Due to the issue of climate change and the clamour for green and cleaner energy, a lot of countries are exploring alternative sources of energy apart from fossil fuel. One of the sources that is becoming increasingly popular in Norway is wind. The wind is harnessed through wind turbines to generate electricity.
Oftentimes, people use the term windmill as a synonym for wind turbine; however, although they have some similarities, they are not entirely the same. While windmills are ancient technology that were employed to harness the wind for milling all types of grain, Wind turbines are more recent technology used specifically to generate electricity. You can read this article for more information on these two infrastructures.
In this article however, our focus is on understanding how wind turbines work. We will explore how these towering structures employ the forces of the wind to generate electricity and how they contribute to the wind energy revolution all over the world.
Table of Contents
The Basics of Wind Energy
When the surface of the earth is heated albeit unevenly, the result is what we know as wind. Due to the fact that the surface of the earth comprises of different types of water and land, the rate at which the earth absorbs the heat of the sun differs from place to place.
So when we talk of wind energy, it just basically refers to the kinetic energy that is present when air masses move or are stirred. This natural resource is a renewable source of energy that has smaller footprints on the environment; its effect being less than that of fossil fuels and some other sources of energy. For example, a wind turbine does not pass out emission that can contaminate the water or air neither do they need to be cooled with water.
With proper harnessing of this alternative, using fossil fuels to generate electricity is greatly reduced which in turn reduces the extent of air pollution and emissions of carbon dioxide. Additionally, the physical structure also has smaller footprints than other infrastructures used in the generation of electricity.
Ideally, a group of these structures which are commonly referred to as wind farms are sited on mountain ridges, open land or offshore (in lakes or on the ocean). These locations reduce whatever negative impact these structures may have on the environment.
Anatomy of a Wind Turbine
This infrastructure has 5 basic or major parts and they are as follows:-the foundation, the tower, rotor and hub, Nacelle and generator. There are other smaller and minor parts but we will focus on the main parts:-
In onshore installations, the foundation is buried in the ground; it is a heavy and solid mass of concrete that is engineered to support the whole structure and withstand the forces of the element that will act on it.
In offshore installations, the foundation is laid underwater and cannot be seen on the surface. However, if the installation is far away from sea, the base will float but still have enough mass to sustain and carry the weight of the structure and the forces of the elements when exerted on it
These days, the towers of wind turbines are made of round steel tubes and they go from the foundation all the way to the nacelle. This allows the rotor to be exposed to high speed winds because the higher the turbine, the more access they have to high wind speeds that cannot be gotten at ground level.
The reason why the tower is made of tubular steel is so that it can carry and sustain the weight of the hub, nacelle and blades. One basic requirement for this part of the structure is that it must be the same height as the diameter of the circle that the blades form when they spin. This part of the structure is quite heavy which is why the construction company assembles it and other major parts at the installation site with heavy duty equipment.
Rotor and Hub
The rotor is the part of the turbine that rotates and it is made up of 3 blades. These 3 blades are connected by a central part known as the hub. Although 3-blade turbines are the most common, it is not compulsory that the structure must have 3 blades. However, a 3-blade rotor has some advantages with the major one being optimum efficiency.
These blades are not sturdy in themselves but they are hollow and constructed with composite material that is lightweight and strong. This construction makes them lighter and sturdier and also bigger which enable them to generate more power.
For aerodynamic purposes, the blades mimic the shape of the wings of an aeroplane. They not flat but have a twist between the tip and root. These blades can rotate as much as 90° around their axis and this movement is known as the pitch.
The hub’s function is to secure the blades while letting them rotate in sync with the other parts of the turbine.
This is the part that carries the mechanical parts also referred to as the drivetrain that are needed for the conversion of the rotation of the blades to energy. Looking at it from afar, one may assume that this is a small section of the entire structure compared to the blades and tower.
However, this part sometimes weight more than 100,000 pounds (50 tons) and has to be transported with special equipment. A normal flatbed trailer cannot handle the weight hence the need for supersize weight-carrying equipment.
This is the part that ultimately converts the power of the wind to energy that produces electricity through the process of electromagnetic induction.
Understanding the Conversion Process
Like we have seen from our exploration of the major part of this infrastructure, most turbines have 3 blades and when they are hit by wind, the start to rotate. This rotation in turn causes a disk in the turbine to rotate; note that the blades are usually in front of the turbine.
The physical force generated through the rotation of the blades is transferred to the generator; this force generated is known as aerodynamic force. It is this force that converts the energy to electricity.
There are two factors that affect this process and they are how the wind hits the blades and the speed of the blades’ rotation:-
How the Wind Hits the Blade
For this process to be effective, the wind has to hit the blades directly. To ensure that this happens, small sensors are attached to the turbine which adjusts its direction and positions the blades to be hit by the wind directly. This solves the problem of the blades not receiving the force of the wind directly.
The Speed of the Blades’ Rotation
The second issue is the speed at which the blades rotate; it must not be too fast. In order to ensure that the blades do not rotate too fast, a form of resistance is added to it. This slows down the blades and allows them to generate more power.
In order to maximize the quantity of power harnesses, an amplifier is placed in the middle of the two links. This amplifier has gears of different sizes which help to increase the rotations before the energy gets to the generator.
There are 2 reasons why the blade rotating too quickly is not desirable. The first reason is that the noise made in the process of the fast rotation is usually intense and goes a long way. So the speed is reduced for the sake of people within earshot of this noise.
Secondly, if the rotation is too fast, it can be dangerous as it can spin the turbine to pieces.
You can visit https://bestestrøm.no/slik-lager-vindmøller-strøm/ for more information on this conversion process.
Types of Wind Turbines
There are two main types of wind turbines and they are Horizontal axis and Vertical axis.
These are the types of turbines that come to mind for a lot of people when we talk about these strictures. They oftentimes have 3 blades and operate in an upwind motion. This means that the turbine pivots at the top of the tower in order for the blades to lean in the direction of the wind.
These types are Omni-directional which means that they face all directions and do not have to be adjusted in the direction of the wind to be effective. These types come in different varieties with the most popular being the one made by a French inventor named Darrieus. This particular one comes in an egg beater style and is named after its inventor.
These structures are often categorized by where they are installed and these are onshore and offshore turbines. The onshore ones are the ones that are installed far out in the sea or ocean while the off shore ones also known land-based are the ones that are installed in open lands, mountain ridges or anywhere else apart from water bodies.
Wind turbines represent cleaner and safer source of energy which provides electricity. Many countries are considering ways of harnessing this alternative in a bid to combat climate change and help preserve our eco-system.
Norway is one of the leading nations in the wind energy industry and they are still working on developing and deploying more turbines both onshore and offshore. This therefore means that her citizens can look forward to enjoying dividends from this cleaner source of energy more in the coming years.