Wind energy is based on harnessing the power of the wind to generate electricity, but do you know what’s behind the process and how an onshore wind farm works?
Many of us have seen one of these wind machines that we misnamed “windmills”, either in their surroundings, on an endless car journey full of horizons to discover, or on a screen. Wind turbines, which is what those responsible for transforming the designs of Aeolus into an inexhaustible channel of renewable energy for our use are really called, are technologically advanced equipment that bear many aesthetic similarities with the mills that have historically populated the landscapes of many countries (mainly dedicated to grinding grain thanks to a mechanical action as a result of harnessing the wind), although the harnessing of energy and its conversion into electricity, in addition to many other things that we will see later, makes them very different. So let’s see how an onshore wind farm works and which actors are behind this type of green energy.
To understand how this type of energy works, the first thing to think about is that a wind turbine is not an individual element, but part of a larger and more complex entity: a wind farm. Individual wind turbines do exist in the case of small consumers, but that is a different story. This wind turbine is connected, both electrically and from the point of view of sending and receiving information, with the rest of the wind turbines and different elements that make up a wind farm. Thus, at all times, thanks to the sensorisation and intercommunication of the different elements, the operating company of the wind farm is aware of the real-time status of each wind turbine: mechanical problems, energy generated, electronic problems, technical stoppages…
This is why an onshore wind farm is made up of the following elements in order for the whole system to work properly:
- Wind turbine: It is responsible for generating electricity through the physical action of the wind on the blades, which are connected to the rotor by means of an element called a hub. Each wind turbine can have a power that varies from 0.5 to 7 MW, depending on its size. The energy generated comes out in medium voltage thanks to the transformer and medium voltage switchgear housed inside in most cases, or at the foot of the wind turbine in exceptional cases.
- Medium-voltage electrical network: These are the arteries of the wind farm through which the electricity flows to its consumption.
- Substation or connection point: This element is responsible for raising the generation voltage to the transmission voltage and feeding the energy generated into the transmission or distribution grid.
- Transmission or distribution lines: Very recognisable actors, thanks to their distinctive towers, which are responsible for transporting the green energy to our homes.
In this way, once the turbine comes into operation, by means of the rotational movement, it causes the generator installed in the nacelle to produce electrical energy thanks to the transformation of mechanical energy into electrical energy. In turn, the transformer raises the voltage, to avoid electrical losses, and the energy is fed into the medium voltage network, where it runs through underground wiring – in some countries such as the USA or Brazil this route is aerial – together with the energy generated by other wind turbines. At this point, the electrical energy reaches the transformer substation to be raised to high voltage and facilitate its evacuation to the transmission or distribution network, being distributed to the end consumer thanks to the role of the high and medium voltage transmission lines located on the electrical towers.
What parts does a wind turbine consist of?
Now that we know the basic functioning of the onshore wind farm, it is time to zoom in on the wind turbine as an individual element, since its operation explains fundamentally how the energy generated by the wind is first converted into mechanical and then into electrical energy. To do this, let us first look at the parts that make up these modern contenders of Don Quixote.
- Blades: These are the visible protagonists that collect the wind energy and transform it into mechanical energy that drives the rotor. Their dimensions are gigantic, ranging from 40 to 165 metres in diameter depending on the model.
- Rotor: This element, similar to the rotor of a propeller aeroplane, is formed by the hub which is the connection point of the blades, joining them into a set of parts, and allowing the wind movement to be transmitted towards the interior of the nacelle.
- Nacelle: Far from being the housing of an aircraft cockpit, this is an enclosed part containing complex elements that are essential for converting the mechanical energy of rotation into electrical energy.
- The multiplier: This is the main element in charge of generating speed changes inside the machine to pass the mechanical energy to the generator.
- The generator: It is in charge of converting the kinetic energy of the wind into electrical energy.
- Tower: In addition to being a simple giant pole on which the structure of the blades and the nacelle is erected, this large cylinder contains fundamental elements for the correct distribution of electricity:
- Wiring: This runs inside the tower and transports the newly created electrical energy through the internal elements.
- Transformer: This element, which can be either inside or outside the tower itself, is responsible for raising the electricity to medium voltage to avoid losses.
- Medium voltage switchgear: This is a critical element similar to a domestic switch; it is a mechanical switching device (opening and closing) that allows the current generated to be transported or its flow to be interrupted both under normal circumstances and under specific abnormal conditions. Its fundamental function is to protect the transformer against possible problems.
- Foundation: This is the element that supports the weight of the entire wind turbine, anchoring it to the ground.
- Medium voltage network: The arteries that run through the entire installation and which allow the renewable electrical energy generated to be evacuated.