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Wind energy

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Exploitation of wind energy is among the oldest methods of obtaining energy from the environment. It is experiencing a renaissance today in the light of limited resources and now contributes to the generation of electrical current in many countries. However, the inconsistency of wind means that it can only be utilised in conjunction with other energy sources or reservoirs. In Germany the maximum achievable contribution is currently considered to lie between 20 and 25%. It currently amounts to about 7%.

Conversion of wind energy to electrical energy is achieved by a synchronous or asynchronous generator, depending on the type of wind power plant employed. The first case involves the brushless (i.e. without commutation) generation of alternating current, while carbon brushes and collectors are employed for current generation in asynchronous generators. This often occurs under extreme conditions. Frequently erected near coasts or offshore, the systems are exposed to salty corrosive air. When erected at high altitudes (as is frequently the case in China), the plants are required to operate reliably in conditions characterised by low temperatures and extremely low air humidity. Collector systems which transmit the electrical energy generated must withstand up to 5 MW output. Severe vibration often adds to the difficulties here. Despite this, collector systems of this kind are required to maintain reliable contact.

Metal-graphite composite materials provide particularly good prerequisites for these requirements, with their robust and corrosion-resistant behaviour and good frictional characteristics enabling continuous operation free of malfunctions. These characteristics can be objectively adapted to ambient conditions through impregnation of graphite with different functional media. The same materials are also employed for other purposes in wind power generators (e.g. for earthing the rotor shaft and the entire unit, as a lightning conductor or in motors for adjusting the angular deflection of the rotor).

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