Wind Energy
Keith Etheridge
The Kidwind Project
St. Paul, MN
michael@kidwind.org
Wind Power
- History
- Technology
- The Wind Resource
- Wind in the Classroom
KidWind Project | www.kidwind.org
Early “Windmill” in Afghanistan (900AD)
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
Disadvantages
• Omnidirectional
• 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)
– 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
Horizontal Axis
Wind Turbines
• Rotors are usually Up-wind
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
KidWind Project | www.kidwind.org
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 | www.kidwind.org
• 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?
Wind Energy in the Classroom
Standards/Skills
• Scientific Processes (Collecting & Presenting Data,
Performing Experiments, Repeating Trials, Using
Models)
• Use of Simple Tools & Equipment
• Forces Cause Change
• Energy Transformations (Forms of Energy)
• Circuits/Electricity/Magnetism
• Weather Patterns
• Renewable – Non Renewable Energy
Middle
balloon
~3m
streamers
Kite or balloon string
• Building Wind
Turbines
• Assessing Wind
Resource
• Mathematics
Secondary
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Advanced Blade Design
School Siting Projects
Data Analysis
Advanced Math
Circuits, Wind Farms, Battery Charging, and Hybrid Systems
KidWind Project | www.kidwind.org
Questions???
The KidWind Project
www.kidwind.org