The area between the layers of glazing (panes) of a window.

A total life cycle cost divided into equal amounts.

Draft that is caused by temperature differences in the air.

An enzyme complex, produced by fungi and bacteria, capable of decomposing cellulose into small fragments, primarily glucose.

The mean wind speed over a specified period of time.

see Peak Power

A drag-type wind machine that can react to wind from any direction.

A device that measures the intensity of direct beam solar radiation.

Turbines in which the rotor speed increases and decreases with changing wind speed, producing electricity with a variable frequency.

The pressure of the steam or water in a boiler as measured; usually expressed in pounds per square inch gauge (psig).

The ratio of solar collector array area to actual land area.

The unit of magnetic field intensity equal to 1 dyne per unit pole.

The housing around a motor that supports the active parts and protects them. They come in different varieties (open, protected) depending on the degree of protection required.

A light source composed of a metal base, a glass tube filled with an inert gas or a vapor, and base pins to attach to a fixture.

A means to increase the thermal efficiency of a steam electric generating system by converting some waste heat from the condenser into electricity. The heat engine in a bottoming cycle would be a condensing turbine similar in principle to a steam turbine ...

A facility or piece of equipment that produces electricity.

A type of (geothermal) heat pump that uses well (ground) or surface water as a heat source. Water has a more stable seasonal temperature than air thus making for a more efficient heat source.

A compound used to make certain types of solar photovoltaic cells.

A heat storage system that uses a heat storage medium, and where the additional or removal of heat results in a change in temperature.

A type of heat pump that transfers heat from outdoor air to indoor air during the heating season, and works in reverse during the cooling season.