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Active methods for less noise

An optimised profile and blade design, wing attachments and modified trailing edges are among the passive technologies for wind turbine noise reduction. Their strength is  hat they do not need any additional energy in order to be effective. The results are also relevant for the development of quieter turbomachines and cooling fans.

In a complementary project, scientists from the Institute of Aerodynamics and Gas Dynamics at the University of Stuttgart are researching active technologies for noise reduction. In the research projects, ActiQuiet and ActiQuieter, they have investigated the active, flat suction of the boundary layer on the rotor blade. This suction is performed using one or more suction pumps that are integrated in the rotor. The strength of this method is that it can be optimally adapted to the respective flow conditions of the blade. The objective is to avoid as much noise as possible with the smallest possible energy demand and without impairing the wind turbine’s performance capability. In the first stage, the method is experimentally tested on a profile and is also numerically tested with a CFD simulation program. The result was a suction configuration, in which the suction strength and position of the air outlet are optimised.

On the basis of these promising results, the second stage was about adapting the method to the conditions of a conventional, industrially manufactured wind turbine. The tests have been very promising. The active suction via a broad range of possible operating conditions leads to noise reduction and improved aerodynamics. With a calculated noise reduction of up to 5 dB, the increase in the wind turbine’s power generation was higher than the additional energy expenditure for the suction pump. Only if a noise reduction of more than 5 dB is intended and the pump output has to be correspondingly high does a negative overall energy balance occur. A possible counter strategy could be found in the installation of several smaller pumps rather than one big pump. The objective of this investigation was to be able to make a decision about a prototypical implementation on the basis of scientific and industrial results.

With the active and passive methods, there are technologies in development that could contribute to further sinking the noise emissions of wind turbines in the future.

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Addresses

Project management BELARWEA
DLR, Standort Braunschweig

Industrial advisory board BELARWEA
ENERCON GmbH

Industrial advisory board BELARWEA
GE Renewable Energy

Industrial advisory board BELARWEA
Nordex SE

Industrial advisory board BELARWEA
Senvion Deutschland GmbH

Industrial advisory board BELARWEA
Siemens Gamesa Renewable Energy

Project management ActiQuiet and ActiQuieter
Universität Stuttgart, IAG

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