Sound tuning for wind turbines

Together with the entire Product Development team, the Senvion Patent Department is constantly looking for innovative approaches that will make Senvion and the wind industry better, cheaper or more adaptable in the future. In this case, the Senvion colleagues have jointly managed to find a patent solution for sound emissions from the turbines in the truest sense of the word. The “Hamburger Wirtschaft” magazine has taken a close look at the innovation:

Senvion has developed an innovative procedure for reducing the operating noise of wind turbines. The innovation and patent center has selected it as ‘Patent of the Month.

Wherever wind turbines are installed, one topic generally arises sooner or later: are the turbines too loud?

It is a fact that roughly one third of German gross electricity consumption is currently covered by renewable energy sources. In 2016, wind energy usage in particular was further expanded in Germany. According to the register of installations of the German Bundesnetzagentur for Electricity, Gas, Telecommunications, Post and Railway, new onshore wind turbines with a total power of 4,402 megawatts were commissioned. This represents a 10 percent increase on the previous year. One of the manufacturers of wind turbines is Senvion GmbH (up to 2014: REpower Systems), which has its German headquarters in Hamburg.

Less and less space is available for wind farms. To achieve more power, old turbines are being replaced with new ones and increasingly wind farms are being built closer to residential areas or nature reserves. “The importance of noise protection has increased,” says Ulrike Keltsch, head of the patent department at Senvion. In addition to residents, animals can also be disturbed by the operating noises.

In summer 2015, Senvion's Development department applied for a patent for a procedure that can reduce the sound volume of the wind turbines in operation. The noise emissions of wind turbine generators include broadband noises that form a masking noise. However, narrowband noises may also be audible under certain circumstances; for example they can be caused by a generator or a gearbox of the wind turbine. The invention consists of a noise emission control device for a wind turbine that reduces any noises that may arise by surrounding them with the broadband noises that are more pleasant for humans and animals. This is achieved by means of an active noise source that emits a masking noise in at least one spatial direction in a frequency band around the individual sound frequency.

“This control device is not yet available,” says Keltsch. “Our turbines are quiet enough for the existing wind farm sites.” Senvion's engineers frequently develop their inventions preventatively, looking to the future. However, since the requirements regarding generating volume are in-creasing, the turbines themselves will also increase in size , and Keltsch believes that it is perfectly possible that the invention will come into use. If a customer wants a noise reduction measure, for a new construction or a retrofit, prototypes of the control device would then be in-stalled and tested in an existing wind farm, Keltsch states. “We would probably have to perform two to three correction cycles before the invention is implemented perfectly,” says Keltsch. Then Senvion would talk to the suppliers, clarify the supply chain, order the necessary individual parts, and finally manufacture the product in a small production run. The invention could then be tested in practice, and be ready for operation within four to twelve weeks.