Modern wind turbines generate electricity by using wind to spin their blades.  This rotational motion spins a generator, which generates electricity.  The following describes wind turbine major components in more detail.

Blades

The blades capture the convert the wind energy into rotational energy that can be turned into electricity by the generator. Blades are constructed from materials including wood (core), foam (form), fibreglass and Kevlar. 

Wind turbine blades are shaped like aerofoils. Aerodynamically, they are more like an aircraft wing than the angled vanes featuring on old wind mills.

The wind turbine blades are bolted to the pitch bearings mounted in the hub. Pitch bearings allow the blades to rotate, regulating the amount of wind energy extracted by the turbine.

Nacelle

The nacelle is essentially a box containing the generator, gearbox and other auxiliary systems including cooling and lubrication systems.

View of the back of the nacelle of a Vestas wind turbine. Note the wind vane for measuring wind direction and the anemometer for measuring wind speed, mounted on the back of the nacelle

Generator

Wind turbine generators vary in technology.  They can be based on induction machines, permanent magnet generators or even synchronous machines. They convert the rotational energy of the blades, via the main shaft to electricity.

Gearbox

Many wind turbines contain a gearbox. Wind turbine gearboxes convert the low rotational speed of the blades into a speed suited to the generator.  Wind turbine gearboxes can have conversion ratios of 1:100.  This is a unique application. Most (general) gearbox applications require reduction gearboxes. Reduction gearboxes convert high speed/low torque into low speed/high torque. On a wind turbine the application requires conversion of high torque at low speed into high speed.  This presents challenges for the gearbox manufacturers. As a result, gearboxes present a high portion of the ongoing cost of wind turbine major component failure costs.

Wind turbine gearbox and generator
View of wind turbine gearbox (foreground) and generator (background) as installed within the Nacelle

Tower

The wind turbine tower is typically a large steel tube.  Its height often exceeds 80m. Therefore, the tower must be constructed in sections and joined on site using bolted flanges.  The tower contains a ladder and usually a lift, to enable wind turbine technicians to access the nacelle.

Electrical Cabling/Transformer

Electrical cabling moves electricity from the generator, down the tower and back to the substation. The substation sends the energy to the electrical transmission or distribution system. Typical wind turbine generators operate below 1000V.  This voltage is transformed to 22kV or 33kV via a wind turbine transformer. The transformer is either located in the nacelle, or at the bottom of the tower (inside or outside).  Increasing the voltage allows efficient and economical transportation of power from the turbine through the wind farm, to the substation.

Wind turbine tower cable loop
Cabling exiting the nacelle and entering the tower. The cables are fixed to the tower walls. A loop of slack cable must be provided at the top of the tower to allow the nacelle to rotate and face into the wind. Periodically the wind turbine must shut down to untwist the cabling.

Pitch System

The blades are connected to pitch bearings and drives which enable the blades to be rotated or pitched. Pitching the blades controls the power output. The blades are angled either to extract the maximum energy from the available wind, or to curtail the power such that the wind turbine’s rated power and design loads are not exceeded.

Pitch systems can be hydraulic or electrical, and rotate with the blades in the spinner (or hub).  This presents design challenges bringing power and signals from the stationary nacelle, into the spinning hub.  Pitch-related alarms are a common cause of breakdowns on wind turbines.

Yaw System

The yaw system consists of electrical motors and gearboxes that rotate the nacelle upon the tower. This ensures the blades are always facing into the wind.  Poor nacelle alignment can result in wind turbine underperformance and asymmetrical stresses across the drivetrain.

Wind Turbine Controller

The wind turbine controller is more like an industrial computer than a PLC.  It makes decisions that maximise wind turbine production while keeping the equipment safely within operating limits.  It records analogue data from attached sensors and logs alarm and event data. This SCADA data is then sent to a central server to be stored for later analysis.

Bachmann, Mita Teknik and Deif controllers are popular within the wind industry.

Examples of wind turbine controller tasks include:

  • Starting the turbine when the wind speed exceeds the minimum level. This is achieved by commanding the blades to pitch to catch the wind
  • Regulating the power output by altering the angle of the blades into the wind
  • Keeping the turbine pointed directly into the wind by analysing data from a nacelle-mounted wind vane
  • Shutting down the turbine if a signal from a temperature sensor indicates a wind turbine component is too hot.
  • Sending alarm data to the wind turbine SCADA system to alert wind turbine technicians to a breakdown
Bachmann MPC240 Wind Turbine Controller

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