We have all either driven past wind turbines or seen them on television, but have ever wondered, “how fast can wind turbines spin?”
They do not look like they are spinning very quickly, but is that the case? Or is it just because you see them from afar that they look rather slow?
Really, how fast do the windmills spin?
Standard turbines can go at 100 mph with ease, but larger designs with heavier blades may spin at 180 mph.
Enter the World of Wind Turbines
Used for the purpose of generating electricity, a wind turbine converts the kinetic energy of the wind into a more usable form of energy.
Because of their motion and the force acting upon them, all moving objects have kinetic energy.
And the same concept applies to wind turbines.
Once it generates the power, it is fed into the national grid and then distributed to different consumer locations.
But, when it comes to power generation, it hugely depends on how fast those wind turbines spin.
Fact: There is a minimum range for the turbine to generate power and it is called the cut-in wind speed.
Learning about the speed of Wind Turbines
Those massive wind turbines may look rather slow from a distance, leading one to believe that their blades also do not rotate that fast.
It will come as a shock to you to learn that your opinion is so far from the truth.
So, how fast can a wind turbine spin? Well, speed depends on many factors.
But, depending on the wind direction and speed, a conventional wind turbine would rotate at a rate of 15 to 20 RPM.
What Affects the Speed of Wind Turbines?
So many factors play a role in determining the speed of wind turbines.
For instance, size plays a big role here, as these turbines are available in different sizes for different purposes.
- Small turbines are available to supply power to rural cabins and homes.
- Community-scale turbines power up businesses and homes in a community.
- Industry-scale turbines form a wind farm to power up the National Grid.
And as these turbines get larger, their speed increases at the same time to make up for the load.
Similarly, the speed will change with a change in the number and size of blades.
For instance:
Horizontal Axis Turbines
These turbines usually come with 3 blades connected directly to a rotor shaft. Since they are at the very top of a tower, they can achieve a very high speed.
Vertical Axis Turbines
They are not as common mainly because they are not as effective as horizontal axis turbines.
They are usually not that fast and are often used to supply power to individual properties.
Fact: Wind turbines usually work better at a low cut-in wind speed because it allows them to generate some power for longer.
Wind Turbine Speed and RPM
The RPM of a wind turbine is one unit of rotational speed measurement.
As the name implies, this metric provides information on how many complete rotations per minute a wind turbine blade achieves.
A complete rotation occurs when a blade, which begins at an angle with the horizon, travels around its axis of rotation until it reaches the same angle.
Someone talking about wind turbine RPM generally refers to the blades’ speed. Remember, a normal wind turbine will have a blade speed in the range of 15-20 revolutions per minute (RPM).
The purpose of the blades is to turn the power generator that converts wind energy into electricity.
The normal RPM for the generator in a wind turbine is between 1800 and 2000.
How Fast Can Wind Turbines Spin?
Wind turbines can achieve a very high spinning speed. And as mentioned already, the length of the blade has a role to play.
In many cases, the tip of a blade can easily hit a speed of 100mph, and it often goes up to 180 mph, depending on the velocity of the wind.
When speaking of wind turbine speed, it is important to get an idea about the survival wind speed.
How Is Turbine Speed Measured?
Knowing the overall length of the blade and the distance its tip travels during one rotation is essential to measure the turbine speed accurately.
For this, we have to use this equation: 2∏r
It means if the radius of a blade is 120ft, you have to multiply it by 2 first.
The answer is 240ft, which needs to be multiplied by pi (3.1415) to get the circumference of the cycle. In this case, it will be 753.96ft.
In case, the blade’s tip travels that distance in 4 seconds, simply divide the circumference (753,96) by 4 to get the speed in feet per second (188.49ft/sec).
More about Survival Wind Speed
What is meant by “survival wind speed” is the highest possible gust force the wind turbine can withstand without damage.
In most situations, wind turbines can easily withstand a minimum wind speed of 112mph to 145mph.
In addition, for installations in more extreme or rare conditions, wind turbines can be tailored to achieve a much higher survival wind speed.
Furling-equipped microturbines can continue to produce electricity up to the survival wind speed.
But non-furling turbines will stop working once wind speeds reach the cut-out wind speed.
The Wind Speed Beyond Survival Speed Limit
Wind turbines normally sustain little damage in winds greater than the indicated survival speeds.
Therefore, the survival wind speed is essentially more of an insurance or safety factor.
It is true because wind turbines use different mechanisms to prevent any damage to the blades.
For instance:
Automatic Cut-Off
The rotors will automatically stop turning whenever the wind speed reaches the Survival Speed, which is set by the manufacturer.
Feather Blades
The feathers mitigate excess rotating torque when built into a blade’s outer edge. They ‘unfeather’ and continue working normally as the wind speed drops.
Fact: The cut-out wind speed refers to the maximum speed a turbine can tolerate before shutting down.
The Maximum Speed of a Wind Turbine
For optimal performance, all turbines can reach their top-rated speeds.
When extreme weather strikes and the wind speed exceeds the survival speed, the turbine requires a fail-safe to protect the blades and the engine.
If you talk about the safe wind speed, it usually ranges between 89 mph and 161 mph.
But, the most common survival speed is somewhere around 134 mph. And based on other factors, the maximum speed is somewhere close to 180mph.
Can Wind Turbines Spin Too Fast or Too Slowly?
The truth is that manufacturers utilize different mechanisms to protect a wind turbine from spinning too fast or too slowly.
When a turbine spins a bit too slowly, it allows the wind to pass through without pushing the blades.
In other words, a wind turbine is not going to function properly if the wind speed is less than 5mph.
On the contrary, if a turbine spins too fast, it can:
- Result in a mechanical issue
- Create a blockage against the wind
Therefore, it is important to pay attention to whatever maximum speed a turbine is designed to handle.
It is not uncommon for wind turbines to shut down if the wind speed goes beyond 55mph, but it also depends on many other factors.
Measuring the Performance of Wind Turbines
Paying attention to how fast a wind turbine spins will have an impact on its performance, but there are other ways to measure performance.
A wind turbine’s efficiency is mostly determined by looking at its power curve.
Power curves for wind turbines can be estimated from the turbine’s blueprints.
Remember, the predicted electrical capability of the turbine at various wind speeds is plotted on the vertical axis.
Obtaining a measured power curve is crucial for compact permanent magnet generators. It is essential in this case because the measured curve may differ from the predicted one.
In addition, a power curve is not always applicable. It is affected by the local atmospheric conditions, including wind speed and direction, humidity, and temperature.
Fact: A turbine for a specific region is selected by analyzing its rated wind speed as well as the typical wind speed for a particular site.
Takeaway
How fast can wind turbines spin? The speed at which wind turbines spin can vary based on many factors.
Of course, atmospheric conditions play a role, but the blade’s size and the wind turbine itself also matter.
But in most cases, larger turbines can easily hit 180mph, but for most, the survival speed stays close to 112-145mph.
