Under the First Law of Thermodynamics, efficiency is the ratio of work or energy output to work or energy input, and cannot exceed 100 percent. Efficiency under the Second Law of Thermodynamics is determined by the ratio of the theoretical minimum energy ...

A device for converting mechanical energy to electrical energy.

A heat storage system that uses a heat storage medium, and where the additional or removal of heat results in a change in temperature.

A raw material that can be converted to one or more products.

A material that can be used to store thermal energy as latent heat. Various types of materials have been and are being investigated such as inorganic salts, eutectic compounds, and parrafins, for a variety of applications, including solar energy storage ( ...

A type of turbine in which combusted, pressurized gas is directed against a series of blades connected to a shaft, which forces the shaft to turn to produce mechanical energy.

The point or outdoor temperature where the heating capacity of a heat pump matches the heating requirements of a building.

The amount of visible light that passes through the glazing material of a window, expressed as a percentage.

A measure of air purity that is equal to one complete air change (in an interior space).

Solid fuels made from primarily wood sawdust that is compacted under high pressure to form small (about the size of rabbit feed) pellets for use in a pellet stove.

The amount of BTU's/hour or kW's produced by a heating system from the burning of a fuel.

A group of wind turbines interconnected to a common utility system through a system of transformers, distribution lines, and (usually) one substation. Operation, control, and maintenance functions are often centralized through a network of computerized mo ...

The measure of seasonal or annual efficiency of a heat pump operating in the heating mode. It takes into account the variations in temperature that can occur within a season and is the average number of Btu of heat delivered for every watt-hour of electri ...

The amount of work accomplished by electrical power, usually measured in kilowatt-hours (kWh). One kWh is 1,000 Watts and is equal to 3,413 Btu.2.The energy of moving electrons.

Air brought into a building from outside to replace exhaust air.

A federal agency established in 1933 to develop the Tennessee river valley region of the southeastern U.S., and which is now nation's largest power producer.

A thermal storage wall is a south-facing wall that is glazed on the outside. Solar heat strikes the glazing and is absorbed into the wall, which conducts the heat into the room over time. The walls are at least 8 in thick. Generally, the thicker the wall, ...

The arrangement, proportion, and design of windows in a building.

The decomposition of organic material to alcohol, methane, etc., by organisms, such as yeast or bacteria, usually in the absence of oxygen.

A diagram that indicates the average percentage of time that the wind blows from different directions, on a monthly or annual basis.