EWE helps generate 2,300 MW of wind energy on land, for example. The giant towers with their large rotor blades are thus a common sight in many places. However, not everyone knows how wind turbines work exactly. Let us show you what components are used in wind turbines, how they work and how electricity from turbines is fed into the network.
How wind turbines work
Wind turbines are currently Germany’s most important producers of renewable energies: in 2021, 23.1% of Germany’s electricity came from wind energy (Fraunhofer ISE 2022). This energy is obtained from over 31,000 wind turbines in onshore and offshore wind farms.
How does a wind turbine work?
The basic way a wind turbine works to generate wind energy looks simple at first glance: wind sets the rotor blades in motion, which then generate energy. But what elements are found inside the large towers? How can the rotor movement produce electricity that we can ultimately use in our homes? To answer these questions, we need to take a look at the components in a wind turbine.
Structure of a wind turbine
Wind turbines basically consist of a high tower with rotors at its top that turn. To ensure wind generates as much movement as possible, the following typical design has prevailed since the 1980s: three long rotor blades are attached at equal distance from one another to the nacelle at the top of a long tower.
The rotor blades are aerodynamically shaped and positioned in such a way that they can be adjusted to the wind speed and direction to optimum effect. What’s more, they generate comparatively little noise while rotating and are usually made of durable glass-fibre reinforced composite.
The height of the turbine determines the efficiency coefficient
The longer the rotor blades are, the greater the efficiency coefficient is. For this reason, rotor diameters up to 120 m are possible in large wind generators. To ensure as much wind as possible can be captured with the large rotor diameter, the tower also needs to be very high since the wind is stronger and more constant at higher air layers. The power extracted from wind turbines increases by around 1% with each metre in height.
The wind turbine tower needs to be built on a deep foundation made of concrete and steel to ensure the tower is perfectly stable. Individual turbines are between 40 and 160 m high, depending on the conditions at the wind farm location.
The most important components in a wind turbine are located in the nacelle, which forms the top of the tower and to which the rotors are attached. In addition to numerous measuring systems, this cover housing contains a gear box and a generator to produce electricity as required in each individual model.
A long cable route runs down through the tower. A box is usually installed at the base of the wind turbine. This is the transformer which changes the voltage level of the electricity generated so that it can be easily fed into the network. How do all these components work together to actually generate and transfer electricity?
How is electricity generated in a wind turbine?
To understand how electricity is generated in a wind turbine, it is best to take a look at the cover housing interior, where the gearbox, generator and, finally, the transformer are responsible for producing and utilising electricity.
Measurement instruments on the nacelle roof record the wind speed and direction constantly. Readings from these instruments are used to turn the nacelle to face the wind and place the rotor blades at an optimum angle to set them in motion. This movement is based on the aerodynamic force principle, in a similar way to aircraft. The lift produces a torque, which rotates the rotor.
As with all types of energy generation, wind turbines are unable to convert all the kinetic energy from wind into electricity.
What are the different steps taken to generate electricity in a wind turbine?
1. Wind interacts with the wind turbine rotor blades in the form of kinetic energy and sets them in motion. The rotation of the blades produces mechanical energy.
2. In turbines with a gearbox, the gears transform the low rotor speed of few rotations per minute into a more favourable speed for the generator of up to 1,500 rotations per minute.
3. Wind turbines that do not have gears transfer the mechanical energy via the hub and directly to the generator, which is consequently larger and heavier.
4. Inside the generator, the rotary movement generates an electrical voltage, i.e. electrical power, between 400 and 1,000 V using electromagnetic induction.
5. A transformer at the turbine base or in the nacelle converts the electricity produced by the generator to a voltage between 10 and 30 kV. The electricity can then be transported into the local network and the homes where it is consumed via high-voltage lines or underground cables, for example.
How much power does a wind power station produce?
Due to energy losses, a wind power station is only able to produce a nominal output that is significantly lower than the energy from the incident wind. A wind turbine’s efficiency coefficient currently stands at roughly 45 to 50%. Having said that, a wind turbine can generate up to 15 million kWh of electricity a year with this efficiency coefficient under good conditions. This nominal output can provide up to 4,000 homes with electricity.
Wind turbines thus have a very positive energy balance, unlike other energy carriers. The energy consumed for their production and construction can be offset by their output during operation within three to six months.
Can wind energy be stored?
One of the challenges that wind energy poses is that wind energy production is subject to fluctuations. On average, wind turbines can only be operated 75% of the time. This is because the wind must not be too light or too strong.
A wind turbine’s rotors start turning when the wind reaches a speed of 2 to 4 m/s and achieve their maximum output at a wind speed of 12 m/s. However, if there is a storm or a very strong wind, operation must be halted when the wind reaches a speed between 28 and 35 m/s to prevent any damage.
Excess wind energy also goes to waste if there is surplus production in the network that cannot be consumed. A possible solution to this problem would be to store wind energy. Electricity produced in wind turbines is currently fed directly into the network. If different storage solutions were used, wind energy could also be consumed at times when there is no wind and thus not go to waste when there is surplus production.
Different possible ways of storing wind energy are being tested and researched at the site. One option under investigation is the storage of wind energy in large batteries. Another highly promising means is transforming the energy into hydrogen. Hydrogen can store energy as an intermediary gas or liquid and then be reconverted into electricity when required. In light of this, EWE is currently undertaking a pilot project for underground storage of pure hydrogen in Rüdersdorf, near Berlin. As part of the project, we are exploring how this type of storage creates new opportunities for making use of renewable energies.
Expanding the use of wind energy in Germany is a priority due to its climate-neutrality, positive energy balance and future prospects. EWE is also participating in the expansion of wind turbines and other renewable energies to pave the way to a green future with a joint venture Alterric GmbH with the Aloys Wobben Foundation.
