How Long are Wind Turbine Blades?

Wind turbine blades can vary considerably in shape and size, and there is no one “perfect” blade length.

Wind turbine blade length can range from 18 to 107 meters (59 to 351 feet) long.

For example, the largest turbine, GE’s Haliade-X offshore wind turbine, has blades up to 351 feet (107 meters) long!

The blade length will depend on the size of the wind turbine, wind speed in your area, and other factors such as local regulations or restrictions.

This article takes a closer look at the relationship between wind turbine blades and efficiency.

The importance of wind turbine blade length

 

Drag and force power in wind turbines
The effect of lift and drag forces on wind turbine’s blades (Creative Commons CC0)

Wind turbine blades are shaped like an airplane wing. When wind pushes on the blade, it causes two powers: lift and drag.

The lift force is performed perpendicular to the wind flow (the blade), causing it to rotate.

The drag force is parallel to the wind flow and acts as a resistance force that slows down the blade’s spinning speed.

When designing a wind turbine blade, you must consider both the lift and drag forces to determine how long your blade must be:

  • Too much drag, and the blade won’t be able to spin.
  • Too much lift and the blade will spin too fast and could break.
The relation between the wind turbine's height and efficiency
The relation between the wind turbine’s blade length (rotor diameter) and power output by Fatiha Youcef Ettoumi

How wind conditions affect wind turbine blade length

Chart relation of wind speed to rpm.
Chart relation of wind speed to RPM by Esmar Budi

The length of wind turbine blades is mainly determined by the wind conditions in the wind farm area.

In high wind areas, longer blades can capture more energy and generate electricity faster, so it makes sense to invest millions of dollars in building them.

However, one problem is that higher wind will cause the blades to spin faster, which puts a lot of stress on the shaft and bearings. This is why in some cases, you might want to design a thicker blade with a relatively high drag to prevent the blades from spinning too fast.

In low wind areas, longer blades are not very common because less wind is available to generate electricity and are therefore less likely to be worth the investment.

How Heavy is a Wind Turbine Blade?

Wind turbine weight vs length
Wind turbine weight vs. length by José Manuel Gordo

Modern wind turbine blades are typically made from fiberglass or carbon fiber, making them light and robust but expensive to produce.

The average weight of one blade can range anywhere between 20 metric tonnes for smaller turbines, up to 55 metric tonnes for large offshore turbines.

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