via David Wojick
On July 26, CFACT President Craig Rucker sent Virginia Governor Glenn Youngkin a letter warning him of the serious risk of blade failure at a massive offshore wind facility under construction off the coast of Virginia. The warning was based on a recent blade failure off Nantucket that left fiberglass fragments strewn across the beach. Virginia is also at risk.
In this article, I present some basic information about that risk. The facility will be one of the largest in the world, with 176 massive turbines. The pile driving has just begun, so no blades have been installed yet. This is a good time to err on the side of caution.
The Nantucket turbines, made by GE, are the largest turbines in operation today, generating 13 MW of power, each driven by three giant blades measuring 107 meters long. For those who don’t know the metric system, that’s 351 feet. The Virginia turbines are even larger, generating 14 MW and measuring 108 meters (154+ feet) long. They’re made by Siemens Gamesa, or SG for short.
The GE turbines and blades have been in production for two years, so there is some operational experience. The SG turbines and blades are new to production, so there is no experience with them. One could say they are being beta tested off the coast of Virginia.
The novelty itself is a major concern. With three blades each, there are a staggering 528 blades, totaling more than 57,000 meters (187,000 feet or 35 miles) in length. Getting the first production blades to this enormous length was certainly a risk.
Multiple or even systematic failures are certainly possible. A reasonable engineering approach would be to build a few and see how they perform over time. Also note that the prototypes are based in Europe, so these propellers have never been tested in a hurricane, which is something the Virginia coast is prone to.
Now let’s look at a little bit of the stress physics of the blade, because it’s pretty cool. SG has a quick look on their website, saying:
“The rotational forces found in operating offshore wind turbines exert MASSIVE STRESSES ON THE ARMS and the rest of the wind turbine structure. (Emphasis added) With blade tip speeds of around 90 metres per second – that’s 324 kilometres per hour! (201 mph!) – and an expected lifespan of over 25 years, high quality and innovative design is a must. For a 108 metre blade, the rotational forces are around 80 million newton metres, and the stress on the blades and structure is enormous! To put that into perspective, the pull on a human shoulder when rotating a 1 kg weight in an outstretched arm is only about 10 newton metres!”
(80 million newton meters is equivalent to about 59 million pound-feet of torque).
With these huge and intense pressures, the novelty of the SG blade becomes an even bigger issue.
First, they’re made in an unusual way. GE and other major manufacturers make the blades one half at a time, then glue the two halves together. Making a half tube is relatively simple, just lining a trough-like mold with fiberglass. Gravity is your friend, and inspection is easy.
SG, on the other hand, makes the entire tubular blade all at once. I don’t know how, but it can’t be simple. Gravity wants to deform the tube, and testing must be difficult. Also, while SG has made a lot of smaller blades this way, their giant blades are a different composition. Because of the extreme stress, they added carbon fiber.
In short, we have a new blade that is massive, highly stressed, built for the first time in an unusual way with new components and never tested in a hurricane. The high risk of the novelty for Virginia is obvious.
But there is another big risk, a business problem if you will. SG no longer exists as a corporation. It has been taken over by its major shareholders to avoid bankruptcy. The reason, as Reuters reports, is that “quality issues and acceleration issues have caused an annual net loss of 4.6 billion euros ($5 billion).”
In Virginia, we are witnessing the largest wind turbine ramp-up in history, where high quality is a must. One has to wonder if SG is up to the task at hand at this time, and that question signals a major risk. Not only does SG have a deep history of problems, it is also in the midst of a restructuring.
Given these novel circumstances, it would certainly be unwise to attempt to introduce 35 miles of untested blades without further consideration. Therefore, Craig Rucker wrote to Governor Youngkin.
Image Idaho National Laboratory Creative Commons
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