Blade Aerodynamics and AEP with PowerCurve

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. Sign up now for Uptime Tech News, our weekly email update
on all things wind technology. This episode is sponsored
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www.weatherguardwind.comIntelstor - https://www.intelstor.com 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.