Wind Turbines

3. COMPONENTS AND FUNCTIONING OF A WIND TURBINE

types of wind turbines used nowadays

The machines used to transform the kinetic force of the wind into electricity are called wind turbines. They are divided into two main groups: those with a horizontal axis and those with a vertical axis. Although today multi-blade or vertical axis wind turbines continue to be installed, especially in low-power models, the horizontal axis wind turbine, considered the most efficient, is by far the most widely used today and, without a doubt, the model that has been developed the most and is used the most is the horizontal axis and 3 blades ("traditional" wind turbine).

Also in a very specific way, we can find variants to the traditional one, with 2 blades (twin-blade wind turbine) a single blade, or even wind turbines are being developed without them ("vortex" wind turbine).

the three bladed wind turbine

The most widespread wind turbine model at present, and the one that is developing the highest performance, is the three bladed model. It is a design that reaches the perfect balance, today, between power offered and installation cost.

The basic principle of operation of the wind turbine is as follows:

Taking advantage of the kinetic energy of the wind, we move some blades.
The blades transform the force into a rotational force that, through an axis, and multiplying the speed of rotation by means of a gear box, drives the rotor of a generator.
The generator converts this energy into electrical energy.
A transformer adapts the energy produced to the grid used in the area.

main parts:

Rotor: front part of the turbine, which is made up of the hub and blades of the turbine.

Hub: part of the rotor that serves to connect the blades to the Nacelle .

Blades: they are designed to rotate in the wind.

Nacelle: it houses the internal components: the transmission system, the generator, and the electrical and control systems.

Tower: supports the rest of the components and serves as access

Foundation: handles all stress and loads of the turbine and transmits them to the ground.

blades

They are designed to rotate in the wind. They move the turbine generator. The most modern turbines generally consist of three blades. The largest blade manufactured so far is 107m long. Through a mechanical, electrical or hydraulic system, the blades rotate, in order to adapt to the speed of the wind and keep a rotor speed as constant as possible. The pitch system is in charge of looking for the required angle in the blade for the different conditions: work, stop, service.

The blades are made of light materials, mainly fiberglass, with reinforcements of more rigid materials such as wood or carbon fiber. The design of the blades is studied so that the required thrust is achieved according to the angle of attack at which they are placed, and so that in the stop position or flag they achieve, by themselves, stopping the wind turbine.

The blades are attached to the hub by means of a bolted flange.

The blade when rotated creates an aerodynamic force that can be divided into two: Thrust and Normal Force.
The Normal force (Drag) is what contributes to the rotation of the Rotor.
Thrust (Lift) does not spin us and is an unwanted but inevitable effect.

blade structure and construction

the hub

It is a very important joining point, since it holds the blades and transfers their weight and supported forces. Therefore, its main component is the chassis, made of cast steel.
The hub also contains the blade turning (pitch) system. Pitch systems are currently almost always hydraulic, but there are also electrical or mechanical models, powered from the nacelle. A bearing connects the blade and the hub casting, making possible to rotate the blade.
To drive the rotation in wind turbines with a hydraulic system, a hydraulic group driven from the nacelle is controlling the cylinders that move the bearings.
Finally, the hub is covered with fiberglass panels that give the aerodynamic shape and protect the internal elements.

blade bearings

hub-blade connection

power train

This system transmits the movement produced by the wind from the blades to the generator. This component is responsible for raising the speed of the blades to the generator through a gearbox. In addition, the transmission system, or power train, is responsible for transferring loads and weights from the rotor to the chassis.

Typically, the transmission system comprises a shaft with one or more bearings, the gearbox and the braking system.
The shaft (blank) is in charge of transmitting the rotor spin at low speed (12-15 rpm) and, connected to the nacelle chassis by means of one or more bearings, transmits the weights to the tower and the foundation.

The gearbox is made up of a series of gears that multiply the speed to make it useful for the production of electrical energy. The output speed is about 1500 rpm (100 times the input speed) and the generator will be connected to its high speed shaft.
The gearbox is also fitted with a braking system (usually a disc brake similar to a car's one) to aid when stopping by turning the blades.

turning system

Between the nacelle and the tower we have the turning system, also called yaw system, which is able to orient the rotor in the direction of the wind. To maximize production and control blade forces, it is essential to be able to move the turbine in the wind. The measuring instruments that the turbine equips measure both the direction and the speed of time, and that data is read by the controller, which drives the yaw system.

The turning system has a bearing that is powered by electric motors and a braking system to keep the rotor in the desired position.

the generator

Located next to the transmission or gearbox. It is the component that is responsible for transforming the movement of the blades into electrical energy. The currently world's largest turbine produces 12 MW.

The generator is mechanically connected to the gearbox, which spins it at about 1500 rpm (speed varies constantly due to wind changes). Due to the turn, electric currents appear inside it, which we will connect to a series of electrical and electronic equipment in order to transform and use that electricity. The electricity supplied by the generator is in Low Voltage (below 1000V).

control system

We are talking about the components that transmit and process the information from the different sensors and the conditions in which the machine is: temperature, wind, wear, need for service ... the data of the different components are measured and a controller analyzes it and also sends the measurements to a remote control center, from where the conditions of each and every one of the turbines that are in operation are analyzed.

To control the power delivered, semiconductors, which can be electronically controlled, are used.

cooling system

Due to the great power generated, the moving mechanical components, and the extreme temperatures in which the wind turbines have to work, cooling systems are installed, where oils, antifreeze, air ventilation systems, electric heaters, etc. are combined to ensure adequate working temperatures in each of the elements of the turbine.

other systems

Inside the nacelle we can find other systems that help the general functioning and facilitate operations and maintenance: fire detection and extinction systems, vibration control systems, a crane module to raise and lower spare parts from the nacelle to the ground, interior lighting etc.

Finally, the nacelle is covered with fiberglass panels that protect and isolate the interior components and with hatches in the ceiling to facilitate the entry of natural light.

electricity conversion

In order to transport the electricity produced minimizing losses, it is necessary to raise the voltage. Through transformers we are going to raise and lower the electrical voltage to adapt it to the needs of the network.
Each wind turbine is equipped with a transformer that adapts the voltage provided by the generator to that of the local network where the turbine is installed. The transformer will be installed, depending on the wind turbine model, in the nacelle or in the tower. While the generator produces voltages below 1,000 V, the transformer raises them to values between 10,000 and 40,000 Volts.
Through different stages of transformation, the voltage is adapted for the transport and distribution of electrical energy.
From a large control center, the different sources of electricity generation are connected and disconnected to satisfy the instantaneous demand of users.

tower

The tower is the component that supports the rest of the turbine. The tower provides access for workers to carry out the maintenance tasks necessary to keep the machine running. The height and diameter of the tower will vary depending on the wind in the area, the weight, specific forces to be supported and the number and type of blades that the wind turbine will have mounted.

The towers are manufactured by steel sheets that are rolled and welded in sections, which are connected to each other by screwing in the park.

Inside the tower we will have control systems, to be able to see the state of the turbine and connect / disconnect it without having to go up to the nacelle. We will also find the general connection and disconnection breakers of the wind turbine to the grid, and other lighting, communication and control systems. The tower has a ladder to access the nacelle and the rotor, with different intermediate platforms, and in some cases it has an elevator to facilitate maintenance.

foundation

The foundation is responsible for transmitting to the ground the total loads that the wind turbine supports. In onshore installations, they are made of reinforced concrete, while in marine installations, steel structures are used that are "nailed" to the seabed. Floating platforms have also been developed, which remain anchored to the ocean floor.

steel structure and connection piece

first tower section being assembled

sea foundations

docking area and connection with the tower

summary video

windturbine functioning

STARTING THE WIND TURBINE.

When the turbine detects wind in any direction, by the wind speed sensors (turbine anemometers), the controller makes the following orders to the wind turbine, through the corresponding motors:

Between 2 - 3 m/s. Sends the order to position the rotor against the wind. This order is called turbine orientation.
From 3 m/s. The order to disengage the brakes to allow the turbine to rotate is given, and to begin to rotate due to the effect of the wind alone. It also sends the position command of the blades progressively
Rpm => 1500. When the generator sync speed is reached (depending on the wind, one generator or another with different speeds is selected), the generator is connected to the grid.
Direct network connection. From this moment, the generator is directly connected to the general electrical network, sending the energy to the national system. The speed is constant and limited only by the frequency of the network. When the wind is strong, there is a limitation of power in the blades by increasing the turbulence of the air flow.
Variable pitch. The wind turbine is controlled by acting at the pitch angle, capturing or limiting the power extracted from the wind. The generation speed can be variable.

STOPPING THE WIND TURBINE.

It can happen for the following reasons:

High winds. When the wind exceeds a range (> 25 m/s or 90 km/h), or when an error is detected based on the reading from the wind sensors to the controller.
Operation error. A malfunction is detected by the sensor information.
Stop due to little wind. The sequence starts if little generation or very low winds are detected.
Manual stop. It is carried out under the supervision of the operation and maintenance personnel, for maintenance of the wind turbine, or because its production is not necessary due to low electrical demand in the network.

The turbine stop may follow two procedures:

Soft stop. The order is sent to the blade angle actuators (pitch) increasing the blade degrees to 90º. Simultaneously, the generator is switched off and a gradual increase in pressure is made in the hydraulic braking circuit.
Emergency stop. It occurs in the event of major errors, danger to persons or integrity of the turbine. Brakes are applied with maximum pressure from the first moment.

home

Page updated

Google Sites

Report abuse