Blade for a wind turbine comprising means for retaining a spoiler at a retracted position

A method of controlling a wind turbine, the wind turbine comprising a tower, a nacelle mounted to a top of the tower, a hub being rotatably mounted to the nacelle, and at least one blade mounted to the hub, the blade comprising a blade body, an active member mounted to the blade body and configured to move between a retracted position and an extended position to change an aerodynamic property of the blade, a bladder which is configured to be connected to a pneumatic or hydraulic system of the wind turbine to move the active member when the bladder is filled by a fluid supplied by the pneumatic or hydraulic system, or when the fluid is removed from the bladder by the pneumatic or hydraulic system, the method comprising:

• a retaining step to prevent the active member from moving towards the extended position, wherein the retaining step comprises:
• a) a suction step to control a predetermined fluid pressure within the bladder which prevents the bladder from inflating due to a pressure build up due to centrifugal forces on the fluid inside the bladder, which is created when the hub rotates, wherein a flexible portion is provided which is configured to move or maintain the active member to or in the retracted position, wherein the active member comprises a movable portion and an airfoil portion with the flexible portion therebetween, and the airfoil portion is positioned a distance away from the bladder;
• or
• b) the bladder is fixed to a baseplate at a first discrete location of the baseplate, and the active member is fixed to the baseplate at a second discrete location of the baseplate, the first discrete location and the second discrete location being spaced apart from each other along the baseplate, the baseplate being fixed to the blade body, wherein the active member is pressed and/or retained in the retracted position by the suction means configured to apply a negative pressure in the bladder.

A blade for a wind turbine, comprising:

• a blade body;
• an active member mounted to the blade body and configured to move between a retracted position and an extended position to change an aerodynamic property of the blade;
• a bladder which is configured to be connected to a pneumatic or hydraulic system of the wind turbine to move the active member when the bladder is filled by a fluid supplied by the pneumatic or hydraulic system, or when the fluid is removed from the bladder by the pneumatic or hydraulic system;
• and
• a suction pressure reduction element contacting the active member and the blade body downstream of a trailing edge of the active member or at the trailing edge itself, the suction pressure reduction element being configured to reduce a suction pressure induced by an airflow on the active member when the active member is in the retracted position, so that the active member is prevented from moving towards the extended position.