Wind power

Question 1

Q1: What are the two main types of wind turbines?

Answer 1

Horizontal Axis Wind Turbines (HAWT) and Vertical Axis Wind Turbines (VAWT)

Question 2

Q2: What is the Betz Limit?

Answer 2

The theoretical maximum efficiency for a wind turbine set at 59.3%

Question 3

Q3: What is the purpose of a gearbox in a wind turbine?

Answer 3

It transfers mechanical energy from the rotor to the generator adjusting speed

Question 4

Q4: What is the role of turbine blades?

Answer 4

They capture wind energy and transfer it to the rotor

Question 5

Q5: What is the function of an inverter in a wind turbine?

Answer 5

It matches the generator’s output frequency to the grid’s frequency

Question 6

Q6: Describe the two types of drive trains in wind turbines

Answer 6

Integrated: Compact but harder to replace; Modular: Separate components easier maintenance

Question 7

Q7: What is pitch control?

Answer 7

Adjusting blade angles to optimize power output and prevent overspeeding

Question 8

Q8: How does yaw control work?

Answer 8

It keeps the turbine facing the wind using a yaw drive and motor

Question 9

Q9: What is the difference between stalling and furling?

Answer 9

Stalling: Increases blade angle to reduce speed; Furling: Turns blades away from wind to reduce exposure

Question 10

Q10: What factors affect wind power output?

Answer 10

Swept area (A) air density (ρ) wind speed (v) power coefficient (Cp) tip speed ratio (λ) and pitch angle (β)

Question 11

Q11: Write the wind power equation

Answer 11

𝑃=12𝐶𝑝𝜌𝐴𝑣3P= 21​ C p​ ρAv 3

Question 12

Q12: What is tip-speed ratio (TSR)?

Answer 12

The ratio of blade tip speed to wind speed

Question 13

Q13: What is capacity factor?

Answer 13

The ratio of actual energy output to the maximum possible output

Question 14

Q14: Why is proper turbine spacing important?

Answer 14

To reduce wake effects and maximize energy output

Question 15

Q15: How is land area for a wind farm estimated?

Answer 15

Based on rotor diameter and spacing requirements (typically 8D x 8D)

Question 16

Q16: Why is air density important in wind power generation?

Answer 16

Lower air density reduces available wind energy

Question 17

Q17: How does wind speed change with height?

Answer 17

Wind speed increases with height above ground

Question 18

Q18: What type of wind speed distribution is typically used for site evaluation?

Answer 18

Weibull probability distribution

Question 19

Q19: What are the major challenges of wind power?

Answer 19

Intermittency location-specific performance aesthetic and noise concerns weather vulnerability maintenance needs and high initial costs

Question 20

Q20: How long is the typical lifespan of a wind turbine?

Answer 20

20-25 years

Question 21

Q21: What is a Horizontal Axis Wind Turbine (HAWT)?

Answer 21

• Axis of rotation is parallel to the wind stream.
• Generator and gearbox are located at the top of the tower.
• Requires a yaw mechanism for alignment.
• High power coefficient and efficiency.
• Expensive and complex to install.

Question 22

Q22: What is a Vertical Axis Wind Turbine (VAWT)?

Answer 22

• Axis of rotation is perpendicular to the wind stream.
• Generator and gearbox are located at the base of the turbine.
• No yaw mechanism needed as it works from all wind directions.
• Low power coefficient and efficiency.
• Cheaper and simpler to install

Question 23

Q23: What is pitch angle?

Answer 23

the angle of the blade relative to the plane of rotation is known as the pitch angle

Question 24

Q24: What is angle of attack?

Answer 24

the angle of the blade relative to the apparent wind

Question 25

Q25: What is lift and drag?

Answer 25

• Lift Force is perpendicular to the direction of motion. We want to make this force Big!
• The Drag Force is parallel to the direction of motion. We want to make this force small.

Question 26

Q26: What is happening in regions 1-4 of the control objectives?

Answer 26

• Region 1: Turbine is stopped: wind speed is too low
• Region 2: The rotor speed is varied to ensure that the λ is kept at an optimal level with changes in the wind speed to ensure the production of maximum power.
• Region 3: Maintain rated rotor speed and power. The
  control objective in region 3 is to limit power production. This is achieved by limiting both torque and rotor speed of the wind turbine generator in order to ensure that constant rated power is obtained from
  the wind.
• Region 4: wind turbine is stalled to avoid catastrophic failures due to high wind speeds which can mechanically damage the turbine

Question 27

Q27: What is the benefit of a fixed-speed wind turbine?

Answer 27

frequency of the AC voltage is fixed, as the rotor speed in the generator is constant.

Question 28

Q28: Why would a wind turbine speed be variable?

Answer 28

such that Cp=Cpmax