The development of renewable energy sources is crucial in the fight against global warming and for the preservation of our planet’s natural resources. Wind energy, along with solar energy, has received a lot of attention recently. So, what is then a vertical axis wind turbine? As we know that wind turbines have been around for ages and have allowed humans to harness the power of the wind. The wind turbine may transform the kinetic energy of the wind into the mechanical energy of rotation, which can then be utilized to drive a load like a generator or a water pump for purposes like electricity production or water conveyance. Wind turbines can be classified as either a horizontal axis or a vertical axis depending on the orientation of the spinning axis. There are further different types of vertical axis wind turbine and horizontal-axis wind turbines.
Types of Vertical Axis Wind Turbine
Based on their mode of operation, The different types of vertical axis wind turbines are-
- Drag-type vertical axis wind turbine
- Lift-type vertical axis wind turbine
1. Drag-Type Vertical Axis Wind Turbine
The Savonius wind turbine, developed by Finnish engineer Savonius in 1922, is a prime example of a drag-type VAWT. The shape is made up of two semi-cylinders that are rotated 90 degrees with respect to each other and positioned on the outside of the axis. The wind turbine is simple to get going because of the difference in drag between the convex (low drag) and concave (high drag) sides. Efficiency, however, is low. Approximately 0.18 is the efficiency that has been found in the published works. The drag blade travels at a somewhat sluggish pace, typically not being able to compete with the wind’s velocity. Although drag-type VAWTs are not very efficient, they are useful for pumping water and getting lift-type VAWTs going because of their high torque at low speeds.
2. Lift-Type Vertical Axis Wind Turbine
Darrieus’s wind turbine, a representative of the lift-type VAWT, was developed in 1926 by a French engineer by the name of Darrieus. The rotation of the wind turbine is propelled by the lift created by a series of lift blades with air foil-like cross sections. Because of its curved blades, the typical Darrieus wind turbine is able to transform the centrifugal energy of the blades into tensile force. Because of its resemblance to an eggbeater, this type of wind turbine goes by that name as well. Straight-bladed Darrieus wind turbines are sometimes known as H-rotor wind turbines.
The efficiency of a Darrieus wind turbine is quite high (up to about 0.4) when the blades are spinning at a speed greater than the wind speed, but it is not easy to self-starting because the blades’ angle of attack (AOA) cannot be maintained in a proper range when stationary or at low speed, making it difficult to generate enough lift. In order to achieve self-starting, the lift blades are often configured with the drag blades.
A VAWT’s efficiency is often lower than a HAWT’s, but the two are theoretically extremely close. And since wind can enter a vertical axis wind turbine from any direction, the generator doesn’t have to be mounted on the tower above the main shaft, freeing more space. Due to its low center of gravity and other design features that make it capable of operating in unstable air flows, the structure is straightforward and can be easily deployed even in challenging locations like those found in mountains, cities, and the like. Thus, despite the fact that commercial operations of vertical axis wind turbines have not been particularly fruitful thus far, there is still room for their use. With this, you have learned about the two types of vertical axis wind turbine. After this, let’s also learn what is vertical axis wind turbine.
What is Vertical Axis Wind Turbine?
After learning about types of vertical axis wind turbine, let’s also learn what is vertical axis wind turbine & how it works, in detail. Among the many types of wind turbines, the Vertical Axis Wind Turbine is one of the most common types of turbines installed in homes for the goal of generating renewable energy. The vertically-moving rotor shaft of this turbine is attached to either two or three blades. Thus, the movement of the turbines is analogous to the spinning of coins. The generator of this turbine is located at the base of the tower, and the shaft is enclosed by the rotating blades.
The rotors in a vertical-axis wind turbine have a vertical orientation, and the blades rotate around a vertical shaft. So, they use the wind to create electricity. The wind turns a rotor that is mechanically coupled to an electrical generator. The blade, shaft, bearing, frame, and blade support are all elements of a wind turbine with a vertical axis.
An alternative method of producing electricity is the use of Vertical Axis Wind Turbines (VAWTs). Historically, their “yaw-less” design has limited them to serving just a narrow subset of the market for commercially accessible wind turbines. When compared with Horizontal Axis Wind Turbines (HAWTs), the current generation of VAWTs has a lower power coefficient and is therefore less efficient. However, recent studies have shown that these wind turbines may be even more suitable for use in wind farms. Many studies have been conducted on this specific wind turbine design. The absence of a blade-orientation mechanism and the presence of a mechanical component (the multiplier and the generator) on the ground make it easier to do maintenance. However, manufacturers have largely abandoned vertical-axis wind turbines (save for low-power applications) in favor of horizontal-axis wind turbines since they don’t require any training at start-up and are therefore less subject to significant mechanical limitations. Oddly enough, in contrast to the conventional windmill’s horizontal axis, the first constructions built to generate electricity had a vertical axis. They benefit from having the control members and the generator on the ground floor, where they are much more convenient to reach. Since the 1920s, several variations have been tried, with mixed results; nevertheless, two constructions have been successfully industrialized.
The Savonius rotor (named after its inventor) uses the same idea of “differential drag” found in anemometers to generate rotation: the faces of a hollow body exert varying amounts of force, resulting in the generation of a motor torque that causes the assembly to spin. The motor torque is increased as a result of the air flowing between the two halves of the cylinder.
The most common design for wind turbines is based on the work of Darrieus, who discovered that they produce a cyclical variation in their output (a French engineer who filed the patent in the early 1930s). Their principle of operation relies on the fact that a profile positioned in an airflow at varying angles is subjected to forces of varying direction and intensity, generating a motor torque that causes the device to rotate. Forcing of this sort is produced by combining the right displacement velocity of the profile with the wind velocity. This prevents the device’s rotation from the beginning on its own. When the wind turbine is not in motion, it must be propelled by a separate mechanism (use of the generator as a motor, for example).
Despite the fact that some big industrial projects have been completed, vertical-axis wind turbines are still underutilized and often disregarded. The energy sensor’s proximity to the ground does, in fact, compromise its performance due to the effects of turbulence and wind gradient. As a result of these restraints, they are also vulnerable to aeroelasticity issues.
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Block Diagram: Vertical Axis Wind Turbine
Illustrated above is a block diagram of a typical vertical-axis wind turbine. The power produced by this can be used for any load. As a load, the automated lighting system is utilized here. An LED, LDR circuit, battery, and gearbox round out this schematic of a Vertical Axis Wind Turbine (VAWT).
- Gear Box: In a wind turbine, the primary function of a gearbox is to increase the rotational speed of a low-speed shaft so that it may connect to a high-speed shaft carrying an electrical generator. Gears within the gearbox of a wind turbine are subjected to significant cyclic loading due to uneven wind loads that are stochastic within the environment.
- Rechargeable Battery: The wind turbine’s generator will store the electricity it produces in its rechargeable battery.
- Generator: The wind turbine generator transforms mechanical energy into electrical energy. If you’re familiar with generators used in conventional power systems, you might find these a little out of the ordinary.
- LDR Circuit: Light-dependent resistor (LDR) circuits are used to activate the light switch.
Vertical Axis Wind Turbine Working Principle
Once the wind starts turning the turbine, it will start producing electricity. In this setup, the tasty VAWT is employed in the lighting. This turbine, when set in motion, provides mechanical input to the generator, which subsequently converts this motion into electrical energy.
- The turbines are installed on the medians of major highways. The turbine’s wings are bent so that the wind may propel it in both directions along the two-lane road. Here, we make advantage of wind speed in several ways, depending on the situation.
- Gears are part of the Gearbox, which is coupled to a wind turbine with a vertical axis. The shaft of the electric generator is attached directly to this gearbox. The gearbox in this system will increase the turbine’s internal rotations and deliver them to the generator as a mechanical input once the wind starts blowing. Accordingly, the generator will use this input to produce the output as electrical energy, which will then be stored within the rechargeable battery.
- Using the vehicle speed and a turbine, power is produced and stored in the battery. The power reserve is put to use by the automatic lighting system. An LED and a light-dependent resistor (LDR) are also part of the LDR circuit, along with a resistor, transistor, battery, and LED (Light Emitting Diode).
- The emitter of the LED is linked to the ground while the collector terminal of the transistor is connected to the LED negative terminal. Here, the negative lead to the LDR while the positive leads directly to the power supply.
If you connect the LDR circuit straight to the battery, it will begin functioning as a light detector. Light-emitting diodes (LEDs) will consequently turn on once the ambient light level drops below a predetermined threshold. To turn lights on or off automatically, this LDR circuit can be used. At nightfall, when the Sun’s rays are weaker, an LDR will pick up on them and power an LED. With this, you are fully aware of vertical axis wind turbine working principle. After this, you should further learn about vertical axis wind turbine applications.
Vertical Axis Wind Turbine Applications
After learning about the vertical axis wind turbine working principle, it’s time to explore vertical axis wind turbine applications. The following are some examples of where a wind turbine with a vertical axis would be useful.
- Used for domestic wind power.
- Appropriate for use in private dwellings.
- These turbines can generate electricity in unsteady conditions, such as gusty wind and turbulence, making them useful in emergency situations.
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Advantages of Vertical Axis Wind Turbine
The advantages of vertical axis wind turbine are as follows:
- Creating these turbines is more cost-effective than making horizontal axis turbines.
- Compared to other types of wind turbines, this one is easier to install.
- They can be moved from one place to another.
- Low-velocity blades reduce the danger to bystanders and flying birds.
- They possess the ability to operate in harsh environments, such as those found in mountains, where winds can be highly unpredictable.
- They are a viable option in areas where buildings of greater height are forbidden.
- They work quietly, which is very important in residential areas.
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Disadvantages of Vertical Axis Wind Turbine
After learning about the advantages of vertical axis wind turbine, you should also try understanding the disadvantages of vertical axis wind turbine.
- Because not all of the blades generate torque simultaneously, vertical systems can only generate power at a certain rate. The other blades are merely propelled forward. When the blades are turning, they encounter more resistance.
- Although turbines can operate in strong winds, their performance may be hindered by issues like low beginning torque and dynamic stability if they aren’t in the conditions for which they were intended.
- The wind turbines are too low to the ground to take advantage of the stronger winds that are more common at higher elevations. These are more challenging to install if the installer prefers to put the structure on a tower. On the other hand, a vertical system is easier to install on a flat surface like the ground or the roof of a structure.
- At times, vibrations might be a problem and potentially amplify turbine noise output.
- Turbulence caused by the motion of air at ground level can heighten the sensation of vibration. Bearings might be damaged by this action. There may be an increase in maintenance expense as a result. The blades of previous generations were easily bent and cracked, which ultimately led to the turbine’s failure.
- Small devices mounted on tall buildings or other structures may be subjected to jostling pressures, which can cause lateral stress and necessitate regular maintenance and the use of stronger, more robust materials.
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