Pre-bending – the distinguishing feature of LM blades

LM blades are pre-bent, which means they flex towards the wind when mounted and are not subject to loading.

LM Wind Power developed this pre-bending solution for several reasons.

Clearance to the tower: One of the design parameters when we develop new blades for a particular wind turbine is the tip to tower distance. We have to design the blades so that they do not strike the turbine when turning, even in strong winds.

There are different ways to do this. One is to tilt the rotor so that the blades are not at right angles to the nacelle when viewed from the side. Using the same principle, it is possible to cone the rotor, thus ensuring clearance for the blades. However, both these methods require adjustments to the nacelle design to position the centre of gravity accurately.

Pre-bending the blades means that the nacelle design stays compact. Bending of the blades from their resting position to the tower is greater. LM blades are straightened in correlation with the approximate average wind strength at the erection site.

Lighter blades: Pre-bending the blades means less material is required. The blades do not need to be quite as rigid because the amount of allowable bending is greater. This makes it possible to use less material overall and fewer processed materials, which means we not only produce lighter blades, but they are cheaper as well. Lighter blades make it possible to increase the length and thus make them more capable of producing more electricity.

Larger swept area: When blades are exposed to the wind, they normally bend backwards, thus slightly reducing the rotor area. Pre-bending the blades means the opposite. In maximum wind conditions, the rotor area is also at a maximum. Rotor area is crucial for the annual production of the wind turbine.

LM Wind Power has a patent for pre-bending blades. More about our patents