From mysterious white etching cracks to cutting-edge material innovations, Malloy Wind‘s expert Cory Mittleider reveals the complex world of gearbox bearing failures that plague wind turbines. Learn why traditional monitoring may not be enough and what operators need to know about the latest solutions to keep their gearboxes running reliably. Read the EPRI article Cory references: https://restservice.epri.com/publicdownload/000000003002021422/0/Product
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Welcome to Uptime Spotlight, shining light on wind energy’s brightest innovators. This is the progress powering tomorrow.
Allen Hall: Welcome back to the Uptime Wind Energy Podcast Spotlight, where we tackle the technical challenges and innovations in wind energy. I’m your host, Allen Hall, joined by my co host, Joel Saxum.
We’re excited to welcome back one of our most popular guests, Cory Mittleider from Malloy Wind. In his previous appearance, Cory shared his expertise on main bearing failures. And many of you reached out asking for a deep dive into gearbox bearings. Today, Cory returns to do exactly that. As Malloy’s business unit manager, he and his team have diagnosed and solved countless gearbox bearing issues across different turbine platforms.
Having spent over 15 years in power transmission, Cory has become a specialist in understanding why these critical components fail and, more importantly, how to prevent those failures through better bearing selection and maintenance practices. Cory, welcome to the Uptime Wind Energy Podcast Spotlight.
Thanks for having me again. All right, so we’ve got a lot of requests to hear about gearbox, bearing, and what the issues are with those bearings. Gearboxes is something I know a little bit about. But you’re the expert. I hear a lot of complaining from the field. What is happening to gearbox bearings at the minute?
Cory Mittleider: Sure. Gearbox bearings has been an interesting one for me. So when I started in wind in 2011, it was generator bearings and gearbox bearings is where I started learning about this stuff. A lot of the generator stuff was electrical fluting damage. That’s pretty well figured out how to avoid that.
The gearbox one was a little more complex than that. And I don’t know if you’ve heard of. NREL’s Drivetrain Reliability Conference that’s happened for the last 12 plus years now. That’s a recurring topic for the last every single year, right? Is gearbox bearing failures. A lot of the conversation that started back in the day and is still going on is around what they call white etching cracking or white etching failures.
And back, in say, 11 and 12, A lot of the conversation was around was around that. It was around, the oils in the gearboxes. It was around coatings and bearing types and how they could affect the bearing itself to improve the life. And, specifically when it comes to gearbox bearings That was really hard back in the, the service providers and the operators themselves weren’t used to having to replace gearbox bearings.
They maybe weren’t even planning on having to replace gearbox bearings, right? But they started to see these problems. They started to get their head around the scope and how to identify them early and started to dig into it. There’s been a lot of investigations from bearing manufacturers, from third parties, from operators.
into those failures for over a decade now.
Allen Hall: I remember looking into some of the early gearbox issues and you’re talking about some of the failures I am actually familiar with. Those had a lot to do with just sort of basic fundamentals of like lubrication and loading, which were not obvious at the time.
Have we overcome some of those sort of basic bearing issues, or do they still exist out in the field?
Cory Mittleider: I started going to this drivetrain reliability conference in 2015. So I was a couple years later than the initials. But some of the earliest things I remember was slip occurring, right?
From typically I think the scenario that was presented on was high speed low load scenario. Yep. Such as bringing a turbine online, and I remember a chart very vividly from NREL’s outfitting of the high speed bearings on their test 1 5, right? The rollers should be rolling at 400 RPM, but their only roll, or the cajun roller assembly should have been going 400 RPM.
But it was only going 100 RPM meaning there was a ton of slip, a differential speed between the rollers and the inner ring raceway surface. There was some, oils that got fingers pointed at them for essentially being readily available to, to release hydrogen ions. And as we look back at wet etching cracking and the information that’s been collected over the years and investigated I think most people agree that hydrogen embrittlement is a big factor in that, um, there’s certainly components of material cleanliness that are involved in that conversation as well.
It’s a lot of investigation there. And to answer your question, is it still happening? I’ve got this report from an organization called EPRI. I found it on their website. It’s called Wind Turbine Gearbox Reliability Assessment. And they have listed what is it, seven points that lead to most of the gearbox related issues.
related failures and I’ll just read them off. It’s high contract stresses leading to pitting and spalling, bearing race slippage, macro pitting due to skidding and bearing slippage, wear due to inadequate lubrication, race cracking due to white etching formation, low quality materials and material defects or inclusions.
and improper bearing design leading to non uniform stresses or loads. And this was published December of 2021, right? So this is a couple years old, but it’s pretty, pretty recent from an accumulation of data, having time to digest and put out a report. This is pretty recent. And when I look at some other things in here that are really interesting 42 percent of gearbox related downtime is from high speed and intermediate bearings.
The other 58 percent is gearing related or maybe some of the other stages, but 42 percent are from high speed and intermediate bearings from those failure modes that I described. So the takeaway in my mind, as much as that’s something to be aware of and watch out for if it’s high speed and intermediate bearings, those often are replaced up tower.
So you can do that scopal work up tower. Another thing that’s also in the report they’re talking about that uptower scope of work costs somewhere between 15, 000 and 70, 000, right? So you can guess the sooner you catch that, you’re monitoring your CMS, you’re looking for inner ring defects or cracked inner ring or whatever, maybe sometimes outer rings falling as well.
If you can catch that sooner, get that replaced sooner, there’s less debris generated, there’s less additional ancillary components that need to be replaced or serviced. And that keeps it closer to that 15, 000 Scope of work,
Joel Saxum: of course, right? Let me ask you a question about that then. So to find that early enough, we’re usually always talking CMS, right?
And we know there’s a CMS usually from the factory. If it’s a Vesta, whatever they, if they’re doing an FSA, they’re monitoring that from afar. But there is aftermarket CMS for drivetrain monitoring that, like Onyx Insight comes to mind and there’s a couple of other brands out there, of course, would you recommend?
Cause this is a conversation we just had not too long ago with a bunch of people about blades and other reliability things. Would you recommend someone to shadow monitor a like a drivetrain CMS, even though they’re maybe they’re. Full service, agreement already has one. Do you think that’s smart?
Do you think that’s a good spend on money?
Cory Mittleider: Unfortunately what I’ve heard is it seems like no matter the application, gearbox, blade bearings, anything I’ve heard quite a few operators say that when they got to the end of warranty period or end of service agreement periods, they didn’t know what happened.
They didn’t know if X component had been replaced at all, or if it had been replaced five times. I guess I would certainly encourage operators to do everything they can to understand their own equipment. Is that making sure they get the reports from the people that are currently hired to service that?
Maybe it’s as simple as that. Maybe those are behind the wall, and they don’t get access to those. And there probably is some merit in understanding or maybe even say, shadow monitoring or double checking some things on their own to understand their asset. Ultimately it’s their asset.
And They’d be best off to know what’s going on with it. Yeah.
Joel Saxum: So let me ask you another question. With all of the, and this is monitoring inspection related. So to, to catch problems early. So CMS is one tool, right? Another tool is like an Uptower Borescope inspection. Of course, to me, end of warranty is an absolute must to have a third party come in and look at the, do a bore scope inspections, end of warranty.
Is there any other times that you recommend that, or do you recommend that to do every year like we do blade inspections, or what does that look like for you?
Cory Mittleider: The nice thing about gearbox bearings, especially in these high speed and intermediate positions that we’re talking about. The tried and true CMS tools really do a good job, is my understanding.
You can see those, the signatures are well developed they’re high speed enough to stand out. It’s not like main bearings where it’s tougher because it’s such a low speed, right? They blend into the floor on low speeds like that. So my understanding of what most operators do is they watch the CMS, they’ll look at other clues, they’ll look at temperature sometimes they have the the oil particle counting stuff to compliment that as well which the more ways you can monitor your equipment, the better, right?
So that makes sense. And usually what I understand is they’ll see some alarms, whether it’s any of that, or maybe the technician reporting noise, right? Those happen from time to time too. And then they’ll call in that bore scope. They’ll call in that physical inspection. The signature says it’s an inner ring on the high speed, but let’s look around.
It’s just double check and see if we’re, here. There’s a little more to it than just trust in that. Let’s get some eyes on it and figure it out, establish the scope of work. You might see some more stuff to be prepared for when you call in that crew to do a high speed
Joel Saxum: a high speed job. I remember talking to some people over in Denmark and they had an uptower kit that was like, they carried it up tower in a Pelican case.
And when they popped it open, it was a whole set of testing gear for testing oils. oils and lubes and greases and different things up tower where they could just take a small sample out of what was existing there and tell you the particulate levels and tell you if it’s been overheated or burnt up or what kind of life is left in it.
Does that service, have you heard of that service existing in the states? I’m
Cory Mittleider: not familiar with the, called the mobile oil lab type of thing. But it probably has some merit in spot checking. I think one of the things that’s been learned in the last decade, as we talked about WEC failures and gearbox.
Gearbox maintenance, essentially. I think there’s been a better job at paying attention at stuff like that. So I think there’s been an improvement, not just in the bearing technology and how they service it, but just staying on top of things, taking them seriously and doing it preventatively.
Allen Hall: From the design standpoint, Cory, the white edge cracking seems like something that could be designed out, but there maybe was a misunderstanding of how the lubrication, specific lubrication work with specific bearing sets and the loading that was there causing that slipping to occur.
And then which doesn’t seem obvious at first, but when you start thinking about it, like slippage is bad, it creates stress points in these bearings and then. Basically cracks them until they fail catastrophically. Are there more constraints on what the lubrication is and how often it needs to be checked if it becomes a critical piece to the success of a bearing?
Cory Mittleider: Oh we’ve had some conversations about lubrication on different bearing applications and ultimately confidence in lubrication is critical. To Perry Life. Absolutely. Debris can’t, minimize that water, minimize that presence of lubrication. The thing that makes wind turbines so difficult though is the environment and the variable load, right?
When we live in our industrial side of the business, you’ve got a processing plant, a production facility. A lot of times that gearbox, for example, is under more or less constant load. It’s probably in a building. That’s moderately environmentally controlled. Neither of which you have in a wind turbine, right?
You’ve got gusts. You’ve got, South Dakota, January last year, it was negative, 19 degrees, negative 44 wind chill. Now the turbines have a low limit cutoff, right? But even that’s pretty low, right? So you’ve got that and then we’ll get up to 110. And that’s the South Dakota environment.
You’ve got dry environments, you’ve got wet environments. There’s a lot of things that make it tough to have one thing work all the time, right? With that oil having to work for high speed bearings, low speed bearings. Ball bearings, roller type bearings, all inside one gearbox.
Allen Hall: I remember not long ago where additives were the thing.
There was a lot of sales of additives being sold. put into gearboxes to improve the lifetime of the gearbox. But it turns out from what I remember that some of those additives were actually causing some of the failures because it was not working the way that it in theory should have worked.
Cory Mittleider: Yeah, I think some of the early additive packages were pointed at as being more readily available to shed the hydrogen.
And generally, from a hydrogen embrittlement point of view for those that aren’t familiar essentially, you’re stripping off because you have the slipping and this kind of localized high pressure. It can generate localized high heat. It can essentially strip a hydrogen ion off of the chain of this additive, for example, and then coincidentally, when you take the two surfaces, a roller and a raceway, that’s that, that if lubrication isn’t present, separating them and they touch, the asperities touch and rub, that’ll create a negatively charged surface.
So you don’t have your positively charged hydrogen ion right next to your scar, your fresh surface that’s negatively charged. And then it attaches. And when that hydrogen ion attaches there, it weakens the bonds within that’s that steel structure, that alloy structure, and then your same stress cycles that Barry is built to last with it not being as strong, those bonds will break down sooner and sooner.
And essentially you end up with iron sand under the surface, these little pockets of copper. You know what I like to call iron sand under the surface. Now you have this discontinuity of material and it doesn’t carry the load and then it cracks and that’s A really short description of what leads to the white etching cracking phenomenon that’s been seen.
There’s some talk about even potentially electricity playing a contribution in the gearbox. Now an operator was telling me that about that maybe about a month ago. And then those hydrogen ions there’s also some observations that I’ve been seeing that they may want to collect, essentially.
near the impurities, near the inclusions within a steel alloy too, right? No steel is perfectly clean. There’s always something going on in there. Manufacturers do everything they can to minimize that and make them a rounded type instead of sharp edge type. But those are some of the factors that are currently still being talked about when it comes to WEC.
So to battle that, is there a specific oil that you recommend as being a bearing expert? We don’t deal a ton with the lubrication itself. Dealing with the bearings working with the manufacturers, we can tell you what characteristics we want the oil to have our viscosity at temperature, things like that.
But there’s a lot going on there. And I guess put it this way, I’m not well versed enough in oils. We could talk to the engineers at the bearing manufacturers to get some of those lists, but what we found in the last several years, specifically against this list of seven bullet points from this EPRI report, for example, is we’ve seen, we’re, like I said, this started in 2011 ish.
When I started to get involved. So your regular bearing that most items ship with, whether it’s your electric motor on your vacuum cleaner at home, the ball bearings in your wheel hub of your car, or wind turbines. They’re through hardened steel alloy. No coatings, no nothing on them typically.
That’s entry level. and they’re designed for raceway fatigue. And just like the other bearing applications we’ve talked about, all these things aren’t raceway raceway rolling contact fatigue. These are the other things that happen, right? So as the WEC thing started to come to life, one of the first responses from bearing manufacturers, from turbine OEMs, from gearbox OEMs was black oxide.
You guys are familiar with black oxide, I think, right? We even talked about it on our talked about main bearings a bit and Allen, I think it was you that brought up we call it a coating, but I don’t like that word as it pertains to black oxide specifically because it’s converted material, right?
It’s not applied afterwards. That’s what I would call a coating. Black oxide is actually converted material. steel alloy. The surface, again, that’s about two, three microns thick, really thin layer. And it’s exactly what it sounds like. It’s oxide. It’s oxidized steel, right? So it does have some benefits.
It essentially makes the the, surface of the raceways and the rollers fuzzier improving oil adhesion, trying to build up that, that oil layer, increasing your lambda to avoid the smearing, to avoid that contact, to avoid the the asperities touching leading to that scar, that negatively charged surface.
It can only do so much.
Allen Hall: But that’s so true though, because we, when we think of bearings, we think of everything being really smooth and rolling so easily. But when you talk about lubrication you need to have a surface to attach to, to provide that little thin layer of oil so that it does operate for a long period of time and removing that surface is going to be catastrophic in a lot of cases.
Cory Mittleider: And you’re right, you look at a ball bearing on your table, on your bench or something it looks, and they’re polished, they look incredibly smooth. But just like anything, you put it under a microscope and you start to see little peaks and valleys. I call them asperities, right? The roller has those asperities, the raceways have those asperities and it’s something that different bearing manufacturers control in different ways.
It’s something, it’s each manufacturer’s secret sauce on how they do those things a little bit, right? They put as Different effort into different places. But the whole goal with bearings and lubrication is to make sure those asperities don’t touch.
Allen Hall: Exactly. It’s much like a cylinder wall in a, in an engine.
When you watch them build an engine on these high end engines, everything’s so smooth and looks so great. Except for that cylinder wall, which they intentionally brush so that oil remains in that cylinder to lubricate that piston as it goes up and down. The same thing happens in a bearing. Just at a smaller level, it’s not as gross as scratching, but there is a surface there to hold oil properly and lubricant properly.
Losing that surface is really a delicate matter. I think people don’t understand that’s where the magic is. It’s right at that surface level because that white edge cracking was a result of slippage due to lubrication and the surfaces of the mating surfaces not being quite right. Boom.
Now we got a huge problem. And Cory, I think you’re right. A lot of the wind turbine world is so different than most bearing applications. You’re really putting a lot of stress on that. Are there more updated bearings that can handle the tough environment like South Dakota?
Cory Mittleider: Yeah. So something that progressed as the white etching cracking conversation progressed, and this isn’t unique to wind.
When you look at any bearing manufacturer has a catalog of different, uh, materials, heat treatments, coatings, things like that, that they can apply depending on the application. And one of the first upgrades often used for bearings in demanding applications is case carburizing, right? So instead of using a higher carbon content alloy, and through hardening it, Where it’s the same hardness throughout the cross section of the ring.
You use a low carbon alloy base material. And then you put it in a atmosphere with a high carbon atmosphere. You heat treat it for a period of time and you have a shell. Almost imagine cutting an M& M in half, right? You have a harder shell and a little bit of a kind of springy shock absorber type core.
Like a golf ball, yeah, so there’s that, and that’s, like I say, that’s pretty well known. That’s in a lot of different industries, a lot of different applications where our case hardened bearings are the next upgrade often. Something that in my experience going back to 2012, 2013 is there’s actually different versions of case hardening though.
So case carburized is the one that, that typically people are familiar with. It’s the. The standard case hardened version but one that we’ve had a lot of success with specifically in the last 10, 11, almost 12 years now is one that’s case carbon nitrided. So in addition to the carbon in the atmosphere being deposited in the part there’s also nitrogen that’s ends up getting added to the part.
And. Also, the, even the steel alloy is different. So now that’d be probably more what I’d call a medium carbon alloy steel. So it’s not the low carbon alloy steel. It’s not the high carbon alloy steel. It’s a little bit in the middle. Specifically there’s one manufacturer that we’ve worked with a lot on this and that’s NSK and they, what they call it is super tough.
They have a whole family of different materials, different alloys and heat treatments. And this is the one that’s found, we found to work really well in wind. Gearbox bearing applications and one of my my earliest example with a success story on the super tough bearings was actually the Getz.
I’m sure you’re familiar with the Getz gearbox. It had a little bit of a reputation for chewing up and spitting out planet bearings. The first one that I remember was I think it was late 2012. I got installed up tower in March of 2013 after the site was online for about three and a half, four years.
It had already failed a set of planet bearings, and that gets Gearbox. But they were able to do an uptower repair to replace that. And after doing that, the site, we talked about different monitoring methods. I don’t think that site had CMS on their Gearboxes. And never mind, planets are a little trickier because you can’t directly touch them right with the probe through the housing.
They’re floating around. One of the things that they did is they checked the filters. On a six month basis. Just look for some metal particles. That’s how they found it the first time. That’s how they probably find it again. So last update I got from them before they did some other work on the turbine, was that seven years later, so 2020 that when they looked at the Berry Raceways, they still looked brand new.
They still looked great. And the gets with its reputation was one that really stood out to me as successful. Now, between that seven year window we’ve sent a lot more to the field. We’ve done a lot more follow up and other things too, but that’s probably the longest and maybe biggest wow. Realization when it comes to the benefits of different materials, alloys, and heat treatments.
The other thing about bearing technology, ISO dictates that they have to have certain level of cleanliness and minimize particle size and count and type in the alloy. But again, that’s another thing that’s secret sauce on a per manufacturer basis per bearing manufacturer.
And what I’ve learned that NSK does in particular is they just publicized this maybe a year and a half ago now. They do what they call micro UT. So they’re essentially using a an in house developed ultrasonic testing on the bar stock. before the ring is even formed. So that allows them not to look at a sample and cut off a sample, polish it, put it under the microscope and say the sample was good.
So we qualify the whole bar or the sample was bad. So we scrapped the whole bar. They’re able to do that as a non destructive. type of test. So even if there is theoretically a bad spot in a bar, they can cut out this spot of the bar and then continue to keep using the rest as they make the forging.
So that’s another area that as we continue to have deeper and deeper conversations with operators right now that level of design intent and manufacturing diligence is really starting to be observed just now, in my opinion It was important the whole time. We’re just getting to that level.
We’re getting caught up to all the tiny little pieces, the less visible pieces, that can be impactful.
Allen Hall: Now, this is why we need you on the podcast, Cory, because you can explain all of this great bearing issue and resolutions to us, non bearing people. And I know we went across a lot of non bearing people out in the field that just need a little bit of advice.
And if you do need advice, you need to go to Molloy Wind. And check out their website. And Cory, how do they do that?
Cory Mittleider: Yeah, our our website’s at molloywind. com. One of the places that I like to point people is there is a I think it’s called resources tab with some tech articles that we’ve written largely around bearings there’s some gearbox bearing stuff main bearing, blade bearing stuff on there usually around what we’ve seen for failures in different applications.
And then when it comes to the gearbox bearing topic, there’s a couple pages with even the typical gearbox bearing configurations for high speed and intermediate. I have some pictures of on there showing how some use tapers and cylindricals, some use ball bearings and cylindricals in those high speed and intermediate positions.
Because they’re not all done the same. They’re not all implemented the same. Um, and then there’s also some pages as it comes to Gearbox Berries outlining the the, call them the coatings and conversion coatings materials information as well, black oxide and super tough, for example there’s some information there showing that.
Allen Hall: Yeah, so check out malloywind.com or you can reach out to Cory via LinkedIn. Cory, thank you so much for being with us again. I learned a tremendous amount. I’m almost, 10 percent of what your knowledge is. Boy the bearing information is so useful in the field. I really appreciate this.
Cory Mittleider: Yeah, thanks for your time.
https://weatherguardwind.com/malloy-wind-gearbox-bearing/
Pardalote Studies Australian Blade Erosion and Heat Fatigue
Rosemary Barnes, CEO and founder of Pardalote Consulting, joins to discuss their new grant-funded study of blade erosion and heat fatigue in Australia.
Sign up now for Uptime Tech News, our weekly newsletter on all things wind technology. This episode is sponsored by Weather Guard Lightning Tech. Learn more about Weather Guard’s StrikeTape Wind Turbine LPS retrofit. Follow the show on YouTube, Linkedin and visit Weather Guard on the web. And subscribe to Rosemary’s “Engineering with Rosie” YouTube channel here. Have a question we can answer on the show? Email us!
Welcome to Uptime Spotlight, shining light on wind energy’s brightest innovators. This is the progress powering tomorrow
Allen Hall 2025: Well, Rosemary, welcome back to the show.
Rosemary Barnes: Thanks, Allen. Great to be here. For, it’s been a while since we did one of these one-on-one episodes, like a, yeah, a proper, proper guest.
Allen Hall 2025: Well, this is kind of a celebratory episode because your company, Pardalote Consulting, has been awarded, uh, some funding from the Australian Capital Territory’s government for the Energy Innovation Fund.
Rosemary Barnes: It’s a really good program that the ACT government has to try and get energy innovation In the state. It’s not a state actually, it’s technically a territory. Little more than just Canberra, the city. Uh, but there are actually quite a few, like, really interesting energy-related companies here, partly ’cause of the, the fund I think helps, but also just tracing back like, [00:01:00] uh, y- you know, in the 20-teens, Australia had a really conservative government that hated renewable energy, and the ACT government had a commitment at that time to 100%, um, 100% renewable electricity for the, the government.
And that was one of the only programs that was resulting in a lot of, um, you know, clean energy projects being built, and one of the conditions that they put on that, uh, for people that would win PPAs with the ACT was that you had to have your headquarters in Canberra. So we’ve actually got quite a few, quite a few really cool, innovative companies out of here.
Um, like Neoen’s headquarters here. Windlab, uh, yeah, was, was founded here and still has a lot of people here. Pardalote obviously, and you know, a few other companies as well. So despite it being a small city of like, I don’t know, maybe it’s up to 400,000 or something people by now, um, yeah, there is actually quite a lot going on here for energy.
Allen Hall 2025: And the Energy Innovation Fund is funded by the wind and solar operators in the area, and your particular [00:02:00] effort has really global consequences. You’re focusing on two areas involving how wind turbines survive Australia, but more, uh, of relevance is to just really tough conditions which exist not just in Australia but around the world.
What two areas are you going to focus on?
Rosemary Barnes: Yeah. So the two focus areas are leading edge erosion and high temperature fatigue, which we can probably get into the definitions of those in a minute. But basically my, um– what led me to wanna have a project like this was that when I moved back to Australia in 2021, I– and I started working in O&M, uh, I noticed that the wind turbines that I would look at, the blades that I would look at here behaved really differently to the ones that I worked with overseas.
You know, es- especially with leading edge erosion, like often I would be doing a condition assessment of a, you know, a new wind farm. Um, might only have been operating for, you know, two years. That’s a pretty common time for people to get in and do a condition assessment [00:03:00] because their warranty period is about to end and they wanna, you know, make sure that everything is okay.
Um, and I would just notice that often, like 90, 100% of blades would already have bad erosion after just a couple of years, which is super-duper fast. And then there are some tools available to check, um, like what kind of erosion are you likely to experience on your site. Like is it a higher severity erosion site or a, a low severity one?
Um, and you basically, you know, the status quo globally is to just look at the annual rainfall, um, and the tip speed. And if you’ve got, you know, high for both of those, that’s a bad erosion site. And if you’ve got low for both of those, it’s a, a low erosion site. But when I plotted out the wind farms that I knew had really bad erosion problems onto, you know, a chart with those two axes, I just saw a random distribution of dots.
You know? Like, this was not– uh, this had no predictive value for Australian wind farms. And so that led me to believe that, okay, um, you know, things are a bit [00:04:00] different here. Makes sense, you know, most of the knowledge that we have about how wind turbines operate, it’s been developed and validated mostly in Northern Europe.
You know? Like it’s, it’s Denmark and the surrounding countries that had, like, the bulk of the early wind energy. First few decades of knowledge were, you know, were mostly there. Of course, there were some other, um, places that had wind turbines, but, you know, most of the The OEMs have been operating for decades, came from Denmark.
And I know when I lived in Denmark, the rain there is very different to the rain in Australia. So in Denmark, it’s basically always raining, right? Like, it’s just… Like, even if it’s not raining, you’re still gonna get wet when you go outside ’cause it’s just, like, the air has this just amazing ability to just hold onto moisture.
Um, but it’s very, very gentle. But, you know, over an entire year of most days having gentle rain, that adds up to a lot. Whereas in Australia, and especially if you go, like, north to Queensland, it rarely rains. It’s mostly just dry, and when it [00:05:00] does rain, it’s like a tap turns on, and I, I swear you will get bruised from the rain droplets hitting your skin.
You know, they just have so much energy in them. So I think that that i- you know, when you look at just the overall rainfall, you really hide something important about how erosion, um, can progress. Then, um, there’s other places in Australia that have very different characteristics. Again, they don’t have that kind of really intense rain but, you know, some of those sites are also having really bad erosion.
And so it just occurred to me, I did a lot of research, you know, into what’s going on and, you know, the academics are studying erosion a whole lot, and they’ve got, you know, a lot of standardized tests and, you know, products are developed according to these standardized tests. But the standardized tests don’t actually resemble reality, and especially they don’t resemble reality in Australia.
And so my client started asking me, “Okay, you know, the products that we have are, are terrible. We have to replace them every couple of years. It’s, um, causing big problems with also [00:06:00] the amount of energy that you’re losing.” One of the types of, um, leading-edge erosion or leading-edge problems that we have in Australia is that the, the coatings tend to peel off and make these, like, big flakes which will just massively disrupt the airflow, can cause y- you know, at least a few percent AEP loss, and maybe up to five.
And even worse than the AEP loss is the revenue loss because it affects it most at, you know, lower wind speeds. Um, you get a bigger hit than at rated wind speeds. So there’s a variety of problems going on with leading edges in Australia, which mean that I, I basically… My clients would ask, “What product should we put on to prevent having to, you know, constantly replace this?”
‘Cause it costs, like- you know, 30, $40,000 per turbine to replace the protection, not to mention, you know, one or two days of downtime. It’s expensive, and I basically, I didn’t have a good answer for them. What, what product should they put on? I don’t know. No, we, we don’t know. One, we don’t know what the [00:07:00] specific, um, characteristics are that are…
what the specific local environment, local conditions are that are accelerating leading-edge erosion, one. And two, all of the products tend to be tested around this, you know, there’s this protocol that academics have come up with, and they’ve kind of like assumed that this is representative of how things behave in the field, and it’s– I don’t think it’s particularly true anyway, but it’s especially not true in Australia.
There are a few companies that are testing to different standards. Um, definitely applaud them. But without knowing wha- what are the conditions truly like in Australia, uh, it’s really hard to advise, like, what kind of tests should you be demanding from a product you’re considering to be sure that you’re gonna put it on and not gonna be replacing it again in two years.
Allen Hall 2025: Because that’s really the trouble in Australia is when you get offered products They have been tested generally in somewhere in Europe and maybe in the United States, and then when they go to [00:08:00] Australia, it’s really unknown as to how those products will do, which is a huge risk for the Australian wind market as to what to choose, how to choose, is it– what’s real in terms of test data.
So now you’re gonna go out and do what? Are you gonna put sensors out by the wind farms? Are you gonna try to do more of a statistical summary of the actual environment around wind farms using existing data? What’s the approach here?
Rosemary Barnes: It’s all of the above, but the part that is supported by the grant is that we’re gonna have enough money to be able to buy some scientific-grade sensors and put them on, um, a sample of Australian wind farms.
So we’re gonna be looking at a lot more characteristics about the rain than simply is it raining now, you know, how many millimeters per hour. We’re also gonna be investigating, you know, every kind of characteristic of, of that, um, of that rain, um, including, yeah, like the, the energy that’s in it, for example.
A, a bunch of stuff. I won’t get into every single [00:09:00] parameter. Um, and you know, other things as well, like measuring UV, solar radiation, um, particles, because, you know, in Australia we have a lot of dirt roads, which I know is very common in wind farms around the world, but Australian dirt roa- roads are always dry and dusty, like 99% of the time, so that’s one of the things that y- you know, maybe that’s causing a difference.
Um, so basically putting sensors all over a bunch of wind turbines and then monitoring the erosion, um, a combination of some real-time monitoring and also looking at inspection, um, drone inspection images annually. We also have a- an option where we’ll just be using SCADA data and inspection images, so that’s like a lower cost version where we can combine that with the findings from the scientific-grade instrumented turbines to build up a picture of what types of conditions lead to accelerated erosion.[00:10:00]
Allen Hall 2025: So the SCADA data will, will have some information inside of it, you think, that, uh, will correlate to the weather outside?
Rosemary Barnes: It has some Additionally, we can look up, um, you know, just the weather data, like how many millimeters fell during which 15-minute interval throughout the day, what was the temperature.
SCADA will tell us also what the temperature was, um, what the speed of the turbine was, so you can calculate the tip speed, ’cause that’s an important thing. Um, yeah, so it’s, it’s two, it’s two tiers of data collection. The scientific grade sensors, as you can imagine, are, are really expensive and y- you know, the, the grant project has contributed a, a lot of funding, um, but it’s not enough to put those, yeah, put a little mini lab on top of every turbine across Australia, obviously.
So that we’re using s- doing selectively, and then we can increase the number of wind farms that are included in the study by just doing this, um, cheaper version of the SCADA [00:11:00] plus, uh, weather data that’s available.
Allen Hall 2025: So what are some of the risks on the temperature side for all the high-temperature regions of Australia that have wind turbines?
Clearly it’s generally warmer in Australia than it is in, in Scandinavia and Northern Europe. What kind of temperatures are we talking about on the ground?
Rosemary Barnes: Uh, well, temperatures here can get pretty close to 50 degrees. Um, and if you’ve ever been inside a wind turbine blade on a, even a mildly hot day, you’ll know that the temperature inside a wind turbine, and especially inside the blade, is much hotter than what it is, uh, what the ambient temperature is.
So this project is one– I’ve actually been talking about this project for, yeah, like over 10 years now. Ever since I started, I moved to Denmark, started working for a wind turbine manufacturer, I had done– I had just finished doing my PhD on composite materials, structural design, and analysis. So, um, yeah, very, very familiar with, [00:12:00] you know, how composite materials work and, in particular, the effect that temperature has on them.
I mean, like most materials, when composites get warmer, they get softer, and that is really important for a w- a wind turbine blade. You know, if it gets, um, less stiff, then you’re gonna get a lot more strain, and that is going to affect your fatigue behavior. Y- you know, fatigue is just the application of a little bit of, a small amount of strain.
It’s not gonna cause damage, but when you apply it millions, tens of millions of times, like you do in a, o- over a wind turbine’s operate, um, operating lifetime, then that builds up. And, you know, wind turbine blades are a very fatigue-driven design. Um, it’s one of the most important things to consider when you’re designing a wind turbine blade.
And so when I got to Denmark and I learned how materials are qualified and how the qualification is treated in the certification process, I just realized it’s not particularly conservative, and also that some of the assumptions that are made that [00:13:00] wo- again, they worked really well in more moderate climates where wind turbines have had most of their developmental history.
You know, it’s not such a big deal there if you test at room temperature. Your wind turbine blade is spending most of its operating lifetime at room temperature or below. It’s, it’s rarely, you know, above 30 degrees in Denmark and most of Northern Europe and, you know, also a lot of, um, a lot of America, not, not all of it But, um, in Australia it has just extended periods above that temperature and even exceeding the temperature where, you know, wind turbines have an operating limit and after that they will shut down.
But the operating limits are based on ambient temperature. It’s not based on what’s the temperature in the laminate, which is what really matters for blade lifetime. So anyway, I’ve been obsessed, like honestly obsessed about this issue for 10 years. Talked about it with anybody who would listen . But then when I started working in O&M in [00:14:00] Australia and I started seeing some wind farms with an abnormal number of cracks early…
again, early in their lifetime, you know, I think one of the wind farms I was looking at was maybe three years old or four at the time. I think it was three actually, and had a lot of cracks, and I looked at a few years in a row and it was more and more cracks every year and I’m like, “Oof, this really looks like end of life fatigue behavior.”
A- actually it’s not, y- you know, there’s this concept of a bathtub curve where, um, when you’re looking at failures in components, in, in anything, not just in, um, wind turbine blades, but you know, like you’d start– it’s called a bathtub because, you know, when it starts operating, you’ll get quite a lot of failures.
Anything big, any manufacturing defects or anything are gonna cause failures quite fast, and that kind of drops off over time as all of those, uh, get addressed. And then you have, you know, the bulk of your operating life, it’s like pretty low level, pretty, pretty constant for a long time and then as you get towards the end of the [00:15:00] life, you start to see failure rates rise up again.
That’s your fatigue failures, your end of life fatigue failures. And so when I saw the same types of cracks more and more each year, I’m like, “This looks like, you know, the foot end of the bathtub, not the head end.” And, uh, it made me worried and I’ve now seen that across a few wind farms in Australia at, um, hotter places.
There’s a few blade types that are more prone to it than others, but at this point it’s still a suspicion that that’s what’s going on. I mean, a suspicion backed by a lot of, a lot of theory and knowledge of how the certification process works. But this project now we’ve got some funding to actually go put some sensors onto wind turbines, actually learn what the temperatures are in the blades throughout the whole laminate, um, not just the, you know, on the outside surface or not just the ambient temperature, but actually, you know, develop a temperature gradient across the whole, um, the whole laminate in the blade shell.
Um, and [00:16:00] then we’re going to be doing a bunch of modeling basically to look at what is the effect of these different temperatures that blades are really seeing and how much would we expect to… that to decrease a lifetime. And then we should also be able to say, you know, if you have this issue in your wind farm, you might be able to change your operation a little bit and extend your lifetime a lot.
Because this one, it’s real– like, in contrast to leading edge erosion, leading edge erosion is just, it’s, you know, every wind turbine has it to a certain extent, and it, it’s always there, but it’s a relatively minor cost to fix it. You know, like it sounds like a lot, like 30, $40,000 per wind turbine, but, um, you know, compared to if you’ve got to replace every blade across your fleet because they’re all, you know, at the end of their life after five years, you know, that’s obviously shocking.
And, you know, that’s a bad example, but even in a y- you know, like a less extreme example, maybe [00:17:00] after 15 years you have to do a, you know, a f- a fleet-wide campaign to strengthen blades or something. It’s, you know, m- many millions of dollars for that, and so it c- could make sense to be able to learn, okay, what, what hours of operation should we be avoiding?
Additionally, because when it’s super-duper hot in Australia, usually you’ve got heaps of solar power and the electricity price is not that high. So I, I think that there– and I don’t, obviously, before we’ve done the project, I don’t know what the threshold is. But in both cases, we will be aiming to improve the knowledge of how you can operate to avoid these periods of accelerated damage.
Allen Hall 2025: Do you think you’re seeing more fatigue-like damage due to the blades operating when it’s hot or not operating when it’s hot, with maybe less airflow around the blade and maybe less cooling going on is just a temperature soak At rest? [00:18:00]
Rosemary Barnes: Yeah. It’s interesting because the temperature is higher if it’s not rotating, um, because you get a whole lot of, um, convective heat, heat transfer when the turbine is operating.
So your temperatures are not gonna get as hot when operating as when they’re standing still. However, if it’s standing still, they’re only very lightly loaded. Like, yes, they’re gonna get, um, blown by, by gusts and, um, have a little bit of bending, but it’s, it’s very, very small compared to, uh, if it is y- you know, operational loads.
Uh, assuming that you’re not in the middle of a s- a storm. But yeah, a storm probably doesn’t come with 50 degrees temperatures.
Allen Hall 2025: And what part of the blade is susceptible to these higher temperatures? Is it the resin? Is it the fiberglass or carbon fiber? Or is it the, the glue, the bond joints? What part are you focused on?
Rosemary Barnes: The resin is the main part that I’m focused on. It gl- it could be an issue for glue too, actually. I haven’t even looked into what the, um, yeah, temperature assumptions are with, with glue, with [00:19:00] bond lines. But the failures that I’m seeing in the field are not, are not bond line issues. It’s, it’s, um, a laminate problem.
Allen Hall 2025: What about balsa and foam inside of the blade? Are they affected by the temperatures or are they pretty temperature stable?
Rosemary Barnes: I don’t think they’re affected at these kinds of temperatures, no. They, they don’t really do much actually. The, the core materials, like it, it is very important that they’re, that they’re there, but their job is really to keep the fiberglass separated from its- itself to make it stiffer.
So, um, yeah, that’s, that’s unlikely to be a, a major source of problems.
Allen Hall 2025: So this study is gonna work over about three years, and you have a number of wind farms that are participating. Are you looking for more wind farms to participate in Australia?
Rosemary Barnes: Yeah. Yeah, definitely. I mean, we can, um, have as many as, as people want to join.
We’ve got quite a good selection so far. Definitely can always welcome more. A, a bit limited in how many can get the really, um, good sensor [00:20:00]package, because the grant funding is a, you know, a certain amount, and that’s paying the bulk of those sensors. So, um, those spots are limited. So if anybody wants to really zone in on what is specifically causing erosion on their site, you know, if you know that you have got leading edge protection that is not good enough and you have to replace it soon, but you don’t know what to replace it with, then, you know, that would be the kind of wind farm that might want to consider, yeah, joining this and, um, you know, getting these sensors on their, um…
We’re putting them on top of the nacelles, most of them. Um, yeah, so that would be a good match then. Um, and then, yeah, for the ones that are doing the SCADA data and, um, weather data- There’s not such a, a hard limit on how many we can have join like that. So yeah, we can have more, more like that.
Allen Hall 2025: In the temperature fatigue effort, i- is that still looking for participants or are there particular wind turbine types or manufacturers that you’re [00:21:00] looking for to participate?
Rosemary Barnes: Yeah, I think, um, I, I mean yes, we can have more of those. That’s a simpler, a, a simpler issue as well. The sensors are not so expensive and, um, it’s, yeah, it’s a, it’s a simpler project to join that one. We only need, you know, a couple of turbines per site, so it won’t be such a, uh, an involved process to get everything up on into the turbines.
And in terms of who might like to join that, I would say anybody that is in a really hot area where, you know, where they see a lot of days over 30 degrees, and if they see any days, you know, getting into the high 40s, then I would say that that’s worthwhile. Or even I have seen this issue in some milder sites, um, yeah, depending on the, on the blade type as well.
It is more common with polyester resins. They have a, a lower op- uh, maximum operating temperature than epoxy resins. But then also just anybody that has noticed just, hey, [00:22:00] we’ve got a lot of cracks, and it seems like we’re getting more and more cracks every year, which to be honest, can be hard to keep track of if you’re…
If you’ve got a full service agreement, uh, you know, an OEM managing your wind farm The early signs of this are gonna be category one and category two cracks. They’re not in exactly the same location. It’s, you know, it’s a tricky one. Normally, if you’re looking at a serial issue, then you’re going to have, uh, well, you know, your ideal pattern for a serial issue is the exact same thing happening over and over again.
And so it is harder to pull this out. It also really would be very rare for it to be happening in the first two years or three years, whatever your serial defect liability period is. So it’s quite hard. But, um, another group of wind farms that might like to consider it is if you know that in, you know, a certain number of years you have to renegotiate your service agreement or, you know, it ends and you might have to take over yourself, then this’ll be a really good way for you to [00:23:00] understand, you know, have I got a ticking time bomb here?
Um, because it’s not something that you’re gonna be aware of if you haven’t been, you know, doing some really, really in-depth shadow, shadow monitoring of your blades, you know, running your own inspections and looking at every single damage, not just category three, four, five, but lower ones. So yeah, I mean, there’s a, a wide variety of people that, that could be interested in joining.
Allen Hall 2025: Are you expecting a number of manufacturers that make leading-edge protection or involved in resin creation, some– there’s a number of resin companies and a variety of resins that are used globally, sort of interchangeably at times. Are you expecting some of those companies to participate in this effort just to learn about the Australian environment?
Rosemary Barnes: I think it would be a good opportunity to test out some products and see how they behave in the Australian context. I think that that would be a really good selling point, but I, I have to say that most of the companies doing that sort of thing that wanna enter Australia, they don’t [00:24:00] really consider…
Like, from the perspective of wind farm owners in Australia, if you can’t show us wind farms in Australia where this has worked and, you know, show us a before or after, you know, the old LEP lasted Two years and our LEP is going on four years now with no damage. It, you know, unless you’ve got a before and after like that, you can tell us however many turbines that you’ve got installed around the world, but, um, we don’t consider it validated, y- you know?
It’s not validated for Australian conditions yet. And I do have this same discussion over and over again with, you know, not just leading edge protection, but all kinds of, um, you know, manufacturers of whatever doodads that you put on to improve a, a wind turbine. It’s so different to Australia. Things break so fast.
And I’m talking everything, you know, like vortex generators fall off and, um, yeah, like, uh, you know, bits of lightning protection systems fall off, seals just [00:25:00] crumble and disintegrate. Um, and it, you know, we’re very wary of, of new products. So I, I do– I mean, I’m thinking of it more from my client’s point of view than from the product manufacturer’s point of view.
But one thing that I wanna get out of this pro- project is to be able to answer one of the most common questions that I get is, which is, what leading edge protection should I be putting on my turbine? And for now, I don’t know. I, I know a range of products that don’t work in Australia, and not much more than that.
So, um, yeah. And it’s also, you know, Australia’s a very varied place with lots of different kinds of climate too. So it’s not gonna be like, you know, the product that works in Queensland is the same one that’s gonna work in Tasmania, which is the same one that’s gonna work in Western Australia. You know, um, so it, this project is gonna really pull out what are the site specific issues you’ve got at your site and what kinds of, um, you know, tests would we need to see a product um, perform in order to know that this [00:26:00] is gonna last on your site.
Allen Hall 2025: W- what is the outcome of this project or these two projects? Are they gonna be reports or, uh, a, a continual monitoring system that’s designed for the Australian environment? How do you see this going?
Rosemary Barnes: Yeah, so one part of it is, um, developing a way to identify periods of accelerated damage and to know not to operate during that time.
So we call it protective operation. Uh, so that would, uh, help you if, yeah, you’re trying to extend the life of something or increase the amount of time before you have to repair, then y- you know, that would be useful to have that knowledge. And it will be as simple as just an alert saying, “Hey, accelerated damage conditions.
Consider, you know, if you wanna keep on operating.” And, you know, if the price of electricity is super high at that time, they may want to push through, and if it’s low, they probably won’t want to. So that’s one thing. Um, especially, you know, as wind turbines get to their, near the end of their life. I’ve got some clients whose wind farms only have, you know, [00:27:00] maybe five years operation left.
They just simply don’t wanna repair their leading edge protection again. They just, they, they don’t wanna do that. So they would be happy to, you know, reduce operation a bit and have their turbine limp through to the end of the period. Y- you know, you want everything to wear out at once. You don’t want brand-new leading edge protection on a turbine that’s going to come down in a couple of years.
Um, so, you know, that’s, that’s one part of it. And then the other thing is, you know, turbines earlier in their lifetime, how can we optimize the maintenance schedule with leading edge erosion? Um, so, you know, like it’s a lot cheaper to, uh, replace the LEP if you get– catch it early, but then you don’t wanna be catching it too early and replacing it, you know, constantly when you, you don’t need to.
So, um, yeah, it, this, having this knowledge will enable a site-by-site operations and maintenance strategy with respect to leading edge protection. We also have some sites who are having trouble. They’ve got a full service agreement, and the OEM is [00:28:00] responsible for, um, doing the leading edge erosion repairs and protection replacement, but the owner is on the hook for paying for it.
At the other end, we’ve got people with full service agreements where technically the, um, manufacturer is supposed to be doing the leading edge protection and paying for it, but they argue about what, when does it need to be done. Because, you know, um, the operator might think if there’s no structural risk, then we don’t need to be replacing it.
And in the meantime, you’ve got turbines spinning around for years and years and years with, you know, these huge flakes of leading edge protection s- you know, causing the flow at the tip of the turbine to, to detach and to stall, and horrible aerodynamics, huge losses in power generation and revenue. And they’re having a big fight about, you know, is this necessary to do or not?
And then, you know, they’re just gonna put the exact same product on again ’cause the [00:29:00] OEMs are re- all really, really wedded to their own particular brand. It’s like, “Well, last time we had this product and it was factory applied, it lasted one year before it s- it was worse than, you know, if it wasn’t there at all.
Uh, we don’t really want you to put that one on again.” And so, you know, having the information that they need to be able to, you know, really bring data to these discussions and, you know, makes a, yeah, data not drama. That’s a, a good approach I think, um, for any kind of negotiation and especially in the case of leading edge erosion.
And then for the high temperature fatigue part of the problem, aside from, you know, just wanting to know are your blades aging, should you be looking at remediation action or changing the operation, the other really big key thing is, uh, you might need to have a fight with y- your OEM about if this turbine has been designed and operated correctly.
And so then having the data from this, um, project is going to give you the information that you need to come into that [00:30:00] argument with, again, the data not the drama. Um, and to, you know, in- increase your chances of succeeding in that kind of really tricky negotiation.
Allen Hall 2025: So if you’re an OEM or a manufacturer of equipment, an ISP, an operator, pretty much all aspects of wind operations, you probably ought to be getting a hold of Pardalote Consulting and Rosemary to talk about the opportunity to participate in this study.
How do people get ahold of you to, to do that?
Rosemary Barnes: People can go to our website, pardaloteconsulting.com, and get in touch via the contact form there, or you can, uh, look me up on LinkedIn, Rosemary Barnes. That’s probably the easiest, fastest way to get ahold of me personally.
Allen Hall 2025: Well, Rosemary, congratulations on the Energy Innovation Fund Awards and the new three-year effort.
If you are interested in participating with Pardalote Consulting and working with Rosemary and her team [00:31:00] in Australia, reach out to her on LinkedIn and get that process started, because this report and the data from all this analysis that’ll happen over the next couple of years will be important to the wind industry.
So you need to spend some time and get ahold of Rosemary and get this process started now. So Rosemary, congratulations. Uh, thanks for being back on the podcast, and looking forward to, uh, the next couple of years. It sh- should be exciting.
Rosemary Barnes: Thanks so much, Allen.
We all understand that there are ultra-conservatives living all around us, but does anyone truly believe that our schoolteachers are ruining our society by teaching children the truth about U.S. and world history? Science? Current events?
Slavery and Jim Crow laws were bad. Fascism is bad. Our scientists are telling us that CO2 emissions are causing world temperatures to rise, destroying our planet’s capacity to support life.
Whom do these concepts upset?
There is nothing dumb about the question posed at left. Democracies fail, falling into “banana republics” constantly. The rate at which democracies become tyrannies is so great that some of them never make the news. Can you tell me anything about the governments of Eritrea or Chad?
What makes the situation in the United States is, yes, that it’s happening here in the United States, the very last place anyone would have suspected it.
You might have thought that Americans wouldn’t have voted for their nation to become Russia or North Korea.
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