Posted on 02/02/2023 9:56:52 AM PST by Leaning Right
Those pics were just random pics from a "windmill collapsed" Google image search. However, doing a Google Lens search on the image turned up this story (among others):
HUNTER, Okla. — Enel Green Power North America is investigating why a wind turbine belonging to the company collapsed Tuesday, May 21, 2019, near this rural community."Enel Green Power North America is working with the turbine manufacturer GE to investigate an incident that occurred yesterday involving a turbine failure at our Chisholm View II wind project in Grant County, Oklahoma," the company said Wednesday in a statement. The wind farm's footprint extends into both Grant and Garfield counties.
According to EGP, there were no injuries as a result of the incident.
The turbine was part of Enel Green Power's 6,000 acre, 64.8 megawatt Chisholm View II wind farm, located immediately east of Hunter.
This wind farm was built adjacent to the original, much larger, Chisholm View project, which sits on 45,000 acres. Construction of Chisholm View II began on the project in summer 2012, and the wind farm began operating in 2016, adding another 64.8 megawatts to the first project's 235 megawatts.
Access to the turbine was blocked Wednesday morning for safety, an Enel Green representative near the site said. Nobody had been within 300 feet of the GE 2.4 megawatt turbine since it collapsed, he added, though one employee had piloted a drone up to the wreckage earlier in the day, attempting to assess structural damage.
Workers were waiting on an Enel Green investigation team to arrive at the site to determine cause, he said.
"Our first concern, as always, is ensuring the safety of our workers, contractors and the surrounding communities, and given the ongoing nature of the investigation, we ask that the community avoid the area of the incident," the statement said.
This story will be updated as more details become available.
So there you go. Hunter, OK, May 21, 2019. I used to work in commercial broadcasting, so I'm familiar with tower wind loading. (I'm not a structural engineer by any stretch, just a broadcast engineer.) But we did have to obtain certified stress analysis of our 1,000' broadcast tower before we added a new antenna, additional transmission line, or different lighting, not only for wind but also wind plus icing.
As I speculated in another post on this thread, I think the common element to these tower collapses and also tower fires is failure of the blade feathering system, causing wind loads that exceed tower design limits. Yes, they should be able to withstand 80-100 MPH winds, but that also assumes a properly feathered blade system offering minimal resistance. If the blades get stuck in a power producing pitch, or the azimuth motor that rotates the doghouse to face directly into the prevailing winds fails, that can 1) cause more wind resistance than the tower was designed for (collapse,) and/or 2) overspeed the gearbox and generator (fire, if only the blade pitch mechanism fails but the doghouse is still facing the wind.)
New bolts wont help, as the tubes themselves are breaking.
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It has not been my observations that the ‘tubes are breaking’...that’s not to say it hasn’t happened but I can’t think of any recent examples of that. Once a failure happens, the tubes of course ‘break’ but if I was to go back through numerous IWT failure records, this typically is not the genesis of the failures... it’s usually something else and ‘tube failure’ happens as a secondary thing. If your observations are different than that, I’m very interested to look at any examples of it.
As can be summarized from some of my other posts here, there are many failure mechanisms but the fatigue of tower flange bolts is the most common one. Fatigue as a failure mechanism primarily depends on two things... how stressed something is and how many cycles it is put through (simplified for the purpose of this discussion). Thus by inference, changing out the bolts is absolutely required at some point since this restarts the clock on counting the number of stress cycles. Having said that, there are many failure mechanisms... and preventive measures such as changing out the bolts doesn’t reset the clock on anything else.
So there you go. Hunter, OK, May 21, 2019.
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Yup, that’s the one I was thinking about. The pictures I’d seen earlier of that one were taken from a different angle.
Regarding your other comments on blade feathering, fires etc, I can agree with some of that but would qualify it. I don’t think the data supports a position that tower collapses and tower fires relate to ‘failure of the blade feathering mechanism’ as a common element. No doubt there have been fires and collapses in high winds where those protective measures failed but there have been even more collapses and fires which were not in in winds when the blade feathering or rotor rotation mechanisms even needed to be employed. More to the point with this is that even if the feathering mechanism does work just fine and the rotor is turned so that it is not facing into the wind when wind speeds exceed the limit, drag increases as the square of wind speed and this increases the tensile loading of the tower bolts and the number of stress cycles the bolts are put through… and all this simply brings the bolts closer to an eventual fatigue failure which may be well after the fact of a high wind event. As for ‘overspeeding the gearbox and generator because of blades stuck in a power producing pitch’, this has happened but most of the fires were simply the result of something else failing that got hot (such as a bearing) and ignited the oil…. and most of those were during what would be called ‘normal operating conditions’.
The point that I want to make with this is very simply this… There seems to be a perception that IWT failures are the result of something extraordinary having occurred. That does happen but a more common failure mechanism is that stuff just wears out and is doing so at a rate that is faster than what wind farm operators want to admit to…. and by ‘wearing out’, this is most referring to fatigue from cyclical loading whether that is due to changes in wind speed/direction or due to cyclical loading of the rotor and support structure that relates to the normal rotation of the rotor when generating power. If one wanted to suggest that this means that what should be regarded as normal engineering design limits are being exceeded, I can agree with that.
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