C1 Connections: The Innovative Wind Turbine Foundation Interface

In this Uptime Spotlight, Joel Saxum discusses the C1 Wedge
Connection with Managing Director of C1 Connections, Jasper Winkes.
They explore how this innovative wind turbine foundation interface
addresses challenges in the expanding offshore wind industry,
especially for larger turbines. The design benefits include
structural enhancements, faster installation, lower maintenance
needs, and possible cost savings for both offshore and onshore wind
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on all things wind technology. This episode is sponsored
by Weather Guard Lightning Tech. Learn more about Weather
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www.weatherguardwind.comIntelstor - https://www.intelstor.com Joel
Saxum: I'm Joel Saxum filling in Allen Hall's shoes as your host
for this innovation focused guest episode of the Uptime Wind Energy
podcast. Today we're talking about wind turbines and massively
important connections in between the towers and transition pieces.
Bolted L flange have been used for decades to connect steel
cylindrical structures. We know this. However, as the wind industry
continues to push structural engineering limits with increased
capacity for these behemoth wind turbines, specifically offshore, a
need for new tech to solve the loading problems has emerged. Enter
stage the C1 Wedge Connection. With over seven years of development
and two years in the field Jasper Winkes and team have developed
the next generation of steel structure connections. Jasper, welcome
to the show. Jasper Winkes: Thank you very much for having me. Joel
Saxum: Great. So we, you and I talked a little bit off air about
kind of the technology where it's been, where it's coming, where
it's going, but it's driven by offshore industry trends, right?
We've all seen, if you look in the North sea, small turbine big,
Bigger, all of a sudden now we're 15 megawatts and some people
around the world are talking about what could be the next
generation. What are those trends that are driving your technology?
Jasper Winkes: Yes, indeed. As you mentioned, we've seen a massive
growth in turbine size over the years. And on one hand, that's of
course the growth of the rotor. And they always say the rotor is
the motor. So you need large rotors to extract energy from the
wind. But of course, large rotors also require tall towers. So we
see that there's an exponential increase in overturning moments
over the past years whereby essentially the bolted L flange has now
reached the point where it is already struggling to deal with the
loads and soon will no longer be able to take the loads. And of
course, where that point lies is really project specific but it's
an issue that has been flagged by many industry experts for years
already. That L flange has been used since we started putting steel
together hundreds of years ago, so in, but in a turbine, you see
the L flange in between every tower section in even up in the
tower, some places, right on, in a cell on blades, whatever. But
what we're focused on is tower connections and even the transition
piece and some of that monopile interface. So where, and what are
the issues that these, the traditional L flange technology, you
explained it to me, maybe you can explain it here to our listeners.
Yeah indeed, we see that the heavy loaded connections, and of
course, the more down the substructure, the heavier loaded the
connection is, because you've got a longer lever arm to where the
rotor is pushing on the structure itself. You see there are
overturning moments which are already approaching one giga newton
meter. For people to put it in perspective, that's a 50 kilometer
long stick, and then you lift a Tesla at the very end. So it's
massive loads that need to be transferred through these interfaces.
And the problems that companies are having is, first of all,
there's a limited number of bolts that you can put on a certain
circumference. So for a bolt at L flange to scale up further, at a
certain moment, you cannot fit any more bolts on the circumference.
So then the next logical step would be to grow in bolt size. But
for a long time, the M72, so a metric dimension stud size was the
largest stud in the industry. But we now see a massive base where
some companies are considering M80 and even M90. And that basically
brings you into a field where on one hand also your flanges are
growing massively in size. But also the tools that you need to
handle. We're talking about tools that can easily weigh 70, 80 or
maybe even more kilos. So there's a real challenge in getting those
connections made and then on top of that everything of course needs
to be done under time pressure. Because there's this expensive
installation vessel that needs to wait for either the transition
piece or the tower to be connected to the foundation. And we want
to solve that issue. Joel Saxum: Yeah, so the other, you go bigger
in bolt size or you need more bolts so then all of a sudden your
tower would just start increasing in diameter to a point where it
doesn't, the cost efficiency isn't there anymore in the tower.
Jasper Winkes: Yeah, so at a certain moment you would have to
increase your base diameter, but of course a larger base is exactly
in the splash zone attracts more wave loading, which results in
more fatigue damage in your foundation. So The optimum is basically
not having to increase your interface diameter that much, but still
being able to connect it properly. And our connection technology
allows that because you have a higher ultimate capacity, a much
higher fatigue capacity, and we can enable both safer and faster
installation. Joel Saxum: Okay, so let's dive into the technology
itself now. I've looked online and I've checked out some of your
white papers and this stuff and it looks to me, you guys have done
a great job of marketing the thing because. From someone who is not
a structural engineer, I can look at it and go, okay, that makes
sense. But maybe you can explain in better words than that. Jasper
Winkes: Let's kick off with the reference. The reference is the the
L flange, which is essentially two flange bodies, which are
connected to a tower and foundation. So let's focus on that
interface for now. They're welded at the factories and offshore
they need to be connected. So it's basically a flange that's
protruding inwards into the tower and they are sticking studs in.
But it also means that the stud or the bolt is not in the line of
the, where the load is transferred. So it's an eccentric connection
by default. What we have is we also have a flange connection.
However, the flanges are different. We have a fork shaped upper
flange and a shaft shaped lower flange, which are welded to both
the tower and the foundation. And they slide into each other. And
then we have a fastener that is radially inserted from the inside
of the tower in that fork shaft combination, and thereby pulls the
shaft on top of the fork. And it's essentially a preloaded
connection, with the main difference being that it's not eccentric.
So we have a centric connection, so it's directly in line with the
load transfer path. But we are generating a very high preload with
a stud which is basically perpendicular to the load introduction.
And we are increasing the load by the means of wedges. So we are
pulling two wedges together that essentially force two bodies
apart. And that way people can see it, of course, online how that
generates a symmetric preloaded connection. Joel Saxum: Okay. So I
think the, one of the most important things here when I look at
this is, okay, if I'm a traditional flange connection, it's
literally on my desk here, I have two coffee cups. It's like
setting two coffee cups on top of each other. And then the crane
has to hold the top piece and you got to figure out how to get the
studs or the bolts in and make it all line up, or maybe put some
pins in or something. So you have this. this moment or this time
during construction or during connection that is I don't know how
to explain it. It's a highly critical moment. All hands on deck.
Make sure this thing goes perfectly right because you're not only
trying to put load down, but you're trying to align it to get into
the holes correctly. But your technology and like the way you weld
the flange on is the way the flanges are designed. You remove that
critical moment where once it sets, it's. It's in place. Jasper
Winkes: Yes, indeed. So Indeed, current installation of L flanges
has this time critical also safety critical moment where you're
trying to land two flanges and with some kind of pins, they try to
line up the holes. We've taken that in into consideration when we
designed our connection. So essentially when the upper flange,
which is then part of the tower is lowered onto the foundation,
there are several guides and bumpers that align the tower directly
in the right orientation. Such that the moment that the flanges
connect, we have a quick connection system that directly connects
the tower to the foundation. And once that connection has been
made, the crane can directly disconnect the tower from the yeah,
the tower can be directly released and you can start lifting, for
example, your nacelle. So you can save significant amount of time.
Joel Saxum: The safety part of this is a big thing. Talking.