Method for de-icing a blade of a wind turbine, a wind turbine and use thereof

1. A method for de-icing a blade of a wind turbine, after the wind turbine has been idle for a period of time, comprising:

establishing a predefined azimuth angle in a controller;

positioning the blade in the predefined azimuth angle; and

shaking ice off the blade, comprising:

creating a controlled acceleration condition of the blade and subsequently creating a controlled deceleration condition of the blade by oscillatingly actuating at least one of a pitch mechanism of the blade to oscillate the pitch of the blade about an initial blade pitch rest position, a yaw mechanism of the wind turbine to oscillate the yaw of the wind turbine about an initial wind turbine yaw rest position, and a rotor of the wind turbine to oscillate the rotor about an initial rotor rest position.

2. The method according to claim 1 further comprising positioning the blade in the predefined azimuth angle before the controlled acceleration condition is created.

3. The method according to claim 1 , wherein positioning the blade in the predefined azimuth angle includes positioning the blade in a substantially downwards pointing direction before the controlled acceleration condition is created.

4. The method according to claim 1 , wherein positioning the blade in the predefined azimuth angle includes positioning the blade in a first substantially sideways pointing direction before the controlled acceleration condition is created.

5. The method according to claim 4 , further comprising:

positioning the blade so that it points in a substantially opposite direction of the first sideways pointing direction; and

creating a further controlled acceleration condition and a further controlled deceleration condition while the blade is positioned in the opposite sideways pointing direction.

6. The method according to claim 1 , wherein the controlled acceleration condition and the controlled deceleration condition are created repeatedly.

7. The method according to claim 6 , wherein the controlled acceleration condition and the controlled deceleration condition are created repeatedly at a frequency substantially similar to a natural frequency of the blade or in phase with the natural frequency.

8. The method according to claim 1 , further comprising detecting an icy condition on the blade before creating the controlled acceleration condition and the controlled deceleration condition.

9. The method according to claim 1 , wherein creating the controlled acceleration condition and the controlled deceleration condition of the blade includes actuating one or more actuators of the wind turbine.

10. A wind turbine, comprising:

a tower;

a nacelle rotatably coupled to a top of said tower for yaw motion;

a rotor rotatably coupled to said nacelle for rotational motion,

at least one blade rotatably coupled to said rotor for pitch motion, and

a de-icer for de-icing said blade, wherein said de-icer comprises:

a pitch mechanism for imparting pitch motion to said blade,

a yaw mechanism for imparting yaw motion to said nacelle,

a rotational mechanism for imparting rotational motion to said rotor,

an actuator for actuating at least one of said pitch mechanism, yaw mechanism, and rotational mechanism, and

a controller operatively coupled to said actuator and configured to position said blade in a predefined azimuth angle and shake ice off said blade by creating a controlled acceleration condition of the blade and subsequently creating a controlled deceleration condition of the blade, the controlled acceleration condition and the controlled deceleration condition of the blade being created by the actuator by oscillatingly actuating at least one of said pitch mechanism to oscillate the pitch of said blade about an initial blade pitch rest position, said yaw mechanism to oscillate the yaw of said nacelle about an initial nacelle yaw rest position, and said rotational mechanism to oscillate the rotation of said rotor about an initial rotor rotational rest position.

11. The wind turbine according to claim 10 , further comprising a detector for detecting an icy condition on said blade.

12. The wind turbine according to claim 10 , further comprising an azimuth angle detector for detecting an actual azimuth position of said blade.

13. The wind turbine according to claim 10 , further comprising a rotor actuator for positioning said blade in the predefined azimuth position during the de-icing of said blade.

14. The wind turbine according to claim 10 , wherein said wind turbine blade comprises hydrophobic surface material.

15. The wind turbine according to claim 10 wherein said wind turbine is a Megawatt wind turbine that cause ice to be shaken off the blade.

16. A method for de-icing a blade of a wind turbine, after the wind turbine has been idle for a period of time, comprising:

creating a controlled acceleration condition of the blade that causes inertial forces in a direction that does not lie within a rotor plane defined by the blade of the wind turbine; and

creating a controlled deceleration condition of the blade that causes inertial forces in a direction that does not lie within the rotor plane,

wherein the inertial forces cause ice to be shaken off the blade,

wherein the steps of creating a controlled acceleration condition of the blade and creating a controlled deceleration condition of the blade are accomplished by oscillatingly actuating at least one of a pitch mechanism of the blade to oscillate the pitch of the blade about an initial blade pitch rest position, and a yaw mechanism of the wind turbine to oscillate the yaw of the wind turbine about an initial wind turbine yaw rest position.

17. The method according to claim 16 , wherein creating a controlled acceleration and deceleration condition of the blade further comprises actuating a pitch mechanism of the blade.

18. The method according to claim 16 , wherein creating a controlled acceleration and deceleration condition of the blade further comprises actuating a yaw mechanism of the wind turbine.

19. The method according to claim 16 , wherein creating a controlled acceleration and deceleration condition of the blade is achieved without rotation of the blade within the rotor plane.

20. The method according to claim 19 , further comprising positioning the blade in a predefined azimuth position before creating the controlled acceleration condition in the blade.