Technical Requirements for Rotor Blades Operating in Cold Climate

The increasing size of wind turbines up to multi-Megawatt turbines and the increasing numbers of turbines being installed at inland sites even in complex terrain in mountainous areas require special equipment of the rotor blades. However, a commercial serial-produced anti-icing or de-icing system has not yet been proved reliable over many years. Just the opposite is the case. There have been reports about damages in prototype heating systems, and some manufacturers change to special coatings of the blade's surface instead of heating systems. Where are the problems in integrating heating systems into the highly flexible large blades? Which methods are used today and which possible solutions can be taken instead? Starting with the various shapes of leading edge icing, trailing edge icing and blade surface icing, special strategies of operation for different control systems such as pitch, stall and active stall controlled turbines are discussed. Recommendation is given how to optimise the operation strategies of the supervisory systems of the various types using blade heating or not. Also the affect of icing on the rotor blades properties like its natural frequencies and on the blade fatigue and ultimate loads are discussed. Guidance is given which ice fragments at which rotor blade size have to be taken into account for ice throw calculations. (orig.)