WIND TURBINES BLADES

The main curiosities of wind turbines and its blades revealed

#R&D #wind power #renewable energy

Have you ever wondered how a wind turbine tower can support so much weight? Or why they are all orientated in the same direction? This is the nature of wind turbines, the giants of renewable energy.

Wind farm in Serra do Burgo (Orense, Spain).#RRSSWind farm in Serra do Burgo (Orense, Spain).

When travelling by road a little way away from cities you must have come across a wind energy farm. It is curious to see how wind turbines appear to work in sync. It's like watching a football team, with all of the members placed strategically and turning in the same direction.

It may seem like a coincidence, but it is not: All of the details of the operation are governed by well-studied and well-defined research. Find out more about them!

 How is wind transformed into energy?

Why are the most commonly used wind turbines those with three blades?
Throughout history, there have been many types of turbines or machines that were used to take advantage of the kinetic energy produced by the wind. Of all of these, the most used and widespread in our days — and likewise chosen by Iberdrola — is one which has three blades moving with respect to a horizontal axis. This is the most efficient option from the technical point of view: having fewer blades leads to better balance.

Why do they always face in the same direction?
Like a field of sunflowers, wind turbines are always oriented in the same direction so that, instead of following the sun, they may follow the wind and harness its potential energy. This is achieved thanks to a weather vane that they all have on top of the nacelle. This weather vane indicates to the control whether the rotor is correctly positioned against the wind.

How does the wind manage to move the blades?
Sometimes it is hard to imagine how the blades of a wind turbine, laden with such size and weight, are able to be moved by a wind with normal characteristics. The reason is due to its shape, the so-called aerodynamic profile: When the wind blows perpendicular to them, a lift force is generated that causes the movement.

How does the tower hold up so much weight?
A wind turbine tower is the structural component onto which the rotor and the nacelle are fixed. Moreover, it supports the entire force of the wind. The key is in its design and composition, as it must be able to bear the weight of up to 15 adult elephants.

Do you know how the blades of a wind turbine are made?#RRSSDo you know how the blades of a wind turbine are made?

 SEE INFOGRAPHIC: Do you know how the blades of a wind turbine are made? [PDF]

Find out about the manufacturing phases of the blades

1. Manufacturing of the beam: this is the inner part of the blade and is composed of materials formed of fibreglass and carbon pre-coated with epoxy resin - a thermostable polymer that hardens when mixed with a catalyst agent.

2. Manufacturing of the shells: they cover the girders and are made of fibreglass. In addition, they are covered by a layer of paint, which provides protection.

3. Assembly and curing: after obtaining the two shells, the next step is to bond the girder between the two shells and have them pass through an oven to form a single firm and strong structure.

4. Finishing: once the leading and trailing edges of the blade are finished, the structure undergoes a new inspection prior to the blade being moved to its destination wind farm.

5. Transportation and installation: the blades of a wind turbine are very heavy, massive structures. The blades of the Wikinger offshore wind farm, for example, have a lenght of 67.5 meters. The require specialised forms of transport that are capable of loading these structures and carrying them to their destination. At the destination, an experienced team of people assembles the blades and the rotor on the nacelle.

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What materials are used?
Most blades are made with fibreglass-reinforced polyester or epoxy. Carbon fibre or aramid (Kevlar) is also used as reinforcement material. Nowadays, the possible use of wood compounds, such as wood-epoxy or wood-fibre-epoxy, is being investigated.

How is maintenance carried out?
There are two types of maintenance: preventative and corrective. The former consists of periodic inspections to determine the condition of the blades and identify any damage. These checks are made using different techniques – from the ground, with high-precision telephoto lenses, climbing the blades with ropes, cranes or lifting platforms and remotely, by using drones. Corrective maintenance meanwhile consists of the repair or reconstruction of the blades and nacelles to correct any damage that appears, both on the surface and within the structure.

How are the blades repaired?
Wind turbine blades can suffer cracks, damage caused by the impact of lightning and birds or openings in the leading or trailing edge, among other damage. The repair tasks are performed by workers at height, who hang from the blades with ropes or are lifted up to them on suspended platforms. At present, alternative repair and cleaning systems, such as drones, are being looked into to prevent operators from having to climb up to the turbines.

How does one decide where to install a wind farm?
In order to analyse the viability of a wind farm project, an assessment must be carried out on how much the wind farm would produce during its useful lifetime. To achieve this, some of the main criteria are the wind characteristics and the air pressure and temperature. The measurement campaign allows data extracted from four or five meteorological towers to be translated, judging by several years (2-3) and at different heights of 50 or 60 meters.

 Supercomputing