Companies that operate wind farms in North Dakota say they’re working on tweaks to make sure tractors and migrating birds don’t inadvertently set off the lights atop wind turbines at night.
Under state law, newer wind farms had to install technology by the start of 2020 to mitigate the lights so that they don’t cause an eyesore by blinking bright red all night. The operators have put in radar-based systems meant to keep the lights off unless an aircraft flies in the vicinity.
But members of the Public Service Commission, which pushed for the law, say they’ve noticed the lights seem to stay on more often than they had expected.
Wind farm operators told the PSC at a meeting Friday that they have observed the same thing.
The primary culprit seems to be birds, especially those flying south for winter.
“The system either recognizes the flock as an aircraft or it has enough uncertainty about what it is detecting to default to the activation of the light system,” said Dave Sederquist, senior regulatory consultant with Xcel Energy, which has installed the technology on its Foxtail wind farm in southeastern North Dakota.
Representatives from Xcel and NextEra Energy said they are working with the companies who built the systems to fine-tune them so that only aircraft trigger the lights.
Agricultural equipment, road traffic and the weather also can cause the lights to pop on, said Chris Kozlowski, director of business management for NextEra. The developer uses the technology on four of its wind farms in North Dakota, including on a portion of the Oliver wind farm northwest of Mandan and the Emmons-Logan wind farm southeast of Bismarck.
When NextEra first installed the technology, the lights blinked about 60% of the night, he said. The company has made improvements to the systems, and now they blink about 20% of the time, he said.
The lights always blink briefly every night as a test to ensure that nothing is malfunctioning.
“Safety is the No. 1 priority as we apply this new technology at the wind sites,” Kozlowski said.
The lights sit atop wind turbines and blink every few seconds to alert pilots flying in the dark.
Some people who live near wind farms have complained that the lights are a nuisance and ruin the night sky. With those concerns in mind, the PSC pushed for the Legislature to pass a law in 2017 requiring that wind farm operators install light mitigation technology on their projects. While newer wind farms have already installed it to meet the first deadline imposed by the law, sites permitted before June 2016 have until the end of 2021 to comply.
“It’s really an important piece for the industry, to be the best possible neighbor it can be and to minimize impacts in places that are rural,” Commissioner Julie Fedorchak said.
The radar-based technology is known as an “aircraft detection lighting system.” It sits atop a tower within a wind farm and communicates to the surrounding turbines when the lights should start blinking.
Wind farm operators have purchased the technology from one of several vendors worldwide. The technology can cost anywhere from a few hundred thousand dollars to over $1 million, depending on the size and location of the wind farm.
The radar system is the only kind of light mitigation technology approved so far for wind turbines in the United States. Another type known as a “lighting intensity dimming solution” awaits approval from the Federal Aviation Administration.
That proposed technology would keep the blinking lights on at night but dim them based on the weather and visibility conditions, said Jeff Grabner, managing director of wind for Technostrobe, which is developing the system.
Such a concept prevents a person nearby from experiencing the shock of the lights suddenly turning on in the dark at their full intensity when a plane flies by, he told the Tribune in an interview.
The system works by equipping some of the turbines within a wind farm with a visibility sensor.
“The sensor is taking a reading of the particle density in the air,” Grabner said. “It can measure sleet, snow, rain, dust, fog, you name it.”
The technology first went before the FAA several years ago. Technostrobe did not initially secure the agency’s approval and is now trying again. The company heard back in July that an independent lab had completed its initial testing of the product.
The next step, he said, is for the FAA to deploy it in a test-run at an airport. A pilot would fly around the technology while the intensity of the lights increases and decreases.
Canadian transportation officials approved Technostrobe’s technology this past June, and it’s in use at a wind farm in Quebec. The lights at the site are dimmed to 10% of their full intensity two-thirds of the time they operate at night, Grabner said.
He called light mitigation technology for wind turbines “a growing topic of discussion across the country.” Other states and communities are beginning to consider requirements similar to those of North Dakota, which was the first in the nation to impose such a law.
Discussion surrounding the technology is likely to come up again when the Legislature convenes in January.
The PSC has prefiled a bill that would give the commission the ability to grant a waiver or an extension to wind farms on installing light mitigation systems.
The state’s 2017 law became problematic for one developer when it sought a permit to build a wind farm in Ward and McLean counties.
The Minot Air Force Base raised concerns about the radar-based system Southern Power intended to use for its proposed Ruso Wind project. The Air Force flies hundreds of helicopter missions each year to intercontinental ballistic missile sites, some of which are located near where the company sought to erect the turbines.
The PSC denied the company a permit this past March, with several commissioners indicating they felt there was no wiggle room within the law to make an exception for the project.
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