A chemical element (impurity) added in small amounts to an otherwise pure semiconductor material to modify the electrical properties of the material. An n-dopant introduces more electrons. A p-dopant creates electron vacancies (holes).

Water in vapor form; used as the working fluid in steam turbines and heating systems.

The period marked by successive crossing of the earth's meridian by the sun; the hour angle of the sun at a point of observance (apparent time) is corrected to true (solar) time by taking into account the variation in the earth's orbit and rate of rotatio ...

Steam available directly from a boiler under full pressure.

A method used to estimate building heating loads by assuming that heat loss and gain is proportional to the equivalent heat-loss coefficient for the building envelope.

A type of solar photovoltaic device made in a continuous process of pulling material from a molten bath of photovoltaic material, such as silicon, to form a thin sheet of material.

A unit of pressure [hydraulic (liquid) or pneumatic (gas)] that does not include atmospheric pressure.

A component of a heat pump that reverses the refrigerant's direction of flow, allowing the heat pump to switch from cooling to heating or heating to cooling.

The amount of power density in sunlight received at the earth's surface at noon on a clear day (about 1,000 Watts/square meter).

A pre-cut layer of insulation applied around a water heater storage tank to reduce standby heat loss from the tank.

Air that is returned to a heating or cooling appliance from a heated or cooled space.

The value or purchasing power of a dollar in a specified year carried forward or backward.

The resistance between metallic contacts and the semiconductor.

A measure of the surface burning characteristics of a material.

Electromagnetic radiation whose wavelengths lie in the range from 0.75 micrometer to 1000 micrometers; invisible long wavelength radiation (heat) capable of producing a thermal or photovoltaic effect, though less effective than visible light.

A vehicle with an engine capable of operating on two different types of fuels.

A term used to describe solar thermal, central receiver, power systems, where an array of reflectors focus sunlight onto a central receiver and absorber mounted on a tower.

A solar thermal electric central reciever power plant ("power tower") located in Barstow, California, and completed in 1981. The Solar One had a design capacity of 10,000 peak kilowatts, and was composed of a receiver located on the top of a tower surroun ...

A solar heating system that preheats water or air that is then heated more by another heating appliance.

A type of window having two layers (panes or glazing) of glass separated by an air space. Each layer of glass and surrounding air space reradiates and traps some of the heat that passes through thereby increasing the windows resistance to heat loss (R-val ...