Post on 23-Dec-2015
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