Operation

A wind turbine is a device that transforms the kinetic energy of the wind into mechanical energy.

Currently, almost all wind turbines are of the horizontal-axis, three-bladed type.

The operation of old wind turbines, similar to windmills, was based on the principle of drag resistance offered by the blades against the wind. This non-aerodynamic design led to a very low conversion efficiency of the wind’s kinetic energy into mechanical energy at the machine’s shaft, with values around 12%. Modern turbines operate under the principle of lift force developed on the blade due to its aerodynamic design, similar to an airplane wing. Advances in the aerodynamic and structural design of the blades have increased the conversion efficiency to values close to the theoretical limit.

The main systems of a wind turbine are:

• Energy Capture System. (Located externally)¹
  • Rotor: Includes the hub and the blades.
  • Blades: Elements that capture wind energy and transmit its power to the hub. Blades can be of two types:
    • Fixed Pitch: In this type, the blade’s position remains fixed. For these systems, when the wind speed exceeds a certain value and it becomes necessary to limit the captured energy, the blade’s profile enters aerodynamic stall, causing turbulence that keeps the extracted energy within certain limits.
    • Variable Pitch: Those that modify their position, i.e., the angle formed by the blade’s profile with the incident airflow. They allow control of the mechanical energy supplied to the wind turbine by modifying this angle.
  • Hub: Connects the blades to the low-speed shaft. It is coupled to the wind turbine’s low-speed shaft.
• Transmission System.
  • Low-Speed Shaft: The wind turbine’s low-speed shaft connects the rotor hub to the gearbox. Inside, hydraulic or electrical system conduits run for the actuation of aerodynamic brakes, variable pitch, and control of the rotor’s sensors.
  • Gearbox: At its input is the low-speed shaft, and through a system of gears, it ensures the output shaft, the high-speed shaft, rotates at a higher frequency (between 80 and 50 times faster, depending on the turbine model).
  • High-Speed Shaft: Rotates at approximately 1,500 revolutions per minute (rpm), enabling the operation of the electrical generator. It is equipped with a mechanical disc brake for emergencies.
• Yaw System.
  • Yaw Motors: In large wind turbines, a mechanism is needed to position them facing the wind. This circular movement is achieved with motors and reducers fixed to the nacelle that engage with a toothed ring on the top of the tower, called the yaw bearing. The correct positioning signal is received from the turbine controller, based on readings from the wind vane and anemometer installed on each wind turbine.
  • Yaw Brake: Their mission is to prevent unwanted radial movements of the nacelle, either due to the effect of the incident wind or rotor rotation. They also reduce wear on the yaw gears. Their actuation can be hydraulic or electric, acting on brake calipers or an electric motor, respectively.
• Generation System
  • Electrical Generator. These are the turbine elements responsible for converting mechanical energy (in rotational form) into electrical energy. The electricity produced in the generator is conducted to the base of the tower, where it is transformed (voltage is stepped up and current is reduced) and sent to the grid.
  • Power Cabling. Transports the generated electrical energy from the alternator to the tower base transformer, passing through various protections for over/under voltage, overcurrent, or frequency, thus preventing possible damage to the grid or the turbine itself in case of contingencies in the wind turbine or distribution network.
  • Internal Transformer. Steps up the generation voltage from 690V or 1,000 V (depending on the wind turbine) to 20 kV, reducing the current and thereby electrical losses and cable heating.
• Control System.
  • Turbine Controller. The controller continuously monitors the wind turbine’s conditions, collects operational statistics, and regulates switches, hydraulic pumps, valves, and other wind turbine components.
  • Control Sensors. They are used to measure the physical parameters for turbine operation and supervision. The electronic signals are used by the electronic controller to connect the wind turbine when the received signal is correct. The controller will automatically stop the equipment if the information received from the sensors is erroneous, in order to protect the turbine.
  • Control and Regulation Signals. From the turbine controller, based on the analysis of sensor information, commands are generated that affect the operation and functioning of the wind turbine.
• Support System.
  • Tower. Supports the nacelle and the rotor. It can be tubular or lattice (the latter, although cheaper, are falling out of use as tubular ones are much safer). They have several sections to facilitate transport. The connection of the different sections is done via bolts on the connecting flanges.
  • Foundation. This is the part that allows the structure to remain vertical. Its mission is to absorb the stresses from the rest of the structure and transmit them to the ground.
• Hydraulic System.
  • Pressure Unit. Responsible for supplying hydraulic fluid at a specific pressure to allow the actuation of capture, yaw, or transmission systems.
  • Hydraulic Conduits. Channel the hydraulic fluid to the point of use.
  • Control Valves. Adapt the pressure and flow of the fluid based on the actuator to be driven.
• Cooling Systems.
  • Fans. Operate as required by the controller to create an air circulation.
  • Heat Exchangers. Dissipate heat from the component to be cooled (generator, gearbox, or hydraulic power unit) to the air stream created by the fans.

1. The remaining systems are located inside the Nacelle, which contains the wind turbine's key components, including the gearbox and the electrical generator. Service personnel can enter the nacelle from the turbine tower.