UE 06: Wind Power

Question 1

Energy yield of a wind turbine - weibull distribution

True or false?

A smaller k-value means very variable wind speeds.

A larger k-value means very constant wind speeds.

Answer 1

True!

Question 2

True or false?

Energy yield of a wind turbine - weibull distribution

• Arctic regions –> k = 1
• Central Europe –> k = 2
• Trade wind regions –> k = 3 - 4

Answer 2

True!

Question 3

What is missing?

Energy yield of a wind turbine

• Assumption: Central Europe (k = “…”)
• In this case a simplification is possible:

Advantages of using “…”:

• “…”
• “…” is known for many locations
• The yield calculation of wind turbines of many manufacturers is based on the assumption of “…”

Answer 3

Energy yield of a wind turbine

• Assumption: Central Europe (k = 2)
• In this case a simplification is possible:

Advantages of using Rayleigh distribution:

• Requires only the mean wind speed
• Mean wind speed is known for many locations
• The yield calculation of wind turbines of many manufacturers is based on the assumption of a Rayleigh distributed wind

Question 4

How is the theoretical upper limit of the power of a wind turbine defined?

Answer 4

Theoretical upper limit of the power of a wind turbine

• Due to aerodynamic, electrical, and mechanical losses there is a theoretical limit on the fraction of wind energy that can be extracted by an ideal (lossless) wind turbine
• Maximum power coefficient: c_Betz = 0,593
• P_Betz,i = P_wind,i * c_Betz
• P_wind_turbine = P_wind,i * c_p,i
• P_Betz,i >= P_wind_turbine

Question 5

Describe the basic structure of typical horizontal axis wind turbines (HAWT).

Answer 5

Basic structure of typical horizontal axis wind turbines (HAWT)

• Rotor blade
• Rotor hub (‘Nabe’) and blade pitch mechanism
• Rotor shaft (‘Welle’) and bearings (‘Lager’)
• Gearbox (‘Getriebe’)
• Rotor brake
• Generator
• Electric switch boxes and control systems
• Bedplate
• Yaw system
• Power cables
• Tower
• Grid connection (transformer)
• Foundation