Wind turbine blades: design, curiosities and more

Curiosities, construction and design of wind turbine blades

Have you ever wondered how a wind turbine tower can support so much weight? Or why they all face the same direction? That’s wind turbine blades, the giants of renewable energy.
Surely when traveling on the road and a little away from the city you have come across a wind farm. It’s curious to see how the wind turbines blades seem to work in sync. It’s like watching a soccer team, with all its member strategically placed and rotating in the same direction.
It may seem a coincidence, but it’s not: all the details of their operation are governed by well-studied and well-defined reasons. Let’s discover them.

How do wind turbines work?

Wind turbines blades produce electricity by harnessing the natural energy of the wind to drive a generator. Wind is a clean, sustainable source of energy that never runs out, and the transformation of its kinetic energy into electrical energy produces no emissions.

Wind turbines blades are the natural evolution of windmills and today are high-tech devices. Most turbines blades generate electricity as soon as the wind reaches a speed of between 3 and 4 meters per second, generate a maximum power of 15 meters per second and are disconnected to prevent damage when there are storms with winds blowing at average speeds of over 25 meters per second during a temporary interval of 10 minutes.

Why are three-bladed wind turbines the most commonly used?

Throughout history, many types of turbines or machines have been used to harness the kinetic energy produced by the wind. Of all of them, the most widely used and widespread today is the one with three blades moving along a horizontal axis. This is the most efficient option from the technical point of view: the fewer the blades, the better the balance.

Why do wind turbines blades always face the same direction?

Like a field of sunflowers, the wind turbines are always oriented in the same direction so that, instead of following the sun, they follow the wind and make the most of its potential energy. This is achieved by means of a wind vane on top of the nacelle, which indicates to the control system whether the rotor is correctly positioned in the direction of the wind.
Wind turbine blades: design, curiosities and more - Crosby Airpes

Characteristics of a wind turbine

Multiplication effect

The rotor (a set of three blades mounted on the hub) turns a slow shaft connected to a gearbox that increases the rotational speed from about 13 to about 1,500 revolutions per minute.

Automatic guidance

The wind turbine blade automatically orients itself to take maximum advantage of the kinetic energy of the wind, based on the data recorded by the wind vane and anemometer incorporated in the upper part. The nacelle rotates on a crown located at the end of the tower.

Generation of power

The gearbox, through the fast shaft, transfers its energy to the coupled generator, which produces electricity.

Blade rotation speed

The wind rotates the blades, which start to move at wind speeds of about 3.5 m/s and provide maximum power at about 11 m/s. In very strong winds (25 m/s) the blades are placed in flag and the wind turbine is slowed down to avoid excessive stresses.

Evacuation of the power

The energy generated is conducted inside the tower to the base and, from there, through a subway line to the substation, where its voltage is raised to inject it into the electrical grid and distribute it to the consumption points.

Monitoring of the system

All critical wind turbine blades functions are monitored and supervised from the substation and the control center to detect and resolve any incident.

Other wind turbines FAQ’s and curiosities

Some of the most frequently asked questions around wind turbine blade design and wind farms are the following.

How does the wind move the blades?

It is sometimes difficult to imagine how the blades of wind turbines, with such size and weight, manage to move in normal wind conditions. The reason lies in their shape, the so-called airfoil: when the wind hits them perpendicularly, it generates a lift force that causes them to move.

How does the tower support so much weight?

The tower of a wind turbine is the structural component on which the rotor and the nacelle are fixed. It also supports the full force of the wind. The key is in its design and composition, as it has to be able to support the weight of up to 15 adult elephants.

Wind turbine blade material

Most blades are made of polyester or glass fiber reinforced epoxy. Carbon fiber or aramids (Kevlar) are also used as reinforcing material. Nowadays, the possibility of using wood composites, such as wood-epoxy or wood-fiber-epoxy, is being investigated.

How is maintenance carried out?

There are two types of maintenance: preventive and corrective. The first consists of periodic inspections to determine the condition of the blades and to find possible flaws. These checks are carried out using different techniques: from the ground, with high-precision telephoto lenses; by climbing the blades with ropes, cranes or lifting platforms; and remotely, using remote-controlled drones. Corrective maintenance consists of repairing or rebuilding the blades and nacelles to repair any damage that appears, both on the surface and in their structure.

How are blades repaired?

Wind turbine blades can suffer cracks, damage caused by lightning and bird strikes, or openings in the leading or trailing edge, among other damages. Repairs are carried out by workers at height, who hang from the blades with ropes or are lifted to the blades by suspended platforms. Alternative repair and cleaning systems, such as drones, are currently being studied to avoid the need for operators to climb the turbines.

How do you decide where to install a wind farm?

In order to analyze the feasibility of a wind energy project, it is necessary to make an assessment of how much the wind farm will produce during its useful life. To achieve this, one of the main estimates is the wind characteristics, as well as air pressure and temperature. The measurement campaign allows to transfer the data extracted from four or five meteorological towers, measuring several years (2-3) and at different heights, 50 or 60 meters.

Crosby Airpes is your equipment supplier for the installation and maintenance of your wind farms.

We design and manufacture tools for special lifting, installation and transport tasks for the wind energy industry. We develop customized solutions adapted to the needs of your project.