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 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 ...

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

A type of power generating facility that pumps water to a storage reservoir during off-peak periods, and uses the stored water (by allowing it to fall through a hydro turbine) to generate power during peak periods. The pumping energy is typically supplied ...

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.

A device used to interrupt or break an electrical circuit when an overload condition exists; usually installed in the positive circuit; used to protect electrical equipment.

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

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 ...

The temperature to which air must be cooled, at constant pressure and water vapor content, in order for saturation or condensation to occur; the temperature at which the saturation pressure is the same as the existing vapor pressure; also called saturatio ...

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 point ...

Air with a weight of 0.075 pounds per cubic foot with an equivalent density of dry air at a temperature of 86 degrees Fahrenheit and standard barometric pressure of 29.92 inches of mercury.

Also known as "power towers," these use fields of two-axis tracking mirrors known as heliostats. Each heliostat is individually positioned by a computer control system to reflect the sun's rays to a tower-mounted thermal receiver. The effect of many helio ...

This is the concept of how long a device or process can operate properly without needing maintenance or replacement.

An approximate unit of heat produced by a resting person, equal to about 18.5 Btu per square foot per hour.

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.

An energy saving device in a heat pump that, during the cooling cycle, recycles some of the waste heat from the house to heat domestic water.

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.

Crops grown specifically for their fuel value. These include food crops such as corn and sugarcane, and nonfood crops such as poplar trees and switchgrass. Currently, two energy crops are under development: short-rotation woody crops, which are fast-growi ...

A door-like device located at the mouth of a fireplace chimney flue for controlling the direction and flow of the draft in the fireplace as well as the amount of oxygen that the fire receives.

The ratio of chemical substances necessary for a reaction to occur completely.