A gas that does not react with other substances; e.g. argon or krypton; sealed between two sheets of glazing to decrease the U-value (increase the R-Value) of windows.

The process of using heat that is rejected in one part of a cycle for another function or in another part of the cycle.

A device that produces mechanical energy directly from two heat reservoirs of different temperatures. A machine that converts thermal energy to mechanical energy, such as a steam engine or turbine.

A configuration of an electrical circuit in which the positive lead is connected to the negative lead of another energy producing, conducting, or consuming device. The voltages of each device are additive, whereas the current is not.

A measure of the amount of energy lost during the generation, transmission, and distribution of electricity.

A component of a water heating system that opens at a designated temperature or pressure to prevent a possible tank, radiator, or delivery pipe rupture.

A wheel that is designed to use the weight and/or force of moving water to turn it, primarily to operate machinery or grind grain.

The ability to send or wheel electric power to a customer over a transmission and distribution system that is not owned by the generator (seller) of the power.

Any material that has a limited capacity for conducting an electric current. Certain semiconductors, including silicon, gallium arsenide, copper indium diselenide, and cadmium telluride, are uniquely suited to the photovoltaic conversion process.

A discontinuance of electric power supply.

The power output of a device under specific or nominal operating conditions.

An electric current induced by radiant energy.

The change in the power available in the wind due to changes in the windspeed or velocity profile; the windpower profile is proportional to the cube of the wind speed profile.

A solar energy concentrating technology that uses a linear receiver that tracks the focal area of a reflector or array of reflectors.

The compound (working fluid) used in air conditioners, heat pumps, and refrigerators to transfer heat into or out of an interior space. This fluid boils at a very low temperature enabling it to evaporate and absorb heat.

A product of crude oil that is used for space heating, diesel engines, and electrical generation.

A type of incandescent lamp with an interior coating of aluminum that reflects light to the front of the bulb. They are designed to spread light over specific areas.

The amount (percent) of light that is reflected by a surface relative to the amount that strikes it.

For valves and fittings, implies that they are suitable for working pressures between 125 to 175 pounds per square inch.

The addition of dopants to a semiconductor.