Weather Guard Lightning Tech

Vineyard Wind Battles GE Vernova, UK Funds Blade Innovation

Fraunhofer studies uptower carbon blade repairs, Vineyard Wind’s fight with GE Vernova deepens, the UK backs offshore innovation, and a 26-year Horns Rev study tracks how birds adapt to turbines.

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The Uptime Wind Energy Podcast, brought to you by StrikeTape. Protecting thousands of wind turbines from lightning damage worldwide. Visit striketape.com. And now your hosts.

Allen Hall: Welcome to the Uptime Wind Energy podcast. I’m your host, Allen Hall. I’m here with Rosemary Barnes, Yolanda Padron, and Matthew Stead. Fraunhofer has published peer-reviewed feasibility research in wind energy science. And Rosemary, I don’t know if you read wind energy science, but there’s a lot of good information there about wind turbines and mechanical aspects.

Not much on the electrical side, but a lot about mechanical. Uh, in, in, in wind energy science, uh, they had a discussion or an article about repairing damaged pultruded CFRP spar cap planks while the blade stays on the turbine. Using finite element analysis on a 81.6-meter [00:01:00] blade from a seven-megawatt offshore turbine, the researchers found that a shear web window cut out as short as one meter drops buckling resistance from 20.7 times critical load to four times critical load, a reduction of over 80%.

The fix? Temporary external clamping frames with a pre-tensioned span-wise rod to carry gravity loads, combined with internal push rod assemblies and external stringers profiles to restore buckling resistance, all installed and removed uptower. Wow. I know we’ve discussed the carbon pultrusion repair situation and how critical that is or h- how difficult it is.

I didn’t realize it was that difficult, Rosemary, that if you actually try to replace a one-meter section of a carbon pultrusion, you’re re- reducing the, the, what, the, the buckling resistance by 80%? [00:02:00] Holy moly.

Rosemary Barnes: I don’t think that’s even 100% pultrusion specific, right? They’re talking about cutting a, a window in the shear web.

Allen Hall: Yes.

Rosemary Barnes: So that could be for any kind of repair you might have to do that, including if you need to repair, like sometimes you need to repair the, the shear web. Um, and even though, like, they’re not doing a lot of heavy lifting, um, that’s kind of a structural pun, um, they’re still super important. If they’re not there, then you’re gonna have big problems pretty immediately.

The way that it works with repairs is that there’s certain kinds of damage that you know that you can just do uptower. The technicians know they can do it. They don’t need to call an engineer. The engineer doesn’t call- need to call the expert engineer. But when you need to do something a bit unusual, like a whole meter of web removed, then you’re gonna need to get an engineer to, um, dial in the, y- the, to rerun the design codes basically, um, but with this weak structure now to see is this okay and is it okay, you know, uh, [00:03:00] obviously a turbine that is just, um, idle or it’s not even idle, it’s just fixed in place while they’re repairing it, that has different loads on it to one that’s operating.

So, you know, they’ll run that and make sure that it’s safe, um, before they do the repair. So what I really like about Fraunhofer is that they in some ways, like- Maybe it’s not cutting-edge science or engineering because they are largely repeating what is already well known in industry. But the problem is that industry doesn’t tell everybody else.

And so it is, like, such a vital role to then go and illustrate, um, to everybody else what, what’s happening in industry. And they, they are… Like, there is this problem with wind energy where academia and industry are not, um, talking too much, and a lot of the academic stuff just doesn’t relate at all to what’s happening in the industry.

But Fraunhofer do, like, 90, 90% of the time seem to get it at pretty right.

Allen Hall: When a carbon protrusion is [00:04:00] used, that really localizes where the load is versus in, in some of the more fiberglass designs that I’ve seen, the shell is actually taking some of the load. It’s not all in the shear web, so to speak. So doesn’t that sort of focus the loads into one location a little bit more when you move to carbon?

Isn’t that the point?

Rosemary Barnes: Yeah. Well, the carbon fiber is, is a lot, lot, lot stiffer than, um, fiberglass, and it’s, it’s a lot stronger. So yeah, you are designing… I, I mean, always the spar caps have been the main load carriers, the, um, you know, the main laminate, the bit between the shear webs or over the shear webs.

Um, but it’s, yeah, it probably is, um uh, e- exacerbated or the increased effect when you add carbon fiber. But the, the thing about carbon fiber is it’s so susceptible to small damages or small deviations, so like a tiny little bit of fiber waviness, like if your fibers aren’t perfectly straight, then you can easily get a, a crack.

And [00:05:00] carbon fiber can also be a lot less forgiving than fiberglass. It is not uncommon that it will just break, and you didn’t even know there was anything wrong. So that damage intolerance is what led to people moving away from carbon fiber fabric and into pultrusions, because they’re made with perfectly straight fibers.

Um, but it, it raises some, uh, problems of its own because y- yeah, like how do you repair that? You can’t, um, you can’t get the fibers as straight again unless you repair a whole plank, um, because like they look like, like two-by-fours or something. You know, like they look like little fence palings, basically.

Black, black fence palings. Um, and so yeah, you, you’d have to repair, replace a whole one, and then you’ve got like a big chunk of structure that’s missing there, so that’s pretty hard to do uptower. I, I don’t know anybody that does those uptower, actually. Um, m- maybe they can now with this reinforcement method, but I would still not enjoy being in a blade that was missing a, a [00:06:00] pultrusion and up in the air.

Allen Hall: The offshore versus onshore equation, it, it would make more sense onshore to actually drop the blade, I assume. Offshore adds difficulty, but it sounds like with all the rigging a- and assembly that you would have to do offshore, it, it probably is gonna be close in terms of total cost to do an uptower repair versus a downtower repair I would think.

It, it– Wouldn’t you think it’d be roughly right?

Rosemary Barnes: Yeah, like in, in offshore, there’s always more motivation to do complicated, um, expe-expensive uh, things that will save you from having to do something even more expensive, like bringing, um, a whole blade back. Uh, yeah, going out, getting the vessel with the crane, bringing the blade down, and taking it in is just incredibly expensive.

So you can spend a lot of time faffing around reinforcing a blade uptower before you, um, you know, would come o...