Show notes
Rosemary interviews Ivar Knutsen, Senior VP of Technical and Supply Chain at Wind Catching Systems, to discuss their innovative floating offshore wind concept. Wind Catching's design features a grid of small wind turbines that benefit from the multirotor effect and enable easier installation and maintenance compared to traditional large offshore turbines. Wind Catching will also present at the Multi Rotor 2024 seminar June 12-13. You can find more information here: https://multirotor24.zohobackstage.eu/MR24.
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Rosemary Barnes: Welcome to a special episode of the Uptime Wind Energy Podcast. I'm your host, Rosie Barnes, and I have today with me Ivar Knutsen who is the Senior Vice President for Technical and Supply Chain at Wind Catching. Thanks for joining us, Ivar.
Ivar Knutsen: Thank you for inviting us, Rosie.
Rosemary Barnes: Okay, so for those who don't know, I'm just gonna quickly start by summarizing what the concept of Wind Catching is.
So basically it's a grid of wind turbines that is floating offshore. So you've got a whole lot of small wind turbine turbines arranged in the grid, and they're benefiting from being close to together with the multirotor effect, which we'll get into later. And obviously there's also, more modularity all the.
Turbines are arranged in this grid so that they can all yaw at the same time to face a differing wind direction. And yeah I'll hand it over to you Eva to explain more about what the concept is and yeah, why you decided that this was a, an interesting company to get involved with.
Ivar Knutsen: It has become apparent to us that there are fundamental differences Between a bottom fixed and a floating wind turbine and they those differences are so big that you might need to Take a second look at that, you need to maybe consider a completely new approach to the design, but also to the operation.
So we find that multi rotors have three or four key benefits. One is that you're actually able to avoid. The infamous tow to port. If the turbines are sufficiently small, you can handle them offshore and perform a turbine replacement offshore without using a crane vessel. You just need to bring people aboard a unit as long as you have the right technology to, to do that.
And as, as we see it, there are no options for. Return to port for big single rotor floaters today, there are many concepts out there, but we don't see any of them as being tackling the real problems is that it's going on in an offshore environment with a lot of motions. The other thing we also find very interesting about multirotors is that you decouple the turbine development from the sort of the development, both on the supply chain, but also on capacity.
So if you can go from 20 to 30 to 40 megawatts without developing new turbines for every single step, that's interesting. If you can use the same turbine, But you can change your installed capacity by building on your support structure. That is a very interesting part of the multirotor concept.
And the other thing is that with a standardized turbine, you can actually enable a much broader supply chain. You can enable local content in each country because the sophistication required to turbine is much lower. And the reason for that, this is that if you now look at the biggest turbines and the turbines expected to come later.
With blade lengths of 120, 130 meters to overcome the scaling effect where the weight of those blades should scale cubically with the length. They actually scale by the square and that is done by introducing more and more sophisticated technology in the blade design and manufacturing, which is really important.
Prohibitive to local content. You can't build those plates just anywhere.
Rosemary Barnes: Let's cover though what you said about the modularity and the supply chain. So I think that's really interesting. I think that's something that most people are aware of that, modular technologies tend to reduce their cost faster.
If you look at the difference between solar panels and wind turbines, that's a big difference is that the solar panels are a lot more modular and they're yeah, can make the exact same thing many more times, which tends to lead to, yeah, getting better at manufacturing that thing and, making it cheaper.
Then there's other physical thing that you mentioned about how the structural scaling laws, the amount of wind that you capture it scales with the square of the length of the blade, but the volume scales with the cube. So you actually. Don't get a better structural outcome from having a big, one big rotor.
You have a better structural outcome, like a, less material should be able to be used if you have a lot of small rotors than one equivalent large one. Yeah, so maybe you can talk a little bit more about that benefit that you expect to get from the modularity and the supply chain.
Ivar Knutsen: What we're working on now is a 40 rotor unit. So a 40 rotor floater which we see as perhaps the lower scale or at least the lower region of what we see as a fully commercial, not the pilot size, but they fully commercial size. And I say for three rotors and the turbine we are designing is a one megawatt, 30 meter diameter turbine.
So 40 rotors is 40 turbines 40 megawatt. Having said that we have. That kind of scalability on the turbine rating, we wouldn't probably wouldn't differ in turbine diameter in rotor diameter, because that has implications on the, how the design of the structure, not only the, how you scale the structure, but the whole sort of arrangement of the structure.
But of course, turbine rating is something you can play with on project specific basis, because we do see project. Different types of projects, different types of markets. Even if you start looking at electrification projects, where what we see, interestingly, when I say electrification electrification of oil and gas platforms, which is, has been done in Norway for some time, and it's probably coming to Scotland as well.
They are often very clear and they have a clear cap on what they can receive of power because their facilities can't receive any above, any sort of access power can't be Received or utilized.
Rosemary Barnes: So yeah, you mentioned a couple of terms there that not everyone might be familiar with. So you mentioned that there the rating is higher.
Ivar Knutsen: So meaning basically we have a higher rated wind speed and a bigger generator relative to the rotor size.
Rosemary Barnes: Yeah. And it's usually an economic optimization to figure out what that size should be. And you've come up with a different answer than. Than others. Is that what you're saying?
Ivar Knutsen: Absolutely. And and it's an interesting question because you're coming back to why our turbines like they are today. And that's not a straightforward question to answer, because there's so many, there's an evolutionary history that has led them in a certain direction. But if you consider very large offshore turbines today, we see that the rated wind speed has gone down.
typically gone down to now. If you see turbines 10 years ago, they were maybe had ratings of 12 meters per second. And now we're see down to 10. 5. You could get immense capacity factors by just reducing it down to say rating at a five meter per second. And you would get like a very good capacity factor, but it doesn't make sense.
Rosemary Barnes: You wouldn't get a lot of annual energy production though.
Ivar Knutsen: Yeah. So what I would say is that for very large rotors what I believe is that the cost of generator size, so increasing a generator size by 5 percent for a 15 megawatt turbine is, has immense consequences. First off, you actually have to build this, but you have to install it and you have to transmit the rotor loads through this.
And this comes from the same kind of scaling law, but that applies to us as well. It just applies in the other direction. So we have a very, a much, much lower impact on that. So we could increase our generator size or decrease our generator size by 20%. And it wouldn't really matter too much.
Rosemary Barnes: Because it's still a very small generator compared to what we're used to handling.
Ivar Knutsen: Yeah. So you're saving three tons of generator weight per turbine, maybe if you make a substantial change. And as long as you can handle the turbine well. Why not just make a big generator? And that's what we're doing.
Rosemary Barnes: Yeah. Okay. That's really interesting. And I'm sure that there are, a thousand different little tiny things like that, that are different for your design than a regular configuration. But I just want to go back to one other technical point that you mentioned that people might not be familiar with.
You said one P and three P that's a tower passing frequency, right? Which I guess when you've got a single. tower with a, a three bladed rotor on it, then that's obvious what that means every time that the yeah, there's a certain frequency of when the blades are passing the tower. Your design has this big grid latticework there's not just one tower and three blades anymore, there's What have you got, 120 blades if you've got three blades per rotor and all sorts of components of a tower latticework.
That's opening a huge can of worms structurally, right? Because I know that,