Method for de-icing at least one rotor blade of a wind power installation

A method comprising:

• de-icing at least one rotor blade of a rotor of a wind power installation, wherein the rotor is able to be operated at a variable rotating speed and the wind power installation generates an output from wind, the de-icing comprising:
• checking for an icing situation on the at least one rotor blade;
• and
• changing from a normal operation of the wind power installation without de-icing to a de-icing operation when an icing situation has been identified;
• wherein in the de-icing operation:
• the at least one rotor blade is heated for de-icing;
• and
• the rotating speed and/or the generated output are reduced as a function of at least one environmental condition of the wind power installation;
• wherein the at least one environmental condition is selected from the list including:
• an external temperature of the wind power installation;
• and
• a wind speed in a region of the wind power installation
• wherein in a partial-load operation, when the wind speed is below a nominal wind speed, the rotating speed increases as the wind speed increases, wherein:
• the wind speed dependent increase in the de-icing operation has a smaller gradient than in the normal operation;
• and/or
• in the de-icing operation, the wind speed dependent increase has a smaller gradient:
• the higher a degree of icing;
• and/or
• the lower the external temperature.