Why Have Wind Turbines Been Designed With Three Blades, No More No Less?

Why Have Wind Turbines Been Designed With Three Blades, No More No Less?

For centuries, human beings, the wind has been an important source of energy, from sailboats to windmills. As a sustainable alternative to fossil fuels, wind power has gained popularity in recent years. Wind farms have started dotting coastlines, and deserts across the world, and by now you’ve probably noticed their distinct wind turbine design [1].

How do wind turbines work?

Traditional windmills usually had 4 to 8 blades and were utilized for goals like grinding grain and pumping water. They could work with low wind speeds as well. However, modern wind turbine generators (WTGs) have cut-in and cut-out speeds. The cut-in speed (typically between 10 and 15 meters per hour) is when the blades start rotating and generating power. As wind speeds increase, more electricity is generated until it reaches a limit, known as the rated speed. This is the point that the turbine produces its maximum, or rated power. As the wind speed continues to increase, the power generated by the turbine remains constant until it eventually hits a cut-out speed (varies by turbine) and shuts down to prevent unnecessary strain on the rotor [2].

The rationale behind designing wind turbines with three blades

How does wind turbine design affect wind power generation?

More blades for wind turbines mean more disturbance in the wind and resulted in less energy being captured by each blade. Because they disturb the airflow that can be extracted energy from them. Thus, more blades make the airstream less efficient for energy extraction. Moreover, adding more blades to WTGs makes the rotor heavier which leads other parts of wind turbines like the nacelle and tower to be stronger in order to support it. Being stronger of these parts requires more materials and finally increases the cost of each turbine. Therefore, the question arises here: why not have wind turbines with one blade or two blades?

How many Blades wind turbines should have?

One-bladed wind turbines would be the optimum number when it comes to energy yield. Of course, you only need one blade to perform the function of sweeping the entire wind stream, but experts often use two or three blades for mechanical reasons [3]. The idea of a one-bladed wind turbine is not so crazy as it first sounds as indicated by NASA’s experiment with one 15-meter long blade on its test turbine at Plum Brook, Ohio in 1985 [4]. Two firms tried to commercialize this concept: Messerschmitt-Bölkow-Blohm (MBB), and Riva-Calzoni. While they were never commercially successful. On top of these facts, one blade could cause the turbine to become unbalanced, and this is not a practical choice for the stability of the turbine [1]. Furthermore, they produce more noise and uneven load.

The energy yield of two blades would be greater than three, but it would also have its own drawbacks. Two-bladed wind turbines are more prone to a phenomenon known as gyroscopic precession, resulting in wobbling. Gyroscopic precession is the resultant action or deflection of a spinning object when a force is applied to this object. This action occurs approximately 90° later in the direction of rotation from the point where the force is applied. This wobbling would create further stability issues for the wind turbine. This would also place stress on the component parts of the turbine, causing it to wear down over time and become steadily less effective [1].

In conclusion, the three-blade wind turbine is the best choice for large-scale electricity generation by wind power. Because it is the ideal compromise among cost, design, and energy yields. Despite the fact that three-bladed WTGs have become the standard model of clean energy production in recent years, that doesn’t mean they always will be. Engineers are still working on better, more efficient wind turbine designs for future energy generation efforts [1].

Did You Know?

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Including the correct coordination, project name, capacity, and… you can check out our Offshore Wind Map here.

Author: Hesam-Edin Hayati Soloot & Amir Hayati Soloot


[1] Interesting Engineering, “The Scientific Reason Why Wind Turbines Have 3 Blades”, written by Saoirse Kerrigan.

[2] Department of Energy, “How Do Wind Turbines Survive Severe Storms?”.

[3] Wind Works, “Photos of One-Bladed Wind Turbines by Paul Gipe”.

[4] Wiki Media Commons, “Mod-0 Wind turbine”.

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