Story by Eric Worrall –
![wind_turbine_bearings[1]](https://wattsupwiththat.files.wordpress.com/2014/08/wind_turbine_bearings1.jpg?quality=83)
A few years ago, I used to know a senior wind turbine engineer. One evening, over a few beers, he told me the dirty secret of his profession:
“The problem is the bearings. If we make the bearings bigger, the bearings last longer, but making the bearings larger increases friction, which kills turbine efficiency. But we can’t keep using the current bearings – replacing them is sending us broke. What we need is a quantum leap in bearing technology – bearing materials which are at least ten times tougher than current materials.”
At the time there was very little corroborating online material available to support this intriguing comment – but evidence seems to be accumulating that bearings are a serious problem for the wind industry.
Siemens citing bearing failures as part of the reason for a substantial fall in profit;
http://www.offshorewind.biz/2014/05/07/siemens-energy-division-profit-down-54-pct/
In the announcement of the opening of a new Siemens research facility;
http://www.greenoptimistic.com/2013/03/19/siemens-wind-turbine-research/
“… The Brande test center would evaluate the main parts of their wind turbines such as main bearings …”
http://www.geartechnology.com/newsletter/0112/drives.htm (an attempt to make direct drive turbines, to reduce bearing wear)
“… More accurately, it is typically the bearings within the gearbox that fail, in turn gumming up the gearbox, but that’s a story for another time. …”
http://en.wikipedia.org/wiki/Burbo_Bank_Offshore_Wind_Farm
“… During summer 2010 Siemens decided to change the blade bearings on all 25 turbines as a pre-emptive measure after corrosion was found in blade bearings found on other sites. …”
Of course, there is the occasional video of catastrophic turbine failure;
Suggestions the industry is trying to conceal the scale of the turbine fire problem;
All of which creates an interesting question – just how much of our money is the government prepared to waste, to keep their wind dream afloat? If the costs are far greater than the industry admits, how long is the wind industry going to carry that additional hidden cost, before they try to push the costs onto taxpayers, or abandon wind technology altogether?
http://www.dailymail.co.uk/news/article-2116877/Is-future-Britains-wind-rush.html
“just how much of our money is the government prepared to waste, to keep their wind dream afloat?”
All of it.
DD More August 26, 2014 at 10:02 am
Ralfellis – Are they back?
The problem could not be solved in the time available and Rolls-Royce had to switch back to titanium blades. The RB211’s troubles contributed to the 1973 bankruptcy of the company.
_______________________________
Rolls are now the second largest aero-engine manufacturer in the world.
Yes, the carbon blades were a failure, but the backup titanium blades were the company’s salvation, because they proved to be a world-beating design and are now (semi) copied be most other companies. Interestingly, these huge blades are made flat, and then heated and blown up like a balloon. Its a very secret technique.
And in a correction to my last, the Rolls Trent engine is a 3-shaft engine. The inner shaft rotates at 10,000 rpm, the intermediate shaft at 7,500 rpm and the outer fan-shaft at 3,300 rpm.
And this is what happens when a blade falls off:
And this is what happens with a wind turbine has a blade failure:
And this is what happens when they catch fire:
https://www.youtube.com/watch?v=p5KvJjI21i0
And they chop birds too:
And this is how little force you need, to pull one down (bit of a worry):
Ralph
ralfellis
August 26, 2014 at 12:10 pm
…
This is what happens to jet engines when they “chop birds”
..
http://4.bp.blogspot.com/-3rttFE8Ordc/TdWrN3OowXI/AAAAAAAABgk/2WqQge3RY6o/s1600/miracle_on_the_hudson.png
David L. Hagen
August 26, 2014 at 7:27 am
Life cycle costs rule – bearings are critical
Extremely high durability bearings HAVE been developed. – by Pratt & Whitney – for a $> 1 billion RD&D investment.
The Billion-Dollar Bet On Jet Tech That’s Making Flying More Efficient
David,
Very interesting!
Thanks,
Mac
They should probably switch to hydrostatic bearings, and could also simplify things by having the main shaft run a hydraulic pump which in then drives a hydraulic motor connected to the generator, and by running the hydraulic lines down the tower, the generator can be on the ground.
In polite conversation, I raise the contention that wind turbines are merely a way of turning bald eagles into kilowatt-hours. It should be easy to figure out the conversion ratio. Are bald eagles a renewable resource? If so, we can then revert to burning whale oil.
Is it possible that a bird strike imposes a direct transient load on the bearings while the strike is occurring, if the bird is large enough?
Or is it simply more likely that events such as sudden strong wind gusts impose multi-directional loads which cannot be easily accounted for without making the bearings so large that their friction reduction efficiencies are affected?
Well then the “green” thing to do is to put these things out in the deep blue sea and add salt water, worse weather, and for sure gum up the bearings, thats the ticket.
It is my understanding that significant transmission efficiency losses are associated using hydraulic motors and hydraulic lines as power transmission coupling devices, with the energy losses appearing as heat in the transmission fluid. The last time I checked — twenty years ago admittedly — these contraptions don’t have a very good record for reliability because of leaks, seal deterioration problems, etc.
The term oil subsidies is another one of these political terms that are designed to elicit an emotional response from the general population. Very few of us are in favor of giving tax dollars to the oil companies. They don’t need it. When you start to look for what the subsidies are, it is hard to find them. I found a good description from Forbes http://www.forbes.com/sites/energysource/2012/04/25/the-surprising-reason-that-oil-subsidies-persist-even-liberals-love-them/ . The largest subsidy, over $1B, is for the strategic Petroleum Reserve. The second $1B goes to farmers as a fuel tax exemption because why pay road taxes when tractors hardly ever use the roads. The third largest subsidy, $570m, is for the Low-Income Home Energy Assistance Program.
There are other tax credits that are not Oil Company specific. Companies like Microsoft and Apple also use them. They are designed to keep jobs in the US.
None of those are subsidies. The government is not “giving” money to the oil companies in any of those situations.
#1 – The government is BUYING a product
#2 – The government is NOT CHARGING farmers (Oil companies get no benefit out of a tax exemption for farmers)
#3 – The government is GIVING money to poor people, not the oil companies.
You are right that it is a political mess. A subsidy is when money is given to a person or company. “Not taking money” is not giving. A robber who leaves you $20 is not “giving” you $20.
I wonder if any kind of bearing on these things could work. A roller bearing can support a significant load, at least compared to a ball bearing, since the weight is spread over a larger (although still admittedly small) area. However, a roller bearing doesn’t like any kind of whipping motion in the shaft it supports. For that you need a ball bearing which doesn’t object to a whipping motion. I’ll bet that on these wind turbines the bearings are subjected to both: extremely heavy weight from the massive blades; and a bending or whipping motion imparted on the shaft since it’s unlikely the wind force is going to be equal across three blades of that size. Ah, but there’s another problem: the shaft is loaded both perpendicular to its rotation and also parallel to its rotation – the wind that’s rotating the blades also wants to pull that shaft out of the housing. And, then there’s the gearbox: what was claimed to be the original problem before bearings were mentioned. The gearbox steps the 17rpm rotational speed of the blades up to 1,500rpm; almost a 100:1 gearing. Ultimately the problem with a wind turbine is probably a problem of scale against concept. To be (somewhat) feasible they have to be huge. But the basic concept, on a huge scale, is likely an affront to sound engineering. And, for a flawed concept to then be pursued we must not point the finger at engineering. We must point it at politics.
Wind turbines- The VESPAS of the Sky
tom & keith ….others
you guys have a pretty good slant on this thing however I would like to point out that seawater (and that includes salt air) is in actuality a very mild acid. it takes a very different metalurigical technology (read EXPENSIVE) to survive in the maritime environment than on land a couple of hundred miles from the coast. one of the most important things is to wash the stuff down with fresh water occasionally (say every couple of days) for a start.
next the alloys that have any chance of surviving in this environment are EXPENSIVE. just exactly what the “investor types” will want to stay away from. now every time I heard a European sales representative making a pitch they included phrases like “the best materials available” and “laboratory tested in the finest laboratories on the continent” which made me wonder if there was rampant fraud in the metals dealing industry. in that end of the world.
now you have to keep in mind one thing. Siemens is a German outfit. German to the core and past. every thing they make is super precise. however it might be just a bit to precise for this service. these windmills might just need room to flop around a bit to survive. on occasion I saw ships winches that were built just a little too “sweet” that had to have a file taken to them to get them to work. ships do bend and twist a bit at sea you know.
there is a condition in finely finished machinery whereby under load (vibration) at the microscopic level a high point in the finish will pierce the oil film between two elements and destroy the corrosion resistance imparted by the oil film itself. instantly a tiny speck of corrosion will form and flush away leaving a tiny pit. in the seawater world the rush of water flushes this away and exposes an new area for another cycle. this continues on until the mechanical element fails. it is called “fretting corrosion”. it is the reason that when machine tools are shipped they are very heavily clamped between their slides and the sliding components. this also happens in ball, roller, and tapered roller bearings.
which leads us to: JUST WHERE IN THE HE)) ARE THE BEARING SEALS. you know those rings etc. that keep the oil in and the water out. no one has mentioned those in this discussion or have the continental smart guys managed to head fake the need for those.
I have been looking at the internal layout and machinery in the upper pods of these things for several years now and I have gotten the feeling that the drawings were drawn by teenagers that spoke one language and checked by pre teens that spoke another. and that was for the good stuff.
in other words THESE THINGS ARE MADE TO RUN TIL THE CHECK CLEARS THE BANK, THEN ………….
PK
BJ Hanssen (@BJHanssen) on August 26, 2014 at 3:54 am
Post ruined by the last paragraph and linking to The Daily Mail *twice*. Linking to the Daily Mail is a credibility killer, and for good reason.
Even if you are not an AGW believer, I don’t understand why you would be against developing renewables.
Not far from where I live in Belgium is a company called Hanssen who make gears for wind turbines. Any connection?
This wind generation fiasco is going to end in a way that is ugly but at the same time beautiful.
Reblogged this on gottadobetterthanthis and commented:
There is a simple rule with rotating machinery, build it big and massive compared to the load on it. Such is not possible in windmill applications. Keep the rotating machines well lubed, and they will last a while. That proves very impractical on top of a tall tower. Accordingly, without adequate mass, without adequate maintenance, and without adequate lubrication, what goes around, stops, especially in marine environments.
Windmills do not work, and they will never work. Just can’t.
How much pain will we take before we wise up?
Lonnie –
You are correct about building machine stuff big and massive. Not nearly so true with rotating mechanisms, because it costs money to speed up and bigger brakes to slow it down or stop it. It’s best to size it per application. Trust me also: You don’t WANT a big massive rotating arm or disc or blades spinning around, not if you don’t have to. Anything moving is best kept to the minimum weight possible. Unless it is a flywheel, which needs to be heavy.
You are much more correct on the importance of lubrication. But the bearings being way up on top of a 200-260 foot tower isn’t necessarily a terribly difficult thing to deal with. It just takes good engineering. You just have to have a lubrication system that pumps the lube into the bearings. Preferably doing it so that it pushes out the lube already there and carries grit with it out of the bearing. Yes, the system has to lift the lube up. Best to have a reservoir up there for the final pumping into the bearings, and have a way of refilling the reservoir from down below. Most plants I’ve worked in lube like once a month or so. If the reservoir holds a good deal more than 12 shots of lube, then the maintenance person only has to come buy once a year.
But one would also have a vibration sensor on each bearing and thermocouples, too. Vibration and heat are the two signs of impending failure. Either one can signal to the maintenance crew that that turbine needs to be attended to. With millions at stake (the darn things have been known to tear themselves apart.)
If the lube schedule is kept up (it should be automated) the darn thing should last decades, especially at only 22 RPM max. Bearings are designed for like 90 million revs. Using 22 rpms (at about 30 mph wind, which they avoid operating in, I believe), and running 3/4 of the time, 90% of turbine bearings should last for about 10 years. 80% should last 20 years, and 70% should last 30 years – more or less.
BTW, Here is what one of the leading US Bearing makers has as a Rule of Thumb:
• Doubling load reduces life to one tenth. Reducing load by one half increases life by ten,
• Doubling speed reduces life by one half. Reducing speed by one half doubles life.
Nothing can be done about the weight of the blade assembly. That is what it is – about 72,000 pounds (33,000 kg) for the biggest ones. So using the other rule, even a little bit slower can help a LOT. And if the wind averages only 15 mph, the life span should be 20 years for 90% of the bearings, etc. . .
ALL quality bearings are designed to have similar life spans, that 90 million or thereabouts. And YET, they are not lasting – which means that some factor has not been DEALT WITH (i.e, designed for). If that is so, the dsigners should hang their heads in shame a bit, because that isn’t supposed to happen. But when you do that on something that has thousands upon thousands made, and all of them have the same flaw – it’s time for the engineer guillotine.
in the style of the famous irishism, ‘If I wanted to get to sustainable energy, I wouldn’t start with windmills’
Th bearing problem is massive.
You have the worst case possible.
A cantilever shaft with a massive blade assembly on one end, so the bearings are taking massive side thrust.
Situations of low or zero wind in which the blades stop for considerable periods of time, making the actual flattening of balls/rollers and indentation of cages not possible, but likely.
Operation in an area of inevitable wind shear as blade tips approach ground level so that cyclic thrust and torsional load variations will inevitably happen.
Massive subsonic thumps as the blade wake crosses the tower causing torque thumps to be transmitted back to the blades and gearbox.
Tip speeds approaching 200mph where the possibility of occasional transonic flows off the tips will give additional hard vibration through the blades and shaft.
Massive gyroscopic effects if the head assembly needs to be slewed through azimuth to meet the actual wind direction when operating. Those transmit increased side loads onto the bearings.
Operation in inimical regimes of water and air mixtures and often a string magnetic field and salt spray, leading to rapid corrosion both mechanical and electro chemical .
Asymmetric build up of dust, dirt, ice and other contaminants and wear from contact with dust and dirt and other airborne abrasives on the blades leading to out of balance lateral and vertical bearing loads.
It is a miracle that the mean time between failures on the average turbine is as high as it is – 6 weeks is about standard expected period in which something will need to be attended to.
We really should consign this technology to a museum. Its a totally useless way to generate minuscule amounts of electricity at massive costs.
NO one needs it and if they knew as much about it as engineers do, they sure wouldn’t want it.
THIS IS NOT ROCKET SCIENCE, FOLKS.
This litany of woe is, well it’s kind of funny, the way you try to make this single rotational device sound like it’s as hard to do as the Hubble telescope.
Speaking as a senior mechanical design engineer with 40 years under my belt:
“massive side thrust.” – It is called “radial load” and it is the first thing you look at in designing these. You SIZE the bearing based primarily on its radial load.
“the blades stop” – And? So what? You design for this. It is straightforward engineering.
“wind shear as blade tips approach ground level” – And? SO what? The rotor is only going max 22 rpm.
“that cyclic thrust and torsional load variations will inevitably happen.” – this is driven by a max wind speed of 34 mph. Whoop de doo.
There is next to no rotational resistance. These 35 meter blades have ALL the mechanical advantage”, if you have any idea what that is.
“Tip speeds approaching 200mph” – Maximum tip speed for propellers and fans is 122m/sec. I find the max tip speed for wind turbines is only 15m/sec (234 mph), less than 13% of maximum. The limiting factor is the propeller material, with a sufficient safety factor. But this application isn’t even REMOTELY close to the material limitations.
“Massive subsonic thumps as the blade wake crosses the tower causing torque thumps to be transmitted back to the blades and gearbox.” – So, if it is not tearing the blades apart, what is the problem. The bearing if properly designed into the mechanism should be able to take all that and much more. It is a problem for the blades, not for the bearing. Bearings are not delicate little flowers that crush at the first breeze. All bearings are built for some level of shock and radial load and axial load. They ARE after all used in industrial applications.
“Massive gyroscopic effects” – WTF? Now you are stroking everyone, right? Hoping we don’t know sh** from shinola? At 22 rpm max, WHAT Gyroscopic effect? The bearing hardly even knows it is turning. You have centrifugal force and angular momentum. But gyroscopic effects? Color me very very doubtful.
“Operation in inimical regimes of water and air mixtures and often a string magnetic field and salt spray, leading to rapid corrosion both mechanical and electro chemical.” – The typical wind turbine is not in a sea spray environment. Any or all of these that apply to the BEARINGS can and ARE dealt with via shields and seals, which will keep all of those”inimicals” out.. This basically has nothing to do with the bearings, which is the topic under discussion. If anything the bearings are normally at most exposed to rain, snow, and perhaps fine dust particles – and all of those happen only very intermittently.
“Asymmetric build up of dust, dirt, ice and other contaminants and wear from contact with dust and dirt and other airborne abrasives on the blades leading to out of balance lateral and vertical bearing loads.” – Oh, Gawd, now you are just being silly. VERY LARGE fans going at 450-600 RPMs and pushing REALLY dirty air don’t have this imagined problem to the point where the violins are need, so we can feel sorry for the sweet, little wind turbine blades – going at their ridiculously SLOW 22 RPMs. No, dust collecting on them should not be a problem for the propeller undertaker.
“It is a miracle that the mean time between failures on the average turbine is as high as it is – 6 weeks” – Bull. Bullsheit. The senior wind turbine engineer said that 10% failed in the first THREE YEARS. If they only lasted 6 weeks “between failures”, there wouldn’t BE any wind turbines out there. Everyone would have thrown up their hands and gone home.
With all of your “THE SKY IS FALLING ROUTINE HERE” are you sure you are not a global warming altar boy?
Literally, from a design mechanical engineer’s POV, basically everything you said here is nonsense.
What? Did you think you could snow all of us here?
Lots of potential problems have been discussed re the main shaft bearings…. some of them quite severe.
But keep in mind that these are but cousins to aircraft propellers. In the aircraft propeller the most problematic bearings are usually not in the crankshaft or gearbox, but the bearings which retain the propeller blades to the hub yet still allow the blades to change pitch. After more than 50 years in the business, well-respected makers of aircraft propellers still have a very difficult time building examples which do not fail in this area, as the forces can be huge, cyclical, and often unpredictable.
And the failure modes are nearly instantaneous and very destructive. Talk to an airplane owner about the potential costs if their propeller becomes subject to recurring inspections because the type develops a history of service problems.
Here is an industry article on the subject:
http://m.machinedesign.com/mechanical-drives/bearing-failures-cause-serious-problems-wind-turbines-there-are-solutions
it sounds upbeat but that may be because they are selling something.
A question was asked further up on how much power a wind turbine consumes to maintain it’s systems and to regularly rotate the composite fibre blades to prevent blade distortion and creep during idling periods.
The grid power usage of idle wind turbines seems to be one of those bits of information kept under close wraps by the turbine manufacturers and the wind turbine industry as to admit that they are withdrawing considerable amounts of power from the fossil fueled grid would be tantamount to admitting a further gross inefficiency in having to rely on grid power when they were not producing their own power.
Whether the turbine industry actually ever pays for their idling power use is another question that is never revealed so the answer is probably, they don’t!.
Any usage of grid power by the turbines should be deducted from their total supposed and claimed power generation output but never are as that use is never revealed.
Obviously the amounts of grid power consumed by an individual turbine or farms of turbines depends on a large number of factors and is highly variable, increasing in percentage terms as the turbines age and become increasingly inefficient which according to UK data, is by about 15 years old. The turbines by then are becoming a very marginal economic investment due to blade deformation, mechanical induced drop off in performance and rapidly increasing maintenance requirements and this despite massive publicly funded subsidies.
This usage of grid power by the wind turbine industry has been looked at and assessed here ;
Wind Power Realities; http://windfarmrealities.org/u-minn-and-vestas-reality-check/
To quote the relevant and rather surprising amounts of grid power usage by a Danish located Vestas V82 1.65 mw turbine .
_________
“finally, we have a measurement of just how much electricity they consume! 50 kw is quite a bit higher than my previous findings, which originated in industry statements and cash flow calculations. Recall that the average Danish turbine produces about 376 kw (1650 * .228). So a V82 operating in Denmark consumes roughly 13% of what it produces. No wonder they want to keep this quiet”.
[ / ]
So it seems that in some cases, perhaps most cases, wind turbines consume as much as the equivalent of 13% of their total output in [ fossil fueled ] grid energy to maintain their systems when they are not generating and / or are idle.
See also ;
Energy consumption in wind facilities
http://www.aweo.org/windconsumption.html
I wonder if anybody has given a thought to bearing lubrication.
Maybe it’s something that only occurs to a person who has had to deal with boat trailers, but– bearing lubrication is what makes the little beasties hold up for long periods of time. Keep the things lubed, and just maybe you won’t have to replace them so often.
Well, it’s a thought anyway.
My profession is FAA/EASA certification of electronic hardware for commercial aircraft. My specialization is Electromagnetic interference and indirect effects of lighting strikes. A few years ago I did some consulting for a major wind turbine manufacturer. It seems as though the generators are being damaged by lightning strikes.
The blades are the highest point around and the bases are well grounded. There are perhaps thousands of generators installed that are not adequately protected from the effects of lighting strikes.
Late to the thread but a simple search for “abandond wind farms” should give anyone “clear optics”
Any engineers or other knowledgeable people reading this that know how the very large hydro power generator(?)/alternator(?) turbines solve the bearing problem?
These devices are huge and the bearing load must be quite large. How do they do it? One doesn’t hear of them having catastrophic failures very often.