Wind is growing in importance as a source of electric power around the world.
Utility-scale wind farms use large wind turbines, with typical capacities of 1.5–3.0 MW each. Each unit has a nacelle mounted on a 60- to 120-metre tower. Three 35-metre or larger blades are mounted on a shaft that rotates in each nacelle. Shaft power is transferred to a generator also located in the nacelle, and the resulting electricity is fed through a collector system to a transformer station connected to the power grid.
The following information has been taken from the Wind technologies schematic, which is viewable online at: http://northlandpower.com/WhatWeDo/Technologies/Wind.aspx
Nacelle - The nacelle houses the mechanical and electrical machinery that produces electricity. It is the size of a city bus (about 11 metres long), weighs more than 60 tonnes and swivels on the top of the tower to face the turbine into the wind for maximum productivity.
Turbine Blades - Each of the 30-40 metre hollow blades weighs 6 or more tonnes and is designed to flex in response to wind intensity. Each functions like an airplane wing, creating life to turn the rotor (three blades plus hub) as wind flows across their surfaces.
Hub - Each blade is connected to the hub with up to 100 bolts. The connection system allows the blades to pivot the hub, changing their pitch or angle relative to wind direction. Together, the hub and blades form a rotor up to 90 metres in diameter. The rotor rotates at 10-22 revolutions per minute and is connected to the main, low-speed shaft.
Low-speed main shaft - A large-diameter, low-speed shaft connects the rotor to the gearbox.
Gearbox - This mechanism, sometimes called the drive train, contains a gear system that accelerates the low-speed shaft rotation more than 100 times and transfers it to the high-speed shaft connected to the power generator.
High-speed shaft - A smaller-diameter shaft connects the gearbox to the generator.
Mechanical brake - Turbine speed at high wind velocities is controlled primarily by "feathering", or reducing the pitch of the blades. A secondary disc brake mounted on the high-speed shaft serves as a fail-safe backup that can stop the turbine completely.
Electrical generator - An asynchronous, four-pole generator converts mechanical force (torque) of the high-speed shaft into electricity.
Generator cooler - This system cools the generator as it works and heats up.
Yaw mechanism - Electrical motors and gears turn the nacelle so the rotor always faces into the wind.
Electronic controlled - A computer continuously reads information collected from the wind measurement devices and monitors the condition of the wind turbine. It controls the yaw mechanism and blade pitch to regulate the main shaft rotation at a relatively constant speed. This optimizes electricity production under varying wind conditions.
Hydraulics system - This system adjusts the pitch of the blades to aerodynamically accelerate or reduce the rotation or the rotor and low-speed shaft.
High-voltage transformer - The transformer raises the voltage from the turbine generator to intermediate distribution grid voltage. On some models of turbine, this component is located at the base of the tower.
Anemometer and wind vane - These devices which measure the speed and direction of the wind respectively, signal the electronic controller to start the wind turbine at wind speeds as low as 4.0 metres per second (14 km/h, 8 knots) and to stop it when wind speed is in excess of 25 metres per second (90 km/h, 49 knots). This protects the turbine from excessive force. Their signals also direct the yaw mechanism, which turns the nacelle and rotor into the wind.
Tower ( 70-120 metres tall ) - The steel tubular tower is assembled in sections that taper from the base to the nacelle, It can be as high as a 30-storey office building and positions the turbine where it cannot harm humans or animals and where the winds it receives is not diminished by ground effects. Technicians climb a 350-450 rung ladder inside the tower to inspect and service the nacelle.
Foundation ( 7 metres deep ) - A typical foundation is 150-cubic-metre of steel-reinforced, concrete foundation about 7 metres deep and weighing 360 tonnes. The tower is attached by 120 or more bolts anchored deep within the foundation.
Electricity substation - Wind farm turbines are linked by underground cables that transmit electrical energy and production data to a substation from which the power is fed into the higher-voltage electricity supply grid of the local utility.