This set of Wind Energy Questions and Answers for Entrance exams focuses on “Wind Turbine Types and their Construction – 2”.
1. What is the main disadvantage of a horizontal axis wind turbine?
a) Easy operation at near ground winds
b) Does not self-start
c) Difficult operation at near ground winds
d) High starting torque
Explanation: The main disadvantage of any horizontal wind axis turbine is that it cannot be operated at near ground winds. This is due to the height of the tower and size of the blades. However, most of them are self-starting and do not have a high starting torque.
2. Which of the following materials are used to make a rotor blade of a wind turbine?
a) Glass fibre reinforced polyester
Explanation: Rotor blades are made using glass fibre reinforced polyester (GRP). It is a material made impregnating a matrix of fibre glass mats with a polyester. This polyester is hardened after impregnation.
3. Which of the following materials can be used to make a rotor blade of a wind turbine apart from glass fibre reinforced polyester (GRP)?
a) Silicon, germanium
b) Epoxy, carbon fibre
Explanation: Apart from GRP, epoxy and carbon fibre can be used to make rotor blades. Though carbon fibre is lighter and has higher material strength, it is expensive. Silicon and germanium are generally used in semiconductor industry.
4. Fatigue testing of rotor blades subject the blades to an oscillation in _______ direction.
Explanation: During fatigue testing of rotor blades, they are oscillated in the flapwise direction for millions of cycles. A typical flapwise test takes about three hours. Depending on the results of a fatigue test, we comment on whether a rotor blade can withstand high wind speeds or not.
5. Which of the following are the major parts of a wind turbine system?
a) Tower, rotor, water storage tank, air compressor
b) Tower, rotor and blades, air compressor, vacuum pump, electricity generator
c) Electricity generator, nacelle, rotor and blades, power converter, building
d) Tower, nacelle, rotor and blades, power converter, electricity generator
Explanation: Tower, nacelle, rotor and blades, power converter, electricity generator and wind shaft are the major parts of a wind turbine system. Water storage tank, air compressor and vacuum pump are not used in a wind turbine system.
6. What is the main function of tower in a wind turbine system?
a) Acts a support to all other components used in wind turbine system
b) Acts as an antenna for wireless radio communications
c) Acts as an electric pole for power transportation
d) Destabilizes the wind turbine system
Explanation: The main function of tower in a wind turbine system is to support the other components. It also stabilizes both, the rotor and blades which eventually convert wind energy to electrical energy via mechanical energy.
7. Which of the following towers is used for small wind turbines?
a) Hybrid tower
b) Guyed pole tower
c) Electric pole
d) Wooden pole
Explanation: The guyed pole tower is used for small wind turbines. It is a single vertical pole supported by guy cables from different sides. An electric pole is specifically used for electricity transportation. Wooden pole is a general purpose pole and can be used for a variety of applications.
8. What is a hybrid type tower?
a) Guyed tower
b) Guyed tower and wooden tower
c) Thin and tall lattice type guyed tower
d) Guyed tower and electric pole
Explanation: Unlike the guyed tower which uses a single pole, the hybrid tower uses a thin and tall lattice type tower that is supported by guy cables. It is a hybrid of both, lattice type and guyed type towers.
9. Nacelle is a kiosk that houses ______
a) a MOSFET
b) a diode
c) a wifi router
d) a yaw drive
Explanation: Nacelle is a big box that houses various components like power converter, yaw drive, gearbox, etc. MOSFETs and diodes are discrete electrical components used to realize various electrical and electronic circuits. Nacelle does not house a Wi-Fi router.
10. What is the main function of gearbox in a wind turbine system?
a) Multiples rotation speed to generate electricity
b) Divides rotation speed to generate electricity
c) Multiples rotation speed to consume wind energy
d) Divides rotation speed to consume wind energy
Explanation: The blades rotate slowly and this speed is not sufficient to generate electricity. So, the main function of a gearbox in a wind turbine system is to multiply the rotation speed to a sufficiently high level so as to generate electricity.
11. What is a pitch drive motor?
a) A motor that senses wind direction
b) A motor to control the angle of blades
c) A motor to ensure nacelle faces in the direction of the wind
d) A motor to rotate the blades
Explanation: A pitch drive motor is a motor used to control the angle of blades. Pitching is the process of rotating the angle of blades to cut maximum wind for harvesting energy.
12. What is a yaw drive?
a) A device used to support and stabilize other components
b) A device used to house various energy conversion components
c) A motor to ensure that nacelle faces the wind
d) A device used to track wind direction
Explanation: A yaw drive is a motor to ensure that the nacelle faces in the direction of the wind. This advocates maximum energy extraction from the incoming wind. It is controlled by a PLC that uses wind vane to track the net direction of wind.
13. What is the cost of a wind turbine per megawatt?
d) $1 million
Explanation: As of 2019, a wind turbine costs about $1 million per megawatt. Manufacturing the rotor blades consume most of the budget. Depending on the size and material used, the cost may vary. For example, carbon fibre is expensive when compared to glass fibre.
14. Wind turbines require regular maintenance.
Explanation: Wind turbines require regular maintenance to ensure reliability and maintain initial efficiency. They are generally serviced after 3-4 months of usage. In best case, they are available to generate energy 98% of the time.
15. Offshore wind turbines are not erected in water bodies.
Explanation: Offshore wind turbines are erected in water bodies like oceans or continental shelves. They are used to harvest energy from winds flowing above the water bodies. They generate about 40% more electricity as compared to other wind turbines on land.
Sanfoundry Global Education & Learning Series – Wind Energy.
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