The period marked by successive crossing of the earth's meridian by the sun; the hour angle of the sun at a point of observance (apparent time) is corrected to true (solar) time by taking into account the variation in the earth's orbit and rate of rotatio ...

The value or purchasing power of a dollar in a specified year carried forward or backward.

The ability of an electric power consumer to purchase electricity from a supplier of their choice without being physically inhibited by the owner of the electric distribution and transmission system to which the consumer is connected to. (See also Open Ac ...

The ratio of average energy demand (load) to maximum demand (peak load) during a specific period.

The deferment of certain loads to limit electrical power demand, or the production of energy during off-peak periods for storage and use during peak demand periods.

Solar radiation reflected from the ground onto a solar collector.

A pre-cut layer of insulation applied around a water heater storage tank to reduce standby heat loss from the tank.

A stationary or rotating vent used to ventilate attics or cathedral ceilings; usually made of galvanized steel, or polypropylene.

Fabricated as a single structure.

A component of a heat pump that reverses the refrigerant's direction of flow, allowing the heat pump to switch from cooling to heating or heating to cooling.

A construction element used to cover the exterior of wall framing and roof trusses.

A unit that equals 20 long hundredweight or 2,240 pounds. Used mainly in England.

A solar heating system that preheats water or air that is then heated more by another heating appliance.

The total distribution of electromagnetic radiation emanating from the sun. The different regions of the solar spectrum are described by their wavelength range. The visible region extends from about 390 to 780 nanometers (a nanometer is one billionth of o ...

A heat exchanger in which two fluids flow in opposite directions for transfer heat energy from one to the other.

Electromagnetic radiation whose wavelengths lie in the range from 0.75 micrometer to 1000 micrometers; invisible long wavelength radiation (heat) capable of producing a thermal or photovoltaic effect, though less effective than visible light.

A single photovoltaic device.

A popular term used for an evaporative cooling device.

A type of solar thermal system where sunlight is concentrated by a curved reflector onto a pipe containing a working fluid that can be used for process heat or to produce electricity. The world's largest solar thermal electric power plants use solar troug ...

A unit of volume equal to 1 cubic foot at a pressure base of 14.73 pounds standard per square inch absolute and a temperature base of 60 degrees Fahrenheit.