byJohn Zavalney

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How can wind be used more efficiently?How can wind be used more efficiently?

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QUICK WRITE PROMPT

In your notebook list as many factors that you can think of that would have an effect on the efficiency of wind turbines.

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How can wind be used more efficiently?How can wind be used more efficiently?

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1. Wind Turbine Blade Design• Use your kit to experiment on blade design

or• Watch wind turbine blade design PowerPoint

KidWind turbine blade design PDF

LESSON_bladedesign.pdf

Wind Turbine Wind Turbine Blade DesignBlade Design

PowerPoint adopted from PowerPoint adopted from The Kidwind ProjectThe Kidwind Project

Number of Blades – One• Rotor must move more

rapidly to capture same amount of wind– Gearbox ratio reduced– Added weight of

counterbalance negates some benefits of lighter design

– Higher speed means more noise, visual, and wildlife impacts

• Blades easier to install because entire rotor can be assembled on ground

• Captures 10% less energy than two blade design

• Ultimately provide no cost savings

Number of Blades - Two

• Advantages & disadvantages similar to one blade

• Need teetering hub and or shock absorbers because of gyroscopic imbalances

• Capture 5% less energy than three blade designs

Number of Blades - Three

• Balance of gyroscopic forces

• Slower rotation– increases gearbox &

transmission costs– More aesthetic, less

noise, fewer bird strikes

Blade Composition Wood

Wood– Strong, light weight,

cheap, abundant, flexible

– Popular on do-it yourself turbines

• Solid plank• Laminates• Veneers• Composites

Blade CompositionMetal

• Steel– Heavy & expensive

• Aluminum– Lighter-weight and easy

to work with– Expensive– Subject to metal fatigue

Blade ConstructionFiberglass

• Lightweight, strong, inexpensive, good fatigue characteristics

• Variety of manufacturing processes– Cloth over frame– Pultrusion– Filament winding to produce

spars• Most modern large turbines

use fiberglass

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

Lift & Drag Forces

• The Lift Force is perpendicular to the direction of motion. We want to make this force BIG.

• The Drag Force is parallel to the direction of motion. We want to make this force small.

α = low

α = medium<10 degrees

α = HighStall!!

Airfoil Shape

Just like the wings of an airplane, wind turbine blades use the airfoil shape to create lift and maximize efficiency.

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

Fast

Faster

Fastest

Tip-Speed RatioTip-speed ratio is the ratio of the

speed of the rotating blade tip to the speed of the free stream wind.

There is an optimum angle of attack which creates the highest lift to drag ratio.

Because angle of attack is dependant on wind speed, there is an optimum tip-speed ratio

ΩRV

TSR =Where,

Ω = rotational speed in radians /sec

R = Rotor Radius

V = Wind “Free Stream” Velocity

ΩR

R

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

According to The Department of Energy the United States could get 20% of all it energy from wind power

the movie “FUEL”

If the United States could get 20% of all it energy from wind powerit could create over 50,000 high paying jobs.

James Walker President AWAEAthe movie “FUEL”

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The GOOD the BAD and the FUTURE Of wind generated energy

AssessmentAssessment

Wind Farm location web Quest use the link below to navigate to several web sitesthat provide information about wind farms including

• Back ground•Government & Global Policy

•Environmental•Wind industry

•Economic Consumer and Citizen reports

http://www.web-and flow.com/members/polson/webquest/webquest.htm#bg

Web-and-flow.comOffshore Windfarms in the

United States?by Pamela Olson

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• Gather research and resources• Putting your PowerPoint together

The GOOD the BAD and the FUTURE Of wind generated energy

AssessmentAssessment

Work on FINAL PROJECT

PowerPoint Presentation