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Offshore Wind Turbines Could Mess With Ships’ Radar Signals

Offshore wind development has the potential to transform the nation’s energy supply by providing clean power directly to big coastal cities. In fact, the Biden administration is pushing to develop 30 gigawatts of offshore wind capacity by 2030—enough to power 10 million homes and reduce carbon emissions by 78 million metric tons.But a new study might throw a wrench in those plans. It turns out that massive wind turbines may interfere with marine radar systems, making it risky for both big ships passing through shipping channels near offshore wind farms and smaller vessels navigating around them. While European and Asian nations have relied on offshore wind power for more than a decade, the big wind farms proposed off the US continental shelf are larger and spaced further apart, meaning that ships are more likely to be operating nearby. These farms are proposed along the East Coast from Massachusetts to North Carolina, as well as for a handful of locations off the California coast, according to data from the US Bureau of Ocean Energy Management.A panel of experts convened by the National Academy of Sciences, Engineering, and Medicine concluded in a report issued last week that wind turbines can create two different problems. First, their steel towers can reflect electromagnetic waves, interfering with ships’ navigational radar systems in ways that might obscure a nearby boat.The turbine's rotating blades can also create a form of interference similar to the Doppler effect , in which sound waves shorten as a moving object approaches the observer. In this case, the spinning blades shorten and distort the radar signals sent from passing ships and can produce what’s called “blade flash” on a ship’s radar screen. These flashes can create false images that look like boats and could confuse a human radar operator on the bridge.“If you have something that's moving toward you and you are illuminating it with a radar signal, then the signal that is returned will actually have what's called a phase shift. Essentially, it appears that you have the object coming closer,” says Jennifer Bernard, professor of electrical and computer engineering at the University of Illinois Urbana-Champaign and a member of the National Academies panel that produced the report. Bernard says that phenomena does not completely block the radar image, “but it does create clutter and makes everything a little bit more washed out, because now some things are still and some things are moving. So that makes everything a little bit more difficult to interpret.”In the report, the US Coast Guard raised concerns that the radar interference may also hamper search-and-rescue efforts for ships that get in trouble around wind farms.“These are large machines in the ocean and will impact marine vessel radar. That's inevitable,” says Bill Melvin, chair of the panel and deputy director for research at the Georgia Tech Research Institute. “We recommended that investment should be made to study and understand the problem in more detail and also further develop the proposed mitigating solutions.”