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Energy Terms

A material that extracts one or more substances from a fluid (gas or liquid) medium on contact, and which changes physically and/or chemically in the process. The less volatile of the two working fluids in an absorption cooling device.

The component of a solar thermal collector that absorbs solar radiation and converts it to heat, or, as in a solar photovoltaic device, the material that readily absorbs photons to generate charge carriers (free electrons or holes).

The passing of a substance or force into the body of another substance.

A type of air cooling device that uses absorption cooling to cool interior spaces.

In reference to a solar energy conversion devices, the degree to which a substance will absorb solar energy. In a solar photovoltaic device, the factor by which photons are absorbed as they travel a unit distance through a material.

A process in which cooling of an interior space is accomplished by the evaporation of a volatile fluid, which is then absorbed in a strong solution, then desorbed under pressure by a heat source, and then recondensed at a temperature high enough that the ...

A system in which a secondary fluid absorbs the refrigerant, releasing heat, then releases the refrigerant and reabsorbs the heat. Ammonia or water is used as the vapor in commercial absorption cycle systems, and water or lithium bromide is the absorber.

In a solar thermal system, the ratio of solar energy striking the absorber that is absorbed by the absorber to that of solar energy striking a black body (perfect absorber) at the same temperature. The absorptivity of a material is numerically equal to it ...

A component of a heat pump that stores liquid and keeps it from flooding the compressor. The accumulator takes the strain off the compressor and improves the reliability of the system.

A term used to describe precipitation that has become acidic (low pH) due to the emission of sulfur oxides from fossil fuel burning power plants.

The use of mechanical heat pipes or pumps to transport heat by circulating heat transfer fluids.

The power (in Watts) used by a device to produce useful work. Also called input power.

A solar water or space-heating system that use pumps or fans to circulate the heat-transfer fluid from the solar collectors to a storage tank subsystem.

Without loss or gain of heat to a system. An adiabatic change is a change in volume and pressure of a parcel of gas without an exchange of heat between the parcel and its surroundings. In reference to a steam turbine, the adiabatic efficiency is the ratio ...

An electronic device that controls the rotational speed of motor-driven equipment such as fans, pumps, and compressors. Speed control is achieved by adjusting the frequency of the voltage applied to the motor.

A building material made from clay, straw, and water, formed into blocks, and dried; used traditionally in the southwestern U.S.

Microorganisms that require free oxygen, or air, to live, and that which contribute to the decomposition of organic material in soil or composting systems.


The mixture of gases that surrounds the earth and forms its atmosphere, composed of, by volume, 21 percent oxygen, 78 percent nitrogen.

A measure of the rate at which the air in an interior space is replace by outside (or conditioned) air by ventilation and infiltration; usually measured in cubic feet per time interval (hour), divided by the volume of air in the room.

In solar heating systems, a type of solar collector in which air is heated in the collector.