrees Fahrenheit.

An electric motor rated at less than one horse power (hp).

The energy liberated in a chemical reaction, as in the combustion of fuels.

A device used to compress air for mechanical or electrical power production, and in air conditioners, heat pumps, and refrigerators to pressurize the refrigerant and enabling it to flow through the system.

The smallest self-contained, environmentally protected structure housing interconnected photovoltaic cells and providing a single dc electrical output; also called a panel.

A liquid byproduct of wood combustion (or distillation) that condenses on the internal surfaces of vents and chimneys, which if not removed regularly, can corrode the surfaces and fuel a chimney fire.

An apparatus for measuring force or power, especially the power developed by a motor.

A slab floor that sits directly on top of the surrounding ground.

The measure of the instantaneous energy efficiency of room air conditioners; the cooling capacity in Btu/hr divided by the watts of power consumed at a specific outdoor temperature (usually 95 degrees Fahrenheit).

A type of furnace or reactor in which the emission of sulfur compounds is lowered by the addition of crushed limestone in the fluidized bed thus obviating the need for much of the expensive stack gas clean-up equipment. The particles are collected and rec ...

A fluorescent lamp that has a tubular shape.