Rotor blade de-icing system

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A rotor blade de-icing system , also known as a rotor blade de- icing system, is a device that is used to keep the rotor blades of wind turbines free of ice. The aim is to achieve additional yields in frosty months and to reduce mechanical loads on the system due to ice accumulation, which means that cool climates up to the Arctic Circle can now also be used for wind energy use. De-icing is usually carried out by heating the rotor blades with heating resistors or by ventilating them with the waste heat from the nacelle.

background

During certain weather conditions , ice can form on the rotor blades in winter , mainly at high humidity and low temperatures. This reduces the efficiency as it changes the shape and thus the aerodynamic profile of the blades. There is also often an imbalance in the rotor and an increase in the weight of the blades. The result is a higher sound level and vibrations, which in turn increase the loads on the system and have a negative effect on the service life of the wind turbine. In addition, falling chunks of ice (the so-called ice throw ) can pose a danger, which is why the closer area around wind turbines should be avoided during periods of frost . For these reasons, wind turbines are automatically switched off when ice forms on the rotor blades, which, however, is associated with a loss of yield. In order to avoid this, wind turbine manufacturers experimented very early with various types of rotor blade de-icing, with the results not being satisfactory until the end of the 2000s. With the construction of more and more wind turbines in cold climate regions in Northern Europe and North America, the problem of ice formation moved more into focus, which is why the development of rotor blade de-icing systems was accelerated towards the end of the 2000s. In the meantime (as of 2013), most wind turbine manufacturers offer rotor blade de-icing systems as optional special equipment for their systems.

functionality

Since early attempts to provide the rotor blades with an ice-repellent coating had not proven to be very successful, modern rotor blade de-icing systems usually work by heating the rotor blades. The type of heating can differ from system manufacturer to system manufacturer.

There are various rotor blade de-icing systems. Enercon uses z. B. to a system of heating resistors at the rotor blade root, where the heated air is blown through the rotor blade by a fan. This keeps the temperature of the rotor blade at approx. 4 ° C, which prevents the formation of ice on the blades. With this system, the heating requirement for the E-70 and E-82 plant types is 85 kW , around 3–4% of the nominal output of these wind power plants. In two test runs of two E-82-2MW in winter 2009/10 at the locations in Dragaliden in the north of Sweden and in Kryštofovy Hamry in the Czech Republic, after deducting personal requirements, an additional yield of 48% and 54% respectively could be achieved. This corresponds to about 10 times the additional consumption by the heating system. However, these locations have favorable climatic conditions for ice accumulation and are therefore not easily transferable to other locations.

In contrast to Enercon, Nordex relies on partial de-icing. Only the aerodynamically particularly important leading edges of the rotor blades are heated by means of resistance heaters mounted directly under the wing surface. If the sensors mounted on the nacelle register that the system is beginning to freeze, the de-icing system is switched on, allowing the wind turbine to continue running. It is also possible to defrost during standstill with subsequent restarting. During test runs in the winter of 2010/11 in northern Sweden, an additional yield of over 25% was found in the frost months compared to a system of the same construction that was not equipped with a rotor blade de-icing system. The additional yield in 2011 as a whole was 8%, while the self-energy requirement of the de-icing system was 0.3%.

Web links

Individual evidence

  1. ↑ Erich Hau: Wind power plants: Basics, technology, use, economy. Berlin / Heidelberg 2008, pp. 275f.
  2. ↑ The nominal output of the E-70 is 2.3 MW, the E-82 is offered with a nominal output of 2 MW, 2.3 MW and 3 MW. See also the list of Enercon wind turbines .