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What Are Vanes?

A vane is a broad blade that is pushed by wind or water and is attached to a wheel-like mechanical part.

While designing the vanes for your wind turbine some important factors to consider would be:

  1. Size
  2. Shape
  3. Angle of Attack
  4. Material
  5. Number of blades

Size​

Larger vanes capture more wind which is why commercial wind turbines have long, huge blades. The amount of energy a turbine can capture/generate is directly proportional to the square of the blade length.

Shape​

To have the least amount of resistance, it is important to have an aerodynamic design. A long sleek design as seen on turbines reduces the air resistance experienced by the blades. Additionally, it is easier to turn larger vanes at a low wind speed.

Angle of Attack​

The angle at which the wind hits the blades is called the angle of attack (AoA). For eg: If you hold your hand out of a moving car (don’t do it, it’s dangerous!) and your hand is facing the wind, the wind is attacking your hand at 90 degrees and you’re capturing the maximum amount of wind. But if your hand is parallel to the wind, you don’t feel as much force pushing your hand and you’re barely capturing any wind.

The AoA determines the lift and the drag. So what exactly are lift and drag?​

When an airplane takes-off, the wings are shaped in such a way that the wind is able to give the wings a “lift” to help the plane take-off whereas drag is the opposite and slows down the wings.

When you have your hand facing the wind you capture a lot of it, but you experience the maximum drag as well. But if you tilt it slightly, you still capture a decent amount of wind with lesser drag.

Finding the right compromise between the lift and the drag is all about finding the right AoA.

Material​

The material of choice should be strong and lightweight as:

  1. Lightweight: Because we want the vanes to turn easily even at low wind speeds and turn fast to generate maximum output.
  2. Strong: The sleek design of vanes needs to be structurally very strong to withstand high speed winds.

When thinking commercially consider availability, corrosion resistance, ease of manufacture, cost etc.

Time to Think!​

  1. What materials can you think of that are lightweight and strong that can be used to build a commercial wind turbine?
  2. Another factor that could affect vane design or the turbine design would be the number of blades. Do you think more wings is better?

Evaluating the Efficiency​

The more output or electricity a wind turbine generates, the more efficient it is. But how do you measure the generated output?

The energy generated by a wind turbine can be measured in Watts (W) or kiloWatts(kW). Since, the energy is produced over time, the unit kiloWatt-hours (kWh) is generally used. Remember that efficiency is a wide subjective metric and does not depend entirely on the power output generated. What if a wind turbine generates a large amount of power, but has a short lifespan of operation? What about the amount of power going into operating the turbine? How does the input power compare to the output power?

Time to Think!​

  1. Faster winds generate more energy, but what could be the potential downside of operating a turbine at high wind speeds?