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Wind farm hopes to install light dimming system under extension

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wind turbines (copy)

Wind turbines stand out against the colorful sky of the setting sun at a wind farm located in the rolling prairie hills a few miles northwest of Crown Butte Lake in Morton County. The blinking red lights atop the towers indicate their presence to any pilots flying nearby.

State regulators are giving a wind farm in southwestern North Dakota another year to install technology to mitigate the blinking red lights atop its turbines, with the hope that a new dimming system pans out.

Montana-Dakota Utilities will have until the end of 2022 to equip its Thunder Spirit wind farm near Hettinger with technology so that the lights don't blink bright red all night long. The company asked for the extension because it's interested in a system known as Lighting Intensity Dimming Solution, which adjusts the intensity of the lights based on weather and visibility conditions. The technology developer, Technostrobe, is in the process of securing approval from the Federal Aviation Administration, a necessary step before dimming systems can be installed at wind farms in the United States.

The dimming system has received approval from a Canadian transportation agency and is in use at a wind farm in Quebec.

"This technology is pretty promising," PSC Chair Julie Fedorchak said at a commission meeting last week. "It makes sense to me to allow the technology to develop and see if we can try it and test it at this site to see how it works."

Fedorchak said the commission's approval of the extension for Thunder Spirit is not meant as a sign that it will grant one for every wind farm operator that asks.

The North Dakota Legislature in 2017 passed a law mandating that wind farms install light mitigation technology. The FAA requires lights atop wind turbines to alert pilots to the presence of the giant towers at night, but when the lights blink bright red, they can be a nuisance at night to people living nearby.

Just one type of technology to mitigate the lights is available so far: a radar-based system that keeps the lights off unless an aircraft flies in the wind farm's vicinity. It's been installed at a number of newer wind farms in North Dakota that had to meet a deadline at the end of 2019 to install mitigation technology.

The deadline for older wind farms such as Thunder Spirit is the end of this year.

MDU sought bids for the two types of mitigation systems. The radar-based one is expected to cost more than $3 million, whereas the dimming technology is anticipated to cost under $1 million, Fedorchak said.

In its application for an extension, MDU said it's in its "customers' best interest to delay the installation of currently approved light-mitigation technology given the higher costs and operating expenses when compared with LIDS."

Jeff Grabner, managing director of wind for Technostrobe, told the Tribune he's hopeful a decision from the FAA on the dimming technology will come this year.

If it's not approved, MDU would have to order the radar-based system by November to meet the extended deadline the PSC has granted, company spokesman Mark Hanson said.

Fedorchak said the dimming system could solve concerns raised by Minot Air Force Base about the radar-based system, as the military routinely flies helicopters past wind farms for missions related to intercontinental ballistic missiles buried in the North Dakota countryside. Among the Air Force's concerns is that lights blinking only when helicopters fly past could alert an enemy to their location.

Commissioner Randy Christmann said the military's concerns make the dimming system worthy of further consideration. He said he's been disappointed by the performance of the radar-based systems, which initially kept the lights off only about 40% of the night at some wind farms in North Dakota as tractors and birds inadvertently caused them to blink. Wind farm operators have made tweaks to their systems, and the lights at those facilities now stay off about 80% of the time, one told the PSC at a meeting in December 2020.

"Has it been an improvement? Yes, but it's not having the lights off nearly as much as I'd hoped that it would," Christmann said.

Several newer wind farms failed to meet the 2019 installation deadline and were fined.

Meanwhile, the PSC is advocating for a tweak to the state's light mitigation law that would give commissioners greater flexibility in issuing a waiver or time extension for compliance. The measure, House Bill 1095, has passed the House and now goes to the Senate.

Reach Amy R. Sisk at 701-250-8252 or


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