If wind energy converters are located anywhere near a residential area, they must never become too noisy even in high winds. Most such power units try to go easy on their neighbors’ ears, but even the most careful design cannot prevent noise from arising at times: One source is the motion of the rotor blades, another is the cogwheels that produce vibrations in the gearbox.
These are relayed to the tower of the wind turbine, where they are emitted across a wide area – and what the residents hear is a humming noise. “People find these monotone sounds particularly unpleasant, rather like the whining of a mosquito,” says André Illgen, a research associate at the Fraunhofer Institute for Machine Tools and Forming Technology IWU in Dresden. If the wind energy converters hum too loudly, they are only permitted to operate under partial load: They rotate at a slower speed and generate less electricity.
In some cases the operators have to install additional damping systems or even replace the gearbox – an expensive business. However, the effectiveness of the passive damping systems used until now is somewhat limited: They only absorb noise at a certain frequency. Since modern wind energy converters adapt their rotational speed to the wind velocity in order to generate as much electricity as possible, however, the frequency of the humming sound also varies. Despite noise attenuation measures, humming noises penetrate the surrounding area.
In a joint project with colleagues from Schirmer GmbH, ESM Energie- and Schwingungstechnik Mitsch GmbH and the Dr. Ziegler engineering office, IWU researchers have developed an active damping system for wind turbines. The project is being funded by the “Deutsche Bundesstiftung Umwelt”. “These systems react autonomously to any change in frequency and damp the noise – regardless of how fast the wind generator is turning,” says Illgen.
The key components of this system are piezo actuators. These devices convert electric current into mechanical motion and generate “negative vibrations”, or a kind of anti-noise that precisely counteracts the vibrations of the wind turbine and cancels them out. The piezo actuators are mounted on the gearbox bearings that connect the gearbox to the pylon. But how do these piezo actuators adjust themselves to the respective noise frequencies? “We have integrated sensors into the system. They constantly measure the vibrations arising in the gearbox, and pass on the results to the actuator control system,” says Illgen.
The researchers have already developed a working model of the active vibration dampers, and their next step will be to perform field trials.
Monika Weiner | alfa
The world's most powerful acoustic tractor beam could pave the way for levitating humans
22.01.2018 | University of Bristol
Siberian scientists learned how to reduce harmful emissions from HPPs
22.01.2018 | Siberian Federal University
On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.
We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...
What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...
For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.
Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...
At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.
No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...
Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.
Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...
08.01.2018 | Event News
11.12.2017 | Event News
08.12.2017 | Event News
22.01.2018 | Materials Sciences
22.01.2018 | Earth Sciences
22.01.2018 | Life Sciences