What Rosie Learned in Europe’s Wind Turbine Test Labs

What Rosie Learned in Denmark’s Blade and Lightning Labs
Intro and Risø blade testing
Announcer: 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 Allen Hall, and I’m here with Rosemary Barnes and Yolanda Padron. Rosemary just came back from her long trip to Germany, and a good part of it was also spent up in Denmark. Rosemary, you visited a number of wind-related companies on your travels, so give us a little update.
Rosemary Barnes: I started in Copenhagen and then went over to Roskilde, mostly to see the rain erosion test facilities. But I also got a tour of the rest of the testing, mostly blade testing. There’s a really interesting history to that facility. It started out as nuclear power research and had a reactor there. I didn’t even realize that.
Yolanda Padron: Yeah.
Rosemary Barnes: And incidentally, the reason it turned into a wind facility is that they already had all of these amazing wind measurements for the site. That’s super important if you’ve got nuclear power. If there’s a meltdown, you need to be able to track where the fallout is going to go. So they knew the wind speeds in the region really well. I was told by my friendly guide that that’s the reason it was seen as a really good place to get started on researching wind energy in Denmark. They could put a turbine up knowing what was going on with the wind resource there.
Allen Hall: Niels Bohr worked there, right? Is that part of the history?
Rosemary Barnes: He worked there. I think it was his facility. I think he set it up. I didn’t plan to talk about this, and I haven’t actually verified any of it. I’m just remembering what I was told weeks ago. My understanding is that he set it up to do nuclear power research. They don’t do that anymore, but they do a bunch of energy work. Mostly it’s wind energy, and then a bit with the grid. They’re doing some interesting trials with EV charging and how that can integrate into a grid powered by variable renewables. They’ve got their own little microgrid going on there, and if you participate in the trial, I think you can charge your car for free. All of the businesses I visited in Denmark had rows and rows of EV chargers, though mostly not free.
Allen Hall: So you went to the research labs at Risø, the structural labs there. Did you walk through where they were doing blade testing and some of the structural testing?
Rosemary Barnes: Yeah. There’s actually an American guy there, Derek. He was working at GE in America before that and had worked for TPI for a while, so he brought that expertise to Risø. They’ve got a bunch of test rigs in there for small blades. I can’t remember the exact length, but maybe 20 meters.
Allen Hall: Twenty. Yeah.
Rosemary Barnes: Which was once a full-scale wind turbine blade, but now it’s small scale. It’s mostly for research, trying out various new things. They produce blades for other research facilities as well and test them, and they’re trying out some new manufacturing techniques.
They’re also trying new testing techniques. Normally when you test a wind turbine blade, you start with a static test. You basically get some ropes and pull on the blade hard enough to represent the largest gust that blade should ever experience in its lifetime. After that, you do a fatigue test, where you flap it up and down and side to side, one after the other. That takes months. For really long blades it can take a year, because you can only flap as fast as the natural frequency of the blade. A longer blade has a slower natural frequency, so it takes longer to get through the hundreds of millions of bending cycles it sees in its lifetime.
They’ve got new test methods where they’re trying to do both directions at once. Flapwise is the direction where a gust of wind blows the blade toward the tower. Edgewise is the direction where gravity bends it back and forth as it rotates. Normally you test those one after the other. You put it in one direction and flap it for millions of cycles, then you swap it and flap it the other way for millions of cycles. But now they’ve got actuators that set it off so it traces out an ellipse with every flap. It’s doing flapwise and edgewise at the same time, so you can get through the test faster.
People also want combined loading, because in the field you’ve got flapwise and edgewise loads in some combination at the same time. I get the point of that. But just because it’s two loads at the same time doesn’t mean it represents how those two loads actually co-occur in reality. So I’m not entirely sold on it being a more realistic test. But it is good if they can do those two fatigue tests at the same time and save some months on the testing.
Another thing is that they’re looking at better ways to test torsional rigidity, because that’s more and more important as blades get longer. I believe torsional stiffness varies with the fourth power of the blade length. When blades were very small, it wasn’t remotely a problem. It was kind of like centrifugal loads in a blade. You know they’re there, but they’re not a big deal. If you design a blade that can withstand all the other loads, it’s definitely going to be strong enough for centrifugal loads. That used to be true for torsional stiffness as well, but it’s less and less true as blades get longer.
It’s very hard to test and hard to verify. It’s also hard to model, because the torsional rigidity of a blade has a lot to do with how the adhesive and the glue joints deflect under real loads. That’s probably one of the weakest parts of a finite element model. It’s quite hard to accurately model those thick adhesive joints, because they’re less predictable than composite structures.
The challenging thing is that every time you test something in the lab, some parts of the design will be under-tested and some parts will be over-tested. In the static test, for example, you can do it as simply as putting a single clamp on the tip and pulling on that. But a real aerodynamic load is applied over the whole surface. You can apply several clamps and get a more realistic load, but every clamp stiffens that area. You’re never going to get a failure exactly where the clamp is, because the clamp prevents it from buckling. So you’re distorting things. If you get more accurate in one sense, you’re probably getting further from accuracy in another.
That was one of the threads through all of the testing I watched in Denmark: how much can you accelerate the test without getting away from reality?
LEP rain erosion testing and field trials
Rosemary Barnes: I do think that’s something the industry struggles with. Later on, at Wind Energy Hamburg, I visited a lot of leading edge protection companies, and a lot of them had little samples showing how amazing their material was in the rain erosion tester compared to their competitor’s. And it’s like, yeah, but what did you test? It doesn’t match reality. I hate those little comparison tests, because everybody knows there are all sorts of little things you can do to make a product fail faster. If you just apply your competitor’s product badly and then test it, you can easily crush them. But what’s the point in showing that? When I see companies dissing their competitors, I find it an indication that they don’t have confidence in their own product. So, to go off on a tangent, that’s my hot tip.
Allen Hall: No, that’s a good tangent.
Rosemary Barnes: It’s not the message you think it’s sending when you show your competitor’s product.
Allen Hall: Well, the V-N curve, which is what you’re trying to achieve with rain erosion testing, does give you some predictive capability for what a coating would do at any particular wind farm. I know you’re going to throw a bunch of variables at me, but as a baseline, you have this V-N curve, which is roughly the velocity versus the number of water droplet impacts. What I haven’t seen is people publishing their product’s V-N curve to the engineering world. That doesn’t happen, which is weird, because they spend so much money to get it. Why would you not communicate it to someone like Rosemary, who can then use it to see whether that product will work on a wind turbine somewhere in Australia? I’m really struggling with that, because people spend a lot of time in the rain erosion world trying to get those numbers.
Rosemary Barnes: I feel like I’ve already had a rant about this on an episode.
Allen Hall: I don’t think so.
Rosemary Barnes: Maybe it was how I got into some robust discussions, which some might have interpreted as arguments, with a company complaining that their product is fully validated, that it doesn’t need any more trials, and that everyone should just purchase it for their entire wind farm all at once. And I was saying that you haven’t validated it for their wind farm, so they don’t know.
Allen Hall: Oh, yeah.
Rosemary Barnes: But okay, that cuts both ways. If you had two side-by-side wind farms and one of them had trialed it successfully, then the neighboring wind farm would likely feel like, okay, that’s great, they had good success, we’ll put it in. But I was getting examples like, “We tested this in Texas and it’s perfect.” Okay, good for Texas-adjacent wind farms. They can rejoice that this product works well there after one year, or whatever it was.
But with all the testing you do in the lab, and even the testing you do on site, you don’t actually fully know until you’ve tested your real product in your real environment for the real lifetime. That’s the end of the testing. And by then, of course, it’s 20 or 30 years later and you’ve moved on to the next thing.
Yolanda Padron: Right.
Rosemary Barnes: So you’re only ever filling in the picture. Testing isn’t something that’s ever completed. It should be an iterative thing. I’m not saying you don’t do anything until you’ve put it on a test wind farm and left it for 30 years. What would that mean? We’d be going back to 1996 technology. Okay, now we’re ready to roll out 500 kilowatt turbines.
Yolanda Padron: Yeah.
Rosemary Barnes: You’d never put carbon fiber in a blade or build an offshore wind farm. So that’s obviously not it. But you do need to get feedback from the field. For me, that was the main part of my job when I was in charge of de-icing systems.
Allen Hall: At LM Wind Power.
Rosemary Barnes: Yeah. In that case, you’re putting electrical equipment inside a blade.
Yolanda Padron: You do need to trial it.
Rosemary Barnes: Yeah, you have to do good trials.
Sponsor read and the Danish test site
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I want to ask you about the Danish wind turbine test site. Did you go to Østerild and take a look at the wind turbines being tested?
Rosemary Barnes: Yep, I went out there. It’s been six years since I was last there. Last time, I think the biggest turbine they had was a 7.5 megawatt GE offshore wind turbine. I didn’t actually pay that much attention to it at the time. I think it was being installed. Now they’ve got a 15 megawatt Vestas turbine that was installed in 2022, so it’s been there for quite a while. That’s actually a long time to be at the test site. And there’s a 14 megawatt Siemens Gamesa offshore turbine as well. So that was cool.
You’d think it would be so obvious which turbine you’re looking at, but it actually wasn’t. There was a 6 megawatt turbine next to the 15 megawatt one, and it doesn’t look as much bigger as you’d expect.
Allen Hall: Really?
Rosemary Barnes: What gives it away is how close to the ground the blade goes. On the really big ones, I feel like you’ve got to duck underneath.
Yolanda Padron: I thought so.
Rosemary Barnes: It does feel like it’s basically going to hit the ground every rotation, because offshore wind turbines are huge, and onshore they’d stick the towers up so high. And that site also has a height limit.
Allen Hall: Oh, really?
Rosemary Barnes: Yeah, which matters if they want to test a certain blade length.
Allen Hall: I was talking this morning with John Cella, who’s been on this show before. He used to do validation for GE, and he was telling me that those Østerild test turbines probably have about $2 million worth of instrumentation in them. And I don’t mean normal instrumentation. I mean instrumentation just for the testing, so strain gauges and all that sort of stuff. That’s how seriously people are taking it, to actually learn the real behavior.
Polytech lightning lab and Danish vs. Chinese factories
Allen Hall: And I heard you went up to Polytech to look at some lightning testing.
Rosemary Barnes: Yeah, I did, and it was really cool for me, because the last project I worked on at LM was a heated blade with carbon fiber heating.
Yolanda Padron: Oh.
Rosemary Barnes: That project was about 10% heating and 90% lightning protection. Honestly, that was by far the hardest part of the design challenge, trying not to set the blade on fire with short circuits. I was supposed to go see the lightning test for that blade, but I got stuck at the factory making the first few sets of prototype blades and missed it. I was always annoyed, because then I left the company and never got the chance to see a lightning test again. I’ve always regretted that. I tried hard to go see the test facility when I was in Boston, but then I had to spend a week in a hotel in Montreal instead. So various times in my life I’ve tried really hard to see a lightning test facility, and finally I was able to, because Polytech was kind enough to show me around.
I got to watch some tests, the high voltage test and the high current test. Really cool. I also got to talk with their lightning expert, who knows so much. It’s always amazing when I get to quiz someone who knows a lot.
Allen Hall: Well, I appreciate that.
Rosemary Barnes: I always enjoy getting the opportunity to learn more about lightning, because it’s one of those areas where there’s a little handful of people in the world who understand it reasonably well. I would say ten people or less.
Allen Hall: Agreed. Yeah.
Rosemary Barnes: And those ten people do not agree.
Yolanda Padron: No.
Rosemary Barnes: So it’s good to hear from different people, rather than the one expert over and over again.
Allen Hall: When you give these trip reports, I always find them fascinating, because what you focus on is so different from what most people would focus on. Most people would say, “Oh, that was cool,” or “That was shiny,” or “Look at this, it’s so big.” And then you’re asking, how do I make this live 20 years? Are they bullshitting themselves into believing this is a good process, or does it actually work? It’s such a unique perspective when you talk about the things you’ve seen. You’re not just questioning it. You get into the science of whether it’s real and whether it’s true.
Yolanda Padron: Well, that’s why she’s trustworthy, right?
Allen Hall: Yeah, it’s funny. If Rosemary ever visits your site, I recommend you let her in. But realize she’s not going to ask a bunch of nice, fluffy questions. She’s going to get to the heart of the matter very quickly, and if you don’t have your stuff together, you will feel awkward. That’s probably the right term.
Rosemary Barnes: But yeah, it’s true. Maybe. But I think if you’ve got some good technology, you can appreciate an expert questioning you.
Allen Hall: On the details. Right.
Rosemary Barnes: Somebody who appreciates the extra work you’ve done. Whereas if you just get somebody in who’s going to say “Oh, shiny,” they’d say that whether it was good or bad, so it doesn’t really add anything for people trying to figure out the differences.
But I will say, I love manufacturing. I’ve always loved manufacturing. It was the reason I bothered to move all the way to Europe to work for a big manufacturer.
Allen Hall: Yes, which is unique. Not many people move to do hands-on factory work. That’s not how that works, generally speaking.
Rosemary Barnes: We don’t have any huge manufacturers in Australia.
Allen Hall: Yeah, that’s true.
Rosemary Barnes: It was really interesting, because I went to China earlier this year and saw some of their manufacturing, though for different kinds of products. I haven’t yet been able to see any wind turbine manufacturing in China, which I do want to do. If anybody listening has a wind turbine factory, invite me, please.
But I saw inverter manufacturing, battery manufacturing and testing for those kinds of products, and solar panel manufacturing. It was interesting to compare the Chinese manufacturing to the Danish manufacturing. There were so many more people in the Danish factory. In both cases, they’re using AI interpretation of images, computer vision, as quality control.
Allen Hall: Sure.
Rosemary Barnes: I think that’s obviously a must-do in this day and age. But there were people in the Danish factory, whereas in the Chinese factories there were robots supervised by people.
Allen Hall: Really?
Rosemary Barnes: Yeah, in the Chinese factories. It’s not exactly the same in every one. Some had more or fewer people. But mostly the humans there were doing rework. If something needed repairing, that was a job for humans, whereas the routine work was primarily robots. There were robots at Polytech, but they were robots to make humans’ jobs easier rather than to replace them. That was my interpretation. I had a surface-level view, obviously, and you can draw whatever inferences you want about that. At the right scale, robots are cheaper than people. On the other hand, I think a lot of people feel uncomfortable about robots taking over the world. But it was a real difference in manufacturing, and that was cool to see.
Also, on a personal note, a lot of the people I used to work with at LM, some of the really great development engineers, are at Polytech now in the same group. The same names came up again and again, people I had worked with, and I know they’re very talented engineers. I think that’s fairly recent. It shows they must be planning a bunch of cool, new, exciting technologies, given how heavily they’ve invested in getting really great product development engineers and really great test engineers. So I’ll be interested to see what comes out of it.
Allen Hall: Okay, now you’re teasing. That’s not right. Did you see any great new technology, or did you just feel like it was happening behind closed doors you weren’t allowed behind?
Rosemary Barnes: There were some specific things being tested, but I wouldn’t say it’s cool new technology. And I’m pretty sure I’m not supposed to publicize exactly what it was.
Allen Hall: You can tell us. We will not tell others.
Rosemary Barnes: There are wind turbine designs out there whose durability I was concerned about. When I look at modern wind turbines, there are some exact things where I’m like, that’s not going to last, that’s not going to last, that’s not going to last. Those exact things are being tested for durability at Polytech.
Yolanda Padron: Ooh.
Rosemary Barnes: I don’t know what comes out of that, but I do know they have a good understanding of some of the things I had already foreseen could be a problem in the future.
Allen Hall: Wow. Okay. That’s exciting.
Rosemary Barnes: So I hope that was sufficiently vague to just annoy everyone.
Allen Hall: Just send your comments to Rosemary’s LinkedIn page. She’ll get back to you with all the details, I’m sure.
Air travel, lounges, and outro
Allen Hall: So is that the end of your travels, or did you veer off to some other cool engineering spot in Denmark?
Rosemary Barnes: Well, I was only gone for two weeks, and 70 hours of that was travel.
Allen Hall: Oh my gosh.
Yolanda Padron: Wow.
Rosemary Barnes: That’s what it takes to get to Europe. So I feel like I’ve done a sufficient amount of stuff.
Allen Hall: When I was thinking about this, I thought, you spend a lot of time on an airplane, and it’s helpful to others who travel as much as you do. And Yolanda travels a good bit too. What is up with travel right now? Worldwide, it does seem like there are some issues with passport control. A couple of other people got stuck coming in and going out of Germany. And on the airlines, there seems to be a wide disparity in what you receive depending on what level of service you fly. Did you fly business class over to Denmark from Australia?
Rosemary Barnes: No, I usually book premium economy and try to get an upgrade with points. I used to get the upgrade maybe 60% of the time, and now it’s 0% this year.
Allen Hall: Really?
Rosemary Barnes: When you think about the cost, a business fare is so much more that even if I just took a day or two off on either end, it probably comes out about the same. Do I want the flight and then two days off work, or business class and no days off work? It’s the same sort of thing. And at the value I add with every hour of my time, it doesn’t actually make sense to do the business class flight. It devastates me to say it. But a business class fare costs about five times as much.
Allen Hall: It does. Yeah. Now, did you happen to stop at any of the lounges on your travels?
Rosemary Barnes: Yes. All the lounges, always.
Allen Hall: Okay.
Rosemary Barnes: Always. If you’re traveling internationally, definitely hit a lounge. It changes your whole experience. Honestly, it changes your whole life. Because I fly so much, I’ve got platinum membership now, so I get to go to the first class lounges when I’m flying Qantas.
Allen Hall: On Qantas.
Rosemary Barnes: And the Qantas first lounges are nice. One time, not this trip but the previous one, I showed up and they asked, “Would you like a spa treatment?”
Yolanda Padron: Oh. Oh, nice.
Allen Hall: You’re kidding.
Rosemary Barnes: And it’s a full-on fine dining experience.
Allen Hall: Yes.
Rosemary Barnes: The first class lounges are amazing.
Allen Hall: I had never experienced that until we were coming back from Melbourne. Somehow we got directed to what I thought was the regular lounge, and then we were in this place that was unbelievable. It was like a spaceship had landed in the airport. The level of service was crazy. It was quiet and peaceful and calming, and we had some real food to eat. Unbelievable.
Yolanda Padron: It also really depends on which airport you connect through. My little sister was flying home, which should be an hour-and-a-half direct flight. But she went cheap, so she connected through Las Vegas to get to El Paso. And in that lounge she had salmon and caviar and a mimosa, and then a burger. And I’m like, it’s 9 a.m., how are you eating all this food? But it was really good service.
Allen Hall: The level of service you get in some parts of these airports is unbelievable. I had no idea it existed. And then I realized, oh, this is how Rosemary travels.
Rosemary Barnes: Right. Okay. You finally got to the right lounge.
Allen Hall: Exactly right.
That wraps up another episode of the Uptime Wind Energy Podcast. If today’s discussion sparked any questions or ideas, we’d love to hear from you. Just reach out to us on LinkedIn or email us at [email protected]. A lot of people are emailing us there, and thank you for doing that, mostly to complain about things Rosemary said. If you found value in today’s conversation, please leave us a review. It really helps other wind energy professionals discover the show. And don’t forget to subscribe so you never miss an episode. For Rosie and Yolanda, I’m Allen Hall, and we’ll see you here next week on the Uptime Wind Energy Podcast.