The negative pole or electrode of an electrolytic cell, vacuum tube, etc., where electrons enter (current leaves) the system; the opposite of an anode.

A combustion heating appliance that vents the combustion by-products directly into the heated space. The latest models have oxygen-sensors that shut off the unit when the oxygen level in the room falls below a safe level.

Consist of three main layers. The top layer is near ambient and has low salt content. The bottom layer is hot, typically 160 F to 212 F (71 C to 100 C), and is very salty. The important gradient zone separates these zones. The gradient zone acts as a tran ...

A building structural element that is built onto a building's exterior along the inner edges of all the windows, and extending from the ground to the eaves. Wingwalls help ventilate rooms that have only one exterior wall which leads to poor cross ventilat ...

An air distribution outlet, typically located in the ceiling, which mixes conditioned air with room air.

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

A pump for circulating the heat transfer fluid in a hydronic heating system.

That portion of supply air that is drawn from outside, plus any recirculated air that has been treated to maintain a desired air quality.

The conversion of the complex carbohydrates in organic material into energy.

A unit of apparent power, equal to 1,000 volt-amperes; the mathematical product of the volts and amperes in an electrical circuit.

The weight of a material per unit of volume compared to the weight of the same volume of water.

A component of a hydropower plant; a pipe that delivers water to the turbine.

Energy available as a result of motion that varies directly in proportion to an object's mass and the square of its velocity.

A colorless, pungent, gas (NH3) that is extremely soluble in water, may be used as a refrigerant; a fixed nitrogen form suitable as fertilizer.

The amount of power a wind turbine can produce at its rated wind speed, e.g., 100 kW at 20 mph. The rated wind speed generally corresponds to the point at which the conversion efficiency is near its maximum. Because of the variability of the wind, the amo ...

To disconnect a transmission and/or distribution line; a power line that is not carrying a current; to open a circuit.

A material used to seal areas of potential air leakage into or out of a building envelope.

An apparatus for converting the energy available in the wind to mechanical energy that can be used to power machinery (grain mills, water pumps) and to operate an electrical generator.

In reference to solar energy systems, the angle that a solar collector is positioned above horizontal.

A generic term for liquefied and pressurized gas, ordinarily butane, propane, or a mixture of the two, contained in a cylinder for domestic use.