Wind energy technology has evolved significantly over time. Early references to wind power date back to 400 AD in Buddhist prayer wheels. From the 1200s to 1850s, windmills were widely used in Europe to grind grain and pump water, totaling over 100,000 mills. Modern utility-scale wind turbines first emerged in the late 1980s, with rotor diameters and electrical outputs increasing substantially in recent decades. Today's largest horizontal axis wind turbines have rotors over 120 meters in diameter, hub heights of 120 meters, and can produce over 5 megawatts of power. Key components include the foundation, tower, rotor, nacelle, gearbox, generator, and control systems.

1. Wind Energy Technology
Basics

2. WINDS
WIND ENERGY CLOUDS
HYDRO ENERGY
VEGETATION
CHEMICAL ENERGY
OCEAN
THERMAL
ENERGY
SOLAR
RADIATION
THERMAL WAVE
VELOCITY
RAINS
CO2 + H2O
PHTOSYNTHESIS
SOLAR
ENERGY
INCOMING
RESOURCE
FOSSIL FUEL
COAL
PETROLEUM
NATURAL GAS
FOSSILIZATION
Capital
Resource

5. Uneven heating of earth’s surface and rotation

7. History
~ 400 Reference to wind-driven Buddhist prayer wheels
1200-1850 Golden age of windmills in western Europe, totaling perhaps 10,000 in England, 18,000 in Germany, 9,000 in
Holland, and 50,000 overall
1850-1930 Heyday of the small multi-blade wind machine in the US Midwest—as many as six million units installed
1933 Krasnovsky builds a 100 KW wind machine in the Russian Crimea, near Yalta
1973 The oil energy crisis inspires new interest in alternative energy sources
1974-1980 US Federal Large Wind Turbine Program
1976 US Energy Research and Development Administration (ERDA) small wind machine development program
1981-2009 Wind Turbine Boom-Bust-Green Energy era

8. History
Dutch Windmill
US Farm Windmill
Buddhist Prayer Wheels

9. History
1981-1993 Wind turbine boom in California: more than 12,000 units installed.
1985,1986 US and California tax credits for wind projects expire, respectively.
1991 First commercial offshore wind farm, Vindeby, Denmark.
1996 Kenetech Windpower (US Windpower), largest US and world manufacturer, declares
bankruptcy, [assets sold to Enron Wind, then acquired by GE Wind].
1990-2000 Megawattage of installations in Europe grows at ~20%/year
1998-1999 European manufacturers opened wind turbine factories in US and China.
2004 RE-Power (Germany) 5 MW, 126m-dia HAWT (now 7 MW).
2007 US Department of Energy (DOE) announces goal and program to further WT development.
(details to follow).
2008-2016 US and European Wind booms.

10. Evolution of Wind Turbines
• Wind is a clean, safe, renewable form of energy.
• Although the use of wind power in sailing vessels appeared in antiquity, the widespread use of
wind power for grinding grain and pumping water was delayed until
• the 7th century in Persia,
• the 12th century in England, and
• the 15th century in Holland.
• 17th century, Leibniz proposed using windmills and waterwheels together to pump water from
mines in the Harz Mountains.
• Dutch settlers brought Dutch mills to America in the 18th century.
• This led to the development of a multiblade wind turbine that was used to pump water for
livestock.
• Wind turbines were used in Denmark in 1890 to generate electric power.
• Early in the 20th century American farms began to use wind turbines to drive electricity
generators for charging storage batteries

11. Introduction
• A wind turbine is a rotating machine which converts the kinetic energy of wind
into mechanical energy.
• If the mechanical energy is used directly by machinery, such as a pump or
grinding stones, the machine is usually called a windmill.
• If the mechanical energy is instead converted to electricity, the machine is called
a wind generator, wind turbine, wind power unit (WPU), wind energy converter
(WEC), or aerogenerator.
• Horizontal Axis Wind Turbines (HAWT)
• Vertical Axis Wind Turbines (VAWT)

12. Horizontal Axis Wind Turbines (HAWT)
Upwind Downwind
Upwind and downwind turbines (p.3)

13. Horizontal Axis Windturbine (HAWT)
Current market ~ almost all are HAWTs with two or three blades.
Three-blade machines are being slightly favored. (Number of blades and other
design issues ~ to be treated later.)
Some machines now at 7 MW
(100,000 60-watt light bulbs).

14. HAWT and its Components

15. Components of a Wind Turbine
• Foundation
• Tower
• Rotor
• Nacelle
• Gearbox (in older units)
• High speed shaft
• Generator
• Control system, cooling
unit, anemometer
• Yaw mechanism

16. Turbine characteristics
• Rotor diameter – up to 120 m
• Hub height – up to 120 m
• Peak electrical power output – up to 6 MW now, up to
15 MW foreseen (offshore)
• Cut-in wind speed (typically 3-4 m/s)
• Rated wind speed (typically 15 m/s)
• Cut-out wind speed (typically 25 m/s)

17. Figure 3.4 Progression of rotor sizes over time

19. Nacelle

21. Three Wind Speeds

23. Sample Specifications
Design
Technical Data
Rated Power 5,000 kW
Cut-in Wind Speed 3.5 m/s
Rated Wind Speed 13 m/s
Cut-Out Wind Speed
Offshore Version 30 m/s
Onshore Version 25 m/s
Rotor/Hub height
Diameter 126 m
Height 120m
Speed Range, normal operation approx. 7-12 rpm
Mass
Rotor approx. 120t
Nacelle (without rotor) approx. 290 t