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.

A system of astronomical time in which the sun crosses the true north-south meridian at 12 noon, and which differs from local time according to longitude, time zone, and equation of time.

The lowest wind speed at which a wind turbine begins producing useable power.

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

The number of cycles through which an alternating current passes per second; in the U.S. the standard for electricity generation is 60 cycles per second (60 Hertz).

Water heated for residential washing, bathing, etc.

The direct, diffuse, and reflected solar radiation that strikes a surface.

A system in which a working fluid is used over and over without introduction of new fluid, as in a hydronic heating system or mechanical refrigeration system.

A load management objective that moves loads from on-peak periods to off-peak periods.

A method of depositing thin semiconductor photovoltaic) films. With this method, physical processes, such as thermal evaporation or bombardment of ions, are used to deposit elemental semiconductor material on a substrate.

The process of converting municipal solid waste to energy and/or recovering materials for recycling.

Any wholly or partially enclosed space in which combustion takes place.

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.

The vacancy where an electron would normally exist in a solid; behaves like a positively charged particle.

One millionth of a meter (10-6 m).

A particle of light that acts as an individual unit of energy.

In reference to solar photovoltaic cell manufacure, a method of growing a large-size, high-quality crystal whereby coils heat a polycrystalline ingot placed atop a single-crystal seed. As the coils are slowly raised the molten interface beneath the coils ...

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

This type of heat pump is known as an air-to air system.

A type of combustion heating system in which combustion air is drawn directly from outside and the products of combustion are vented directly outside. These features are beneficial in tight, energy-efficient homes because they will not depressurize a home ...