The environmental, social, and economic impacts of producing a good or service that are not directly reflected in the market price of the good or service.

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).

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.

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

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

The process of forcing, either manually or automatically, a wind turbine's blades out of the direction of the wind in order to stop the blades from turning.

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.

A method of depositing thin semiconductor films used to make certain types of solar photovoltaic devices. With this method, a substrate is exposed to one or more vaporized compounds, one or more of which contain desirable constituents. A chemical reaction ...

The production of energy by a system or appliance at a level less than its design or nominal capacity.

A popular term used for a length of wood or steel used in or for wall framing.

The total radiation incident on a specific surface area over a time interval.

The duration and periodicity of the operation of a device.

As time increases from zero at the terminals of an inductor, the voltage comes to a particular value on the sine function curve ahead of the current. The voltage reaches its negative peak exactly 90 degrees before the current reaches its negative peak thu ...

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 ...

The physical measure of the subjective sensation of brightness; measured in lumens.

A window located high in a wall near the eaves that allows daylight into a building interior, and may be used for ventilation and solar heat gain.

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

A type of hydropower turbine that contains a runner that has water passages through it formed by curved vanes or blades. As the water passes through the runner and over the curved surfaces, it causes rotation of the runner. The rotational motion is transm ...

The storage of compressed air in a container for use to operate a prime mover for electricity generation.

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