Wind Power Glossary

Airfoil—The shape of the blade cross-section, which for most modern horizontal axis wind turbines, is designed to enhance the lift and improve turbine performance.

Ampere-hour—A unit for the quantity of electricity obtained by integrating current flow in amperes over the time in hours for its flow; used as a measure of battery capacity.

Anemometer—A device to measure the wind speed.

Average wind speed—The mean wind speed over a specified period of time.

Blades—The aerodynamic surface that catches the wind.

BTPS- Blade tip power system

Brake—Various systems used to stop the rotor from turning.

Converter—See Inverter.

Cut-in wind speed—The wind speed at which a wind turbine begins to generate electricity.

Cut-out wind speed—The wind speed at which a wind turbine ceases to generate electricity.

Density—Mass per unit of volume.

Downwind—On the opposite side from the direction from which the wind is blowing.

Furling—A passive protection for the turbine where typically the rotor folds either up or around the tail vane.

Grid—The utility distribution system. The network that connects electricity generators to electricity users.

HAWT—Horizontal axis wind turbine

HWT- Honeywell Wind Turbine.

Inverter—A device that converts direct current (DC) to alternating current (AC).

kW—Kilowatt, a measure of power for electrical current (1000 watts).

kWh—Kilowatt-hour, a measure of energy equal to the use of one kilowatt in one hour.

MW—Megawatt, a measure of power (1,000,000 watts).

Nacelle—The body of a propeller-type wind turbine, containing the gearbox, generator, blade hub, and other parts.

O&M Costs—Operation and maintenance costs.

Power Coefficient—The ratio of the power extracted by a wind turbine to the power available in the wind stream.

Power curve—A chart showing a wind turbine’s power output across a range of wind speeds.

PUC—Public Utility Commission, a state agency which regulates utilities. In some areas known as Public Service Commission (PSC).

PURPA—Public Utility Regulatory Policies Act (1978), 16 U.S.C. § 2601.18 CFR §292 that refers to small generator utility connection rules.

Rated output capacity—The output power of a wind machine operating at the rated wind speed.

Rated wind speed—The lowest wind speed at which the rated output power of a wind turbine is produced.

Rotor—The rotating part of a wind turbine, including either the blades and blade assembly or the rotating portion of a generator.

Rotor diameter—The diameter of the circle swept by the rotor.

Rotor speed—The revolutions per minute of the wind turbine rotor.

Start-up wind speed—The wind speed at which a wind turbine rotor will begin to spin. See also cut-in wind speed.

Swept Rotor area—The area swept by the turbine rotor, A = pi R 2 , where R is the radius of the rotor.

Tip Speed-  9 x greater than shaft speed, in feet per second travelled

Tip speed ratio—The speed at the tip of the rotor blade as it moves through the air divided by the wind velocity. This is typically a design requirement for the turbine.

Turbulence—The changes in wind speed and direction, frequently caused by obstacles.

Upwind—On the same side as the direction from which the wind is blowing—windward.

VAWT—Vertical axis wind turbine.

Wind farm—A group of wind turbines, often owned and maintained by one company. Also known as a wind power plant.

Yaw—The movement of the tower top turbine that allows the turbine to stay into the wind.