by David Wojick
On July 26, CFACT’s President Craig Rucker sent Virginia Governor Glenn Youngkin a letter warning him about the serious risk of blade failure in the giant offshore wind facility being built off Virginia. The warning builds on the recent blade failure off of Nantucket, which has littered the beaches with fiberglass fragments. Virginia is also at risk.
In this article, I present some technical background on that risk. The Virginia offshore wind facility will be one of the world’s biggest, with 176 enormous turbines. It is just getting started with pile driving, so no turbine blades have been installed to date. This is an opportune time to undertake caution.
The Nantucket turbines are made by GE, and they are the world’s largest in operation today at 13 MW, each driven by three huge 107-meter-long blades. That is 351 feet for those of us who do not speak metric. The Virginia turbines will be even bigger at 14 MW with blades 108 meters (154+ feet) long. They are made by Siemens Gamesa, or SG for short.
The GE turbines and blades have been in production for going on two years, so have some operational experience. The SG turbines and blades just came into production so there is no experience with them. One could say they are being beta tested off Virginia.
This newness in itself is a great concern. At three blades each, there are an incredible 528 blades with a combined length of over 57,000 meters (187,000 feet or 35 miles) of blades. To take first-production blades to these huge lengths is surely very risky.
Multiple or even systemic failures are certainly possible. A sound engineering approach would be to build a few and see how they did over time. Note, too, that the prototypes were in Europe, so these blades have never been tested in a hurricane, to which offshore Virginia is prone.
Now let’s look at the blade stress physics just a bit, as it is amazing. SG has a quick look on their website, saying this:
The rotational forces found in offshore wind turbines in operation put IMMENSE STRAIN ON THE BLADES and the rest of the wind turbine structure. [Emphasis added.] At a tip speed of approximately 90 meters per second – equivalent to 324 kilometers per hour! (201 mph!) – and a projected lifetime of more than 25 years, high-quality and innovative design is imperative. For a 108-meter-long blade, the rotational forces are around a staggering 80 million newton meters, and the strain on the blades and the structure is intense! To put this into perspective, the force pulling on a human shoulder while spinning a 1 kg object around in an outstretched arm is only about 10 newton meters!
(Eighty-million newton meters is about 59 million pound-feet of torque).
Given these immense, intense strains, the novelty of the SG blades becomes even more of an issue.
To begin with, they are constructed in an unusual way. GE and other major manufacturers build half a lengthwise blade at a time, then glue the two halves together. Building half a tube is relatively simple, just lining a trough-like mold with fiberglass. Gravity is your friend, and inspection is easy.
In contrast, SG builds the entire tubular blade at once. I have no idea how, but it cannot be simple. Gravity wants to distort the tube, and inspection must be difficult. In addition, while SG has built a lot of smaller blades this full tube way, their giant blades are of a different composition. Because of the extreme stresses, they have added carbon fibers.
In summary, we have a newly huge blade, subject to immense stresses, made for the first time in an unusual way with a new composition and never tested in a hurricane. The high novelty risk to Virginia is obvious.
But there is another big risk issue as well; a business issue, if you like. SG no longer exists as a corporation. It was absorbed by its majority stockholder to keep it from going under. The reason, as Reuters puts it, is “quality issues and ramp-up problems caused a 4.6 billion euro (5 billion dollar) annual net loss.”
In Virginia, we are looking at the biggest wind turbine ramp-up in history, where high quality is imperative. One has to wonder if SG is capable of this prodigious task at this time, and that wonder signals a big risk. Not only does SG have a deep history of problems, they are undergoing restructuring.
Given these novelty-laden circumstances, it surely is unwise to try to throw up 35 miles of untested blades without further consideration. Hence Craig Rucker’s letter to Governor Youngkin.
This article has been republished with permission from Cfact.
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