There are two basic types of wind turbines:
- Horizontal-axis turbines
- Vertical-axis turbines
However, there are certain design variations to these two types of wind turbines. In this blog post, we are going to take a look at all the different types of them.
Why Wind turbines? The wind is caused by uneven heating of the earth’s surface by the sun. Because the earth’s surface is made up of different types of land and water, it absorbs the sun’s heat at different rates. One example of this uneven heating is the daily wind cycle.
During the day, the air above the land heats up faster than air over water. Warm air over the land expands and rises, and heavier, cooler air rushes in to take its place, creating wind. At night, the winds are reversed because the air cools more rapidly over land than it does over water.
In the same way, the atmospheric winds that circle the earth are created because the land near the earth’s equator is hotter than the land near the North Pole and the South Pole.
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Types of Wind Turbines
Wind turbines are kind of mechanical machines that harness the energy in the wind to useful forms of energy. Today, wind energy is mainly used to generate electricity. Water-pumping windmills were once used throughout the United States and some still operate on farms and ranches, mainly to supply water for livestock.
It is a mechanical machine that converts kinetic energy of the fast moving winds into electrical energy. On the basis of axis of rotation of the blades, it is divided into two parts.1. Horizontal axis wind turbine (HAWT)2. Vertical axis wind turbine (VAWT)
1. Horizontal Axis Wind Turbine (HAWT)
It is a turbine in which the axis of rotation of rotor is parallel to the ground and also parallel to wind direction.They are further divided into two types(i) Upwind turbine(ii) Downwind turbine
Why Wind Turbines have 3 blades? These Horizontal Axis Wind Turbine FAQS will Amaze You!
(i) Upwind Turbine
The turbine in which the rotor faces the wind first are called upwind turbine.
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- Today most of the HAWT is manufactured with this design.
- This turbine must be inflexible and placed at some distance from the tower.
- The basic advantage of this turbine is that, it is capable of avoiding wind shade behind the tower.
- It requires yaw mechanism, so that its rotor always faces the wind.
(ii) Downwind Turbine
The turbine in which the rotor is present at the downside of the tower is called downwind turbine. In these types of wind turbines, the wind first faces the tower and after that it faces the rotor blades.
- Yaw mechanism is absent in this turbine. The rotors and nacelles are designed in such a way that the nacelle allows the wind to flow in a controlled manner.
- It receives some fluctuation in wind power because here the rotor passes through the wind shade of the tower. In other words the rotor is present after nacelle of the tower and this create fluctuation in the wind power.
2. Vertical Axis Wind Turbine (VAWT)
It is a turbine in which the axis of rotation of the rotor is perpendicular to the ground and also perpendicular to the wind direction.
- It can operates in low wind situation.
- It is easier to build and transport.
- These types of Wind turbines are mounted close to the ground and are capable of handling turbulence in far better way as compared with the HAWT.
- Because of its less efficiency, it is used only for the private purpose.
(i) Darrieus Turbine
Darrieus turbine is type of HAWT. It was first discovered and patented in 1931 by French aeronautical engineer, Georges Jean Marie Darrieus. It is also known as egg beater turbine because of its egg beater shaped rotor blades.
- It consists of vertically oriented blades which are mounted on a vertical rotor. It is not a self-starting turbine and hence a small powered motor is required to start its rotation.
- First the Darrieus turbine is rotated by using a small powered motor. Once it attains sufficient speed, the wind flowing across its blades generates lift forces and this lift forces provides the necessary torque for the rotation. As the rotor rotates, it also rotates the generator and electricity is produced.
(ii) Giromill Turbine:
It is similar to the Darrieus turbine but the difference is that, it has H-shaped rotor. It works on the same principle of Darrieus turbine.
- This turbine has H- shaped rotor. Here Darrieus design which has egg beater shaped rotor blades are replaced by straight vertical blades attached with central tower with horizontal supports. It may consists of 2-3 rotor blades.
- Giromill turbine is cheap and easy to build as compared with Darrieus turbine. It is less efficient turbine and requires strong wind to start. Same as darrieus types of wind turbines, it is also not self- starting and requires small powered motor to start. It is capable of working in turbulent wind conditions.
A Quick Glance at On-Land, Off-shore and High Altitude Wind Energy
(iii) Savonius Turbine
Savonius turbine is HAWT.It was first discovered in 1922 by a Finnish Engineer Sigurd Johannes Savonius. It is one of the simplest turbine among all known turbines.
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- It is a drag-type device and consists of two or three scoops. If we look it from above than it looks ‘S’ shape in cross section. The scoops of these turbines have curvature shape and because of that, it experiences less drag when it moves against the wind instead of moving with the wind.
- Since it is a drag-type machine, it is capable of extracting very less amount of wind power as compared with other similar sized lift-type turbines.
These are the types of wind turbines. How orizontal axis wind turbines ?