Rain erosion wreaking havoc on wind turbine blades stands tall among the toughest engineering challenges to conquer. Tackling this tempestuous problem head-on, R&D Test Systems, hailing from Denmark, emerges as the pioneer behind cutting-edge rain erosion test rigs, extensively employed worldwide to meet the exacting demands of both the wind and aerospace industries. Niels Pedersen, the esteemed Key Account Manager at R&D Test Systems, takes Uptime listeners on an expedition through the labyrinth of rain erosion quandaries, offering a breakdown of the inner workings of the erosion test equipment and glimpses into the forthcoming generation of rain erosion weaponry that will soon find its rightful place at DTU – a leap forward into an even more resilient future.

R&D Test Systems – https://www.rd-as.com
Pardalote Consulting – https://www.pardaloteconsulting.com
Wind Power Lab – https://windpowerlab.com
Weather Guard Lightning Tech – www.weatherguardwind.com
Intelstor – https://www.intelstor.com

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R&D Test Systems

Allen Hall: Welcome to the Uptime Wind Energy Podcast. I’m your host Allen Hall, president of Weather Guard Lightning Tech, and today we’re talking about a major issue facing the wind industry. Leading edge erosion. Leading edge erosion is, is damaged, caused by leading edges of wind turbine blades that hit raindrops, hail, dust, sand, all kinds of particles.

It can lead to a decrease in efficiency, power output, and even premature failure of blades. Engineers and scientists are working on new materials to mitigate leading edge erosion, but they need to be thoroughly tested before being used on a wind turbine. That’s where R&D Test Systems come in. R&D Test Systems builds the whirling arm rain erosion test equipment that many of you have seen on LinkedIn and YouTube.

Now, this test equipment simulates raindrops impacting a wind turbine blade or aircraft up to 170 meters per second. That’s about 600 kilometers per hour. That’s really fast. To discuss this remarkable piece of equipment we have Niels Pedersen, Key Account Manager with R&D Test Systems. Niels, welcome to the program.

Niels Pedersen: Thank you, Allen. 

Allen Hall: So leading edge erosion is this massive issue, which affects pretty much every operator in the world. And the, the, the one complaint is there’s, it is just everywhere and we don’t know what to do about it. Right? That seems to be the big concern is that as they don’t know where to go about it and there’s, there seems to be.

All kinds of solutions in the marketplace at the moment. From coatings to tapes to these new shell devices. It’s really hard to discern what is working at the moment. 

Niels Pedersen: Yeah. Yeah, it really is. And there’s, we see a lot of of coding manufacturers, of tape manufacturers of poly European shield manufacturers tapping into this business because it is such a massive problem.

And, and the business case is essentially really good. If you can solve this problem, then you have a, a really great business case. That is, that is the key thing that, that this is just increasing the, the cost of energy that we need to go and do repairs on the blades offshore especially, and currently you need to do repairs every eight year or something like that.

Depending on the location of the site. 

Allen Hall: Yeah. That, that is key, right? Is that as the, the tip speeds have increased, the blades get longer, there’s, there is more and more leading edge erosion and, you know, numbers vary, but a e p losses typically are somewhere in a percent to 2%. I, I’ve seen AEP losses around 5% on some sites.

It’s amazing how much energy are they losing just because of erosion. And we had talked to a drone operator and asked them what was the number one thing they see in drone inspections? And the answer was, it’s always leading edge erosion. Every blade has leading edge erosion of some level. And I thought that was astounding at the moment.

Cause that was a couple years ago when we, we, I first learned how deep that problem is. That always was interesting to me just because it, it seems like that problem is solvable, but it is a very, very difficult problem to solve as, as we’re finding out. 

Niels Pedersen: Yeah, I had the exact same thought when I tapped into this.

I would call it kind of niche technology and niche problem but it is just such difficult problem to solve and. And you could imagine just these plates experience these massive amounts of rain droplets during a lifetime, just rotating all the time and hitting these droplets at three, 400 kilometers power.

The wear is just really extensive. 

It’s 

Allen Hall: amazing how fast the rain actually eats away at a surface. And having done and been involved in some rain erosion testing myself, until you see it up close, you realize. This rain. Rain will eat through aluminum. It’ll eat, eat through metal. Forget about this fiberglass boxy systems we’re using in winter blades when it eats through metal, it’s.

It’s a little shocking at first. Like, oh my gosh, I don’t know how we’re gonna solve this problem. 

Niels Pedersen: No, we, we are 

using aluminum specimens to calibrate our machine. And it is the soft alloy, but it’s really, it’s eating this aluminum in eight hours or so. That is accelerated test though. Yeah. 

Yes. Oh, sure, sure.

So it tells us how important it’s to actually evaluate materials, and I know for the longest time, There was the industry had, and in aerospace too. Cause I’ve been in aerospace industry a long time. The aerospace industry, and then subsequently the wind turbine industry didn’t really have a solution there.

There were a lot of independent test rigs. I’ll call ’em, like Boeing has a test facility. There’s one for the, from the US Air Force that has a test facility, but they don’t work the same. They’re not consistent and there never was really a standard to go use them. So you, you, you go to the different facilities, you get just two wildly different results and you, you question, well, what’s the validity of any of this?

And I think that’s, at the time is true, but a lot has changed since then, hasn’t it? And in terms of just standardizing what the rain erosion environment 

looks like. Yeah. That was what we saw previously, that the OEMs basically had their own machine and they were qualifying their materials. They purchased from.

From coding manufacturers or whoever who also had a machine to develop and verify their materials. And, but it was all different machines and most of them were kind of homemade. And that’s where we kind of found a, a niche offering in the market. So we made the first machine back in 2014.

Delivered it in Denmark. And, and since then we have then delivered 15 of the same machine, which performance can all be compared. And you can compare from OEM to oem. You can compare from coding manufacturer to coding manufacturer, and even between test institutes and, and and oem. If you’re gonna third party validate your results.

So that’s really a game 

Allen Hall: changer. That’s gigantic in the rain erosion world. And maybe just briefly describe what R&D Test Systems manufacturers, right. It’s, it’s a whirling arm system, so you want to just describe what a whirling arm rain erosion system looks like. So 

Niels Pedersen: basically and contrary to most other rain erosion test sets ups, which.

Basically vary from high pressure washer to a small small spray where going through a circular disc this is the setup that resembled reality the most. And it’s basically we are artificially making a rain field. With a lot of needles, 600 needles. And then we have a small helicopter underneath this rain field.

Free blades mounted on them in the leading edge of the blades, have the test specimens, which can then easily be exchanged to new test specimens. And then we rotating this basically underneath the rain field. And that gives us some really good results and some really high repeatability. And one of the interesting things about this is also since we have the rotary movement, then we actually get the velocity profile of the rain erosion going from different, different velocities.

So you get a lot of inside from this machine, 

Allen Hall: so as, as the blades spin, the water droplets fall and. The blade intercepts them, hits them. So at the, at the surface level, what is happening as that water hits the surface of the test sample? What happens there? Yeah, so, so 

Niels Pedersen: basically, and that’s also fairly new discovery that the rain drop isn’t, in fact just wearing these the surface down.

It is actually micro fracturing the, the surface of the, of the blade and causing fatigue damage. And then in the end causing cracking erosion problems. And, and that’s what happening there. And that’s also why we see different phenomenon of erosion going on at different speeds. And we see a tendency in these machines and in this area of testing that we want to actually reduce the speed to a more realistic speed and then increase the amount of, of rain density instead.

Because that results in more realistic conditions. Cause we’re seeing different phenomenon at higher speeds. Okay, 

Allen Hall: so the airplane analogy to the wind turbine blade may not be applicable cuz airplanes are moving typically faster than a wind turbine blade. 

Niels Pedersen: Yeah. So, so going a little bit, just very briefly into the aerospace industry, it is a different problem.

First of all, they’re not experiencing the same amount of rain only doing takeoff landing typically. Then they experience it typically at higher speeds. But the biggest difference is really that it’s fairly easy to maintain the leading edge of an airplane. They’re in the hangar anyway, once a week, once, twice a week.

Yeah. That’s not the case for wind turbine. 

Allen Hall: No, no. Where it doesn’t get as, as much oversight. So speed matters here. I i, it, the way I’ve seen it described in recent literature is as the droplet hits the surface, it creates like a, an. Miniature microscopic shockwave, and it, it stresses the material and tries to break it apart and micro crack it eventually micro crack it.

And then once that happens, you just, all bets are off. It, it, it just starts to eat away, eat away, eat away. And that, that’s, I, I, I agree with you. That’s a more recent understanding of what is happening and, but that leads back to you have to have. Some sort of test results. You need to have a way to test it because previously it seems like we were just learning from experience in the field.

Some places would have horrible rain erosion. Other parts of the world have very little and we didn’t really under different wind turbines, even though they’re manufactured in the same method, that the blades are pretty much identical as they got longer seem to have in different air sh Air force shapes.

You seem to have different kind of responses. It, it leads to we need to be testing and we need to be testing a lot. Of these coatings and, and your, I think one of the pieces here I was reading about R&D Test Systems rain erosion package that you maybe, maybe, first of all, let’s just describe what the, the, the, the whole system looks like.

Niels Pedersen: Yeah, so, so typically when we deliver system like that, we have it in two 20 foot containers opened up in the sides, and then splice together really creates the test chamber. Then besides that, we have another 20 foot container with auxiliary systems electrical system, water treatment system, and operator facilities.

And that’s approximately half of the systems that we have delivered. This is in this format, and the other half is actually integrated into buildings. It’s a little bit of let’s call it a nicer solution. If you have the space, if you have the building available then you can mitigate noise problems a little bit.

But it’s, it’s really plug and play for us to deliver these machines. We ship these three containers. We have an assembly team coming to site, setting everything up. It’s just sitting there on simple foundation points. I then we have it up and running in a matter of, of weeks or one and a half months or so.

We preassemble everything in our facilities in Denmark. 

Allen Hall: Remarkable. I, I’ve seen pictures of your systems. I think it was at LM Wind Power had purchased one of your systems, and I think you had a press release recently where Dtu has purchased one. 

Niels Pedersen: Yeah, we just had a, a really good sale to dtu. We have had a lot of collaboration with Dtu in terms of different funded projects, development projects.

Especially on the testing method itself and how to increase reliability and understand all the different parameters. And D two have now been granted the funds to, to get a machine for themself. And this is also basically showing that we are not at the end of, of this problem. We still need development.

We still need research. And the machines that they have bought are, it’s gonna be so cool. It’s gonna be delivered in start of 24 up and running. And what Dtu has done is that they have asked, can we increase the amount of rain three times? Can we basically have 1800 needles instead of 600 needles?

Wow. So that’s, I think it’s gonna be a game changer when, when suddenly we can threefold the amount of rain we can, we can put on these specimens. What, what’s the 

Allen Hall: rationale behind that? To increase the number of raindrops 

Niels Pedersen: It is that you’re still, this is still a relatively expensive test to do. So you want to accelerate it as much as possible, and you want to then accelerate with the amount of rain instead of accelerating the velocity.

Because accelerating the velocity gives you these unrealistic phenomenon in the, in the erosion process. So by increasing the rain density, you’re basically just dividing the number of tests you need. Testing time you need by three. It should scale proportional because it’s 

Allen Hall: already an accelerated test, right.

The way that I’ve seen it operate now it, this seasons run for hours, not days to get some least initial 

Niels Pedersen: feedback. Yeah, it is. It is an accelerated test. You can run it at low velocities and basically replicate reality just with a lot of of rain, of course. And we are seeing some customers actually running test campaigns of at plus thousand hours.

To have these real realistic data sets where they can see, they have a lot of measuring points. See exactly how the erosion develops through 

Allen Hall: time. One of the things like you hear from feedback on rain erosion is if you talk to an operator in, let’s say Brazil or talking to an operator in South Africa, Versus an operator in Denmark or the United States as they’re, they’re seeing different kinds of, or different levels of rain erosion.

And you, you kinda scratch your head and go, well, rain is rain, 

Niels Pedersen: isn’t it? Yeah. You would tend to think so, but, but in fact you should consider rain and all other ambient conditions to have an impact on this. Everything from UV exposure to rain droplet size, and of course the amount of rain is just changing from.

Every part of the world to the 

Allen Hall: other. Let me ask about raindrop temperature, cause I’ve heard some discussion about that. Like in colder climates the raindrops are colder versus maybe, you know, in like in a Brazil, in the rainforest where it may be particularly warm, does the temperature have anything to do with rain erosion?

Niels Pedersen: Yeah, we basically seeing that almost every parameter have an influence on this. Everything from rain droplet temperature to ambient air temperature. Of course speed amount of rain, everything like that. And that’s also one of the, the key points from the, from the sales dtu, is that they’re asking for more temperature control on this machine.

So that’s also gonna be the first machine where we can actively cool the ambient air. And what they’re basically trying to do is trying to divide all of these influences on the erosion process, which effects are coming from the temperature in the air and the temperature in the rain 

Allen Hall: droplet.

Okay. That’s very fascinating. 

Niels Pedersen: There’s a lot of things going on, and that has been one of the, the big challenging challenges in, in making this machine is that every small parameter is influencing this. We have seen the water quality coming out of, of the, of the water tap having an impact. Even though we have a water treatment system in this machine, we are just seeing it making a difference to the erosion process.

And we have spent tens of thousands of engineering hours trying to, to get this repeatability up from machine to machine. And, and we are at a really good stage right now where we have. High repeatability, both in the same machine, but also from machine to machine. Is there 

Allen Hall: differences between saltwater and freshwater in terms of rain erosion impact offshore onshore?

I would have to 

Niels Pedersen: guess. So we have never dared to put saltwater in our machine. I don’t blame you. Yeah, 

Allen Hall: it’s mix a mess. But that’s, that’s fascinating. So pretty much every variable that everyone commonly thinks of raindrop size, temperature, air temperature, uv, I think is interesting too. I think that’s it is part of the solution.

Impact how you build these, these test systems. So if you haven’t seen R&D Test Systems, you gotta go to their website because it’s remarkable the work everybody does there. So if you look, if you look at the system, there’s a lot of variables there. And I think this, this makes sense to me that because we don’t know as much as what we probably should know at this point.

We have to not build test equipment that’s very narrow in focus and, and eliminates a lot of parameters. We need to have sort of a wider. Variability, many more control knobs on the piece of test equipment, that that increases the level of complexity for you, doesn’t 

Niels Pedersen: it? It really doesn’t. And on the D C U machine, going back to that we are seeing them basically begging a machine, which they can develop further in the coming years or the coming decade.

We have a huge test chamber for them. So they want to build a high rain erosion test instead. There’s a lot of things going on, and, and it has, has been a real challenge to get this repeatability up and, and trying to pin down all of these different variables 

Allen Hall: impacting the results. R&D Test Systems is full of test engineers.

I think one of the hardest things about being a test engineer is you, you have to kind of solve the science before you build a piece of test equipment. So you have to have a really fundamental understanding of what is happening out there before you can go ahead and then start sketching out how this system is going to work.

How much, how many hours did you guys spend just learning about rain erosion and trying to grasp like what should be done? Yeah, so 

Niels Pedersen: the, the funny thing is that we are really in R&D Test Systems. We’re machine builders and we are not rain erosion experts. And, and we get specification ba basically from our customers and we are project driven company and And we can just see the results and we can have a target of narrowing down these results, increasing the repeatability, and then focusing our energy on that.

And what is actually happening than on, on a miniature level on the surface of the plate is really less of a concern to us. That is the concern of our customers who are operating the machines and looking at results. 

Allen Hall: You manufacturing these rain erosion test rigs, we’ll call ’em. You have several out in the field and in this one at D T U sounds like it’s like next level of a rain erosion test capability.

What’s next for R&D Test Systems in the rain erosion category are you’re gonna build this, this new concept. But if, if I, if I’m an operator, its the same on large operator in Europe or the United States. Shouldn’t I, it seems like I should have one of these test rigs because I wanna understand what’s happening.

I wanna be evaluate what’s going on a little bit. It’s, it’s, it seems like there’s not enough of these in the world yet. 

Niels Pedersen: No. I believe that’s the case. And, and we’re seeing these machines everywhere in the supply chain from the OEMs to the blade manufacturers, to the coding companies and test institutes.

Then backing up the entire supply chain. And there is room for more definitely, because there needs a lot of testing and, and we’re also seeing companies using these just for increasing quality and production sampling testing, different samples, et cetera. So you can never test too much and.

Also the fact that if you are able to, as an OEM or coding manufacturer have your own machine, you are able to turn this knob down with the velocity test for longer durations. That’s not really feasible when you’re going for test institute. So having your own machine really opens that window. And in terms of new developments, there’s been like in the last 10, 15 years, a long time there’s been discussion, shoot.

We do like sandy erosion. Scale erosion stuff like that. And the answer must remain maybe until somebody daress to, to change the machine. And that’s also really the key thing, that now we have this machine and it’s, we have a high repeatability and we can assemble and resembled results from one machine to the other.

And nobody really has to change anything drastically on this design now because this is the window to all existing test results and. Data 

Allen Hall: in the United States, we only have a couple marine erosion test facilities. Like I was saying earlier, they’re, they’re just not uniform. It seems like we could use a dozen of your systems in the United States alone to help solve some of these problems because we’re inundated with different coatings, new technologies, new approaches from universities, from companies all around the world.

There’s just no way to, to evaluate them. And I think you’re right. If you’re a manufacturer of some of these coatings or, or systems, you have to have one of these rain erosion test rigs at your site to do long duration testing. That’s the key. A lot of operators are starting to wise up and realize an hour or two long tests probably isn’t enough.

You actually need to see some, something that’s longer duration and your system does it brilliantly from what I can see. So this, this is amazing. Niels I, I, I think there’s so much to talk about in terms of leading edge erosion. I’m really glad to have you in the program. And, and I, I know I’m gonna get annotated with all kinds of questions, but I’m gonna send them your way.

So how, how, how do people, how do people reach you and how do people reach R&D Test Systems?

Niels Pedersen: So this easiest way is to go to our website, R&Ds as.com find contact information there. They can reach me directly as well. Npe rds.dk. 

Allen Hall: All right, well, great. Yeah. If you have rain erosion questions or interested in purchasing a a, a rain erosion test rig reach out to Niels because The system they’re producing is magnificent.

So Niels, thanks so much for being on the, on the podcast. Love to have you back. Great. 

Niels Pedersen: Thank you Allen. Love to be back.