This set of Energy Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Wind Turbine Operation”.
1. What is the inherent weakness of all wind machines?
a) Their efficiencies
b) Requires powerful winds to make fan rotate
c) Their dependency on the wind speed
d) Cannot be easily repaired
View Answer
Explanation: An inherent weakness of all wind machines are the strong dependence of the power produced on wheel diameter and wind speed, being proportional to turbine wheel area, i.e. to the square of its diameter and to the cube of wind velocity.
2. Why severe fluctuations in power are always undesirable in windmill?
a) Because they pose power oscillations problems
b) Damage of parts due to fluctuations
c) The efficiency of the plant will be reduced
d) Results in damage to the whole plant
View Answer
Explanation: Severe fluctuations in power are always undesirable, because they pose power oscillation problems on the grid and severe strains on the windmill hardware. From an economic point of view, a windmill is designed to produce a rated power output corresponding to maximum, or near maximum, prevailing wind velocity at a given site would generate low powers, with full capacity of the turbine and electric generator unused much of time.
3. Maintenance of constant output at all wind speeds above rating is called _________
a) Numeric rating scale
b) Tenancy
c) Flat Rating
d) TRP
View Answer
Explanation: More cost-effective design to a wind mill to produce rated power at less than the maximum prevailing wind velocity, using a smaller turbine and generator and to maintain a constant output at all wind speeds above rating. This is called flat rating.
4. A wind turbine designed too to come into operation at a minimum wind speed is called _________
a) Cut in velocity
b) Windward
c) Cut out velocity
d) Upwind location
View Answer
Explanation: Due to several loss in efficiency and power at low wind velocities, a wind turbine is designed to come into operation at a minimum wind speed called the cut in velocity. Thus the wind turbine operates with variable load over a narrow range between cut in.
5. Why is wind turbine designed to stop operation at cut out velocity?
a) To protect wheel against damage
b) To make a quick stop in emergencies
c) To improve the efficiency
d) In order to adjust the blades to wind direction
View Answer
Explanation: To protect the turbine wheel against damage at very high wind velocities, it is designed to stop operation (such as feathering the blades) at cut out velocity. Thus the wind turbine operates at rated velocities and at constant power between the rated and cut out velocities and ceases the operation above the cut out velocity.
6. The fraction of time during a given period that the turbine is actually on line is called?
a) Availability factor
b) Flat rating
c) Cut in velocity
d) Cut out velocity
View Answer
Explanation: The availability factor is defined as the fraction of time during a given period that the turbine is actually on line. The actual wind velocity at the propeller hub that determines the turbine power is usually higher.
7. Over load factor is also called as _____________
a) availability factor
b) plant operating factor
c) flat rating
d) cut out velocity
View Answer
Explanation: The overall load factor, also called the plant operating factor and the plant capacity factor is the ratio of the total energy generated during a given period of time to the total rated generation capacity during the same period.
8. How many of windmills are there?
a) 2
b) 3
c) 4
d) 5
View Answer
Explanation: There are two classes of windmill, horizontal axis and vertical axis. The vertical axis design was popular during the early development of the windmill. However, its inefficiency of operation let to the development of numerous horizontal axis designs.
9. Name the windmill which has four blades mounted on a central post.
a) Post mill
b) Smock mill
c) Tower mill
d) Fan mill
View Answer
Explanation: The post mill has blades mounted on a central post. The horizontal shaft of the blade is connected to a large break wheel. The break wheel interacts with a gear system, called the wallower, which rotates a central, vertical shaft. This motion can then be used to power water pumping or grain grinding activities.
10. Name the type of windmill which consists of a sloping, horizontally weather boarded or thatched tower.
a) Post mill
b) Smock mill
c) Tower mill
d) Fan mill
View Answer
Explanation: The smock mill is a type of windmill that consists of a sloping, horizontally weather boarded or thatched tower, usually with six or eight sides. It is topped with a roof or cap that rotates to bring the sails into the wind. It is similar to post mill. It is named so because of its appearance.
11. Which are further improvements on smock mill?
a) Post mill
b) Smock mill
c) Tower mill
d) Fan mill
View Answer
Explanation: Tower mills are further improvements on smock mills. They have a rotating cap and permanent body, but this body is made of brick or stone. This fact makes it possible for the towers to be rounded. A round structure of it allows for large and taller towers.
12. Which type of windmills are been used for primary purposes?
a) Post mill
b) Smock mill
c) Tower mill
d) Fan mill
View Answer
Explanation: The fan type windmill is specifically made for individuals. It is much smaller and used primarily for pumping water. It consists of a fixed tower (mast), a wheel and tail assembly (fan), a head assembly, and a pump.
Sanfoundry Global Education & Learning Series – Energy Engineering.
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