Dr John Campbell has a channel and he does that. First 5 minutes are a summary, the next 25 he goes into medical details about Covid. And he speaks simply.
Asked myself "why not 2", when I saw the thumbnail. Got answer in one minute. Left a like for the efficient answer and left since I'm actually supposed to study.
Just brought to your channel by the algorithm. Excellent video. You have a new subscriber. I love how concise you were at the beginning, but still went into depth afterward. You are great at explaining complex subjects in an easy to understand way. I'm looking forward to watching more of your videos, and seeing your future uploads!
Hello Rosie, nice vídeo! When I studied this at uni, I was taught by my professor that wind turbines with up to 20 blades where usual in the past... We have all seen them in cowboy movies, usually used to pump water from underground deposits. The main advantage of these windmills was that they could self-start easily with really low air velocities so you had a water supply always guaranteed. On the other hand, the efficiency of those windmills was really bad, so even with higher wind velocities, the power outcome would always be low. SO I guess that you could also say that the optimal number of blades for your wind turbine also depends on the use you want to give to it :)
I worked with an engineer who used single blades as a way to game RC race competition rules for a particular race that limited the size of the propeller. He was able to get a larger diameter for his craft, seemed to run great!
@@alan-sk7ky It"s always possible to design the part to withstand the loads. Think about how many bending cycles a car's suspension spring goes through in its lifetime.
I had to think for a minute about what's going on, here. Because the rotor is in motion as it's being turned about it's azimuth, the moment of inertia of the assembly in the azimuthal plane is also changing. Therefore, the torque applied to yaw the nacelle will need to be varied so constant rotation is maintained, stresses on the hub bearings will not be constant, and avoiding harmonic vibration modes of the support structure becomes a big consideration. Is reduced yaw rate not sufficient to ameliorate this problem? One less airfoil likely also results in increased blade length and larger peak inertial moment therefore exacerbating the problem.
How engineers choose number of blades: Ask queen!! Once I have talked with Henk Lagerwey, one of pioneers in wind turbine business, great guy. He (his company) produced 75kW/15m, 80kW/18m and later 250kW wind turbines with two blades. I think this was first turbine with pitch control (passive) and first turbine with invertor regulation. Those turbines were popular in Japan because of ease switch to 50 or 60Hz (invertor). On one dinner with royal family (technology open different doors) queen asked him: "Why your turbine has two blades? For me it is nicer with three blades." He answered: "Your Majesty, you are right, three is better" And his next turbine was three blade turbine. :-)
Good explanation, but you could also add. The wind speed is slower close to the ground and is also affected by the tower. For 2 blade designs the force on the upper blade will be much higher than for the lower blade, and when passing the tower you get extra low force and vibrations. Over water the wind speed will change less with height and 2-blades are therefore common off shore. Another reason is esthetical. Early on in Denmark the general public preferred the sight of slower moving 3-blade design. This is less of an issue off shore where 2-blade designs are more common.
Trade-offs mentioned early and you know you're listening to a fellow engineer! Turning dreams and hard science into practice is at the end of a day an art. And so is making concise but still factual and _pleasing_ videos. Keep it up and thank you!
Thank you for that clear and concise explanation. I’d noticed the spring mechanism on small two blade turbines but I didn’t know what it was for. Now I do.
My first job as an engineer was working on the blades and hub retention design of the Hamilton Standard and KKRV designed 3 and 4 MW wind turbines, with construction starting around 1981. These were the world's most powerful wind turbines at the time at 78 m diameter and proved to be successful. Simplicity and low cost were drivers so as you explained, two filament-wound fiberglass blades saved on material cost (the resin) and this allowed the steel hub casting to be smaller as well. These were downwind, free yaw turbines that used a similar rotor design as found on two bladed helicopters, namely, a teetering rotor with a teeter pin offset by 30 degrees so that teetering causes pitch change to make the rotor self stabilizing. The teetering rotor was especially good at reducing the fatigue load on the blades as they passed through the 'wind shadow' behind the tower. One problem found in service was that an excitation caused the tower to go into a bending mode of vibration which was at times disconcerting to workers at the hub/nacelle level during operation. To make an analogy, this system was similar to a two-bladed helicopter in auto-rotation, where the rotor in-flow comes up around and past the fuselage. As this is an emergency life-saving maneuver, no one complains if there is a little extra jouncing in the cockpit on the way down. However, for a two bladed wind turbine, perhaps a better solution would be an upwind machine with the added cost of an active yaw drive system to avoid the wind shadow excitation. The problem of yawing a two-bladed rotor is similar to tilting the rotor of a two-bladed helicopter. This has been solved by various means and most lower cost helicopter designs use two-bladed teetering rotors. I dont have a preference either way. The machines I worked on were ahead of their time, US Govt funded, and defunded in the Reagan administration in favor of battleships.
There are quite a lot of older two-blade wind turbines in Northamptonshire and into Warwickshire. Many of these were British-made, but production ceased through a lack of subsidy. When German and Danish three-balded turbines entered the UK market, the UK government belatedly turned up the subsidies and the three-bladed design proliferated. Almost certainly, a two-bladed design of relatively modest size was the most sensible choice for Northamptonshire, where suddenly-shifting sea gales are rare. They proved that wind turbines were worth a try, at least.
really liked your video. You got a new subscriber. I didnt anticipate having a different answer than you when you said "if you ask 5 engineers from the wind industry, you will get 5 different answers" but here i am. Another problem with two bladed wind turbines is the aerodynamic force distribution over the rotor plane which will excite the turbine further. There are different effects that play together on this. First of all the natural wind speed distribution. The higher you go, the stronger the wind blows. Because of that the top blade will get pushed harder than the bottom blade. In combination with the rotation of the rotor you get a "nod moment". This is the probably the biggest aerodynamic problem of two bladed rotors. Another important aerodynamic effect is the tower dam. Right in front of the tower, the wind slows down. during the rotation of the rotor, the blades travel through that area. There the blades dont get pushed back as hard as right before or right behind the tower, which also induces a nod moment on the turbine. Those two effects combine on even bladed turbines. On odd numbers they act phase shifted to each other and dont put such a stress on the nacelle. Plus these effects are stronger on lower numbers of blades. This really shows the different aspects you need to consider when designing a wind turbine. Its not as simple as "just a tower with 3 rotor blades". I like the idea of having more blades in the future to make the blades thinner. It could also reduce the rotation speed which would make the turbines less stressfull to look at and maybe more bird friendly.
Some 25 years ago I constructed a model wind turbine with 4 blades just as a school project to illustrate a principle. But it had two rows of blades in tandem ie. two at the front and two at the back. The front blades and the rear blades rotate fully independently and in opposite direction to each other but still connected to the same shaft. It was only made to illustrate a point that you get a lot of untapped air containing K.E. going between the blades of a wind turbine . Quite knowing that only about 47% of the K.E. can be used it would be useful to tap that part that goes through the front blades by putting another set two blades behind.. Also the air that goes through must be affected by the front, by being slowed and maybe given a bit of spin in the direction opposite to the rotation of the front blades and therefore containing some rotational K.E. too. This air leaving the front blades will find it has to go through the rear blades turning them in opposite direction to the front even if at decreased K.E. Notwithstanding the contra rotating blades the magnitude of the rotation of each set will be added at the shaft end producing more rpm and power.
I have started my certification program in the Wind Energy. You are doing great job, thanks a lot, you definitely have at least 1 long-term subscriber! ;)
Absolutely brilliant thank you!! I honestly thought it was just because 2 blades were an older design and they found it more efficient to have 3 and make it move with the wing. Wonderful explanation, you did so in such a comprehendable way, thank you!
Thanks, Rosie for the informative video. I read that turbines with 2-blades have unequal forces when at the 12 and 6 o'clock positions because the upper blade has full wind force while the lower blade has wind that is blocked by the tower. I guess this isn't much of a problem with lattice type towers that allow the wind through. What mystified me was why the blades had to be so long and skinny. Now I see that it saves money. Thanks for giving me a firmer picture in my mind why wind turbine blades are the way the are.
You are right about uneven forces at the 12 and 6 position, onbe day I will make a follow up to this and include more factors and that will be one of them.
Thanks. Nice explanations of some of the trade-offs involved. However (you knew this was coming!), my understanding from some work I did in an M.Eng a few years back m(oh joy, the Betz Limit!), is that the 3 rather than 2 decision was because of visual effects ("visual disruption", perhaps? - can't remember). It seems when an observer looks at a big turbine with 2 blades each, say 50 metres long, the width of the turbine when the blades are horizontal registers as about 100metres, but when the blades are vertical the width is almost nothing, just the width of the tower. So as it rotates there is the effect on the observer's eye, or brain, of something in their vision expanding and contracting, and the effect is even worse if there is an array of turbines. Apparently the same effects are not experienced, to anything like the same extent, with 3 bladed turbines - there's always something about 100 metres wide in view. Manufacturers are very sensitive to minimising visual effects as they are often claimed by objectors to windfarms to induce migraines, depression etc.
I live in Gjølga Norway and I am neighbur with one of the largest windmill Parks in europe (storheia) The wilderness and wildlife was ruined and the area is now dangerous for people and wildlife because they hurl iceblocks up to 200meters. They needed to build 20 meter Wide roads in the Mountain and the untuched wilderness is gone.
Your government, which is hypocritically supported in large part by oil and gas revenues, doesn't care about your wilderness because windmills are oh so Green.
@@e3a3c3 actually, the windmills are polluting since the bugs now are drained and started to release methane. They used to collect carbon, but now they release methane after the capitalist drained the area. The Sami minority lost grazing area for reindeer and the taxpayers get to subsidy the already rich for 20 years. When the subsidiary period of 20 years are over, the project will be abandoned
One of the major reasons I have come across for why 3 blades is more common is due to the ground layer of wind being slower than wind higher up. So a 2 blade design when it is in the vertical orientation, the top blade has clean air, which will provide more torque than the lower blade which has dirty air from all the turbulence of the ground boundary layer, resulting in a mismatch of torque. Where as three blades, when you have one blade in the clean air at the top, you have two blade in the dirty air, resulting in a more even loading of the system
Really thought provoking video. I didn't thought about 2 blade wind turbines as mostly my professors in university taught that 3 blades increases structural stability of tower & decreases oscillatory vibrations.
Yup, in the world of small wind turbines, two-bladers rip themselves apart in short order with the yaw-hammering they suffer when the wind changes direction. Two-bladers end up in a rusty heap near the base of a tower. A tilting hub can help, which is used in larger attempts at 2-blade turbines, but such minimalist-minded designers always place their 2-bladed rotor downwind of the tower, for automatic aim, so once again, even with the tilting hub, the 2-bladed turbines get beat to death by the tower shadow. Ever flown in turbulence? Or ridden in a motorboat bashing waves? Best not to have the blades go thru the tower shadow (wake). Two bladers also tend to look weird running 3 blades run smooth. 5 or 6 blade rotors run ultra smooth, but then you're into a lower Reynolds number with skinnier blades. Slightly lower efficiency, or so theoreticians say, but easy startup and really smooth operation. Three blades is the lowest number than run smooth as a turbine re-aims (changes direction). Two bladers tend to look weird running. I can get away with two-bladers for my multi-rotor turbines because they change direction more slowly, due to a higher moment of inertia about the yaw axis.. To me, forget number of blades, how about number of rotors? Got one outside that's been running for about 8 years continuously with two 2-bladed rotors. Changed the blades once, when the leading edges became eaten away by dust in the desert air and started getting noisy. Termite tunnels is what it looks like. Most people with small turbines never find out about blade erosion because the small turbines almost always break down long before any significant blade erosion sets in. Especially with two-bladers. Almost every small turbine has the same problem: They can't handle truly strong wind events. And if the have only two blades, the turbines seldom last even a year. Most small wind turbine manufacturers have gone out of business, now that solar gotten so cheap. But two-bladers were the first to go. So tempting cuz they make the same power yet need one less blade ($$$). But don't fall for it. Spend a little more and if you only have one rotor, at least get 3 blades on that thang. Solar panels still have to be able to survive a 100 mph wind, but they don't need to spin at several times that high speed in such brutal high winds. So you have millions of solar panels on peoples' roofs, and zero wind turbines. Which brings to mind another common topic in small wind: "Can't I just mount my small wind turbine on my house?" (hint: don't do it!)
Used to make small "turbines" from wood - started with small (~0,5 m each) 2 blade design - at low altitude proved to be not pleasant to eye. Next was 3-blade design (~0,8 m each) that was pretty nice and stable. With some insights went forward and next/final was 5-blade design (~1,1 m each blade) - smooth and beautiful, trying to get rid of as much wood as possible to make blades thin (yet still strong enough) - got each blade weight down to 105-110 g (small difference for balancing as it all was hand work with knife and sand paper). That was like ~15 yrs ago but now remember details after this video - thanks!
Thank-You for these wonderful programs! At the end of a recent one you asked for comments on production, amount other things. I think your shows are all-round great picture-wise and editing, and sound is pretty good. MY ADVICE WOULD BE TO IMPROVE THE SOUND FURTHER. GET A MIC CLOSER TO THE MOUTH OF THE PERSON SPEAKING, monitor the sound with headphones, check the sound carefully in the edit. Particularly with this technical stuff it’s important that people hear clearly. You know this material so it’s easier for you to figure out what is being said, so maybe have another set of ears check it out. The picture is important, but the SOUND is even MORE IMPORTANT. People will put up with an imperfect picture, but bad sound will cause them to switch off and they won’t even know why! Anyway, thanks so much for the totally supersonic shows you are making. I’m seeing this in the US and sharing it as much as I can!
I’m an engineer but I didn’t follow the figure skater analogy. The skater’s spin speeds up when her arms are drawn in because of conservation of angular momentum, bringing the mass of her arms closer to the rotational axis reduces the angular moment of inertia. With a wind turbine the mass of the blades doesn’t get any closer to the rotational axis when the central hub turns. I suspect maybe the instability is more related to the gyroscopic precession effect of altering the orientation of the spin axis? Edit: ok after thinking about this a bit more, the analogy about the skaters spin is not referring to the axis the blades revolve around, but rather the vertical axis of the slew bearing used to point into the wind. So yes the vertical axis slew bearing would need to work harder to turn a 2-bladed rotor when the blades are horizontal (“arms extended”) compared to when they are vertical (“arms raised”), leading to an oscillating effect for every rotation of the blade. Ok I learned something ;)
What a fantastic video! Great explanation, no annoying music and the whole tl;dr at the start then the nice in depth talk afterwards is such a great format. You explain things so nice and clearly too. Thanks!
I wasn't really interested in the question but had some vague intuition of what the answer would be. I have no idea why Google proposed this video to me, but clicked on it on a whim. I am so glad that I did: This is the best technical explanation video I have ever seen. Structure, pacing, technical level of explanations, illustrations, balance between information and humour (2:34!), ... -- everything is just perfect. Congratulations for this little masterpiece. Now I am going to watch a few more of your videos on topics I am not intrinsically interested in.
When I was growing up in the remote desert areas of Australia in the 50s/60s, domestic wind turbines like the British Lucas Freelite, American Wincharger Corporation and Australian Dunlite horizontal axis wind turbines generally had 2 blades. Perhaps it was to do with post-war economic measures; but when accompanying my father who had a job installing windmills, I don't recall any 3 bladed ones !
I had not heard of the stability issues of a two bladed turbine when changing it's orientation to face the wind direction. Of course it does make sense. Very interesting to think about. Thanks for this explaination!
Some years ago i was commissioning some 3 and 6 MW prototype turbines with 2 blades. Very interesting. The main reason they decided for 2 blade was, like you said, the easy offshore installation. The tower vibration was suprisingly low, even during yawing. Later they wanted a dynamic pitch system thet would pitch a little bit during one ration to eliminate the vibration. Another thing was, during storm, the blades should be parked horizontal to keep the force to the power low, even when the yawing did not work. Btw: It looks nice if you have a windfarm with serveral of this 2 bladed and the rotors where synchronised, so they are during all in the same angle and speed :-)
That was a very interesting video! This weekend in Cornwall I passed a wind farm of two bladed turbines (the Cold Northcott site I believe) and it was definitely out of the ordinary, but now I know why! All the turbines where stopped at the time with their blades horizontal which I can't think of a reason for. It did make me wonder more about the process of starting and stopping the turbines, and how quickly they can be "switched on" as such. Keep the good content coming!!!
Oh wow, I have never seen a farm of two bladed turbines, that's so cool. I would guess the blades park at horizontal so they have an equal wind force on them. If they were vertical the one at the top would see higher wind speeds (due to wind shear), so if they are a bit lower the force will be lower, and equal for the two blades. But that's a guess :-)
The reason that aircraft (sitting for long periods in the outdoors) have their propellers parked horizontally is so that both blades receive and shed moisture equally. I would presume that this factor would be more important in colder countries where ice build-up on one blade would effect the balance of the propeller. In the case of wind turbines, having one blade heavier than the other would probably increase the start up wind speed. 🤔??
Yes - love that you explicitly include a stopping point at 1:10. I realise that doing this might make your channels watchtime analytics look bad, but thanks for the humane design. I appreciate it.
Fun fact the largest Wind Turbine Blade up to date has a length of around 107 meters, doing some math it would only take around 30 rpm for the Bladetip to go supersonic, which will rip the whole Turbine apart ... :)
When I used to drive along the E80 route through the mountains in central Italy, it always came as a surprise to see so many single-blade turbines rotating high on the steep hillsides. With their large single arms and squat counterweights, from a distance they looked like they were off-balance and about to shake themselves apart! (Keep your eyes on the road though, as the average speeds seem to be good enough to qualify for Formula 1 racing).
I watched a video about this on another channel a while back, and they had another reason: That if you have an even number of blades, it causes a resonance because the blade with the most force (straight up) is always opposite the blade with the least force (passing in front of the support). Also, I understand that the power generated increases with the number of blades, but not linearly so going from 2 to 3 adds around 50%, going from 3 to 4 adds less than 30%, from 4 to 5 20% and so on, but because the blades are the most expensive part, it’s better stop at 3 blades and put the next 3 blades on a new tower. That way you get more power from each blade than just increasing the number of blades on one single tower. Or at least that’s how I understood the argument.
The first explanation I always heard was the windward shadow that the tower creates due to obstructing the airflow. The second was about the effect of the Earth's boundary layer with larger and larger turbines gets more intractable. The top of the arc at 250 meters has a vastly different windspeed than the bottom of the arc at 50 meters. Three blades better spreads this disparity out across the swept disc. As you have one blade passing over the top in cleaner air, you have two blades creating power in the dirtier, slower air lower down. In propeller aircraft, more blades means lower efficiency from air friction, but higher static thrust. IOW faster acceleration on takeoff, slower cruise speed. I see more blades on wind turbines being better in more marginal wind conditions, perhaps. Or just build taller, where there is always some wind.
Same problem with aircraft. The plane I fly has a 3 blade propeller with variable pitch, it is the standard. The tug at my gliding club has 4 with fixed pitch. It provides good acceleration on takeoff at lower rpm, a variable pitch would have to spin faster at high pitch, is supposed to be less noisy (lower rpm) but has a lower cruise speed and consumes more gasoline at cruise speed because of increased drag. Two blades are ok for very light underpowered or low drag planes.
Ha ha, I later learned that this approach does not please the RUclips algorithm... which is why it has taken nearly a year for anyone much to see this video 😊
@@EngineeringwithRosie Well, It earned you a passionate new sub at least 😅 Also glad to see your newer videos are a lot more professional in terms of audio quality (among other things) 😋
@@EngineeringwithRosie Does "subscriber probability of viewing" influence recommendations? Advertising click-throughs? I wonder if a modest number of hardcore subscribers is better or worse than half a million strays.
@@erikscott5709 I really have no idea what on earth the algorithm is up to. My suspicion is that it is mostly to do with session time of people who watch the video. So if they watch this, and then go on to watch more of my videos, RUclips learns that showing this video keeps eyeballs on the site longer. That would explain why this video never took off originally, but now I have a few other (longer) videos they can show after, suddenly it gets the algorithm's blessing despite having a low watch time That's my interpretation anyway.
It's fascinating but it amazes me that there is not a simple formula that you can plug the variables into and derive a result. I wonder what the deciding factor is in how large to go as well?
Great points. The formula I have covered (briefly) in this video, the question of how large to go, I want to cover in a future video. ruclips.net/video/CavfXOt3Dew/видео.html
@@EngineeringwithRosie When you cover how large to go, I hope it will also cover boat propellors. I guess they are limited by how much they can intrude into the hull of the ship. Look up "Titanic propellors" and you will see something truly fascinating. I wonder why they made THAT choice?
That academic background of summarising the following content as part of the introduction is so appreciated in this form factor. Thanks for the explanation 🎉
Rosie follows the classic presentation format - "tell em what you are going to tell em, tell em, then tell em what you told em". It is classic for a reason - it works.
The weak point with twin blade turbines is not the force variations themselves when they need to adapt to the wind direction!!!!! A twin blade windmill does easily re-orientate to a new wind direction when the blades are in vertical position, as you explained. As from when the windmill has been re-oriented for some degrees ,and the blades come out of that vertical position, they are subject to huge gyroscopic forces. It is this effortless re-orientation with huge gyroscopic destructive forces as a consequence that explains the typical suicidal behavior of twin blade mills.
Fascinating video, presented in a very straightforward and easy to understand style. New subscriber here. Regarding rotational speed, I remember hearing in a documentary that somewhere around 300kmh is the maximum tip speed that can be attained without the blades producing high-amplitude low-frequency noise that carries for kilometers across the landscape. Is noise abatement the only limitation for tip speed? (Beyond the obvious limiting factor of forces trying to rip the blades out of the hub or shake the whole assembly apart) Do prevailing wind conditions in a given location also affect this limit? I never thought about preservation of angular momentum or structural resonance as they pertain to a yawing wind turbine! Great video!
Excellent information, thanks. For *fan* blades, there is another reason to have an odd number of blades - this distributes the noise harmonics, so they can be quieter / less noisy. I have wondered if this is also a factor with wind turbines, but because the rotational speeds are so much lower, maybe it is, but not as critical?
RUclips algorithm brought me here. However, I'll love to witness in real life, a dancing wind turbine like this. Will be fun 4:24 Great explanation. Subbed!
I've always been surprised that turbines with more blades, like 5-10 for example haven't proven to be more efficient. It seems that the majority of wind passing a 3 blade turbine goes right past it, never coming close to a blade to impart energy onto it.
In an optimal rotor design, no matter the number of blades, every air molecule will be affected by a blade. That's why a rotor with less blades needs to turn faster than one with more blades (assuming they're the same width).
Yes two blades is aerodynamically most efficient, because the following blade is nearly always in clear air. This is important because if the following blade encounters turbulence from the one ahead it can trigger aerodynamic flutter. However, two blades is subject to yaw imbalance, this causes the turbine to go out of balance as it yaws putting huge cyclic stress on the rotor hub and the tower that can lead to fatigue. Three blades is the minimum number of blades that avoids yaw imbalance, while following blades are mostly but not always in clear air. Consequently it is the configuration of choice.
3:50 2-blade transient stability: use 2 paired blade sets for 4 blades in series (stacked on rotation axis) and opposite sides of tower turning opposite directions, transmit torque down tower with bevel-geared drive shaft, generator fixed at base. Change rotation axis compass bearing with worm gear control. Program orientation motor to stop during brief intervals when blades align vertically (colinear with tower).
interesting, but I fear the repeated ''impact'' of the second blades crossing the wakes of the first blades. Some planes and helicopters are like this.
@@yanickgenest1324 Also the downwind rotor must contend with wake of tower, at least the bottom half does. Try this: instead of two blades in a line, two blades slightly angled from each other, a boomerang. Center of rotation is in the V, not at vertex. Upstream and downstream rotors angled opposite directions. There is less interference in rotor-wake for the downstream rotor, but it still has the tower wake.
Two blades turbines still operational since 1998 in Flevoland. Much higher wind speed required to spin at its nominal rotational speed, so later on they built them with. 3 blades
In 1980 the german government decided to prove that renewable energy is impossible. They ordered MAN to build a 100m high wind turbine, called GROWIAN, or Große Wind Anlage (great wind device) with 3 MW, the tallest wind turbine of that time. It had 2 blades (now I know why) and big problems with stability and poor function. Finally it was dismantled after only 420 hours running and could show to everybody that wind energy is not possible at that scale.
I viewed another website where the person had a quite a bit of experience and he said a greater number of blades was more practical and produced more in low wind speeds.
I thought a read a study many years ago showing that people found three blades more aesthetically pleasing than two blades. In my personal opinion. Three blades are much more aesthetically pleasing than two blades. Efficiency, costs, longevity, transportation are certainly more important. But millions of people have to look at these everyday. Many people do not like their appearance at all. Many people living close to them suffer from the effects of chronic low frequency pulses they emit. And others hate them for killing endangered birds. All valid perspectives. That’s why we should be using LFTR technology. A walk away safe Nuclear energy power source that produces much less waste than current light water nuclear reactor plants that require electrical power for decades to keep active and spent fuel cool. LFTR stands for Liquid Fueled Thorium Reactor. They do not need a giant steam containment building so they are much smaller and easier to build and maintain. In any kind of accident, they shut down automatically without any power or human intervention required. Besides using Thorium, that is 4 times more abundant than Uranium and is currently treated as a radioactive mining waste product. They can be used to accelerate the breakdown and mitigate the dangers posed by our current nuclear wastes. They can not be easily used to make Plutonium for nuclear weapons, unlike current nuclear reactors. That’s actually why light water reactors were chosen to be used in the first place. To make Plutonium for weapons. So LFTR nuclear power is a Win-Win-Win. If we don’t develop this technology quickly as a huge National Priority. The Chinese and Indians will come to dominate this field of a cheaper, safer, smaller and “green” energy source.
The topic is really interesting, but as an information channel your first priority should be to record clear audio and have clear diction. You need a good condenser mic, EQ, compression, not to mention the audio is really low too.
After 1:21, I have heard the answer to the question posed, if I want more details I can keep watching, excellent! But then she includes in the description the MAGICAL, REQUIRED reference to "combat climate change".
Height of turbines of these type are often designed so that the major force is applied on the higher section because there is less wind drag or ground drag if inland. The major wind push is when the blade is on the high swing or candlestick movement, and the blade shape is dictated by rpm to make sure there is constant laminar flow. Some turbine blades can rotate to adjust angle of attack to maintain high efficiency. Why can we not extract all wind energy? Aerofoils can extract ~86% efficiency while drag type (sheet of paper in the wind) can be maybe 68% efficient. It is about efficiency alone.
More blades can equal more power. Ten blades can equal 5x the power of 2 blades. The limitation is the air flow speed. A jet engine with high air flow has dozens of high pressure blades. I suspect that a wind turbine in a slower 40mph wind would leave turbulent, disrupted air for the next blade if it had very many blades. I'm guessing this is why you see three huge blades instead of ten smaller ones. There may also be a better aerodynamic lift effect out at the fast end of large blade. Longer blades can mean higher velocities. It would be interesting to compare different turbine designs, including a ducted fan wind turbine using a large funnel shape as an intake. It would be interesting to see what kind of wind velocities could result and what kind of different blade designs and advantages might be possible.
Excellent explanation for those of us who are none the wiser but still fascinated. I always thought the number of blades was determined by how many birds and bats needed to be killed.
Major props for putting the "tldr" up front and expanding afterwards. This is a very viewer-friendly video structure and makes me watch on even more
props *chuckle*
At last, a thoughtful video maker that gives you a concise answer right up front with an option to stay tuned to find out more. Thanks Rosie
That's exactly what I thought! Really enjoyed the video because I didn't have to skip through 30 mins of nonsense to get the answer.
Dr John Campbell has a channel and he does that. First 5 minutes are a summary, the next 25 he goes into medical details about Covid. And he speaks simply.
Asked myself "why not 2", when I saw the thumbnail. Got answer in one minute. Left a like for the efficient answer and left since I'm actually supposed to study.
yes! thats also what i liked about it
So so
Just brought to your channel by the algorithm. Excellent video. You have a new subscriber. I love how concise you were at the beginning, but still went into depth afterward. You are great at explaining complex subjects in an easy to understand way. I'm looking forward to watching more of your videos, and seeing your future uploads!
Same here, and this comment perfectly echoes what I feel!
Same story here and same thoughts! +1 on that one!
Same here. 36k subs in one week from now
Hello Rosie, nice vídeo!
When I studied this at uni, I was taught by my professor that wind turbines with up to 20 blades where usual in the past... We have all seen them in cowboy movies, usually used to pump water from underground deposits. The main advantage of these windmills was that they could self-start easily with really low air velocities so you had a water supply always guaranteed. On the other hand, the efficiency of those windmills was really bad, so even with higher wind velocities, the power outcome would always be low.
SO I guess that you could also say that the optimal number of blades for your wind turbine also depends on the use you want to give to it :)
I really thought the single blade was just a joke until i saw the real ones.
And a guaranteed fatigue service life limit of the shaft, what with the cyclic loadings regardless of perfect balance.
I worked with an engineer who used single blades as a way to game RC race competition rules for a particular race that limited the size of the propeller. He was able to get a larger diameter for his craft, seemed to run great!
@@alan-sk7ky It"s always possible to design the part to withstand the loads. Think about how many bending cycles a car's suspension spring goes through in its lifetime.
Yes indeed it was design by jokers! 😂
Fascinating! I hadn't thought about the difference of 2 vs 3 when yawing
Thanks! I only learned that point recently myself, from a colleague involved in a 2 bladed design. Interesting, isn't it?!
It is, really cool. Thanks for the video!
I had to read that several times before I realised you were yawing not yawNing! 😵 😄
I had to think for a minute about what's going on, here. Because the rotor is in motion as it's being turned about it's azimuth, the moment of inertia of the assembly in the azimuthal plane is also changing. Therefore, the torque applied to yaw the nacelle will need to be varied so constant rotation is maintained, stresses on the hub bearings will not be constant, and avoiding harmonic vibration modes of the support structure becomes a big consideration. Is reduced yaw rate not sufficient to ameliorate this problem?
One less airfoil likely also results in increased blade length and larger peak inertial moment therefore exacerbating the problem.
Answers question in a minute and then lets viewer choose to watch for longer answer?
Instant sub!
How engineers choose number of blades: Ask queen!! Once I have talked with Henk Lagerwey, one of pioneers in wind turbine business, great guy. He (his company) produced 75kW/15m, 80kW/18m and later 250kW wind turbines with two blades. I think this was first turbine with pitch control (passive) and first turbine with invertor regulation. Those turbines were popular in Japan because of ease switch to 50 or 60Hz (invertor). On one dinner with royal family (technology open different doors) queen asked him: "Why your turbine has two blades? For me it is nicer with three blades." He answered: "Your Majesty, you are right, three is better" And his next turbine was three blade turbine. :-)
It is amazing how with only one smile can be stable and balanced through the all video!
This is the first actually good explanation of this I've managed to find after working adjacent to wind power for years now. Thank you!
I really appreciate how you started your answer with a summary before going into detail.
Good explanation, but you could also add. The wind speed is slower close to the ground and is also affected by the tower. For 2 blade designs the force on the upper blade will be much higher than for the lower blade, and when passing the tower you get extra low force and vibrations. Over water the wind speed will change less with height and 2-blades are therefore common off shore. Another reason is esthetical. Early on in Denmark the general public preferred the sight of slower moving 3-blade design. This is less of an issue off shore where 2-blade designs are more common.
Absolutely fascinating and fantastic. I had never even imagined an issue with 2 blades being to do with uneven rotation.
I totally like your visual animations!
Trade-offs mentioned early and you know you're listening to a fellow engineer! Turning dreams and hard science into practice is at the end of a day an art. And so is making concise but still factual and _pleasing_ videos. Keep it up and thank you!
Thank you for that clear and concise explanation. I’d noticed the spring mechanism on small two blade turbines but I didn’t know what it was for. Now I do.
My first job as an engineer was working on the blades and hub retention design of the Hamilton Standard and KKRV designed 3 and 4 MW wind turbines, with construction starting around 1981. These were the world's most powerful wind turbines at the time at 78 m diameter and proved to be successful. Simplicity and low cost were drivers so as you explained, two filament-wound fiberglass blades saved on material cost (the resin) and this allowed the steel hub casting to be smaller as well. These were downwind, free yaw turbines that used a similar rotor design as found on two bladed helicopters, namely, a teetering rotor with a teeter pin offset by 30 degrees so that teetering causes pitch change to make the rotor self stabilizing.
The teetering rotor was especially good at reducing the fatigue load on the blades as they passed through the 'wind shadow' behind the tower. One problem found in service was that an excitation caused the tower to go into a bending mode of vibration which was at times disconcerting to workers at the hub/nacelle level during operation. To make an analogy, this system was similar to a two-bladed helicopter in auto-rotation, where the rotor in-flow comes up around and past the fuselage. As this is an emergency life-saving maneuver, no one complains if there is a little extra jouncing in the cockpit on the way down. However, for a two bladed wind turbine, perhaps a better solution would be an upwind machine with the added cost of an active yaw drive system to avoid the wind shadow excitation.
The problem of yawing a two-bladed rotor is similar to tilting the rotor of a two-bladed helicopter. This has been solved by various means and most lower cost helicopter designs use two-bladed teetering rotors. I dont have a preference either way. The machines I worked on were ahead of their time, US Govt funded, and defunded in the Reagan administration in favor of battleships.
Always wondered why 2 blades were not used as they work fine for aeroplanes.
All makes sense now, thanks
You are not only a great engineer but a great communicator too.
4:25 I subscribed when I saw the tower wobbling excitedly
Turbines Gone Wild - Spring Break
There are quite a lot of older two-blade wind turbines in Northamptonshire and into Warwickshire. Many of these were British-made, but production ceased through a lack of subsidy. When German and Danish three-balded turbines entered the UK market, the UK government belatedly turned up the subsidies and the three-bladed design proliferated. Almost certainly, a two-bladed design of relatively modest size was the most sensible choice for Northamptonshire, where suddenly-shifting sea gales are rare. They proved that wind turbines were worth a try, at least.
How interesting, thanks for commenting!
really liked your video. You got a new subscriber.
I didnt anticipate having a different answer than you when you said "if you ask 5 engineers from the wind industry, you will get 5 different answers" but here i am.
Another problem with two bladed wind turbines is the aerodynamic force distribution over the rotor plane which will excite the turbine further. There are different effects that play together on this.
First of all the natural wind speed distribution. The higher you go, the stronger the wind blows. Because of that the top blade will get pushed harder than the bottom blade. In combination with the rotation of the rotor you get a "nod moment". This is the probably the biggest aerodynamic problem of two bladed rotors.
Another important aerodynamic effect is the tower dam. Right in front of the tower, the wind slows down. during the rotation of the rotor, the blades travel through that area. There the blades dont get pushed back as hard as right before or right behind the tower, which also induces a nod moment on the turbine.
Those two effects combine on even bladed turbines. On odd numbers they act phase shifted to each other and dont put such a stress on the nacelle. Plus these effects are stronger on lower numbers of blades.
This really shows the different aspects you need to consider when designing a wind turbine. Its not as simple as "just a tower with 3 rotor blades".
I like the idea of having more blades in the future to make the blades thinner. It could also reduce the rotation speed which would make the turbines less stressfull to look at and maybe more bird friendly.
Really really cool video! Well explained, thank you! Please keep them coming :) Loved the graphics in it too!
Thanks! There are more on the way...
I really appreciate the short answer in the beginning!!
Those turbine animations are the coolest!! Too cute! 😂
Some 25 years ago I constructed a model wind turbine with 4 blades just as a school project to illustrate a principle. But it had two rows of blades in tandem ie. two at the front and two at the back. The front blades and the rear blades rotate fully independently and in opposite direction to each other but still connected to the same shaft.
It was only made to illustrate a point that you get a lot of untapped air containing K.E. going between the blades of a wind turbine . Quite knowing that only about 47% of the K.E. can be used it would be useful to tap that part that goes through the front blades by putting another set two blades behind..
Also the air that goes through must be affected by the front, by being slowed and maybe given a bit of spin in the direction opposite to the rotation of the front blades and therefore containing some rotational K.E. too. This air leaving the front blades will find it has to go through the rear blades turning them in opposite direction to the front even if at decreased K.E.
Notwithstanding the contra rotating blades the magnitude of the rotation of each set will be added at the shaft end producing more rpm and power.
I have started my certification program in the Wind Energy. You are doing great job, thanks a lot, you definitely have at least 1 long-term subscriber! ;)
Absolutely brilliant thank you!! I honestly thought it was just because 2 blades were an older design and they found it more efficient to have 3 and make it move with the wing. Wonderful explanation, you did so in such a comprehendable way, thank you!
The moment you mentioned the figure skater I completely understood the issue. Great analogy.
The best video I have ever come across related to wind turbine
Aw, that's a nice thing to say! You made my day 😊😊
Thanks, Rosie for the informative video.
I read that turbines with 2-blades have unequal forces when at the 12 and 6 o'clock positions because the upper blade has full wind force while the lower blade has wind that is blocked by the tower. I guess this isn't much of a problem with lattice type towers that allow the wind through.
What mystified me was why the blades had to be so long and skinny. Now I see that it saves money. Thanks for giving me a firmer picture in my mind why wind turbine blades are the way the are.
You are right about uneven forces at the 12 and 6 position, onbe day I will make a follow up to this and include more factors and that will be one of them.
I loved figure skating as a kid. I'm excited that you used a figure skater analogy.
A minute in and I knew I had to sub, great work!
Thanks. Nice explanations of some of the trade-offs involved. However (you knew this was coming!), my understanding from some work I did in an M.Eng a few years back m(oh joy, the Betz Limit!), is that the 3 rather than 2 decision was because of visual effects ("visual disruption", perhaps? - can't remember). It seems when an observer looks at a big turbine with 2 blades each, say 50 metres long, the width of the turbine when the blades are horizontal registers as about 100metres, but when the blades are vertical the width is almost nothing, just the width of the tower. So as it rotates there is the effect on the observer's eye, or brain, of something in their vision expanding and contracting, and the effect is even worse if there is an array of turbines. Apparently the same effects are not experienced, to anything like the same extent, with 3 bladed turbines - there's always something about 100 metres wide in view. Manufacturers are very sensitive to minimising visual effects as they are often claimed by objectors to windfarms to induce migraines, depression etc.
Thanks Rosie - a nice easy explanation for us intrigued layfolk. You have a breezy and easily relatable style. Subbed :)
I live in Gjølga Norway and I am neighbur with one of the largest windmill Parks in europe (storheia)
The wilderness and wildlife was ruined and the area is now dangerous for people and wildlife because they hurl iceblocks up to 200meters. They needed to build 20 meter Wide roads in the Mountain and the untuched wilderness is gone.
Your government, which is hypocritically supported in large part by oil and gas revenues, doesn't care about your wilderness because windmills are oh so Green.
@@e3a3c3 actually, the windmills are polluting since the bugs now are drained and started to release methane. They used to collect carbon, but now they release methane after the capitalist drained the area. The Sami minority lost grazing area for reindeer and the taxpayers get to subsidy the already rich for 20 years. When the subsidiary period of 20 years are over, the project will be abandoned
One of the major reasons I have come across for why 3 blades is more common is due to the ground layer of wind being slower than wind higher up. So a 2 blade design when it is in the vertical orientation, the top blade has clean air, which will provide more torque than the lower blade which has dirty air from all the turbulence of the ground boundary layer, resulting in a mismatch of torque. Where as three blades, when you have one blade in the clean air at the top, you have two blade in the dirty air, resulting in a more even loading of the system
Why I haven't found this channel before? Superb! I loved the rotoscoped clips. :)
Really thought provoking video. I didn't thought about 2 blade wind turbines as mostly my professors in university taught that 3 blades increases structural stability of tower & decreases oscillatory vibrations.
Yup, in the world of small wind turbines, two-bladers rip themselves apart in short order with the yaw-hammering they suffer when the wind changes direction. Two-bladers end up in a rusty heap near the base of a tower.
A tilting hub can help, which is used in larger attempts at 2-blade turbines, but such minimalist-minded designers always place their 2-bladed rotor downwind of the tower, for automatic aim, so once again, even with the tilting hub, the 2-bladed turbines get beat to death by the tower shadow. Ever flown in turbulence? Or ridden in a motorboat bashing waves? Best not to have the blades go thru the tower shadow (wake).
Two bladers also tend to look weird running
3 blades run smooth. 5 or 6 blade rotors run ultra smooth, but then you're into a lower Reynolds number with skinnier blades. Slightly lower efficiency, or so theoreticians say, but easy startup and really smooth operation.
Three blades is the lowest number than run smooth as a turbine re-aims (changes direction). Two bladers tend to look weird running.
I can get away with two-bladers for my multi-rotor turbines because they change direction more slowly, due to a higher moment of inertia about the yaw axis.. To me, forget number of blades, how about number of rotors? Got one outside that's been running for about 8 years continuously with two 2-bladed rotors. Changed the blades once, when the leading edges became eaten away by dust in the desert air and started getting noisy. Termite tunnels is what it looks like. Most people with small turbines never find out about blade erosion because the small turbines almost always break down long before any significant blade erosion sets in. Especially with two-bladers. Almost every small turbine has the same problem: They can't handle truly strong wind events. And if the have only two blades, the turbines seldom last even a year. Most small wind turbine manufacturers have gone out of business, now that solar gotten so cheap. But two-bladers were the first to go. So tempting cuz they make the same power yet need one less blade ($$$). But don't fall for it. Spend a little more and if you only have one rotor, at least get 3 blades on that thang. Solar panels still have to be able to survive a 100 mph wind, but they don't need to spin at several times that high speed in such brutal high winds. So you have millions of solar panels on peoples' roofs, and zero wind turbines.
Which brings to mind another common topic in small wind: "Can't I just mount my small wind turbine on my house?" (hint: don't do it!)
Used to make small "turbines" from wood - started with small (~0,5 m each) 2 blade design - at low altitude proved to be not pleasant to eye. Next was 3-blade design (~0,8 m each) that was pretty nice and stable. With some insights went forward and next/final was 5-blade design (~1,1 m each blade) - smooth and beautiful, trying to get rid of as much wood as possible to make blades thin (yet still strong enough) - got each blade weight down to 105-110 g (small difference for balancing as it all was hand work with knife and sand paper). That was like ~15 yrs ago but now remember details after this video - thanks!
Same as aircraft, fly in plane with two bladed props vs three. You will enjoy the three far more.
I was wondering about that when Rosie was discussing the stability issue with two blades.
My plane has 2 blades. She really shakes at certain RPMs.
@@GeneralChangFromDanang Didn't the later models of Spitfire have five bladed props?
Always odd number, but more than two.
Very, very helpful explanation. Please make more videos on this topic deeper into the details.
If they didn't have blades they would be just a stick poking up out off the ground.
LOL
Thank-You for these wonderful programs! At the end of a recent one you asked for comments on production, amount other things. I think your shows are all-round great picture-wise and editing, and sound is pretty good. MY ADVICE WOULD BE TO IMPROVE THE SOUND FURTHER. GET A MIC CLOSER TO THE MOUTH OF THE PERSON SPEAKING, monitor the sound with headphones, check the sound carefully in the edit. Particularly with this technical stuff it’s important that people hear clearly. You know this material so it’s easier for you to figure out what is being said, so maybe have another set of ears check it out. The picture is important, but the SOUND is even MORE IMPORTANT. People will put up with an imperfect picture, but bad sound will cause them to switch off and they won’t even know why!
Anyway, thanks so much for the totally supersonic shows you are making. I’m seeing this in the US and sharing it as much as I can!
I’m an engineer but I didn’t follow the figure skater analogy. The skater’s spin speeds up when her arms are drawn in because of conservation of angular momentum, bringing the mass of her arms closer to the rotational axis reduces the angular moment of inertia. With a wind turbine the mass of the blades doesn’t get any closer to the rotational axis when the central hub turns. I suspect maybe the instability is more related to the gyroscopic precession effect of altering the orientation of the spin axis? Edit: ok after thinking about this a bit more, the analogy about the skaters spin is not referring to the axis the blades revolve around, but rather the vertical axis of the slew bearing used to point into the wind. So yes the vertical axis slew bearing would need to work harder to turn a 2-bladed rotor when the blades are horizontal (“arms extended”) compared to when they are vertical (“arms raised”), leading to an oscillating effect for every rotation of the blade. Ok I learned something ;)
What a fantastic video! Great explanation, no annoying music and the whole tl;dr at the start then the nice in depth talk afterwards is such a great format. You explain things so nice and clearly too. Thanks!
I wasn't really interested in the question but had some vague intuition of what the answer would be. I have no idea why Google proposed this video to me, but clicked on it on a whim. I am so glad that I did:
This is the best technical explanation video I have ever seen. Structure, pacing, technical level of explanations, illustrations, balance between information and humour (2:34!), ... -- everything is just perfect. Congratulations for this little masterpiece. Now I am going to watch a few more of your videos on topics I am not intrinsically interested in.
Well done Rosemary! Loved it.
Thanks Paul, I'm glad you liked it! Your one-bladed turbine photos really helped to illustrate that concept, so thanks for sharing them with me 😁
_Just Have a Think_ sent me over here. I don't know why I hadn't heard of this channel before. Sub earned.
When I was growing up in the remote desert areas of Australia in the 50s/60s, domestic wind turbines like the British Lucas Freelite, American Wincharger Corporation and Australian Dunlite horizontal axis wind turbines generally had 2 blades. Perhaps it was to do with post-war economic measures; but when accompanying my father who had a job installing windmills, I don't recall any 3 bladed ones !
I had not heard of the stability issues of a two bladed turbine when changing it's orientation to face the wind direction. Of course it does make sense. Very interesting to think about. Thanks for this explaination!
Some years ago i was commissioning some 3 and 6 MW prototype turbines with 2 blades. Very interesting.
The main reason they decided for 2 blade was, like you said, the easy offshore installation. The tower vibration was suprisingly low, even during yawing. Later they wanted a dynamic pitch system thet would pitch a little bit during one ration to eliminate the vibration.
Another thing was, during storm, the blades should be parked horizontal to keep the force to the power low, even when the yawing did not work.
Btw: It looks nice if you have a windfarm with serveral of this 2 bladed and the rotors where synchronised, so they are during all in the same angle and speed :-)
What an awesome explanation. You have a great way of explaining things.
That was a very interesting video! This weekend in Cornwall I passed a wind farm of two bladed turbines (the Cold Northcott site I believe) and it was definitely out of the ordinary, but now I know why! All the turbines where stopped at the time with their blades horizontal which I can't think of a reason for. It did make me wonder more about the process of starting and stopping the turbines, and how quickly they can be "switched on" as such. Keep the good content coming!!!
Oh wow, I have never seen a farm of two bladed turbines, that's so cool. I would guess the blades park at horizontal so they have an equal wind force on them. If they were vertical the one at the top would see higher wind speeds (due to wind shear), so if they are a bit lower the force will be lower, and equal for the two blades. But that's a guess :-)
The reason that aircraft (sitting for long periods in the outdoors) have their propellers parked horizontally is so that both blades receive and shed moisture equally. I would presume that this factor would be more important in colder countries where ice build-up on one blade would effect the balance of the propeller. In the case of wind turbines, having one blade heavier than the other would probably increase the start up wind speed. 🤔??
@britishbiker In English the words WERE and WHERE are spelled differently because they mean different things.
@@MrCuddlyable3 😂 I did it just for you xx hope you enjoyed yourself
awesome. Rich content provided in quite simple way with nice graphics. Like good lecture but packed in few minutes.
Yes - love that you explicitly include a stopping point at 1:10. I realise that doing this might make your channels watchtime analytics look bad, but thanks for the humane design. I appreciate it.
Hey Rosie! Your videos are fantastic, very helpful, informative and easy to understand! Amazing! :)
Glad you think so! Thanks 😀
Much better explanation than the one from Real Engineering
Ha ha! Thank you. I guess I should say it is not a competition, but I would kill for the view count that video has!
@@EngineeringwithRosie To different audiences. Real Engineering is working more towards folks with no background knowledge.
Fun fact the largest Wind Turbine Blade up to date has a length of around 107 meters, doing some math it would only take around 30 rpm for the Bladetip to go supersonic, which will rip the whole Turbine apart ... :)
When I used to drive along the E80 route through the mountains in central Italy, it always came as a surprise to see so many single-blade turbines rotating high on the steep hillsides. With their large single arms and squat counterweights, from a distance they looked like they were off-balance and about to shake themselves apart! (Keep your eyes on the road though, as the average speeds seem to be good enough to qualify for Formula 1 racing).
I watched a video about this on another channel a while back, and they had another reason: That if you have an even number of blades, it causes a resonance because the blade with the most force (straight up) is always opposite the blade with the least force (passing in front of the support). Also, I understand that the power generated increases with the number of blades, but not linearly so going from 2 to 3 adds around 50%, going from 3 to 4 adds less than 30%, from 4 to 5 20% and so on, but because the blades are the most expensive part, it’s better stop at 3 blades and put the next 3 blades on a new tower. That way you get more power from each blade than just increasing the number of blades on one single tower. Or at least that’s how I understood the argument.
The first explanation I always heard was the windward shadow that the tower creates due to obstructing the airflow. The second was about the effect of the Earth's boundary layer with larger and larger turbines gets more intractable. The top of the arc at 250 meters has a vastly different windspeed than the bottom of the arc at 50 meters. Three blades better spreads this disparity out across the swept disc. As you have one blade passing over the top in cleaner air, you have two blades creating power in the dirtier, slower air lower down.
In propeller aircraft, more blades means lower efficiency from air friction, but higher static thrust. IOW faster acceleration on takeoff, slower cruise speed. I see more blades on wind turbines being better in more marginal wind conditions, perhaps. Or just build taller, where there is always some wind.
Same problem with aircraft. The plane I fly has a 3 blade propeller with variable pitch, it is the standard. The tug at my gliding club has 4 with fixed pitch. It provides good acceleration on takeoff at lower rpm, a variable pitch would have to spin faster at high pitch, is supposed to be less noisy (lower rpm) but has a lower cruise speed and consumes more gasoline at cruise speed because of increased drag. Two blades are ok for very light underpowered or low drag planes.
a video which start with a TLDR? instant sub :)
Ha ha, I later learned that this approach does not please the RUclips algorithm... which is why it has taken nearly a year for anyone much to see this video 😊
@@EngineeringwithRosie Well, It earned you a passionate new sub at least 😅
Also glad to see your newer videos are a lot more professional in terms of audio quality (among other things) 😋
Same, I subscribed immediately for the same reason. Too many time-wasters on RUclips at the moment, unfortunately incentivised by the algorithm.
@@EngineeringwithRosie Does "subscriber probability of viewing" influence recommendations? Advertising click-throughs? I wonder if a modest number of hardcore subscribers is better or worse than half a million strays.
@@erikscott5709 I really have no idea what on earth the algorithm is up to. My suspicion is that it is mostly to do with session time of people who watch the video. So if they watch this, and then go on to watch more of my videos, RUclips learns that showing this video keeps eyeballs on the site longer. That would explain why this video never took off originally, but now I have a few other (longer) videos they can show after, suddenly it gets the algorithm's blessing despite having a low watch time That's my interpretation anyway.
Liked the presentation and also loved your animations !👍
It's fascinating but it amazes me that there is not a simple formula that you can plug the variables into and derive a result. I wonder what the deciding factor is in how large to go as well?
Great points. The formula I have covered (briefly) in this video, the question of how large to go, I want to cover in a future video.
ruclips.net/video/CavfXOt3Dew/видео.html
@@EngineeringwithRosie When you cover how large to go, I hope it will also cover boat propellors. I guess they are limited by how much they can intrude into the hull of the ship. Look up "Titanic propellors" and you will see something truly fascinating. I wonder why they made THAT choice?
Great explanation! This was question I hadn't realized that I needed answering.
That academic background of summarising the following content as part of the introduction is so appreciated in this form factor. Thanks for the explanation 🎉
Rosie follows the classic presentation format - "tell em what you are going to tell em, tell em, then tell em what you told em". It is classic for a reason - it works.
Great video! I can't believe you've only got 13.4k subs! This was wonderfully concise and a good explanation. :)
She just got a +1 :)
Simple, effective and clear explanations + pleasant speech + nice animations.
Thanks for your work.
Veritasium brought me here and I love this channel!
RUclips just recommended your channel to me. Thank you for your professional explanations. I really enjoy these videos!
The weak point with twin blade turbines is not the force variations themselves when they need to adapt to the wind direction!!!!! A twin blade windmill does easily re-orientate to a new wind direction when the blades are in vertical position, as you explained. As from when the windmill has been re-oriented for some degrees ,and the blades come out of that vertical position, they are subject to huge gyroscopic forces. It is this effortless re-orientation with huge gyroscopic destructive forces as a consequence that explains the typical suicidal behavior of twin blade mills.
Thanks for raising these extra points Dominiek!
This question was in the back of my mind for a long time. Thank you for the best explanation I could imagine.
4:25, that one is an excited turbine. :D
Fascinating video, presented in a very straightforward and easy to understand style. New subscriber here.
Regarding rotational speed, I remember hearing in a documentary that somewhere around 300kmh is the maximum tip speed that can be attained without the blades producing high-amplitude low-frequency noise that carries for kilometers across the landscape. Is noise abatement the only limitation for tip speed? (Beyond the obvious limiting factor of forces trying to rip the blades out of the hub or shake the whole assembly apart) Do prevailing wind conditions in a given location also affect this limit?
I never thought about preservation of angular momentum or structural resonance as they pertain to a yawing wind turbine! Great video!
Excellent information, thanks. For *fan* blades, there is another reason to have an odd number of blades - this distributes the noise harmonics, so they can be quieter / less noisy. I have wondered if this is also a factor with wind turbines, but because the rotational speeds are so much lower, maybe it is, but not as critical?
RUclips algorithm brought me here. However, I'll love to witness in real life, a dancing wind turbine like this. Will be fun 4:24
Great explanation. Subbed!
I've always been surprised that turbines with more blades, like 5-10 for example haven't proven to be more efficient. It seems that the majority of wind passing a 3 blade turbine goes right past it, never coming close to a blade to impart energy onto it.
In an optimal rotor design, no matter the number of blades, every air molecule will be affected by a blade. That's why a rotor with less blades needs to turn faster than one with more blades (assuming they're the same width).
Excellent teaching and learning Observations.
Excellent. I’ve never heard a digestible explanation of the 2-blade turbines’ problems - as the turbine hub is rotated in azimuth.
Thanks!
Yes two blades is aerodynamically most efficient, because the following blade is nearly always in clear air. This is important because if the following blade encounters turbulence from the one ahead it can trigger aerodynamic flutter.
However, two blades is subject to yaw imbalance, this causes the turbine to go out of balance as it yaws putting huge cyclic stress on the rotor hub and the tower that can lead to fatigue.
Three blades is the minimum number of blades that avoids yaw imbalance, while following blades are mostly but not always in clear air. Consequently it is the configuration of choice.
The efficiency is capped by the Betz limit. The number of blades is chosen to optimize the tip speed ratio λ for a given set of wind conditions.
I had an intuition about that instability, but didn't know how to explain it.
3:50 2-blade transient stability: use 2 paired blade sets for 4 blades in series (stacked on rotation axis) and opposite sides of tower turning opposite directions, transmit torque down tower with bevel-geared drive shaft, generator fixed at base. Change rotation axis compass bearing with worm gear control. Program orientation motor to stop during brief intervals when blades align vertically (colinear with tower).
interesting, but I fear the repeated ''impact'' of the second blades crossing the wakes of the first blades. Some planes and helicopters are like this.
@@yanickgenest1324 Also the downwind rotor must contend with wake of tower, at least the bottom half does. Try this: instead of two blades in a line, two blades slightly angled from each other, a boomerang. Center of rotation is in the V, not at vertex. Upstream and downstream rotors angled opposite directions. There is less interference in rotor-wake for the downstream rotor, but it still has the tower wake.
Teknologi yang bermanfaat untuk mereka yang mengembangkan teknologi turbinnya.
Salam hangat dari Indonesia 🙏
Two blades turbines still operational since 1998 in Flevoland. Much higher wind speed required to spin at its nominal rotational speed, so later on they built them with. 3 blades
In 1980 the german government decided to prove that renewable energy is impossible. They ordered MAN to build a 100m high wind turbine, called GROWIAN, or Große Wind Anlage (great wind device) with 3 MW, the tallest wind turbine of that time. It had 2 blades (now I know why) and big problems with stability and poor function. Finally it was dismantled after only 420 hours running and could show to everybody that wind energy is not possible at that scale.
I viewed another website where the person had a quite a bit of experience and he said a greater number of blades was more practical and produced more in low wind speeds.
I thought a read a study many years ago showing that people found three blades more aesthetically pleasing than two blades. In my personal opinion. Three blades are much more aesthetically pleasing than two blades. Efficiency, costs, longevity, transportation are certainly more important. But millions of people have to look at these everyday. Many people do not like their appearance at all. Many people living close to them suffer from the effects of chronic low frequency pulses they emit. And others hate them for killing endangered birds. All valid perspectives. That’s why we should be using LFTR technology. A walk away safe Nuclear energy power source that produces much less waste than current light water nuclear reactor plants that require electrical power for decades to keep active and spent fuel cool. LFTR stands for Liquid Fueled Thorium Reactor. They do not need a giant steam containment building so they are much smaller and easier to build and maintain. In any kind of accident, they shut down automatically without any power or human intervention required. Besides using Thorium, that is 4 times more abundant than Uranium and is currently treated as a radioactive mining waste product. They can be used to accelerate the breakdown and mitigate the dangers posed by our current nuclear wastes. They can not be easily used to make Plutonium for nuclear weapons, unlike current nuclear reactors. That’s actually why light water reactors were chosen to be used in the first place. To make Plutonium for weapons. So LFTR nuclear power is a Win-Win-Win. If we don’t develop this technology quickly as a huge National Priority. The Chinese and Indians will come to dominate this field of a cheaper, safer, smaller and “green” energy source.
The topic is really interesting, but as an information channel your first priority should be to record clear audio and have clear diction. You need a good condenser mic, EQ, compression, not to mention the audio is really low too.
Great concise answer, and then elaborated. If everybody could do that...
After 1:21, I have heard the answer to the question posed, if I want more details I can keep watching, excellent!
But then she includes in the description the MAGICAL, REQUIRED reference to "combat climate change".
Very good video and very good explanation. Big fan of your videos and channel.
Height of turbines of these type are often designed so that the major force is applied on the higher section because there is less wind drag or ground drag if inland. The major wind push is when the blade is on the high swing or candlestick movement, and the blade shape is dictated by rpm to make sure there is constant laminar flow. Some turbine blades can rotate to adjust angle of attack to maintain high efficiency. Why can we not extract all wind energy? Aerofoils can extract ~86% efficiency while drag type (sheet of paper in the wind) can be maybe 68% efficient. It is about efficiency alone.
amazingly well explained! loved the simplicity of the production
hey..after being confused and bored and confused again i stumbled on a diamond..good video
More blades can equal more power. Ten blades can equal 5x the power of 2 blades. The limitation is the air flow speed. A jet engine with high air flow has dozens of high pressure blades. I suspect that a wind turbine in a slower 40mph wind would leave turbulent, disrupted air for the next blade if it had very many blades.
I'm guessing this is why you see three huge blades instead of ten smaller ones. There may also be a better aerodynamic lift effect out at the fast end of large blade. Longer blades can mean higher velocities.
It would be interesting to compare different turbine designs, including a ducted fan wind turbine using a large funnel shape as an intake. It would be interesting to see what kind of wind velocities could result and what kind of different blade designs and advantages might be possible.
This was informative, I enjoyed the discussion of tradeoffs. Keep up the great work!
Excellent explanation for those of us who are none the wiser but still fascinated. I always thought the number of blades was determined by how many birds and bats needed to be killed.