Wind Energy

Keith Etheridge The Kidwind Project St. Paul, MN michael@kidwind.org

KidWind Project | www.kidwind.org

Wind Power

- History - Technology - The Wind Resource - Wind in the Classroom

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 • 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 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 50 kW

400 W 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

Nacelle 56 tons

Tower 3 sections

Workers Blade 112’ long

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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 in the wind

– 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).

Power in the Wind = ½ρAV3

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

– V X V X V

• 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

•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?

Transmission Problems

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 • Building Wind

Turbines

• Assessing Wind Resource

• Mathematics

balloon

streamers

Kite or balloon string

~3m

Secondary

• Advanced Blade Design

• School Siting Projects

• Data Analysis

• Advanced Math

KidWind Project | www.kidwind.org

Circuits, Wind Farms, Battery Charging, and Hybrid Systems

Questions???

The KidWind Project www.kidwind.org