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MN wind turbines shut down over safety concerns from ice  

Credit:  Written by Tom Steward | Center of the American Experiment | February 24, 2018 | www.americanexperiment.org ~~

Wind turbines at a Freeborn County wind farm were shut down this week, due to safety concerns.  A longtime American Experiment source got wind of an incident on Thursday involving a livestock truck that was struck by “ice throw” that may have come from a wind turbine at Bent Tree Wind Farm.

I got a call that a semi-truck had been damaged by ice throw from a wind turbine on Highway 13, south of Hartland.  Law enforcement was on the scene. The truck was southbound and the ice hit the driver’s side, so I guess that means it had to come from a turbine on the east side of the road.  The person who told me said there are turbines really close to the road there.

This photo of the dent in the truck’s cab captures the reflection of one of the turbines in the upper right corner of the picture, showing its close proximity to the highway. The wind farm’s owner, Alliant Energy, temporarily pulled the plug on some turbines, according to KAAL-TV.

According to company spokesperson Justin Foss, a few turbines remained shut-down Friday and workers are continuing to monitoring weather conditions for wind and ice. Alliant Energy shut down some of its turbines on a Freeborn County wind farm after receiving a complaint.

Spokesperson Justin Foss said someone reported ice from a turbine on the Bent Tree Wind Farm hitting a semi-truck on Highway 13.  The farm is located in Hartland. Alliant shut down a “few select turbines” as a precaution, according to Foss.

The incident clearly raises public safety concerns over wind turbines located within range of roads and houses, given the potential danger of being hit by ice projectiles. Our source notes the turbines were allegedly coated with ice for several days leading up to the incident.

It sounds like a slight change in timing or trajectory could have resulted in serious injury or even fatality for the truck driver.  What if this had been a small car rather than a semi-truck?

The turbines are much louder and make a different noise when there is ice on the blades.  So Alliant should have been fully aware they were running turbines with ice on the blades. Why would they even run these turbines when the blades are covered in ice?

Should commercial-size high speed wind turbines operate so close to roads? How many other wind farms also operate next to roads? Our source did the math.

It is especially important because the danger of ice-throw from the turbines come up a lot at all of these wind permit site permits. The state Public Utilities Commission allows these huge 400 and 500-foot turbines 250 feet from the center pole to the public road. They don’t even measure from the end of the really long turbine blades for the setback. This is also WAY shorter than the wind turbine manufacturer’s recommendation. General Electric recommends 1.5 (hub height + rotor diameter).

The Bent Tree turbines are from Vestas, not GE, but the same principles apply. The hub height in Bent Tree is 80 meters/ 262.5 feet.  I think those blades are 145 feet each, so your rotor diameter is going to be about 300 feet. (262.5 + 300) X 1.5 =  843.5 feet.   I looked at Google Earth and found lots of Bent Tree turbines WAY closer than that.

The most likely source looks like this one with the center pole about 300 feet from the road.  That means the tip of the blade could be as close as 155 feet from the road when the ice flies off.

Are some of the Bent Tree turbines located too close to Highway 13 under adverse weather conditions? Is the Minnesota Public Utilities Commission looking into the incident?

The trucker’s close call couldn’t come at a touchier time for another wind farm under consideration in Freeborn County. The temporary shutdown and fallout from the incident will not fail to capture the attention of opponents to the controversial Freeborn Wind Farm proposed for south of I-90 between Albert Lea and Austin.

UPDATE: Wisconsin Power and Light and Alliant Energy have notified the MPUC about steps taken “in an abundance of caution” in response to the incident reported on Highway 13. Here’s most of the letter from Brad Kulpa, Director of Wind Operations, filed on the MPUC online docket.

At approximately 5:00 PM yesterday, a WPL representative at Bent Tree received a voice mail from the Minnesota Highway Patrol stating that Highway Patrol had received a complaint alleging that turbine ice had contacted a semi-trailer truck traveling south yesterday at approximately 4:30 PM along MN HWY 13. The voicemail advised that the incident was being handled as a property damage event, that no citation was being issued, and that there were no injuries as a result. This is the first event in the history of Bent Tree’s operations involving possible turbine ice shedding contact with a passing vehicle.

Following the voicemail from the Highway Patrol, a Bent Tree technician was immediately dispatched to the site to assess the situation and take any turbines offline that were showing signs of ice shedding. The technician reported back to Bent Tree site management that he could find no ice along HWY 13, and that he had not witnessed any turbines shedding ice. However, as a precaution, WPL took 15 turbines
along HWY 13 and secondary roads offline while WPL further investigated the matter. Bent Tree site management also communicated to the Freeborn County Sheriff (as the result of being referred by the Highway Patrol) WPL’s plan to shut down turbines adjacent to roadways while WPL further investigated.

We are managing these turbines based on wind direction. At the present time, 11 Turbines upwind of a road remain offline. We will continue to actively manage the turbines until we can confirm that there is no ice on the blades.

Source:  Written by Tom Steward | Center of the American Experiment | February 24, 2018 | www.americanexperiment.org

This article is the work of the source indicated. Any opinions expressed in it are not necessarily those of National Wind Watch.

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