Components
From Wind wiki
Horizontal axis
wind turbine can be broken down into three main sections: the nacelle, the rotor, and the tower.
The nacelle includes:
• An outer frame protecting machinery from the external environment
• An internal frame supporting and distributing weight of machinery
• A power train to transmit energy and to increase shaft speeds
• A generator to convert mechanical energy into electricity
• A yaw drive to rotate (slew) the nacelle on the tower
• Electronics to control and monitor operation
Description of Nacelle Components
Subcomponent Description
Low Speed Shaft and High Speed Shaft Transmits rotational work from the rotor hub to the gearbox and from the gearbox to the generator.
Gearbox Converts low-speed rotation from the input shaft of the rotor to high-speed rotation, which drives the high-speed shaft of the generator assembly. Wind turbine gearboxes typically use a planetary gear system.
Coupling Attaches the gearbox to the generator. Flexible couplings may be used to reduce oscillating loads that could otherwise cause component damage. Bearings A number of bearings are required for the shafts, gearbox, yaw mechanism, generator, and other rotating parts.
Mechanical Brakes A mechanical friction brake and its hydraulic system halt the turbine blades during maintenance and overhaul. A hydraulic disc brake on the yaw mechanism maintains nacelle position when nacelle is stationary.
Electrical Generator Converts high-speed shaft work into electrical energy.
Power Electronics Couples the generator output to the step-up transformer input, typically with an IGBT bridge, allowing the generator to run at variable speed while still outputting 50 or 60 Hz AC to the grid. Also makes reactive power possible.
Cooling Unit A large fan drives air to convectively cool the generator and gearbox and exhausts waste heat from the nacelle assembly. Ducting directs cool air to the generator.
Yaw Mechanism and Four-Point Bearing Rotates the turbine directly into the wind in order to generate maximum power. Typically, four yaw sensors monitor the wind direction and activate the yaw motors to face the prevailing wind. A four-point bearing connects the nacelle to the tower. The yaw mechanism turns the blades 90 degrees from prevailing winds under high winds to reduce stress on internal components and avoid over-speed conditions.
Electronic Controller(s) (a) A base controller, located at the base of the tower, utilizes PC’s and fiber optics to monitor and record performance data, as well as to facilitate communication between both sub-controllers and external parties. (b) A nacelle controller monitors activity within the nacelle assembly. (c) A hub controller, being used in more recent models, communicates directly with the nacelle controller to more precisely monitor rotor activity
Sensors (a) An anemometer, located on the tower, measures wind velocity and relays data to the yaw mechanism. (b) A wind vane measures wind direction and relays data to the yaw mechanism. (c) A cable twist counter monitors cables within the tower to determine if the turbine has been yawing in one direction for an extended period of time. (d) A thermocouple senses temperature within the nacelle assembly.
The rotor includes:
• Blades, which are generally made of glass-reinforced fiber up to 50m in length. Lighter and stronger carbon fibers are being used in the larger blades. • Extenders attach the blades to the central hub • Pitch drives to control the angle of the blades • The rotor typically has three blades because that number provides the best balance of high rotation speed, load balancing, and simplicity.
Description of Rotor Components
Subcomponent Description
Rotor Blades Blades utilize the principles of lift to convert the energy of the wind into mechanical energy. Stall-regulated blades limit lift, or momentum, when wind speeds are too great to avoid damaging the machine. Variable-pitch blades rotate to minimize their surface area and thereby regulate rotational speed.
Pitch Drive This system controls the pitch of the blades to achieve the optimum angle for the wind speed and desired rotation speed. At lower wind speeds a perpendicular pitch increases the energy harnessed by the blades, and at high wind speeds, a parallel pitch minimizes blade surface area and slows the rotor. Typically one motor is used to control each blade. Power is either electric or provided by hydraulics in the nacelle, and supplemented by a hydraulic accumulator in the event of system failure.
Extenders These steel components serve as a means to support the rotor blades and secure them to the hub
Hub The hub serves as a base for the rotor blades and extenders, as well as a means of housing the control systems for the pitch drive. It rotates freely and attaches to the nacelle using a shaft and bearing assembly.
The tower includes:
• Rolled steel tubes connected in series • Flanges and bolts joining each section • A concrete base serving as a stable foundation for the turbine assembly • Concrete segmented towers and hybrid steel/concrete towers may also be used for large turbines in cases where steel tower section transportation is difficult.
Description of Tower Components
Subcomponent Description Tower This component is typically made of rolled, tubular steel, and built and shipped in sections because of its size and weight. Common tubular towers incorporate a ladder within the hollow structure to provide maintenance access. Utility-scale towers range in height from 60-100m and weigh between 200-400 tons.
Base The base supports the tower and transfers the loads to the foundation soil or bedrock. The foundation size and type depends on the foundation conditions but is typically constructed with steel-reinforced concrete.
Flanges and Bolts These items join tower segments.