Method for shut down of a wind turbine having rotor blades with fail-safe air brakes

1. A method for shutdown of a wind turbine having one or more wind turbine blades, the method comprising:

detecting an operational condition of the wind turbine that calls for an expedited or emergency shutdown of the wind turbine by means other than normal pitch control shutdown;

upon detection of the operational condition, deploying one or more air brake flaps configured on each of the turbine blades by removing electrical power to a fail-safe actuator operatively coupled to each of the air brake flaps, the fail-safe actuator configured to hold the respective air brake flap at a retracted position relative to a suction side of the turbine blade in a powered state of the fail-safe actuator and to release the air brake flap for automatic deployment to an open position upon loss of electrical power to the fail-safe actuator; and

including providing an initial motive force to the air brake flaps upon removing power to the fail-safe actuators to move the air brake flaps to an initial position relative to the suction side of the turbine blade so that airflow over the suction side subsequently acts on the air brake flaps and moves the air brake flaps to a fully deployed position.

2. The method as in claim 1 , wherein the detected operational condition indicates an emergency shutdown command from a wind turbine controller operationally configured with the wind turbine.

3. The method as in claim 1 , wherein the wind turbine supplies electrical power to or receives electrical power from a grid, the detected operational condition indicating loss of the grid.

4. The method as in claim 1 , wherein the air brake flaps are pivotally mounted to the suction side of the turbine blade.

5. A method for shutdown of a wind turbine having one or more wind turbine blades, the method comprising:

detecting an operational condition of the wind turbine that calls for an expedited or emergency shutdown of the wind turbine by means other than normal pitch control shutdown;

upon detection of the operational condition, deploying one or more air brake flaps configured on each of the turbine blades by removing power to a fail-safe actuator operatively coupled to each of the air brake flaps, the fail-safe actuator configured to hold the respective air brake flap at a retracted position relative to a suction side of the turbine blade in a powered state of the fail-safe actuator and to release the air brake flap for automatic deployment to an open position upon loss of power to the fail-safe actuator; and

wherein the detected operational condition indicates that a safety system operationally configured with the wind turbine is not enabled.

6. The method as in claim 5 , wherein the wind turbine safety system initiates braking of the wind turbine for rotor or generator overspeed, excessive vibration, failure of the pitch control system, or controller system failure.

7. The method as in claim 5 , wherein the detected operational condition indicates loss or malfunction of the pitch control system operationally configured with the wind turbine.

8. A method for shutdown of a wind turbine having one or more wind turbine blades, the method comprising:

detecting an operational condition of the wind turbine that calls for an expedited or emergency shutdown of the wind turbine by means other than normal pitch control shutdown;

upon detection of the operational condition, deploying one or more air brake flaps configured on each of the turbine blades by removing power to a fail-safe actuator operatively coupled to each of the air brake flaps, the fail-safe actuator configured to hold the respective air brake flap at a retracted position relative to a suction side of the turbine blade in a powered state of the fail-safe actuator and to release the air brake flap for automatic deployment to an open position upon loss of power to the fail-safe actuator; and

wherein after deployment of the air brake flaps, the method further comprises detecting when the turbine rotor has stopped and whether the turbine blades can be feathered with pitch control to a neutral position.

9. The method as in claim 8 , wherein once the turbine rotor has stopped and pitch control is available, the blades are feathered to the neutral position and the wind turbine is placed in a shutdown state.

10. The method as in claim 9 , wherein power is supplied to the fail-safe actuators to retract the air brake flaps once the wind turbine is placed in a shutdown state.

11. The method as in claim 8 , including providing a sufficient motive force to the air brake flaps upon removing power to the fail-safe actuators to move the air brake flaps to a fully deployed position relative to the suction side of the turbine blade.

12. The method as in claim 8 , wherein the air brake flaps have a top end that is flush mounted with the suction side of the turbine blade in the retracted position of the air brake flaps, the air brake flaps deployable in a generally perpendicular direction from the suction side of the turbine blade.