1. Wind Power and its Science
As one of the powerful energy sources

2. The first windmill / wind turbine
During 500–900 AD, windmills were built in Persia for pumping water and grinding grains.
In 1888, Charles F. Brush used a windmill to generate electricity in Cleveland, Ohio, as is called a wind turbine nowadays.

3. The advantages Small environmental load
Little pollution
Equal to the efficiency of thermal power with a best circumstance
Twice as much as that of solar cells
More secure than other energy sources

4. Usage of wind energy For charging batteries Work saving
Pumping water to storing water when wind is available, etc.
Hybrid generating system
Hybridized with other generators

5. The energy payback time (EPT)
With a 2000-kW class wind turbine,
7m/s of year-average wind velocity
It can create 7 million-kWh electricity a year
 The power consumed by 1,400 households
The average EPT is 3 to 4 months.

6. Measurement of wind velocity
Cup anemometer
World standard
Doppler LiDAR (Light Detection And Ranging)
Using Doppler effect
Able to measure at 200-m height

7. Types of windmills / wind turbines
Horizontal Axis Wind Turbine (HAWT)
More common and commercialized
Dutch windmill
Propeller type, etc.
Vertical Axis Wind Turbine (VAWT) Independent of directions of wind
Darrieus
Savonius
Giromill, etc.

8. Other wind turbines 1 Magnus wind turbine Solar chimney wind turbine
From the effect discovered by Heinrich Gustav Magnus
Using long cylinders instead of blades
Solar chimney wind turbine
Air heated by sun going up in the chimney
The wind turbine installed in the chimney

9. Other wind turbines 2 Diffuser Tip vane
With 10% increment of wind velocity, 30% increment of the power generated
Tip vane
Removing vortex at the tip of the blade

10. How a wind turbine rotates 1

11. How a wind turbine rotates 2

12. Types of wind turbines and the power
A small number of blades
The power becomes larger, but the torque is smaller.
A large number of blades
The power becomes smaller, but the torque is larger.

13. The number of blades and usage of wind turbines/windmills
One or two blades are capable of generating the best power.
However, they get noise most.
Three-blade wind turbines are the best balanced.
Multiple-blade windmills are used for pumping water due to larger torques.

14. Theoretical efficiency of windturbine
The maximum power of windmill received from wind 
The entire power from wind covered by the windmill 
The power coefficient CP (=PMAX/P0) becomes 16/27 = (Lanchester-Betz limit)

15. Practical efficiency of windturbine
Fluid mechanical loss  About 50%
Mechanic loss  About 4%
Electrical loss  About 6%
The practical energy efficiency is 40%.

16. Size of a windturbine and its power
The power of wind
where , A, v are the air density, the area of windmill, and wind velocity, respectively.
Therefore, the power is proportional to the square of the wind velocity:

17. How wind turbines distributed (Making wind farms)
d as the diameter of the wind turbine
Space in the horizontal direction
 from 2d to 4d
Space in the vertical direction
 from 8d to 12d