Designing a Windmill Blade
Hints and Tips for Designing a Wind Turbine Blade
What Is a Wind Turbine Blade?
A wind turbine blade is basically a wing, designed to harness the power of the wind through aerodynamic principles. Like an aeroplane wing, it uses its carefully shaped design to generate lift; causing the rotor to spin and converting kinetic energy into electricity. Despite looking simple and easy to make, every twist, curve, taper and point counts when maximising power!
Designing Your Wind Turbine Blade
Designing a wind turbine blade is all about balancing efficiency, durability, and creativity. Here are some key blade characteristics you might want to think about. Consider how different factors affect performance, and what types of conditions your wind turbine may encounter!
Blade Length
The distance from the centre of the turbine to the tip of the blade.
- Longer blades can capture more wind energy, but can also create more drag, especially in turbulent winds where they might wobble.
- In general, longer blades are more efficient in higher wind speeds and low turbulence, while shorter blades can be better for lower wind speeds with higher turbulence.
- Tip: The drag of the air blade can be mitigated by a good blade shape.
Blade Count
How many blades your turbine has.
Fewer blades (1 or 2): Less blades means less drag. A 2-blade turbine is lighter, can turn faster and is also cheaper. But it may wobble in stronger winds increasing drag and decreasing efficiency
More blades (4+): More blades can capture more wind energy, especially at low wind speeds.
However, more blades mean more surface area and more airflow disruption. This causes drag and slows down how fast the turbine can spin, especially in higher winds.
Blade Angle
The angle between the oncoming wind and the blade’s centre line
Low Angle of Attack: The blade interacts with the wind gently, generating less lift due to minimal airflow deflection.
Moderate to High Angle of Attack: Increased angle creates a larger pressure difference between upper and lower surfaces, generating more lift as airflow accelerates over the top.
Too High an Angle (Stall): Excessive angles cause air to separate and go over the top and bottom of the blade, reducing lift sharply and potentially stalling the blade.
Blade Shape
The shape is what the blade looks like when you cut it down the middle, from the tip to the base. This shape is very important as it helps create lift.
Thickness
The ideal aerodynamic shape would be thin, and consistent along the whole length, so as to reduce drag. However, wind turbine blades need some thickness near the base to support its long shape.
Symmetrical Aerofoil
This is where the top and bottom of the blades look the same, they may be straight or evenly curved like the one shown here.
Advantages: They have a simple design and their strong even shape keeps them steady.
Asymmetric Aerofoils
This is when one side of the blade has a different shape to the other. For example, the top of a blade may be curved like a kite or an aeroplane wing.
Advantages:
The curved side of the blade makes air move faster over it, creating lift (just like an aeroplane wing). This extra lift helps the blade start turning even when there’s not much wind.
Downloads
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Blade Design Pamphlet
Last updated
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Windmill Blade Worksheet
Last updated