Wind Power Glossary

Anemometer - measures the wind speed and transmits wind speed data to the controller.

Blades - the aerodynamic surface that catches the wind. Most commercial turbines have three blades.

Braking System - a device to slow a wind turbine's shaft speed down to safe levels electrically or mechanically.

Capacity Factor - the average power output of a wind development divided by its maximum power capability, its rated capacity. Capacity factor depends on the quality of the wind at the turbine. Higher capacity factors imply more energy generation. On land, capacity factors range from 0.25 (reasonable) to over 0.40 (excellent). Offshore, capacity factors can exceed 0.50.

Carbon Dioxide (CO2) - a naturally occurring gas, and also a by-product of burning fossil fuels and biomass as well as land use changes and other industrial processes. CO2 is the principal greenhouse gas that is produced by human activity and influences climate change.

Climate Change - changes in a climate system over decades or longer. The term often refers to changes in climate that can be attributed directly or indirectly to human activities that altered the composition of the global atmosphere – changes that are beyond the natural climate variability observed over comparable time periods.

Controller - the controller starts up the turbine generator at wind speed of about 8 to 16 mph and shuts off the generator at about 65 mph.

Cut-in Speed - the wind speed at which the turbine blades begin to rotate and produce electricity, typically around 10 mph.

Cut-out Speed - the wind speed at which the turbine automatically stops the blades from turning and rotates out of the wind to avoid damage to the turbine, usually around 55 to 65 mph.

Emissions - the discharges of pollutants into the atmosphere from stationary sources such as smokestacks, other vents, or the surfaces of commercial or industrial facilities, and mobile sources such as motor vehicles, locomotives and aircraft. With respect to climate change, emissions refer to the release of greenhouse gases into the atmosphere over a specified area and period of time.

Energy Payback - the time period it takes for a wind turbine to generate as much energy as is required to produce the turbine, install it, maintain it throughout its lifetime and, finally, scrap it.

Gear Box Gears - connect the low-speed shaft to the high-speed shaft and increase the rotational speed of the shaft to the speed required by the generator. The gear box is heavy and power losses from friction are inherent in any gearing system.

Generator - a device that produces electricity from mechanical energy, such as from a rotating turbine shaft.

Nacelle - the nacelle sits atop the tower and contains the gearbox, shafts, and generator of a wind turbine. Some nacelles are large enough for a helicopter to land on.

Pitch - the angle between the edge of the blade and the plane of the blade's rotation. Blades are turned, or pitched, out of the wind to control the rotor speed.

Rated Wind Speed - the wind speed at which the turbine is producing power at its rated capacity. The rated wind speed generally corresponds to the point at which the turbine can perform most efficiently. Because of the variability of the wind, the amount of energy a wind turbine actually produces is lower than its rated capacity over a period of time.

Rotor Hub - the centre of a turbine rotor, which holds the blades in place and attaches to the shaft. The rotor refers to both the turbine blades and the hub.

Shaft - the rotating part in the center of a wind turbine or motor that transfers power. A high-speed shaft drives the generator. A low-speed shaft is turned by a rotor at about 30 to 60 rpm.

Tower - the base structure that supports and elevates a wind turbine rotor and nacelle.

Wind Turbine - a machine that captures the force of the wind. Also called a wind generator when used to produce electricity. Most commercial wind generators are horizontal axis wind turbines. If wind energy is used directly by machinery, such as for pumping water, cutting lumber or grinding stones, the machine is called a windmill.

Wind Vane - measures wind direction and communicates with the yaw drive to orient the turbine properly with respect to the wind.

Yaw - to rotate around a vertical axis, such a turbine tower. The yaw drive is used to keep a turbine rotor facing into the wind as the wind direction changes.