PowerCurve Recovers India AEP, Silent Edge Cuts Noise

Nicholas Gaudern, CTO at PowerCurve, joins to discuss India AEP gains, DragonScale VGs, and Silent Edge noise reduction.
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Allen Hall: Nicholas, welcome back to the podcast. 
Nicholas Gaudern: Thanks, Allen. Great to be back. 
Allen Hall: So there's a lot going on at Power Curve, and I saw some news online about Power Curve in India. 
Nicholas Gaudern: Yes. 
Allen Hall: Which is a new development. 
Nicholas Gaudern: Yeah, so we've been working in India for, for some years now, and we have, uh, more than 100 turbines out there with our equipment on, primarily vortex generators so far.
And what we're seeing in India is some of the highest AEP gains we've ever recorded with our vortex generators And I think a lot of this is being driven by the fact that in certain parts of India, there's some very unique, uh, environmental conditions, climatic conditions, and there's parts of the year, like the dry season up in [00:01:00] the north of India, where you're getting this very sticky dirt accumulating on the blades.
And it's really quite dramatic when you see the photographs, but that means that the blades are actually starting to, to stall, have flow separation on them. 
Allen Hall: I've seen pictures of that. Yeah. I was really shocked at the time, uh, 'cause I didn't know it was just kind of a black, gooey- Yeah ... kind of tar-like substance- Yeah, yeah
on the blades, and, uh, it, it was only on there a limited time. As soon as the monsoons come through and the rains hit, it would wash, eventually wash it off. Yes. But while it's there, you could see the airflow over the blade surfaces. You, you could definitely see separation happening really early on those blades.
Dramatic. 
Nicholas Gaudern: Yeah, absolutely, and I think the, um... Like you say, it's not all year. No. But it doesn't have to be all year to have a huge impact on, on how many, you know, megawatt hours you're getting out the other end. So there's a few months of the year where this problem is particularly severe, maybe sort of December through to February, something like that.
And what we're finding is that when you see, uh, the power curves for these [00:02:00] turbines, some of them aren't even hitting rated power. They're not able to hit rated power because there's so much flow separation on the blades. 
Allen Hall: Wow. 
Nicholas Gaudern: And that, I mean, just imagine that. You've got a two megawatt turbine, for example.
Maybe it doesn't cast- get past 1.5 megawatts for this, uh, time of the year. I mean, that's crazy. 
Allen Hall: Does the turbine try to adjust itself when that happens? Because the pictures I s- have seen indicates, like, the turbine is pitching the blades to, 'cause it knows- It can- ... 
Nicholas Gaudern: what the wind 
Allen Hall: speed is- I mean, yeah ... and it knows what it should be putting out, and it's not putting that out.
Nicholas Gaudern: It's very turbine specific, kind of controller logic specific, but what we see is even the turbines that try to do something, they're very limited in how much pitch authority they have from the controller. They might be able to just do a little bit, a degree. Okay. Two degrees. You know, very, very small pitch adjustments.
And when you have this kind of dirt on the leading edges, a degree of pitch ain't gonna save you really. Um- N- 
Allen Hall: no. And I think that's what we're seeing. And it's not gonna get that power back. No, no. 
Nicholas Gaudern: No. 
Allen Hall: But does it add extra load onto the blade structurally over [00:03:00] time when you do that? 
Nicholas Gaudern: In terms of the pitching, or- 
Allen Hall: Yeah, in terms of the pitching, where you're trying to be more aggressive on the angle of attack to get the power out of the turbine.
Potentially. And the winds are still pretty strong, you just, the blades are inefficient. 
Nicholas Gaudern: I think it's one of those things where there's, there's so many interconnected items with the dirt and the controller and the structure. It's actually pretty difficult, I think, to say with confidence how much life impact you would have from that.
But what I would say is the more that you might end up trying to pitch, if that's what's going on on some machines, that obviously puts wear on the pitch bearings themselves. But yeah, I think at the moment we're kind of at the beginning of really trying to understand how some of these turbines do deal with this phenomenon.
But what we're trying to do is get to a point where the turbine doesn't really have to deal with it. Because if you fix the problem at the source, which is stop the flow separating, then the controller doesn't really have to, to worry. It doesn't have to try to, to fix it itself. 
Allen Hall: Yeah. That makes a lot more sense.
Just the number of images I've seen over the last couple years from India- 
Nicholas Gaudern: [00:04:00] Yep ... 
Allen Hall: you realize how difficult it is to operate a wind turbine there. 
Nicholas Gaudern: So even when we, um, have this issue for a few months that we're resolving with the VGs, we can still be seeing over the whole year more than 5% increases in annual energy production.
Because those months are really important. Um '
Allen Hall: Cause that's when they need the 
Nicholas Gaudern: power. Yeah, yeah, yeah. Exactly. For sure. And this is primarily coming from the vortex generators towards the tips of the blades. So that's where you're having this, uh, heavy contamination issue, and that's where all the power would be produced.
So kind of the outer third of a blade is 50, maybe 60% of the power production of a turbine, maybe closer to 50. So that means that if you have a problem out there, it's, it's a big problem in terms of your annual energy production. So- 
Allen Hall: Right ... 
Nicholas Gaudern: the VGs are, what they're doing is they are, they're injecting energy back into the flow.
Allen Hall: Redirecting the flow, in a 
Nicholas Gaudern: sense. So, so basically you have all this contamination on the leading edge. It's generating more turbulence. The flow isn't able to retain, uh, remain attached [00:05:00] across the entire chord length. So the VGs are putting energy back into the flow and allowing it to remain attached all the way to, uh, to the trailing edge.
Allen Hall: So even with the blades are dirty- 
Nicholas Gaudern: Yes ... 
Allen Hall: you get that power out- Exactly ... put, that you really desire or- 
Nicholas Gaudern: Yeah ... 
Allen Hall: are paying for. Yeah. You, you paid a lot of money for that turbine- Yeah, exactly ... you need to get the power out of it. 
Nicholas Gaudern: Yeah. 
Allen Hall: And- 
Nicholas Gaudern: So of course, you know, that suggests that if you had a, a super clean blade, you went and pressure washed it, uh, you would get, uh, an increase in power as well, and that's true.
You, you- That's true ... you will do. But that's a one-time thing. Um, so- And 
Allen Hall: it's expensive to do- Yeah ... and time-consuming. 
Nicholas Gaudern: Exactly. Maybe a few days later, the dirt's back. So- Sure ... you know, it's not really a sustainable thing for you to be going out washing these blades the whole time. And washing the blades may not be great for the surface of the blade either.
So, you know, a VG is just sat there the whole time. It doesn't matter if it's dirt, bugs, erosion, frost, it'll recover those losses that, that you're seeing. 
Allen Hall: Do the VG installations in a situation like that, [00:06:00] the actual location differ because of the contaminants that are present and the kind of, uh, leading edge effects that you're seeing?
Do you design it for that environment? Or- Yeah ... is every- Oh, you do. So- Yeah, we 
Nicholas Gaudern: do. I mean, typ- typically our, our VG arrays are turbine model specific. But in India, we're finding we're actually having to be more site specific as well. Oh, 
Allen Hall: wow. 
Nicholas Gaudern: Because some of this contamination is so severe, we've seen that we need to design the VG layout a little bit differently to make sure that we're giving enough, uh, energy recovery potential when you have these really severe, uh, situations.
Allen Hall: Are you using the AeroVista tool to do that? How do you, how do you quantify the contamination that's happened on the leading edge at a particular moment or roughly on scale a- and then try to model that? That just seems like a difficult computation. 
Nicholas Gaudern: It is. And, um, you know, we're, we're getting better all the time.
AeroVista is definitely part of that. So AeroVista's primary function really is to look at, um- [00:07:00] AEP losses due to structural damages, things like erosion. But actually, erosion behaves very similar to dirt when it comes to, like- It, right ... aerodynamic behavior. Yeah. So we can actually use kind of the AeroVista engine to help us understand what is the loss from different levels of contamination.
So we can add contamination levels into AeroVista, as well as, uh, erosion. And we can start to look at, well, what happens if the blade looks like this? What if it looks like this? And then this gets combined with our computational fluid dynamics, our CFD models that we're running, three-dimensional, two-dimensional.
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