Wind Energy Questions and Answers – Wind Turbine Types and their Construction – 1

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This set of Wind Energy Multiple Choice Questions & Answers (MCQs) focuses on “Wind Turbine Types and their Construction – 1”.

1. Wind turbines convert wind energy to ________
a) mechanical energy
b) electrical energy
c) heat energy
d) solar energy

Explanation: Wind turbines convert wind energy to mechanical energy. This mechanical energy is then converted to electrical energy using an electric generator. They neither convert wind energy to heat energy nor to solar energy.

2. Which of the following components of a wind turbine system is arranged in the order in which energy is being converted?
a) Blades – rotor – electric generator – shaft
b) Blades – rotor – shaft – electric generator
c) Shaft – blades – rotor – electric generator
d) Electric generator – blades – rotor — shaft

Explanation: A wind turbine system first converts wind energy to mechanical energy and then to electrical energy using an electric generator. The correct order is blades – rotor – shaft – electric generator.

3. Which of the following are commonly used commercial wind turbines?
a) Vertical and DFIG
b) Horizontal and SCIG
c) Horizontal and vertical
d) DFIG and SCIG

Explanation: Horizontal axis wind turbines (HAWT) or horizontal and vertical axis wind turbines (VAWT) or vertical are commonly used commercial wind turbines. DFIG, SCIG and PMSG are commercially used power generators for wind energy.
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4. What are horizontal wind turbines?
a) Wind turbines are rotate about an axis perpendicular to the plane of ground
b) Wind turbines are rotate about an axis diagonal to the plane of ground
c) Wind turbines are rotate about an axis 30 degrees to the plane of ground
d) Wind turbines are rotate about an axis parallel to the plane of wind streamlines

Explanation: Horizontal wind turbines are made up of blades that rotate about an axis parallel to the plane of wind streamlines. Hence, they are also called as Horizontal Axis Wind Turbines (HAWT). They are the most popularly used wind turbines for commercial wind energy harvesting applications.

5. Which of the following is an advantage of a horizontal axis wind turbine?
a) Blades are to the side of turbine’s center of gravity
b) Blades are parallel to the vertical axis passing through the turbine’s center of gravity
c) Blades are parallel to the horizontal axis passing through the turbine’s center of gravity
d) Blades are positioned perpendicular to the plane of the ground

Explanation: In a horizontal axis wind turbine (HAWT), the blades are positioned to the side of the turbine’s center of gravity. This provides stability to the entire setup. Blades rotate to an axis parallel to the plane of ground.

6. What is an upwind turbine?
a) Rotor of the turbine is behind the unit
b) Rotor of the turbine is in front of the unit
c) Rotor is positioned at the bottom of the tower
d) Rotor is positioned at the center of the tower

Explanation: An upwind turbine is a type of wind turbine where the rotor is positioned in front of the unit. The position is similar to that of propellers used in airplanes. Most of the wind turbines used commercially are upwind turbines.

7. What is the main advantage of an upwind turbine?
d) Manufacturing

Explanation: Tower shadow effect occurs when the tower acts as an obstruction between the blades and the wind. In an upwind turbine, both rotor and blades are attached in front of tower. Thus, the tower shadow effect reduces considerably.

8. What is the main disadvantage of an upwind turbine?
c) A rotor that needs to be placed at some distance from the tower
d) An inflexible rotor that needs to be placed close to the tower

Explanation: The main disadvantage of any upwind turbine is the requirement of placing the rotor at some distance from the tower. This setup prevents problems with a blade strike. They also require a yaw mechanism to ensure that the rotor faces the wind continuously.

9. What is a downwind turbine?
a) Rotor is positioned at the three-quarters of the height of the tower
b) Rotor of the turbine is in front of the unit
c) Rotor is positioned at the bottom of the tower
d) Rotor of the turbine is behind the unit

Explanation: A downwind turbine is a type of wind turbine where the rotor is positioned behind the tower. The nacelle used is typically designed to seek the wind.

10. What is the main advantage of any downwind turbine?
c) Position of the rotor

Explanation: The main advantage of a downward turbine is that the rotor blades can be made flexible. This reduces the cost of manufacturing and relieves stress on the tower at high wind speeds.

11. What is the main disadvantage of a downward wind turbine?
d) Bending of blades at high wind speeds

Explanation: Since the rotor of a downward wind turbine is placed behind the tower, it experiences an increased tower shadow effect. Flexible rotor blades enable bending at high wind speeds. This is its main advantage.

12. What is a vertical wind turbine?
a) Wind turbines are rotate about an axis perpendicular to the plane of wind streamlines
b) Wind turbines are rotate about an axis diagonal to the plane of ground
c) Wind turbines are rotate about an axis 30 degrees to the plane of ground
d) Wind turbines are rotate about an axis parallel to the plane of ground

Explanation: Vertical wind turbines are made up of blades that rotate about an axis perpendicular to the plane of wind streamlines. Hence, they are also called as Vertical Axis Wind Turbines (HAWT). Most of its main components is near the ground unlike a HAWT.

13. What are the types of VAWT?
a) Lift, horizontal
b) Horizontal, vertical
c) Drag, lift
d) Urban wind turbines

Explanation: There are two types of VAWT – drag and lift. Horizontal and vertical wind turbines are classified based on their axis of rotation. Urban wind turbines are specially designed turbines to harvest wind energy in cities and other urban areas.

14. What is the main advantage of a vertical axis wind turbine?
a) Directional and sensitive to wind turbulence
b) Not directional and sensitive to wind turbulence
c) Directional and insensitive to wind turbulence
d) Not directional and insensitive to wind turbulence

Explanation: VAWTs are made up of blades that rotate about an axis perpendicular to the plane of streamlines. Hence, their main advantage is that they are insensitive to wind turbulences and are not directional.

15. What is the main disadvantage of a vertical axis wind turbine?
a) Not directional and insensitive to wind turbulence
b) More drag than HAWTs
c) Less drag than HAWTs
d) High starting torque

Explanation: Vertical wind axis turbines cause more drag than HAWTs as their blades are constantly spinning back into the wind. Their main advantage is that they are not directional and insensitive to wind turbulence. Also, they have a low starting torque and may require an external source to start turning.

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