A slightly sloped roof, usually with a tar and gravel cover. Most commercial buildings use this kind of roof.

In reference to solar thermal collectors, the condition where the heat transfer fluid is flowing through the collector loop under normal operating conditions.

To influence the demand on a power source.

The material through which electricity is transmitted, such as an electrical wire, or transmission or distribution line.

A heat exchanger in a solar water heating system that has two distinct walls between the heat transfer fluid and the domestic water, to ensure that there is no mixing of the two.

A device used to regulate motor speed, or, in a wind energy conversion system, to control the rotational speed of the rotor.

A power plant that produces electricity by the force of water falling through a hydro turbine that spins a generator.

The value or purchasing power of a dollar that has not been reduced to a common basis of constant purchasing power, but instead reflects anticipated future inflation; when used in computations the assumed inflation rate must be stated.

A current carrier, either an electron or a hole, that is in the minority in a specific layer of a semiconductor material; the diffusion of minority carriers under the action of the cell junction voltage is the current in a photovoltaic device.

The loss in static pressure of a fluid (liquid or gas) in a system due to friction from obstructions in pipes, from valves, fittings, regulators, burners, etc, or by a breech or rupture of the system. Pressurization Testing

An energy band in a semiconductor in which electrons can move freely in a solid, producing a net transport of charge.

A building heating, ventilation, and/or air conditioning system that distributes conditioned air to individual zones or rooms.

The component of a solar energy heating system that collects solar radiation, and that contains components to absorb solar radiation and transfer the heat to a heat transfer fluid (air or liquid).

A term for the process of transmitting electricity over transmission lines not owned by the supplier of the electricity to a retail customer of the supplier. With retail wheeling, an electricity consumer can secure their own supply of electricity from a b ...

A building with more than 50 percent of its floorspace used for commercial activities, which include stores, offices, schools, churches, libraries, museums, health care facilities, warehouses, and government buildings except those on military bases.

The unoccupied, and usually unfinished and unconditioned space between the floor, foundation walls, and the slab or ground of a building.

A colorless, odorless, tasteless gas composed of one molecule of Carbon and four of hydrogen, which is highly flammable. It is the main constituent of "natural gas" that is formed naturally by methanogenic, anaerobic bacteria or can be manufactured, and w ...

The push or pull that alters the motion of a moving body or moves a stationairy body; the unit of force is the dyne or poundal; force is equal to mass time velocity divided by time.

One pound of water in vapor phase; is NOT steam pressure, which is expressed as pounds per square inch (psi).

A device that removes airborne particles from breathable air. Negative ions are produced and give up their negative charge to the particles. These new negative particles are then attracted to the positive particles surrounding them. This accumulation proc ...