Wind energy installations are also erected at sites at risk of icing. In the USA, for example, approximately 65% of the wind energy installations are situated at sites at which icing is possible. Different meteorological phenomena may result in ice building up on the rotor blades of wind energy installations. This sometimes causes an increase in mass of up to several hundred kilograms.
Such a large increase in mass on the rotor blades may result in great stresses on and even the destruction of wind energy installations. In addition, so-called shedding of ice may result, that is to say ice is hurled away from the rotor blades. The consequence may be damage to persons, animals and materials.
A possible way of detecting ice on wind installations is sometimes legally prescribed and is used to protect the installation. After ice has been detected, corresponding countermeasures, for example de-icing or stopping of the installation, can be taken.
DE 100 65 314 B4, for example, discloses a method which can be used to detect state changes of a rotor blade, for example ice build-up, of a wind energy installation. Such detection is possible even when the rotor is at a standstill. However, this requires a special, high-resolution sensor which is fitted to the rotor blade and is connected to an evaluation unit. Such a method is very cost-intensive on account of the sensor or a plurality of sensors on a plurality of rotor blades.
It is therefore desirable to specify a possible way of detecting a state change, in particular ice build-up or damage to rotor blades of a wind energy installation, in a cost-effective manner.