Wind Power
Michael Arquin
The Kidwind Project
St. Paul, MN
michael@kidwind.org
The KidWind Project
www.kidwind.org
2
TODAY’S GOALS
Gain a basic understanding of Wind Power
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Why do you care?
A Little History.
What are they made of?
Where we harvest the wind.
Your Design
▫ How many blades should you have?
▫ What shape should they be?
This is strange because…
Wind Energy is the Fastest Growing Energy Source in the World!!
US installed capacity grew 45% in 2007 and
50% in 2008!!!
KidWind Project |
www.kidwind.org
KidWind Project |
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2008: 8,358 megawatts (MW) of new wind energy
capacity installed
50% growth rate!
Brings US total installed wind energy capacity to
25,170 MW
Enough electricity to power the equivalent of close
to 7 million households!
2009 was a slower year due to the economy
KidWind Project |
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KidWind Project |
www.kidwind.org
Why such growth…costs!
1979: 40 cents/kWh
2000:
4-6
cents/kWh
• Increased
Turbine Size
• R&D Advances
• Manufacturing
Improvements
NSP 107 MW Lake Benton wind
farm
4 cents/kWh (unsubsidized)
2004:
3 – 4.5 cents/kWh
Why Are We Talking About This?
Need to Change Perceptions…
Wind Power
- History
- Technology
- The Wind Resource
- Wind in the Classroom
KidWind Project |
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Early “Windmill” in Afghanistan (900AD)
Water Pumpers (still in use today)
Jacobs Turbine – 1920 - 1960
WinCharger – 1930s – 40s
Smith-Putnam Turbine
Vermont, 1940's
Modern Windmills
Orientation
Turbines can be categorized into two
overarching classes based on the orientation
of the rotor
Vertical Axis
Horizontal Axis
Vertical Axis Turbines
Advantages
Omnidirectional
▫ Accepts wind from
any angle
Components can be
mounted at ground
level
▫ Ease of service
▫ Lighter weight
towers
Can theoretically
use less materials
to capture the
same amount of
wind
Disadvantages
Rotors generally near
ground where wind poorer
Centrifugal force stresses
blades
Poor self-starting
capabilities
Requires support at top of
turbine rotor
Requires entire rotor to be
removed to replace
bearings
Overall poor performance
and reliability
Have never been
commercially successful
(large scale)
Horizontal Axis
Wind Turbines
Rotors are usually Upwind of tower
Some machines have
down-wind rotors, but
only commercially
available ones are small
turbines
Proven, viable
technology
Modern Small Wind Turbines:
High Tech, High Reliability, Low Maintenance
Technically Advanced
Only 2-3 Moving Parts
Very Low Maintenance
Requirements
Proven: ~ 5,000 On-Grid
American Companies are the
Market and Technology
Leaders
10 kW
400 W
50
kW
900 W
(Not to scale)
Over-Speed Protection During High Winds
Upward Furling: The rotor tilts
back during high winds
Angle Governor: The rotor turns up and to one side
Yawing – Facing the Wind
• Active Yaw (all medium & large
turbines produced today, & some
small turbines from Europe)
• Anemometer on nacelle tells
controller which way to point rotor
into the wind
• Yaw drive turns gears to point rotor
into wind
• Passive Yaw (Most small turbines)
• Wind forces alone direct rotor
• Tail vanes
• Downwind turbines
Wacky Designs out there…
Large Wind Turbines
450’ base to blade
Each blade 112’
Span greater than 747
163+ tons total
Foundation 20+ feet
deep
Rated at 1.5 – 5
megawatt
Supply at least 350
homes
Wind Turbine Perspective
Workers
Blade
112’ long
Nacelle
56 tons
Tower
3 sections
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Maintenance
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Wind Farms
Off-Shore Wind Farms
Middelgrunden
Importance of the
WIND RESOURCE
Why do windmills need to be high in the
sky??
Turbulent wind is bad wind
Calculation of Wind Power
•Power
the=wind
Power
in theinWind
½ρAV3
– Effect of swept area, A
– Effect of wind speed, V
– Effect of air density, 
Swept Area: A = πR2 Area
of the circle swept by the
rotor (m2).
R
Importance of Wind Speed
No other factor is more
important to the amount of
power available in the wind
than the speed of the wind
Power is a cubic function of
wind speed
▫ VXVXV
20% increase in wind speed
means 73% more power
Doubling wind speed means
8 times more power
KidWind Project |
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43
Everything is not Perfect!!
Key Issues facing Wind Power
Wildlife Impacts
• In the November-December Audubon Magazine, John
Flicker, President of National Audubon Society, wrote a
column stating that Audubon "strongly supports wind
power as a clean alternative energy source," pointing to
the link between global warming and the birds and
other wildlife that scientist say it will kill.
Impacts of Wind Power: Noise
Modern turbines are
relatively quiet
Rule of thumb – stay about
3x hub-height away from
houses
Transmission Problems
•Where is the wind?
•Where are the
population centers?
•Where are the wind
farms?
•How do we get wind
energy from the wind
farms to the population
centers?
Now it is your turn to join the crowd!!!
KidWind Project |
www.kidwind.org
Betz Limit
All wind power cannot be
captured by rotor or air
would be completely
still behind rotor and
not allow more wind to
pass through.
Theoretical limit of rotor
efficiency is 59%
Most modern wind turbines
are in the 35 – 45%
range
Lift & Drag Forces
The Lift Force is
α = low
perpendicular to the
direction of motion. We
want to make this force
BIG.
α = medium
<10 degrees
The Drag Force is
parallel to the direction
of motion. We want to
make this force small.
α = High
Stall!!
Airfoil Shape
Just like the wings of an airplane,
wind turbine blades use the
airfoil shape to create lift and
maximize efficiency.
The Bernoulli Effect
Lift/Drag Forces
Experienced by
Turbine Blades
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Twist & Taper
Speed through the air of a
point on the blade changes
with distance from hub
Therefore, tip speed ratio
varies as well
To optimize angle of attack
all along blade, it must
twist from root to tip
Fastest
Faster
Fast
Rotor Solidity
Solidity is the ratio of total rotor
planform area to total swept area
R
Low solidity (0.10) = high speed, low torque
a
A
High solidity (>0.80) = low speed, high torque
Solidity = 3a/A
Advanced Classroom Blades
Airfoil
Blades
Cardboard
Tube for twisted
blades
Wind Turbine Blade Challenge
Students perform
experiments and design
different wind turbine
blades
Use simple wind turbine
models
Test one variable while
holding others constant
Record performance with a
multimeter or other load
device
Goals: Produce the most
voltage, pump the most
water, lift the most weight
▫ Minimize Drag
▫ Maximize LIFT
▫ Harness the POWER of the wind!
Questions???
The KidWind Project
www.kidwind.org