Spinning blades of offshore wind turbines found to create little noise

Block Island Wind Farm.

From eco RI News (ecori.org)

New research lead by the University of Rhode Island has concluded that offshore wind facilities produce minimal noise above and in the water while the blades are spinning. But the noise and vibrations from building them are a concern.

The research, funded through the Bureau of Ocean Energy Management, began with the construction of Deepwater Wind’s Block Island Wind Farm in September 2015. It continued when the five turbines began spinning in late 2016.

Through acoustic monitoring, James Miller, URI professor of ocean engineering and an expert on ocean sound propagation, found that the sound from the turbines was barely detectable underwater.

“You have to be very close to hear it. As far as we can see, it’s having no effect on the environment, and much less than shipping noise,” Miller said.

Working with a team of specialists from Woods Hole Oceanographic Institution, Marine Acoustics Inc. of Newport, and others, Miller heard ships, whales, wind, and fish. But noise measurements 50 meters from the turbines was hardly audible. Above the waterline, the swish of blades was barely heard, according to Miller.

The noise was monitored using hydrophones in the water and geophones, which measure the vibration of the seabed, on the seafloor.

The vibrations from the pile driving of the turbine’s support structure is a bigger unknown. Miller said the vibrations on the seabed had a surprising intensity that may harm bottom-dwelling organisms such as flounder and lobsters, which have a huge economic value in the state.

“Fish probably can’t hear the noise from the turbine operations, but there’s no doubt that they could hear the pile driving,” Miller said. “And the levels are high enough that we’re concerned.”

To minimize the aquatic impacts, the pile driving started with minimal sound to allow marine life to move away. Pile driving was also prohibited between Nov. 1 and May 1 to protect migrating North Atlantic right whales, which are critically endangered. The pile driving was also limited to daytime so that spotters could search for nearby whales.

This kind of monitoring will continue once construction starts on other Deepwater Wind offshore wind farms such as the Skipjack Wind Farm, off the coast of Ocean City, Md. Additional research will be conducted in the federal offshore wind energy area between Massachusetts and Rhode Island.

In addition to the acoustic impacts, the researchers looked at the impacts of offshore wind facility construction and operations on fishing, habitats and seabed scaring and healing. Studies will eventually be published from that research.

URI expects to study and provide data for the nearly 1,000 offshore wind turbines that have been proposed for installation in the waters between Massachusetts to Georgia in the coming years.

“We’ve become the national experts, which has added to Rhode Island’s reputation as the Ocean State,” Miller said.