It is been explained in my previous article that different types of wind turbines use the wind’s kinetic energy to generate power. In fact, wind energy is known as the cleanest way to generate mechanical and/or electrical power. The obtained energy can be classified based on how the wind energy is harvested; land wind and offshore wind. Read the article below to learn more about this!
Read more: Understanding wind turbine
Today you’ll get to the different types of wind turbines and their advantages and disadvantages in their various applications.
Types of wind turbine
Below are the various types of wind turbines used for power generation.
Horizontal axis wind turbines (HAWTs)
The horizontal axis types of wind turbines are the most used turbine today, even though some limitations occur. The blades propeller-style are designed to rotate around a horizontal axis. Its components include rotor blades that are connected to a shaft which is further connected to a generator that produces electrical energy. These blades look like an aircraft propeller mounted on top of a tower.
In these types of wind turbines, a wind sensor is mounted on a yawing mechanism (called nacelle) so that the turbine can properly align with the wind direction. Therefore, more effective distribution of wind energy is forced on the rotors.
The structure of horizontal-axis wind turbines needs to be strong enough to support the weight of the device components. Some of these components include rotor blades, gearbox, generator, etc. Also, the base must be able to withstand the strong wind that is blown. Although, the nacelle contains a breaking element that helps to immediately stop the blades when heavy or uncontrolled wind occurs.
Among all types of turbines, the horizontal axis wind turbine has higher efficiency and higher power generation. This turbine is often available in two types namely; up-wind and down-wind turbines.
Read more: Things you need to know about turbine
In an Up-wind HAWTs turbine, the wind reaches the rotors before the tower, that is, it faces the wind. This is why the rotors do not suffer from the wind shade behind the tower, resulting in more efficient operation. Also, the system is less susceptible to wear and tear. However, the yawing mechanism adds to the weight of the structure.
In most designs, up-wind rotors are not flexible so that they would not bend or collide with the tower. This often occurs when the speed of wind is high. To further avoid this, the rotor is placed at some distance from the tower. Because of this, the manufacturing difficulties of these types of wind turbines are high. The inflexibility of the rotor blades equals requiring heavier material for blade construction.
These types of horizontal axis wind turbines are less common, but their design looks pretty much alike to the previously explained type. The only difference is the location of the rotor, which is downstream of the tower. In the down-wind types, the wind strikes the tower before it reaches the blades. The design allows more flexibility in the rotor blades, making lighter materials to be used. The benefits of the down-wind include lighter structural weight and better structural dynamics of the tower by taking some of the load off the tower to the blades during their operation.
The down-wind horizontal axis types of wind turbines do not need any yawing mechanism. This is because the rotor and casing are designed in a way the casing would follow the wind direction. Because the rotor is located downstream of the tower, it suffers wind shade, which fluctuates the amount of power generated. Wind shade may also cause fatigue to the system counterparts.
Read more: Different types of turbine
Advantages and disadvantages of horizontal axis wind turbines HAWTs
Below are the benefits of horizontal-axis wind turbines.
- Due to the tall tower base, stronger wind can be accessible.
- Because the blades move perpendicular to the wind, power is received through the whole rotation. This results in higher efficiency.
Despite the good advantages of horizontal axis wind turbines, some limitations still occur. Below are the disadvantages of HAWTs.
- Heavy components such as blades, gearboxes, and generators, are required due to massive tower construction.
- Its components are being lifted into position.
- The height of these types of wind turbines makes them obtrusively visible across large areas. This disrupts the appearance of the landscape and can create local opposition in some cases.
- The down-wind variant suffers from fatigue and structural failure caused by turbulence when a blade passes through the tower’s wind shadow. This is why the majority of HAWTs use an up-wind design as the rotor faces the wind in front of the tower.
- An additional yaw control mechanism is required to turn the blades towards the wind.
- Breaking is required to stop the turbine from spinning in high winds. This will stop the system from high wind destruction.
- Cyclic stresses and vibrations are caused when the turbine tries to turn to face the wind.
Vertical axis wind turbines (VAWT)
In vertical axis types of wind turbines, the rotors rotate a shaft that is installed vertically. This design allows less sensitivity regarding wind direction, which makes it perfect on farms where the direction frequently changes. In another word, no matter the direction the wind blows, the blades would still move and rotate the shaft to produce power.
the vertical axis types of wind turbines have their generator near the ground. Therefore, extra weight is relieved on the rotor and makes the design less complex. This also makes maintenance easier compared to horizontal axis wind turbines. Although, vertical-axis wind turbines have fewer efficiencies than HAWTs because of the significant amount of air drag on the rotors. Less power output is another factor because the wind speed and its flow at a distance from the ground are higher and smoother than at ground level.
Drag-based, or Savonius turbine – they generally have rotors with solid vanes that rotate about a vertical axis.
Lift-based, or Darrieus turbines – have a tall, vertical airfoil style, although some appear to have an eggbeater shape. A wind spire is a type of lift-based turbine even though it’s still undergoing independent testing.
Advantages and disadvantages of vertical axis wind turbines (VAWTs)
Below are the advantages of vertical-axis wind turbines.
- Power is produced in any wind direction.
- A strong supporting tower is not required since most of its components are placed on the ground.
- Low production cost compared to horizontal axis wind turbines.
- Yaw drive and pitch mechanism are eliminated since there is no need for the turbine to the wind direction.
- Easy installation
- Low maintenance costs
- Easy to transport from one place to another.
- Suitable for areas with extreme weather conditions.
- They are installed in urban areas.
- Low risk for humans and birds because blades move at relatively low speeds.
- Efficiency is low because only one blade works at a time.
- The initial push to start is required so that the blades can start spinning.
- Vertical axis wind turbines are very less efficient because of the additional drag created when the blades rotate.
- Vibration is relatively high because the airflow near the ground creates turbulent flow.
- This vibration increases bearing wear which may result in to increase in maintenance cost.
- VAWTs create noise pollution.
Different types of wind turbines are suitable for a reason or more. The horizontal axis types are commonly used due to their effectiveness and a vertical axis wind turbine can be used in any geographical area due to its portability. That is all for this article, types of wind turbines and their advantages and disadvantages.
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