Transcript Ingen lysbildetittel

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Historical Development
of
Wind Turbines
Svein Kjetil Haugset, 2007
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First use of wind - sails
• In use for 6000 years
• ”Catching” the wind in a sail
• Generating a drag force, D
– due to pressure differences
– parallel to the wind
• Drag force, D, on the sail:
phigh
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  w 2  a  cD
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w   v1  u  , relative speed
D
plow
a, area of the sail
cD , drag force coefficient, unity
v1
usail
v3
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“Sailing” the mills in Mesopotamia
• First historic record from 1700BC in
Mesopotamia.
• Afghan records 700AD show the
title: “Millwright” as a common one.
• Mill-ruins in Iran and Afghanistan
shows widespread use
• Known as “Persian wind mill”:
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purely drag devices, using “sails”
fixed direction
slow rotating (slower than the wind)
poor efficiency, less than 10%
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”Sailing” the mills elsewere
• Chinese drag-type mills
– First record in 1219 A.D., possibly much
older
– No screen – the sails were adjusting to
the wind direction
– Could be used in all direction
• Recent design:
– Savounius-type turbines
– Cup aneometers
• Said to be the most “re-invented”
turbine.....
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Turbines in medieval Europe
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First record in Europe in 1185,
Yorkshire.
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The “Windmill Psalter” from
Canterbury, 1270, with picture.
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Horizontal axed – “sails” does not
move parallel with the wind, but
perpendicular to the wind.
•
Lift-force is dominant:
–
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no longer “sails” but “wings”
Wind speed is no longer the limitation
for the rotational speed.
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Drag-type vs. lift-type turbines
• Drag force:
• Lift force:
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D    w 2  a  cD
2
w   v1  u  , relative speed
1
L    w 2  a  cL
2
w  v12  u 2
a, area
cD , drag force coefficient
cL , lift force coefficient
uwing
v1
usail
w
D
u
v1
axis of rotation
axis of rotation
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First industrial revolution?
• Alongside watermills, the only source of mechanical power
– 3-7 kW out-put, depending on size and wind conditions
• Used for grinding
• Long lasting design:
– Great variation in structural design and control mechanisms but the overall
principle stayed the same till the 18th century.
• By the 14th century, it was widely used in whole Europe
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Fortunes to the Netherlands
• Need for drainage lead to new
development
• The new design featured:
– a shaft to lead the power to
ground level.
– possibility to link several mills
together
– gradually improvement in the wing
design.
• Gave the opportunity for new
uses
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Variations in structural design
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Scientific research
•
Design done by craftsmen for 3400
years
•
John Smeaton - first wind scientist?
– Measuring efficiency, CP = 0,28
– Designed the twisted blade.
•
The modern turbine is “ready”:
1. Chambered leading edge (airfoil)
2. Blade-beam at 25% of airfoil length
3. Non-linear twist of airfoils
•
200 years of optimizing still to go!
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Wild West Wind
• Fan type turbines in USA:
– Halladay introduced in 1854
– Aermotor ca 1870
• Autonomous system
– Turned after the wind
– Turned out of the wind at high
speeds
• Higher speed and efficiency
• Widely used
– From 1854-1970: 6 million
– Still in use to day
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Wind goes electric
• First large scale electric wind turbine in
1888: Charles F. Brush
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Ø 17 m
12 kW
step-up gearbox (50:1)
10 / 500 r.p.m.
• First Danish electrical wind turbine in
1891: Poul La Cour
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–
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low solidity (ratio of area)
airfoil shaped blades
higher rotational speed
25 kW
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Modern theory is developed
• Research on propellers and airfoils
– NACA (later NASA) in USA and Göttinger in Germany
– Airfoil and propeller theory was developed
– Modern wind turbines: a spin-off from war-industry (?)
• Albert Betz:
– Worked on the theoretical limit of wind turbines: the Betz’ limit.
• An ideal turbine, independent of design, will only be able to extract 59,3% of the
available kinetic energy in the wind.
– Was important in developing the Blade Element Momentum Methode.
• Ludvig Prandt’l:
– Simplified the complex analysis of Betz.
– Developed Prandt’l Tip Loss Factor:
• Theoretical model for the loss in lift at the tip of a turbine blade
• The theoretical foundation for the modern turbine was made!
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Various attempts:
Hutter, 1968, D:
•2 glass fibres and plastic blades
•Shedding aerodynamic loads
•4000 hours before project was
ended
Gedser Mill, 1960s, DK:
Smith-Putam, 1941, USA:
•200 kW
•1.25 MW, 175 foot
•3 glass fibres blade
•2 steel blades (16 tons)
•Up-wind type
•Down-wind type
•Basis for the Danish concept
•Destroyed after less than 1000
hours
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The Danish Concept
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Three bladed
Up-wind
Dimensioned to withstand gusts
AC – generators
Constant rotational speed
Automatic yawing (turning after the wind)
Stall controlled.
• Great commercial success in the 80s
– The 55 kW sold over 10.000
– Size gradually grew
– VESTAS gained a leading position in the marked
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Growing in the wind
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What now?
• Potential for improving:
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transmission, mechanical gears is the Achilles heal of the turbine
lighter and stronger materials in the blades
individually pitched (regulated) blades
lower sound level
decrease tip-losses
making installations and maintenance more efficient
CUTING COSTS
• Moving the turbines off-shore
– floating installations no one can see (and would not protest against)
• Larger turbines
– 5 MW is built, 7 MW is discussed.
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What have we learned?
• Wind turbines is one of the oldest energy sources we know of
• The development of modern type turbines has taken nearly 900 yrs
• Have had great impact on the economy in various periods
• The modern turbine was made 250 yrs ago
• Basic theory only available in less than 90 yrs
• Still lost of things to do.......