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Allen sat down with Nicholas Gaudern, CTO of PowerCurve, at ACP in Minneapolis to discuss the importance of aerodynamic blade optimizations and upgrades during wind turbine repowering. PowerCurve’s AeroVista tool can help operators address leading-edge erosion and suboptimal blade designs to mitigate aerodynamic losses.
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Allen Hall: Welcome to the special edition of the Uptime Wind Energy Podcast. I’m your host, Allen Hall, and I am at ACP 2024 in Minneapolis with Nicholas Gaudern the CTO of PowerCurve. And PowerCurve is based in Denmark, and they are aerodynamic blade experts. And Nicolas background is with Vestas, and now he’s a freelancer, so to speak, at PowerCurve.
And PowerCurve is where WeatherGuard goes for aerodynamic help. Yes, and a lot of other operators around the world reach out to power curve. So we thought it’d be a good time to talk to Nicholas because of all the repower activity in the United States and aerodynamic upgrades that should be happening on the ground.
Nicholas Gaudern: Yes. Yeah.
Allen Hall: That, that the opportunities being passed by, which is a total mistake, absolutely total mistake. And Nicholas, welcome to the program. And I want to walk through that.
Nicholas Gaudern: Thanks for having me back Allen. It’s really nice to talk to you again and and another show. So always good.
Allen Hall: So in Texas, Oklahoma, Kansas, all over the United States, the IRA bill is kicking in and there’s a lot of repowering happening at the moment.
And when I talk to operators about lightning protection, they’re like, yeah, absolutely. We need to put additional lightning protection on because we know from the previous blades that they were not great. And we’ve heard rumors that these blades are not great. Our new blades are not great. So for lightning protection, that’s pretty easy, but they also don’t they don’t think about the aerodynamic aspects.
Nicholas Gaudern: No not necessarily. And I think it’s it risks being a really big missed opportunity. Yes. Because whenever you’ve got a blade on the ground, that is obviously an easier time to be doing any upgrade work, repair work, enhancement, whatever you want to do. So when you’ve got a blade on the ground, you should absolutely be considering the optimization potential, the aerodynamic optimization potential.
So when you’re repowering, you may think that you have the latest and greatest blade. It’s very unlikely that you do. The blade may have been designed many years ago. And even if it is more recent, we haven’t come across a single blade that we can optimize, not a single one. And that’s not because the OEMs are doing a bad job.
It’s just that they have a lot of different constraints. That can be time pressure, it can be cost, it can be materials, whatever. It maybe means they haven’t spent as much time as they could have done on squeezing every last bit of aerodynamic performance out. Which is fine. Maybe, the business case for them doesn’t support that.
But for the operator, it absolutely does. Because if you can get another half percent, one percent, two percent AEP over the lifetime of that product, That’s a hugely powerful lever to pull.
Allen Hall: Because the blades, let’s just choose a 2X machine. Sure. Which there’s a lot of 2X machines going in the United States at the moment.
Those 2X blades were designed pre pandemic. Yep. Most likely. And they were designed pre 3D aerodynamic analysis. They were designed with the BEM method.
Nicholas Gaudern: Yeah even today using a fully 3D approach is very rare. Yeah. And there are some good reasons for that. Obviously, it is computationally expensive.
But if you really want to optimize a blade, particularly down towards the root, you have to do a CFD based approach. Because that’s very 3D flow down there. And this BEM method, the blade element momentum method it’s been used to design every blade out there. I’m pretty confident in saying that.
I’m sure it’s going to be designing many blades many years to come. Sure. Because it’s good, it’s computationally quick, But it’s not going to give you the best possible blade, particularly when it comes to optimizing that root region or the tip region where the flow is much more three dimensional.
Allen Hall: So I seen VGs on new blades down close to the hub. That’s an option. It appears to be an option for some operators and they’ll do the ones near the hub because the arrow efficiency there is so poor that’s obvious.
Nicholas Gaudern: It is, yeah. The aerofoil is down towards the the hub. They’re basically cylinders, they’re not the kind of thing you would expect to see on a flying device. So they are playing a structural role. They have to be that thick to get enough material into the blade so it’s stiff enough to withstand the loads. So it’s a structurally constrained area of the blade. But that doesn’t mean you shouldn’t pay attention to the aerodynamics.
Allen Hall: At the tip, you don’t see many VGs being added. That’s it. On the ground or even on new blades just being offered. It seems like what happens is the OEMs come back a year or two later, then offer, Hey, we got this aerodynamic upgrade. At that point, it’s like too late because the business case is over.
As soon as you got to get someone on a lift or someone on ropes. It’s just, it’s hard.
Nicholas Gaudern: You need to get more AEP, of course, to pay for it. So you really should think about vortex generators in kind of two, two families, you’ve got root region vortex generators, you’ve got tip region vortex generators. And the ones towards the root, I would say, there’s no reason that every blade shouldn’t have them.
They’re a no brainer. And the reason I say that is because of these thick aerofoils. The thick aerofoils aren’t going to perform particularly well. There’s going to be stalled, three dimensional flow in the root, and vortex generators can help mitigate some of that. So you’re going to get some AP back, but of course, because it’s near the root of the blade, there’s not such a long moment arm.
Even if you get loads more lift there, you can’t just magic more torque, but you should put them there because it’s an easy thing to do and you’ll get some more energy. Of course, they have to be in the right place, we can help with that. Out towards the tip, it’s a little bit of a different problem.
So out towards the tip, if a blade designer has done a good job in principle on a brand new perfectly manufactured blade, a VG near the tip isn’t going to add much energy Because the blade can actually generate all the lift it wants without any problem, the flow is fairly two dimensional, it’s all good.
But I, you’ll notice I use the word perfectly designed, perfectly manufactured, perfect surface condition. Of course we know when we go out in the field that is not the case. Even manufactured blades have some variation in the leading edge shapes. They’re handcrafted products. As soon as they’re exposed to the atmosphere, that surface starts to get a little bit rougher, maybe gets eroded.
And at that point, that’s when the blade is actually going to lose AEP because that leading edge damage of contamination, a ruffling of the surface, all those kind of things, they lose your lift and the increase your drag. So vortex generators towards the tip, they really come into their own when you have this kind of suboptimal blade surface.
Yeah. So that’s why you have to treat them as two, two families. One is boosting the fundamental performance of the blade and the root. The other is recovering losses towards the tip.
Allen Hall: And if you’re an operator in Oklahoma, Texas, Kansas, anywhere, there is a plow field, right? Where there’s farmers and activity, dirt and the dust in the air is doing a Tremendous amount of damage to the leading edges.
Yeah. So if you’ve had turbines out there for two, three years, you know that damage exists and your repower on the farm next door, you should be thinking about putting vortex generators on because of the leading edge erosion effect to keep the power at a high output.
Nicholas Gaudern: It’s a tool for power curve robustness.
Yes. Power curves fluctuate throughout the year and you’re not going to change that different densities, atmospheric conditions, things move around, but VGs are just going to push that average up. Because they’re going to stop you getting into these bad situations where the flow is starting to separate, you’re starting to lose lift, get that increased drag.
If you have a perfect blade with a perfect surface condition, okay, fine. Fine. Maybe focus on the root region only, but I’m yet to see many blades that are perfect.
Allen Hall: No, we’ve seen, Joel and I have traveled around a lot of the Midwest and usually within one year, the leading edge erosion is severe enough that it’s impacting, things.
the AEP performance of that turbine. Yes. Easily.
Nicholas Gaudern: Yeah. And something that I think is probably nice to move on to now is to talk about what, how do you understand what the AEP loss is?
Allen Hall: And that’s the problem. I think engineers, the operators are mostly structural people because they’re trying to fix blades or gearboxes or whatever.
They’re mechanically inclined and they have deep knowledge of blade structure or gearboxes bearing same thing. But there’s not a lot of aerodynamicists on staff because they don’t need to be the way they think about it. But when the answer is an aerodynamic fix or an upgrade, they have trouble trying to understand like what the value is of, say, a VG package.
How do I even evaluate that? Which is where AeroVista comes in, this new product you’ve developed, to provide some guidance there.
Nicholas Gaudern: Yeah, I think that there is a bit of a knowledge gap when it comes to aerodynamics. It’s something that is a little bit more niche, a little bit more specialist. Even the OEMs themselves don’t tend to have large aerodynamic teams as a rule.
So there’s just not as much, I would say, breadth of experience in the industry aerodynamically as there are structurally. And there are some good reasons for that. But if you want to optimize performance you do need to understand the aerodynamics. When we talk about the loss from leading edge erosion of the blade damages, there’s some really scary numbers out there, and 10%, 20%, 25 percent AEP loss. That is just not true. It’s too high. It’s way too high. It’s way too high. And I’m not going to say it’s impossible because you may always find an outlier. We’ve worked on some turbines that were really suffering, but it’s certainly not the average. And, uh, 20 years ago where there was a lot of stall regulated turbines, that’s when leading edge erosion and bugs and dirt really did kill performance.
But we don’t really have stalled turbines anymore so the magnitude of loss has really dropped hugely to the point where you’re now in small single digit percentages. That’s where you should be thinking. But in order to really get a better handle on what that number is, you have to understand the blade aerodynamic performance of the actual blade model you’re dealing with.
So you were taking the, the G2X earlier. Obviously, that has a different aerodynamic design to a similar rotor from a Vesta’s design. It does. If you want to work out what’s going on with the blade, we’ve developed this tool AeroVista, and it’s based on real aerodynamic models of the actual blades in question.
Laser scans of actual blades. Yes. Not models. Not models. Real blades. Yeah. Real blades, real geometry. And if we have the real geometry, that means we can actually go to the computer, we can fire up our CFD simulations or other great aerodynamic tools, and we can understand the performance of every single slice of that blade.
And it’s going to be different from one manufacturer to the next from blade model to blade model. So we build this very detailed aerodynamic model. And then what we do is we take a drone inspection metadata. So the kind of thing that Nerf labs, Sky Specs, Globotics, these kinds of companies gather, we take that data.
and we plug it into AeroVista to say what is the aerodynamic impact of every single damage on that blade. So we can calculate the loss from erosion, from a crack, from a peeling LEP, from lightning damage, everything. And it all goes into the model and we can calculate what you’re losing. And that means that on a fleet level you can then see that breakdown of losses and decide Where to spend your money?
How do you prioritize that O& M budget? How do you claw back those losses that you have from from the erosion and the damage?
Allen Hall: So if I’m Pattern Energy, and I’m going to build the largest wind site in America at Sunzea in New Mexico, which is sandy and dusty, and we don’t have a lot of history in that area, and lightning is also very strong there, and there’s a lot of GE, new GED turbines going in there, brand new Vestas turbines going in there.
Nicholas Gaudern: What is the attack plan then for maintaining your AEP in such an erosive, damaging environment? How do you do that?
That’s definitely where those vortex generators towards the tip would come into their own. Okay. Because they’re going to recover the losses that you would face from erosion, dust, bugs, whatever’s going to be contaminating or changing the surface condition.
But as you operate the sites it’s There’s all kind of decisions you can make, obviously, with regards to what turbine do you fix, when do you fix them, what do you fix them with, how do you upgrade them. And to us, the starting point has to be to understand your loss. And at the moment basically every turbine in the U.
S. is inspected by a drone every year. That’s what happens now. And the infrastructure and the engineering around the structural understanding of that data is really very high. And it’s being used to prioritise repairs. But I would say from what we’ve seen, the aerodynamics is ignored.
Yes. So that, that doesn’t really make sense to us. Because if you’re prioritising work, you have to consider both the structural severity, sure, but also the financial severity, and that means AEP loss. So what Aerovista brings is that additional layer of data, that aerodynamic data layer, to put on top of the structure.
So you can actually prioritize both on financial implication from AEP loss and structural severity.
Allen Hall: So we were talking to Phil Totaro recently about the average power output, sort of AEP, of older wind turbines in the United States versus the newer ones. The newer ones have less power production.
Nicholas Gaudern: Interesting. Yeah, there’s obviously lots of reasons that could be the case. There’s a ton of reasons for it.
Allen Hall: Yeah.
Nicholas Gaudern: Lots of reasons.
Allen Hall: Some of it has to do with the wind speeds. That we’ve had more recently. However, it does start to ring true okay, we have bigger rotor diameters, longer blades.
Nicholas Gaudern: Yeah.
Allen Hall: Maybe a little bit of higher tip speeds. They’re putting it in places where we have a lot of erosion. Yeah. And we’re actually not, we’re less efficient now than we were five years ago.
Nicholas Gaudern: Quite, quite possibly. And as an engineer, as an aerodynamicist, it is interesting to look at this because if you look at the aerodynamic efficiency, like that, that CP, that coefficient of power of a turbine.
It probably has on average declined over the years, even at a design level, but that’s more because we’ve been pushing towards bigger rotors. And a lot of the reason why the CP will have decreased on a design level is you have to use thicker airfoils to enable bigger blades because you have this structural constraint.
So that’s an interesting trend. When I worked at Vestas, it was funny. We should work on these new big rotors, V120, V136, and You maybe couldn’t get the same aerodynamic performance coefficient you had in a V47. But, of course, the amount of energy that big rotor produces dwarfs a V47.
Sure. Oh, yeah. So on a design level, there’s good reason why that ultimate aerodynamic performance may have dropped. But on a fleet level, on a national level, things like, yeah, erosion may well be playing a role. Certainly, we’re finding with The work we’re doing with DTU on the layer cap projects.
This is a collaborative project being run in Denmark between DTU and OEMs and power curve. We’re seeing that, rainfall erosion. It does get worse with tip speed. There’s a direct strong correlation between tip speed and severity of erosion and initiation time.
Allen Hall: Yeah.
So a lot of operators in the United States are not familiar with the work that is happening at DTU and. You and I were both at DTU back in February, not long ago, and I was really amazed at the level of effort and the engineering going into rain erosion, the effects, the physics behind it, what is actually happening offshore versus onshore the size of water droplets, the temperature of the water droplets, all these variable factors that go into leading edge erosion.
That if you’re sitting in Colorado or Texas as a blade support engineer, you just don’t have access to, unless you visit, go to Roskilde and go look, it’s hard to get to that data, but that data does exist. And I think for those engineers in those spots it’s important to reach out to Nicholas and PowerCurve to get updated on what is happening.
Nicholas Gaudern: Absolutely. And I think a lot of what we do as part of our sales process is an education because you know what we’re dealing with is not easy engineering and There’s only so far you can reduce the technical level of an explanation before it becomes a bit meaningless, right?
Part of our job and i’m sure it’s the same at weatherguard you do have to educate on some of The fundamental engineering concepts behind what we’re fixing. So something that we’ve Done a lot of recently is educational webinars seminars Actually getting in front of blade engineers and operators to say, here’s some stuff you may not have known.
Here is how a blade is designed aerodynamically. Here are some of the pitfalls. Here’s some of the potential. And that’s actually a thing we’re offering as a purely educational thing now. So you can reach out to us. We will set up aerodynamic educational webinars, seminars in person, if you prefer, just to help you increase the baseline level of aero knowledge within your organization, because.
That’s good for everyone, right?
Allen Hall: Oh, sure. Yeah. That’s hugely important to get your staff educated on the aerodynamic aspects because that’s what’s producing the revenue. Yep. The blade is where it all starts
Nicholas Gaudern: Without the aerodynamics, you don’t have a wind turbine.
Allen Hall: So are these courses day long, week long?
Nicholas Gaudern: We typically would look for a day or two. We would tailor to the organization and we can have it shorter, longer, can tailor the topics we cover. It’s something that has gone down really well recently. We’ve done it with some big operators. On a personal level, I really enjoy it because I think it, it helps to keep you sharp, right?
If you have to explain all these concepts right down to basics, I think it helps focus the mind. Yeah, I, I love doing them. Get some good feedback.
Allen Hall: I think even in the United States on a lot of the offshore efforts, a lot of staff that’s gonna be supporting them in the United States is new. Yes.
And probably American. Yep. So they probably don’t have a lot of experience in aerodynamic aspects of those gigantic 15 megawatt producing blades.
Nicholas Gaudern: So no, we can talk about that and it can it can form part of, yeah other trading that you may be organizing for your staff.
Allen Hall: I think that you need to have some knowledge and basic understanding of what is being offered out in the fields.
And when you hear about VGs or trailing insurations or. Gurney flaps like what are these devices? What did they do? And why should I care?
Nicholas Gaudern: Yeah, because going back to that earlier discussion on the IRA thing, there’s so many options out there to upgrade your blades, modify your blades.
And you obviously have to spend quite a lot of money to make the IRA scheme work. And we’re actually working with a big US operator right now to install VGs as part of a big IRA upgrade pack. And it’s the perfect time to do it. But obviously you need to understand all those options. Maybe VGs aren’t the best choice for your turbine.
Educate yourself, talk to us. We can help make that make that decision a little bit easier. So how do people reach out to Powercurve? How do they connect with you? So I think LinkedIn, our website, we have we have a good presence. You’ll find all our contact details on the website.
All of us at the company have a LinkedIn page. You can reach out to any of us. I’m Nicholas Gordon. That’s how you’ll find me on LinkedIn. CEO, Niels Brunnen. So yeah just have a look for us online. I’m sure Allen will put a link in the notes for this as well.
Allen Hall: We will.
Nicholas, it’s great to have you back on the podcast and great to see you in Minneapolis.
Nicholas Gaudern: Yeah. Thanks a lot, Allen. Great to talk.
