Wind Turbine Design Methods

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Wind Turbine Design Methods

• Robert Scott
• rscott_at_gatech.edu
• November 1, 2007

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Advantages of Wind Power

• Clean
• Flexible
• Large Potential for Growth
• Economically Viable (most of the time peak
  opportunity)

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Design

• Siting
• Configurations
• Sizing
• Rotor
• Tower
• Generator

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Siting

• Wind speed
• Climate Conditions
• Inland or at sea
• Terrain
• Surrounding Community

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Configurations

• Vertical Axis
• Darrieus
• H-Type
• Savonius
• Disadvantages
• Size limits
• Reliability

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Configurations

• Horizontal Axis
• 3-bladed most common, structures and dynamic
  considerations
• 1 and 2-bladed designs exist, but dont even
  bother.
• Upwind or Downwind

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Sizing

• Designs exist for capacities of lt1 kW up to 5 MW.
• What are you designing for?
• Utilities
• Individual Use
• Special Use

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Rotor

• Diameter
• Larger higher capacity and higher costs, helps
  for lower windspeed
• Blades
• Airfoils
• Shape (Twist)
• Control
• Stall/Pitch regulated
• Rotational Speed

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Rotor

• Control
• Stall/Pitch regulated
• Rotational Speed
• Cut-in, rated, cut-out velocities

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Tower

• Type
• Tubular
• Lattice
• Height
• Tall smoother air
• Short better for construction

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Wind Variability

• The terrain of the site affects the wind speed.
• Higher roughness lengths slow the wind down more
  at low elevations.

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Generator

• Enclosed?
• Gearbox?
• Direct-drive?

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Design Process

• Performance
• Efficiency
• Reliability
• Economics
• Infrastructure ( 1.7 Million per MW)
• Construction
• Operational Costs ( 2 of acquisition costs/yr)
• Subsidies

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The Power Curve
Published power curve for a 1.5 megawatt wind
turbine. Nordex S70. Vc-o 2VR
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Wind Variability

• Model the wind as a probability density function
• The Weibull distribution

For wind,
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What does all this tell us?
Capacity Factor
A capacity factor of 35 for a wind turbine is
considered good.
U 5 m/s ? CF 0.05 U 7 m/s ? CF
0.18 U 9 m/s ? CF 0.42 U 11 m/s ?
CF 0.73
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Sensitivity Studies HOMER
Sensitivity to hub height zH 40 m 500,000K
kWh/yr _at_ 0.087/kWh U 5 m/s 675,000K kWh/yr _at_
0.07/kWh
Sensitivity to wind speed U 5 m/s 225,000K
kWh/yr _at_ 0.15/kWh U 14 m/s 1,000,000K kWh/yr
_at_ 0.055/kWh
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The Power Coefficient

• The power output normalized to the energy
  density of the wind and the rotor area.

Measures the amount of power actually converted
out of the power available in the wind
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Optimized Costs of Energy

• Optimized Cost of Energy
• 0.038/kWh (3 interest)
• 0.040/kWh (4 interest)
• 0.042/kWh (5 interest)
• 0.044/kWh (6 interest)

• High wind speed areas, U gt 10 m/s consistently
• Maximized hub heights, zH 100 m
• Large development Economies of scale reduce per
  unit price of turbines.

Comparison with other fuels Coal 0.02
0.03/kWh Natural Gas 0.05 0.08/kWh Nuclear
0.02 0.03/kWh Note Other fuels, especially
coal and nuclear, benefit from not having to
include their high external costs in the price of
energy. Wind energy also receives a 0.015/kWh
tax credit.
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Useful Websites

• List of wind farms http//www.fplenergy.com/portf
  olio/contents/portfolio_by_source.shtml
• Wind turbine Manufacturers
• http//www.skystreamenergy.com/skystream/
• http//www.enercon.de/en/_home.htm
• http//www.nordex-online.com/en/
• http//www.gamesa.es/index.php/en
• http//www.suzlon.com/
• Current Events
• http//www.cnn.com/2007/TECH/science/10/09/pip.win
  d.energy/
• www.wind-watch.org