A container that holds rock used as the thermal mass to store solar energy in a solar heating system.

The process by which water in air changes from a vapor to a liquid due to a change in temperature or pressure; occurs when water vapor reaches its dew point (condensation point); also used to express the existence of liquid water on a surface.

The U.S. Government's 12-month financial year, from October to September, of the following calender year; e.g.: FY 1998 extends from Oct. 1, 1997 to Sept. 30, 1988.

A type of power inverter that produce a high quality (nearly sinusoidal) voltage, at minimum current harmonics.

The actual power rating that is developed by a motor before losses occur.

A type of heating appliance that extracts so much of the available heat content from a combusted fuel that the moisture in the combustion gases condenses before it leaves the furnace. Also this furnace circulates a liquid to cool the furnace's heat exchan ...

A unit of work done by the force of one dyne acting through a distance of one centimeter.

The two times of the year when the sun crosses the equator and night and day are of equal length; usually occurs on March 21st (spring equinox) and September 23 (fall equinox).

The measure of overall efficiency for a variety of appliances. For water heaters, the energy factor is based on three factors: 1) the recovery efficiency, or how efficiently the heat from the energy source is transferred to the water; 2) standby losses, o ...

A term used to describe heat energy lost from a water heater tank.

The use of two or more different fuels (e.g. wood and coal) simultaneously in the same combustion chamber of a power plant.

A form of solar concentrating collector that does not track the sun.

The process by which a power plant, apparatus, or building is approved for operation based on observed or measured operation that meets design specifications.

A type of solar thermal collector that has tubes (pipes) that the heat transfer fluid flows through that are connected to a flat absorber plate.

An energy system in which the fuel production equipment is in close proximity, or connected to, the fuel using equipment.

A heat exchanger that transfers heat contained in a liquid heat transfer fluid to another liquid.

The average time a minority carrier exists before recombination.

A material formed from the incomplete combustion or destructive distillation (carbonization) of organic material in a kiln or retort, and having a high energy density, being nearly pure carbon. (If produced from coal, it is coke.) Used for cooking, the ma ...

The abrupt and large increase in electrical conductivity exhibited by some metals as the temperature approaches absolute zero.

Turbines in which the axis of the rotor's rotation is parallel to the wind stream and the ground.