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Why Wind Turbines Have Three Blades

425 points by rfreytag 10y ago

Jedd 10y ago
Looks like a fine opportunity to ask - whatever happened to vertical axis wind turbines? They sounded like they had a bunch of advantages, not least a much higher tolerance for extreme wind conditions, less stress on long (suspended) blades, possibly less gearing issues in translating motion back to the ground - but presumably they had / still have distinct disadvantages?
- phonon 10y ago
  http://www.forbes.com/sites/jeffmcmahon/2016/04/29/stanford-small-wind-arrays-can-outperform-conventional-wind-farms-with-no-bird-kill/#293984cd7a9c http://www.forbes.com/sites/jeffmcmahon/2016/04/29/stanford-...
- knodi123 10y ago
  Even sexier (and less field-tested) than vertical turbines are windbelts. https://en.wikipedia.org/wiki/Windbelt https://en.wikipedia.org/wiki/Windbelt > Prototypes of the device are claimed to be 10 - 30 times more efficient than small wind turbines. One prototype has powered two LEDs, a radio, and a clock (separately) using wind generated from a household fan. The cost of the materials was well under US$10. $2–$5 for 40 mW is a cost of $50–$125 per watt.
- pjc50 10y ago
  Scaling issues, I think - they need to be supported at the top as well, and they're dependent on how much weight and wind force the bearings can take. http://www.windpowerengineering.com/design/vertical-axis-wind-turbines/ http://www.windpowerengineering.com/design/vertical-axis-win...
- olau 10y ago
  I think the reason plainly is that they are not competitive, perhaps because their advantages aren't important enough disadvantages for horizontal axis turbines. Wikipedia has a short section: https://en.wikipedia.org/wiki/Vertical_axis_wind_turbine#Disadvantages_of_vertical_axis_wind_turbines https://en.wikipedia.org/wiki/Vertical_axis_wind_turbine#Dis... I think people tend to forget that the big wind turbine manufacturers today started out small, experimenting with various designs before they settled on the three-bladed model. At the moment there's a lot of accumulated research and infrastructure present that allows them to erect giant 3-6-8 MW turbines that can take the hammering of the weather for > 20 years. Competing against this is really, really hard, you really have to a big advantage in your favor and perhaps also decades of research and development.
Houshalter 10y ago
Slightly relevant, here's a really weird wind turbine designed by a computer: http://m.youtube.com/watch?v=YZUNRmwoijw http://m.youtube.com/watch?v=YZUNRmwoijw
- nkoren 10y ago
  That was really fascinating -- thank you!
- NicoJuicy 10y ago
  The note on the video is quite funny: Note: I have since discovered I used the wrong viscosity for air on this experiment, so the results aren't valid for use on the earth. (Maybe Jupiter.)
  - 6stringmerc 10y ago
    While I missed that, I'd have to agree that note is quite amusing. Oops, wrong planet.
  - Houshalter 10y ago
    Ah, well. It's still interesting. The design of the turbine is really crazy and not what I would have expected in any environment. So I suspect if he corrected the parameters, it would still come up with a crazy and clever design for Earth use, that humans wouldn't think of.
- whichfawkes 10y ago
  I have to wonder if there are some imperfections in the simulation which cause it to evolve toward a blade that's optimal for the sim, but not as good in real life. He talks about 20 minute tests, and then later uses a 12 hour test and gets a significantly different power number. I wonder how differently the evolution might proceed if he just had more power to run the full tests on each generation.
- logfromblammo 10y ago
  That was an interesting video, but it was restricted to a 2D simulation on a vertical-axis turbine with exactly 3 blades. A more intricate genetic algorithm that runs a 3D wind model and accounts for the cost of manufacture would almost certainly produce some more novel solutions that completely demolish our preconceived notions of what turbines should look like, just like the "jellyfish" cross-section. But it would also probably not effectively scale beyond the model size. Genetic algorithms almost always exploit any previously hidden little flaws you may have in your model simulator, such as the rounding error on floating point numbers at the limit of their precision, or even the way in which you represent airflows. They evolve to maximize performance in the modeling environment, so if your model is not perfect, the solution does not always translate to reality. As such, you always have to test the evolved solutions in the real world before you can say they are better than the designed solution.
justinph 10y ago
Small turbines do exist. One was installed on This Old House recently: http://www.thisoldhouse.com/toh/tv/ask-toh/video/0,,20961006,00.html http://www.thisoldhouse.com/toh/tv/ask-toh/video/0,,20961006... (jump to about 15:00) But, it does have three blades.
Aelinsaar 10y ago
I like the idea of wind turbines, but in practice I think PV is the way to go (long term). I realize that for now it's a blend of technologies, but PV doesn't kill millions of birds and bats. I grant you, it's better than burning coal, but still we can do better eventually.
- ams6110 10y ago
  PV can kill or destroy habitat of other creatures, though this is probably almost entirely avoided in certain circumstances (rooftop installations, for one) where the damage has already been done.
  - Aelinsaar 10y ago
    Everything we do, does that. Fortunately the places we put PV tend not to be virgin forests or other places we haven't already destroyed for our benefit.
    - TillE 10y ago
      Wind turbines aren't built in virgin forests either. They're generally in farmland, which is pretty well ecologically destroyed already.
      - JoeAltmaier 10y ago
        In California they seem to go just about anywhere. Sure not virgin forest, but maybe native savannah? http://www.energy.ca.gov/wind/overview.html http://www.energy.ca.gov/wind/overview.html
      - Aelinsaar 10y ago
        I never claimed that they were, and bats and birds are prevalent in farmland.
- Houshalter 10y ago
  House cats kill 1,000 times more birds than wind turbines. Even cell towers kill more. It's nonissue.
_Codemonkeyism 10y ago
As a kid I always found it interesting that (some?) Spitfire had 4 blade propellors and the main adversary, the [Edit] Bf109 had 3 [1] and wondered, shouldn't there be an optimum? [1] Not sure both changed the number of blades during WWII.
- rusanu 10y ago
  You mean Bf109 I think. The P-51 started 3 and then moved to 4. Ditto P-47. FW-190 and F6F stayed at 3 whole time afaik. Tempest started with 4. So it varied. But there is a trend of the early (1939) designs to have 3 and the late (1944) designs to have 4. I guess available power from the engine plays a big role, as engines got more powerful they started fitting 4 blades. Using the extra power on 3 blades would require longer blades (which is problematic), spinning them faster (again, problematic as tips reach sound barrier) or increasing the pitch (I guess there are aerodynamic limits for that).
  - _Codemonkeyism 10y ago
    Thanks, how emberrassing, yes Bf109. "I guess available power from the engine plays a big role, as engines got more powerful they started fitting 4 blades." Good one.
  - 6stringmerc 10y ago
    This is a really cool write-up. Another thing that might be of interest was the performance of the aircraft. There's a guy in Texas with 6 non-flying 109s, a couple P-51s, and some other stuff for sale as a lot. He's a former stunt pilot, flew in the movie 'Battle of Britain' and several others. In his words, the 109 handled much better at the limit than the P-51. The P-51 could dive and go very fast, but with poor control. In his opinion the 109 was the superior aircraft. Not sure if it relates at all to the prop discussion, but maybe in the grand scheme of engineering? Those warbirds are fascinating pieces of hardware to me.
- arprocter 10y ago
  Interestingly the prototype Bf109 had two blades. I wonder if it was a carry over from the first world war when guns fired through the propeller, so the more blades the more chance of shooting it off? (There were systems which regulated when the gun would fire to prevent this happening)
mapt 10y ago
* I don't understand his explanation of starting torque. You can jump-start that problem by other means in the alternator. Torque and power should be decoupled anyway by blade pitch. * There is such a huge difference between a 12m blade and a 60m blade that I don't see how the comparison is at all relevant. We played with smaller turbines for decades before we reached this sort of price efficiency. * Betz' law explicitly disavows picking a number of blades: "Assumptions: 1. The rotor does not possess a hub and is ideal, with an infinite number of blades which have no drag. Any resulting drag would only lower this idealized value. ..." * Betz' law is a three-dimensional consequence of convervation laws, not an observation about turbulent blade interactions. "Consider that if all of the energy coming from wind movement through a turbine was extracted as useful energy the wind speed afterwards would drop to zero. If the wind stopped moving at the exit of the turbine, then no more fresh wind could get in - it would be blocked. In order to keep the wind moving through the turbine there has to be some wind movement, however small, on the other side with a wind speed greater than zero. Betz' law shows that as air flows through a certain area, and when it slows from losing energy to extraction from a turbine, it must spread out to a wider area. As a result geometry limits any turbine efficiency to 59.3%." * We already have a good idea what a moderate redesign of the fundamentals of a wind turbine looks like; It points downwind, it's huge like the existing turbines, and its two blades bend. They just need to solve the tower strike problem. https://www.technologyreview.com/s/401583/wind-power-for-pennies/ https://www.technologyreview.com/s/401583/wind-power-for-pen... https://www.technologyreview.com/s/528581/two-bladed-wind-turbines-make-a-comeback/ https://www.technologyreview.com/s/528581/two-bladed-wind-tu...
- brandmeyer 10y ago
  > I don't understand his explanation of starting torque That's because Cringley doesn't, either. The starting torque is entirely provided by the wind, not the grid.
  - beat 10y ago
    I think what he's talking about (not bothering to re-read) is the power required to magnetize the alternator components in the first place, so the alternator works at all. They use electromagnets rather than permanent magnets, because electromagnets are much cheaper, especially at that size. This is a fixed power requirement, so if the alternator can't generate more than that fixed power need to operate, there's no point in running.
dzdt 10y ago
We all love the story about the clever little guy who thinks outside of the box taking down the big giant corporation who does things the way they have always been done. Cringely trys to tell this as such a story, or could be, or could have been. But there is really no evidence backing it, just his desire to tell a good story.
calinet6 10y ago
This is a classic example of sub-optimization (and even if it's hand-wavey pseudo-science and may be wrong, the general concept is still interesting). Each individual wind turbine is optimized to be the "most efficient" it can possibly be. But not in the context of the environment, which requires complex control systems and methods to reduce damage in non-optimal conditions. And not if you take cost and efficiency of the whole system into account; where four times as many small turbines with less complexity run more often and produce more overall output. But hey, each wind turbine is "optimal." Interesting. Most complex systems have this property. Even (especially?) your business.
- nkoren 10y ago
  This kind of thinking contributed to American rocketry being trapped in a local maxima for decades. There are many reasons it became trapped, but one of the primary reasons was that rocket scientists would insist on optimising rocket engines at the expense of every other aspect of the vehicle. "The logic of rocket equation is brutal and inexorable", the NASA rocket scientists would say. "As the performance of the rocket engine decreases linearly, the propellent requirements increases exponentially. Therefore it is imperative to have the highest-possible performance from your rocket engines. The combustion of liquid hydrogen / oxygen is the highest-efficiency chemical reaction, and therefore liquid hydrogen is the only propellant we will consider using for our engines." All of this was correct, but also wrong. It was wrong in a whole-systems context, because: A.) Liquid hydrogen is much lower-density than traditional rocket fuels like Kerosene, requiring far larger and heavier structures to carry the same amount of energy, and larger and heavier engines and plumbing and everything else -- and the structural mass of a rocket matters. B.) Liquid hydrogen will boil off and leak through anything, requiring massive amounts of insulation (again, adding weight), and far stricter operational protocols around the fueled vehicle. C.) Liquid hydrogen is so cold that it will embrittle and shatter ordinary metals and requires much more exotic and expensive metallurgy. and finally, D.) The alternative, kerosene, gives you less efficient engines but also much lighter-weight vehicles -- and sure, per that inexorable logic of the rocket equation, you need to use more fuel for the same amount of payload, but kerosene is cheaper than milk so who fucking cares? Anyhow, the upshot of this is that US rocket scientists spent literally tens of billions of dollars developing hyper-locally-optimised rocketry schemes, most of which failed outright. For the remainder, for every dollar of kerosene they didn't have to buy, they probably spent upwards of $1000 on exotic aerospace hardware. Finally, they gave up and just bought kerosene-based engines from the Russians. So then there's Elon Musk. And of course there's a ton of brilliant rocket science in the Falcon, but much of the reason for SpaceX's success is because it doesn't optimise solely on the rocket science. They optimise for cost as a whole, and consider factors like design, manufacturing, operations, reusability, etc. to be relevant to the question of cost. For example: the Falcon 9 would undoubtedly be more efficient if it had a hydrogen-based upper stage. But doing that would cause it to lose most of its commonality with the lower stage, requiring an entirely new design, manufacturing, and operations workforce. Which would cost several orders of magnitude more than the extra kerosene required to fly a "sub-optimal" rocket. The reason they've already cut the price of launch by about 80% vs. (say) the Space Shuttle is because they optimised the whole system, keeping the unique part count and operational complexity as low as possible. I still sometimes hear old-school rocket scientists grumble about how the Falcon is a less optimised vehicle than the Shuttle, though. They just don't get it. Never will. Anyhow, that was a tangent. Fascinating to think that wind turbines might be amenable to a similar class of disruption.
_Codemonkeyism 10y ago
I'm interested in the results when Cringely builds his farm. For example support costs from thousands instead of hundreds of turbines. How many on one pole are best. Also building costs over time e.g. when costs go down due to robots planting poles etc. which favors farms with more poles above those with fewer poles.
tantalor 10y ago
The 2016 tag is not really necessary; this was published today.
nabla9 10y ago
One graph is worth thousand words. Rotor power coefficient vs. tip-speed ratio. http://i.imgur.com/PONHerZ.jpg http://i.imgur.com/PONHerZ.jpg
- 55acdda48ab5 10y ago
  You have a computer with servos and winches fly parafoil kites to generate power from wind. This is definitely the theoretically optimal answer. It's also very low capital intensity. https://www.youtube.com/watch?v=j-qUaO-xzrY https://www.youtube.com/watch?v=j-qUaO-xzrY
  - jessaustin 10y ago
    Lots of omitted details there. A kite can pull its tether from one location to another location of lower potential energy, but how does it get back to the higher-energy location? If we're talking about a circular train on a circular track, half of the kites must continually have either a lower-drag configuration or a lower-wind altitude. That's plausible, but that's a lot of additional mechanisms, plus a lot of "cancelled-out" wind traction, plus a lot of friction as the train rolls around the track. Will there be power left over for electricity generation? Probably, but it isn't clear that it will be worth all the trouble. If a reasonable prototype exists, it should have been in the video.
tantalor 10y ago
You mean like one of these? http://www.windpowerninja.com/wp-content/uploads/2009/02/old_wind_turbines.jpg http://www.windpowerninja.com/wp-content/uploads/2009/02/old...
vanderZwan 10y ago
Relevant Low-Tech Magazine entries on wind-power, and small windmills: Urban windmills harm the environment [0] > A small windmill on your roof or in the garden is an attractive idea. Unfortunately, micro wind turbines deliver hardly enough energy to power a light bulb. Their financial payback time is much longer than their life expectancy and in urban areas they will not even deliver as much energy as was needed to produce them. Sad, but true. Small windmills put to the test [1] > A real-world test performed by the Dutch province of Zeeland (a very windy place) confirms our earlier analysis that small windmills are a fundamentally flawed technology (Note that the picture shows that almost all windmills tested had three blades) Wind powered factories: history (and future) of industrial windmills [2] > In the 1930s and 1940s, decades after steam engines had made wind power obsolete, Dutch researchers obstinately kept improving the – already very sophisticated – traditional windmill. The results were spectacular, and there is no doubt that today an army of ecogeeks could improve them even further. Would it make sense to revive the industrial windmill and again convert kinetic energy directly into mechanical energy? Unlike this story, which certainly sounds interesting but shares no real data to back it up, Kris de Decker thoroughly digs through sources to write articles backed up by available data as best as possible. [0] http://www.lowtechmagazine.com/2008/09/urban-windmills.html http://www.lowtechmagazine.com/2008/09/urban-windmills.html [1] http://www.lowtechmagazine.com/2009/04/small-windmills-test-results.html http://www.lowtechmagazine.com/2009/04/small-windmills-test-... [2] http://www.lowtechmagazine.com/2009/10/history-of-industrial-windmills.html http://www.lowtechmagazine.com/2009/10/history-of-industrial...
toolslive 10y ago
"why... very often the turbines aren’t turning at all?" Someone told me that demand varies and it's easier to shut down a windmill than a nuclear reactor.
tlb 10y ago
More blades and closer spacing between windmills optimizes power / land area. But what matters is power / capital cost.
- mark-r 10y ago
  He tried to touch on that - making the blades shorter but in greater quantity will drive efficiencies of scale in manufacturing and shipping. And smaller turbines lead to cheaper towers. Hard to know if he's right without crunching actual numbers though.
- CydeWeys 10y ago
  With land area being one factor that goes into capital cost.
Cerium 10y ago
Three blades is the smallest number that reduces the vibrations due to the blades crossing the support structure. When a blade crosses the support its applied force is reduced because the wind is slower around the support. This reduction in forces creates a yawing torque that can lead to unwanted vibrations. Much of the structural stiffness and bearing requirements are related to these effects. Three blades minimizes the effect because when one blade crosses the support the other two blades are out in a Y shape, shortening the force differential when compared to two blades.
- mark-r 10y ago
  There's a question then, why are support towers solid? Maybe they should be made more like the Eiffel Tower?
  - elcapitan 10y ago
    Probably to be more durable, because of the closed surface - the Eiffel tower has very high maintenance costs as it has to be steadily re-painted. It would probably not be necessary that much for modern steels, but unlike wind turbines the Eiffel tower also does not stand close to the coast or directly in the sea, where highly corrosive winds blow.
    - Cerium 10y ago
      Additionally the enclosed space is useful. Inside the wind tower is a lot of equipment. There is the electronics for converting the power and monitoring the wind tower. There is a lift for ease of access to the nacelle. Current wind towers are 80m tall, next generation wind towers are more than 100m to access more reliable higher strength winds.
      - brandmeyer 10y ago
        I don't think this is a strong driver. GE 1.5 MW turbines only have a relatively small space near the base of the tower that is consumed by power electronics and control systems. Siemens has largely gone to a system where everything is in the nacelle. This way it makes it easier to completely test and connect the power electronics and control, since more of the work is done at the factory instead of in the field. Labor and equipment is much more expensive in the field than in the factory.
at-fates-hands 10y ago
Here's a much better Wind Resource Map than the one in the article: http://www.tindallcorp.com/site/user/images/USA_Wind_Map_for_Tindall_Transp_2.jpg http://www.tindallcorp.com/site/user/images/USA_Wind_Map_for...
- scblock 10y ago
  http://apps2.eere.energy.gov/wind/windexchange/wind_maps.asp http://apps2.eere.energy.gov/wind/windexchange/wind_maps.asp has this map plus state by state maps available for download as relatively high resolution PDFs.
manmal 10y ago
It seems Steve Jobs was inspired by Socrates: https://en.m.wikipedia.org/wiki/Socratic_method https://en.m.wikipedia.org/wiki/Socratic_method
elcapitan 10y ago
I would have guessed that it's a trade-off between efficiency and mimizing public outrage in densely populated areas (yes, outside the US that can be an issue). Three blades, when the turbine is not working, block less from the view than a large number of blades (which converge towards giant white surfaces).
lorenzfx 10y ago
I'm not saying he is wrong, but he makes some bold claims without giving any proof. Some examples: > Twelve blades is a nice number. Why twelve? Why not 50, it's a nice number as well. > Lipps turbines can operate in faster winds [...] turbines could be allowed to run 24/7 in any wind with no computer So even in the strongest winds turbines with 40 feet blades do not need to be stopped? > using permanent magnet generators instead of alternators, but those are more expensive > Use permanent magnet generators leading to [...] even lower cost. Which is it now? > what matters isn’t power efficiency per turbine so much as power production per acre of wind farm. Isn't it rather electricity production efficiency in terms of invested capital?
- amelius 10y ago
  I get the feeling that the best answer to the question is that empirical testing (perhaps by simulation) points out that three is the optimal number of blades. This leads me to the question: is it possible to determine a good rotor design by using optimization techniques such as simulated annealing or genetic programming? Or are the simulations too costly?
  - Bartweiss 10y ago
    I can help with this a bit. The simulations are quite difficult - flow simulation is well-established, but it's a big step from that wind farms. You need to simulate many turbines interacting at a specific site, under a variety of conditions. That's not the problem with modeling single turbines, though. Rotor design is hard to simulate productively for the same reason that Cringely's analysis is flawed: many of the biggest factors are unrelated to everyday running. - Even blade counts create resonance patterns that stress your tower. - High solidity designs suffer more stress in storms (even while stopped), so they break more - Noise interferes with putting rotors near houses or over pastures - Storage is difficult and consistency is valuable, so expanding the operating range up to high winds is less useful than expanding it down to low winds And so on. If you model pure efficiency, the sims are pretty easy. If you model real value, you either can't do it, or you get a search space so jagged that finding maxima is hopeless.
scblock 10y ago
There is a lot of bad information here, and it appears there are others in these who are also better informed than the author. Let me just hit up a couple of points that are fundamentally wrong, though. - "Conventional wisdom says wind farms should have their turbines placed in such a way that they don’t interfere with each other, the fear being that placing one turbine too closely in the shadow of another will reduce the efficiency of the showed turbine." True, and this is why we have wake models based to predict the losses from other turbines and optimize placement. - "The rule of thumb, then, is that turbines be placed no closer than seven diameters apart. Keep that number in mind." Not true. You may find that a 7x7 array is relatively common in offshore applications, but a typical onshore application is more likely to be between 2-4 diameters apart in a row, with rows 7-13 diameters apart front to back. - "Oh, and turbines are placed seven diameters apart. That’s it, no CFD." Wrong. But CFD is generally computationally complex, so we usually use models with reduced fluid dynamics equations to make it possible to iterate quickly. See previous comment about wake models. - "In some cases wind farm automation can cost as much as the turbines, themselves." I'd like to see these magical cases. A typical 2 MW turbine costs $2 million to purchase, and about $3-3.5 million total as part of an overall project of 50 turbines. SCADA is a minor fraction of this, as is operations. - "Shorter blades are stronger than longer blades, so the Lipps turbines can operate in faster winds." This is a non-issue. There are very few sites in the world that require even the highest wind speed turbine designs; most of the world is less windy, and the majority of sites benefit from using turbines designed for lower winds. - "Use permanent magnet generators and the turbines could be allowed to run 24/7 in any wind with no computer control required at all, leading to more production at even lower cost." Computer control of turbines is a non-issue, and the cost is minimal relative to the raw materials cost of the machines. - "This is because they use alternators that consumer electrical power to energize their windings so there is no point in turning-on the alternator (energizing those windings) until there’s enough wind to generate a net positive amount of electricity." This is only a little bit correct, and mostly not. Wind turbines by design generally need to be connected to the grid to run, but winding energization is not why they don't start generating until there is enough wind. Turbines are generally on all the time, and typically consume anywhere from 10 to 50 kW at idle. And I don't know why he's using the term "alternators" to describe the turbine generators. The most common generator type is a doubly-fed induction generator, but squirrel cage induction generators, permanent magnet generators, and synchronous generators are often used. Usually turbines are connected to the grid through power converters which allow them to run at various speeds while remaining electrically synchronized with the grid. - "Remember the diameters are smaller so instead of hundreds of turbines we’re talking about thousands of turbines for the same wind farm. Imagine a field of mature dandelions." This is actually a problem. When you can get 100 MW with a 50% capacity factor by building 50 machines in one township in Nebraska, why would you want to build 1,000 machines instead? How is that less complex? - "Try breaking into the industrial wind power business without at least $1 billion in capital. It can’t be done. The incumbent companies like it that way, too." Manufacturing is capital intensive. News at 11. - "Lipps wind farms could be closer to cities and therefore have lower transmission losses, further increasing power output." Wind farm placement is about where the wind resource is. It's an economic decision. - "The result of all this not starting and then stopping is that throughout the year an average workload of 23 percent is reached by inland wind farms, 28 percent for coastal farms and 43 for off-shore." I have to assume his "average workload" here (a term I've never heard in the industry) is equivalent to capacity factor, which is the ratio of actual energy produced to the maximum possible. Most new projects in the windy areas of the US have predicted capacity factors of greater than 40 percent. High wind losses are typically very low, and online time is typically very high. - "China will build the heck out of those smaller blades." China is also building the heck out of the larger blades. China has more wind capacity installed than any other nation. - "And no insane cows, either. Cattle can’t be pastured under wind farms because the motion of the turbine blades and especially their sound drives cows crazy." Tell that to these cows https://www.flickr.com/photos/ashcreekphoto/7793429362 https://www.flickr.com/photos/ashcreekphoto/7793429362 (did he even do an image search before posting that? I've built wind projects on cattle ranches.) Why does this post use such an old, crappy US wind map? Why not the newer DOE wind maps available at http://apps2.eere.energy.gov/wind/windexchange/wind_maps.asp http://apps2.eere.energy.gov/wind/windexchange/wind_maps.asp I'm sure I could go on, but this is just a fundamentally misinformed article. It's trying to make an aerodynamic argument (which I am not qualified to judge) using a mess of bad or incorrect information.
coldcode 10y ago
The more worrying part of this is that you need 1H capital to even try to get into this business if all you do is build the monsters. So that means few competitors (or even one) which makes monopolist behavior and unimaginative thinking likely.
scblock 10y ago
This is only partially related to my other long post here, but it should be mentioned. This article appears to be largely about potential to disrupt the wind industry with outside the box thinking. But in the more than a decade I have been working in this industry the single most disruptive change in project performance was targeting low wind speeds rather than high, and accepting that turbines will have to shut down in higher winds. The main way this is achieved is to take a huge rotor and put it on a small generator. More energy is lost at high winds, but the ramp up from no generation to maximum is much faster. Since most projects spend the majority of their time along that ramp rather than at rated power this results in large gains in annual energy. This means that some sites once considered to be marginal to end up being good to very good. One area I've been working in saw a more than 25% increase in predicted energy for the same capital cost with the new turbine types.
- beat 10y ago
  Wind power is still largely a greenfield industry. There's no point in putting expensive (and risky) effort into suboptimal sites when so many optimal sites are still unexploited. Cringely's assumption that new designs aren't being tried because the industry is stupid is almost certainly wrong. More likely, they're still going after the low hanging fruit, and will start optimizing design for suboptimal locations once they've fully exploited the optimal ones. But there's a lot less profit in using more expensive turbines to harvest less wind.
  - scblock 10y ago
    There are a number of companies and people working on potentially innovative ideas, but it's not an easy thing. Serrated trailing edges and vortex generators are easy enough to test (reduced noise from one, increase energy from the other). Others such as shrouded turbines, or multi-segment blades are difficult. Another thing vendors are doing now is purposefully running generators beyond their design at higher wind speeds (getting 2.2 MW from a 2.0 MW generator, for example), provided that other operating parameters are measured to be within range. This is usually driven by cooling requirements.
neilk 10y ago
Erm, I don't know if I trust Cringely when it comes to this sort of thing. He sold a reality show to PBS, "Plane Crazy (1998)"[1] with the promise he could design and build a small plane in 30 days that was unlike any other that had ever been built.[2] His engineer just flat out refused to produce any plans for this design. He tried to make something like his plane happen anyway, going without sleep for weeks, and had a meltdown on camera. The show eventually had to be about him giving up on his cherished design and building a throwback to biplanes, with a family of artisans who are experienced in building them. I had the feeling that Cringely was trying to channel Steve Jobs and it didn't work out. (Note: Jobs drives other people to do impossible missions without sleep, not himself, and doesn't display his work until it's ready, giving the appearance of effortless superiority). Anyway as for this wind farm idea, the evidence of his friend's alternative propeller design is interesting. But let's also note that that this friend chose not to pursue wind farms, maybe for a reason. [1] http://www.pbs.org/cringely/pulpit/1998/pulpit_19980724_000578.html http://www.pbs.org/cringely/pulpit/1998/pulpit_19980724_0005... [2] EDIT: I am not an aviation person, and my memory of this is poor, but from Googling I see apparently he wanted to make it out of unusual materials, have foldable wings, and put the engine behind the pilot. I have a memory of his design requiring the pilot to straddle the drive train to a front-mounted propeller. I don't know how problematic that is, but I remember it as being presented as a major problem. EDIT 2: To be honest I feel a bit bad now about this being a top-voted comment, as Cringely learned a lesson on camera that many startup people learn behind closed doors – confidence is great, but trying to innovate in too many directions at once will kill you. Maybe that means that he is more cautious now, so perhaps he's really sure this thing will work. On the other hand, it was the first thing I thought of, that maybe he doesn't have a great track record with aviation iconoclasm.
- rhaps0dy 10y ago
  > His engineer just flat out refused to produce any plans for this design Do you know why? I'm thinking maybe it's because it was dangerous for the pilot?
  - neilk 10y ago
    Sorry, I'm relying on my memory of a show I saw like 20 years ago. I know nothing special about aviation. But I just found a contemporary thread about it here from other homebuilt aviation enthusiasts. https://groups.google.com/forum/#!topic/rec.aviation.homebuilt/0uMOHlci8DQ https://groups.google.com/forum/#!topic/rec.aviation.homebui...
trhway 10y ago
The less number of blades - the higher efficiency, should be an odd number to avoid standing wave and symmetric too. Thus 3.
mrfusion 10y ago
Why can't the blades be staggered so they don't follow in each other's wake?
stcredzero 10y ago
This comment on the post is pure gold! Fascinating! It’s not about asking questions, it’s about asking the right questions! The first framing question is efficiency from blade to outlet, but it’s really about effciency from capital markets to factory floor to farm to outlet. That should become a mantra. It's about efficiency from capital markets to revenue per customer.
yason 10y ago
I don't know much about wind turbines and the behaviour of moving volumes of air with regard to airfoils but there's one point I picked off of the article. If I were to put my money either in the most advanced big-farm wind high-tech or in something that is decentralized, mass-produced, and well-abused by all kinds of groups of people, it would be the latter. The article mentions that one billion is not enough to enter the game. That surely excludes a lot of the smartest and brightest people who might come up with new innovations and the billion-scale investments also seek conservative returns, further culling new ideas.
Animats 10y ago
In the 1970s and 1980s there was much more variety in wind turbine design. There were two bladed machines, multi-blade ducted turbines, Darrieus rotors, and other exotic technologies. Outputs were in the 50KW range. Pacheco Pass in Northern California had examples of most of those. Some didn't work too well. Loss of blade accidents were common in the early days, with blades thrown considerable distances. The three-bladed machines won out commercially. Machine size went up because output vs cost decreases with size, at least up to 1-2 MW. Lots of little machines were a pain to install and maintain. Wind generators used to be AC generators synchronous to the grid. But with higher power semiconductors available, putting a big AC-DC-AC converter on the output to sync it to the grid is becoming popular.[1][2] This allows generating some power during low-wind conditions, and provides much more adaptability to wind gusts. When the wind speed changes, the blade pitch is adjusted to compensate, but on big turbines, this takes tens of seconds. Being able to adjust electrically in milliseconds avoids power grid transients. The push for permanent magnet motors in wind turbines is more about converting to direct drive and getting rid of the gearbox. Wind turbine gearboxes are a huge pain, wearing badly for reasons that were only understood in the last few years. [1] http://www.theswitch.com/wind-power/ http://www.theswitch.com/wind-power/ [2] http://new.abb.com/motors-generators/generators/generators-for-wind-turbines/doubly-fed-generators http://new.abb.com/motors-generators/generators/generators-f...
- Ericson2314 10y ago
  Pacheco Pass or Altamont Pass?
  - Animats 10y ago
    Right, Altamont Pass. The Veg-E-Matic for birds - a long, narrow valley filled with row after row of medium-sized wind turbines.
    - Ericson2314 10y ago
      Indeed it is.
eonw 10y ago
this is one of the best articles i have read recently. I too am a big fan of always asking why and trying to buck the trend of "thats just the way it is".
xutopia 10y ago
In some parts of the world they use 2 blades so they can lay down the system when the wind is too high (think tornado/hurricane season)

425 points by rfreytag 10y ago

Jedd 10y ago

Looks like a fine opportunity to ask - whatever happened to vertical axis wind turbines? They sounded like they had a bunch of advantages, not least a much higher tolerance for extreme wind conditions, less stress on long (suspended) blades, possibly less gearing issues in translating motion back to the ground - but presumably they had / still have distinct disadvantages?

phonon 10y ago
http://www.forbes.com/sites/jeffmcmahon/2016/04/29/stanford-small-wind-arrays-can-outperform-conventional-wind-farms-with-no-bird-kill/#293984cd7a9c http://www.forbes.com/sites/jeffmcmahon/2016/04/29/stanford-...
knodi123 10y ago
Even sexier (and less field-tested) than vertical turbines are windbelts. https://en.wikipedia.org/wiki/Windbelt https://en.wikipedia.org/wiki/Windbelt > Prototypes of the device are claimed to be 10 - 30 times more efficient than small wind turbines. One prototype has powered two LEDs, a radio, and a clock (separately) using wind generated from a household fan. The cost of the materials was well under US$10. $2–$5 for 40 mW is a cost of $50–$125 per watt.
pjc50 10y ago
Scaling issues, I think - they need to be supported at the top as well, and they're dependent on how much weight and wind force the bearings can take. http://www.windpowerengineering.com/design/vertical-axis-wind-turbines/ http://www.windpowerengineering.com/design/vertical-axis-win...
olau 10y ago
I think the reason plainly is that they are not competitive, perhaps because their advantages aren't important enough disadvantages for horizontal axis turbines. Wikipedia has a short section: https://en.wikipedia.org/wiki/Vertical_axis_wind_turbine#Disadvantages_of_vertical_axis_wind_turbines https://en.wikipedia.org/wiki/Vertical_axis_wind_turbine#Dis... I think people tend to forget that the big wind turbine manufacturers today started out small, experimenting with various designs before they settled on the three-bladed model. At the moment there's a lot of accumulated research and infrastructure present that allows them to erect giant 3-6-8 MW turbines that can take the hammering of the weather for > 20 years. Competing against this is really, really hard, you really have to a big advantage in your favor and perhaps also decades of research and development.

Houshalter 10y ago

Slightly relevant, here's a really weird wind turbine designed by a computer: http://m.youtube.com/watch?v=YZUNRmwoijw http://m.youtube.com/watch?v=YZUNRmwoijw

nkoren 10y ago
That was really fascinating -- thank you!
NicoJuicy 10y ago
The note on the video is quite funny: Note: I have since discovered I used the wrong viscosity for air on this experiment, so the results aren't valid for use on the earth. (Maybe Jupiter.)
- 6stringmerc 10y ago
  While I missed that, I'd have to agree that note is quite amusing. Oops, wrong planet.
- Houshalter 10y ago
  Ah, well. It's still interesting. The design of the turbine is really crazy and not what I would have expected in any environment. So I suspect if he corrected the parameters, it would still come up with a crazy and clever design for Earth use, that humans wouldn't think of.
whichfawkes 10y ago
I have to wonder if there are some imperfections in the simulation which cause it to evolve toward a blade that's optimal for the sim, but not as good in real life. He talks about 20 minute tests, and then later uses a 12 hour test and gets a significantly different power number. I wonder how differently the evolution might proceed if he just had more power to run the full tests on each generation.
logfromblammo 10y ago
That was an interesting video, but it was restricted to a 2D simulation on a vertical-axis turbine with exactly 3 blades. A more intricate genetic algorithm that runs a 3D wind model and accounts for the cost of manufacture would almost certainly produce some more novel solutions that completely demolish our preconceived notions of what turbines should look like, just like the "jellyfish" cross-section. But it would also probably not effectively scale beyond the model size. Genetic algorithms almost always exploit any previously hidden little flaws you may have in your model simulator, such as the rounding error on floating point numbers at the limit of their precision, or even the way in which you represent airflows. They evolve to maximize performance in the modeling environment, so if your model is not perfect, the solution does not always translate to reality. As such, you always have to test the evolved solutions in the real world before you can say they are better than the designed solution.

justinph 10y ago

Small turbines do exist. One was installed on This Old House recently: http://www.thisoldhouse.com/toh/tv/ask-toh/video/0,,20961006,00.html http://www.thisoldhouse.com/toh/tv/ask-toh/video/0,,20961006... (jump to about 15:00) But, it does have three blades.

Aelinsaar 10y ago

I like the idea of wind turbines, but in practice I think PV is the way to go (long term). I realize that for now it's a blend of technologies, but PV doesn't kill millions of birds and bats. I grant you, it's better than burning coal, but still we can do better eventually.

ams6110 10y ago
PV can kill or destroy habitat of other creatures, though this is probably almost entirely avoided in certain circumstances (rooftop installations, for one) where the damage has already been done.
- Aelinsaar 10y ago
  Everything we do, does that. Fortunately the places we put PV tend not to be virgin forests or other places we haven't already destroyed for our benefit.
  - TillE 10y ago
    Wind turbines aren't built in virgin forests either. They're generally in farmland, which is pretty well ecologically destroyed already.
    - JoeAltmaier 10y ago
      In California they seem to go just about anywhere. Sure not virgin forest, but maybe native savannah? http://www.energy.ca.gov/wind/overview.html http://www.energy.ca.gov/wind/overview.html
    - Aelinsaar 10y ago
      I never claimed that they were, and bats and birds are prevalent in farmland.
Houshalter 10y ago
House cats kill 1,000 times more birds than wind turbines. Even cell towers kill more. It's nonissue.

_Codemonkeyism 10y ago

As a kid I always found it interesting that (some?) Spitfire had 4 blade propellors and the main adversary, the [Edit] Bf109 had 3 [1] and wondered, shouldn't there be an optimum? [1] Not sure both changed the number of blades during WWII.

rusanu 10y ago
You mean Bf109 I think. The P-51 started 3 and then moved to 4. Ditto P-47. FW-190 and F6F stayed at 3 whole time afaik. Tempest started with 4. So it varied. But there is a trend of the early (1939) designs to have 3 and the late (1944) designs to have 4. I guess available power from the engine plays a big role, as engines got more powerful they started fitting 4 blades. Using the extra power on 3 blades would require longer blades (which is problematic), spinning them faster (again, problematic as tips reach sound barrier) or increasing the pitch (I guess there are aerodynamic limits for that).
- _Codemonkeyism 10y ago
  Thanks, how emberrassing, yes Bf109. "I guess available power from the engine plays a big role, as engines got more powerful they started fitting 4 blades." Good one.
- 6stringmerc 10y ago
  This is a really cool write-up. Another thing that might be of interest was the performance of the aircraft. There's a guy in Texas with 6 non-flying 109s, a couple P-51s, and some other stuff for sale as a lot. He's a former stunt pilot, flew in the movie 'Battle of Britain' and several others. In his words, the 109 handled much better at the limit than the P-51. The P-51 could dive and go very fast, but with poor control. In his opinion the 109 was the superior aircraft. Not sure if it relates at all to the prop discussion, but maybe in the grand scheme of engineering? Those warbirds are fascinating pieces of hardware to me.
arprocter 10y ago
Interestingly the prototype Bf109 had two blades. I wonder if it was a carry over from the first world war when guns fired through the propeller, so the more blades the more chance of shooting it off? (There were systems which regulated when the gun would fire to prevent this happening)

mapt 10y ago

* I don't understand his explanation of starting torque. You can jump-start that problem by other means in the alternator. Torque and power should be decoupled anyway by blade pitch. * There is such a huge difference between a 12m blade and a 60m blade that I don't see how the comparison is at all relevant. We played with smaller turbines for decades before we reached this sort of price efficiency. * Betz' law explicitly disavows picking a number of blades: "Assumptions: 1. The rotor does not possess a hub and is ideal, with an infinite number of blades which have no drag. Any resulting drag would only lower this idealized value. ..." * Betz' law is a three-dimensional consequence of convervation laws, not an observation about turbulent blade interactions. "Consider that if all of the energy coming from wind movement through a turbine was extracted as useful energy the wind speed afterwards would drop to zero. If the wind stopped moving at the exit of the turbine, then no more fresh wind could get in - it would be blocked. In order to keep the wind moving through the turbine there has to be some wind movement, however small, on the other side with a wind speed greater than zero. Betz' law shows that as air flows through a certain area, and when it slows from losing energy to extraction from a turbine, it must spread out to a wider area. As a result geometry limits any turbine efficiency to 59.3%." * We already have a good idea what a moderate redesign of the fundamentals of a wind turbine looks like; It points downwind, it's huge like the existing turbines, and its two blades bend. They just need to solve the tower strike problem. https://www.technologyreview.com/s/401583/wind-power-for-pennies/ https://www.technologyreview.com/s/401583/wind-power-for-pen... https://www.technologyreview.com/s/528581/two-bladed-wind-turbines-make-a-comeback/ https://www.technologyreview.com/s/528581/two-bladed-wind-tu...

brandmeyer 10y ago
> I don't understand his explanation of starting torque That's because Cringley doesn't, either. The starting torque is entirely provided by the wind, not the grid.
- beat 10y ago
  I think what he's talking about (not bothering to re-read) is the power required to magnetize the alternator components in the first place, so the alternator works at all. They use electromagnets rather than permanent magnets, because electromagnets are much cheaper, especially at that size. This is a fixed power requirement, so if the alternator can't generate more than that fixed power need to operate, there's no point in running.

dzdt 10y ago

We all love the story about the clever little guy who thinks outside of the box taking down the big giant corporation who does things the way they have always been done. Cringely trys to tell this as such a story, or could be, or could have been. But there is really no evidence backing it, just his desire to tell a good story.

calinet6 10y ago

This is a classic example of sub-optimization (and even if it's hand-wavey pseudo-science and may be wrong, the general concept is still interesting). Each individual wind turbine is optimized to be the "most efficient" it can possibly be. But not in the context of the environment, which requires complex control systems and methods to reduce damage in non-optimal conditions. And not if you take cost and efficiency of the whole system into account; where four times as many small turbines with less complexity run more often and produce more overall output. But hey, each wind turbine is "optimal." Interesting. Most complex systems have this property. Even (especially?) your business.

nkoren 10y ago
This kind of thinking contributed to American rocketry being trapped in a local maxima for decades. There are many reasons it became trapped, but one of the primary reasons was that rocket scientists would insist on optimising rocket engines at the expense of every other aspect of the vehicle. "The logic of rocket equation is brutal and inexorable", the NASA rocket scientists would say. "As the performance of the rocket engine decreases linearly, the propellent requirements increases exponentially. Therefore it is imperative to have the highest-possible performance from your rocket engines. The combustion of liquid hydrogen / oxygen is the highest-efficiency chemical reaction, and therefore liquid hydrogen is the only propellant we will consider using for our engines." All of this was correct, but also wrong. It was wrong in a whole-systems context, because: A.) Liquid hydrogen is much lower-density than traditional rocket fuels like Kerosene, requiring far larger and heavier structures to carry the same amount of energy, and larger and heavier engines and plumbing and everything else -- and the structural mass of a rocket matters. B.) Liquid hydrogen will boil off and leak through anything, requiring massive amounts of insulation (again, adding weight), and far stricter operational protocols around the fueled vehicle. C.) Liquid hydrogen is so cold that it will embrittle and shatter ordinary metals and requires much more exotic and expensive metallurgy. and finally, D.) The alternative, kerosene, gives you less efficient engines but also much lighter-weight vehicles -- and sure, per that inexorable logic of the rocket equation, you need to use more fuel for the same amount of payload, but kerosene is cheaper than milk so who fucking cares? Anyhow, the upshot of this is that US rocket scientists spent literally tens of billions of dollars developing hyper-locally-optimised rocketry schemes, most of which failed outright. For the remainder, for every dollar of kerosene they didn't have to buy, they probably spent upwards of $1000 on exotic aerospace hardware. Finally, they gave up and just bought kerosene-based engines from the Russians. So then there's Elon Musk. And of course there's a ton of brilliant rocket science in the Falcon, but much of the reason for SpaceX's success is because it doesn't optimise solely on the rocket science. They optimise for cost as a whole, and consider factors like design, manufacturing, operations, reusability, etc. to be relevant to the question of cost. For example: the Falcon 9 would undoubtedly be more efficient if it had a hydrogen-based upper stage. But doing that would cause it to lose most of its commonality with the lower stage, requiring an entirely new design, manufacturing, and operations workforce. Which would cost several orders of magnitude more than the extra kerosene required to fly a "sub-optimal" rocket. The reason they've already cut the price of launch by about 80% vs. (say) the Space Shuttle is because they optimised the whole system, keeping the unique part count and operational complexity as low as possible. I still sometimes hear old-school rocket scientists grumble about how the Falcon is a less optimised vehicle than the Shuttle, though. They just don't get it. Never will. Anyhow, that was a tangent. Fascinating to think that wind turbines might be amenable to a similar class of disruption.

_Codemonkeyism 10y ago

I'm interested in the results when Cringely builds his farm. For example support costs from thousands instead of hundreds of turbines. How many on one pole are best. Also building costs over time e.g. when costs go down due to robots planting poles etc. which favors farms with more poles above those with fewer poles.

tantalor 10y ago

The 2016 tag is not really necessary; this was published today.

nabla9 10y ago

One graph is worth thousand words. Rotor power coefficient vs. tip-speed ratio. http://i.imgur.com/PONHerZ.jpg http://i.imgur.com/PONHerZ.jpg

55acdda48ab5 10y ago
You have a computer with servos and winches fly parafoil kites to generate power from wind. This is definitely the theoretically optimal answer. It's also very low capital intensity. https://www.youtube.com/watch?v=j-qUaO-xzrY https://www.youtube.com/watch?v=j-qUaO-xzrY
- jessaustin 10y ago
  Lots of omitted details there. A kite can pull its tether from one location to another location of lower potential energy, but how does it get back to the higher-energy location? If we're talking about a circular train on a circular track, half of the kites must continually have either a lower-drag configuration or a lower-wind altitude. That's plausible, but that's a lot of additional mechanisms, plus a lot of "cancelled-out" wind traction, plus a lot of friction as the train rolls around the track. Will there be power left over for electricity generation? Probably, but it isn't clear that it will be worth all the trouble. If a reasonable prototype exists, it should have been in the video.

tantalor 10y ago

You mean like one of these? http://www.windpowerninja.com/wp-content/uploads/2009/02/old_wind_turbines.jpg http://www.windpowerninja.com/wp-content/uploads/2009/02/old...

vanderZwan 10y ago

Relevant Low-Tech Magazine entries on wind-power, and small windmills: Urban windmills harm the environment [0] > A small windmill on your roof or in the garden is an attractive idea. Unfortunately, micro wind turbines deliver hardly enough energy to power a light bulb. Their financial payback time is much longer than their life expectancy and in urban areas they will not even deliver as much energy as was needed to produce them. Sad, but true. Small windmills put to the test [1] > A real-world test performed by the Dutch province of Zeeland (a very windy place) confirms our earlier analysis that small windmills are a fundamentally flawed technology (Note that the picture shows that almost all windmills tested had three blades) Wind powered factories: history (and future) of industrial windmills [2] > In the 1930s and 1940s, decades after steam engines had made wind power obsolete, Dutch researchers obstinately kept improving the – already very sophisticated – traditional windmill. The results were spectacular, and there is no doubt that today an army of ecogeeks could improve them even further. Would it make sense to revive the industrial windmill and again convert kinetic energy directly into mechanical energy? Unlike this story, which certainly sounds interesting but shares no real data to back it up, Kris de Decker thoroughly digs through sources to write articles backed up by available data as best as possible. [0] http://www.lowtechmagazine.com/2008/09/urban-windmills.html http://www.lowtechmagazine.com/2008/09/urban-windmills.html [1] http://www.lowtechmagazine.com/2009/04/small-windmills-test-results.html http://www.lowtechmagazine.com/2009/04/small-windmills-test-... [2] http://www.lowtechmagazine.com/2009/10/history-of-industrial-windmills.html http://www.lowtechmagazine.com/2009/10/history-of-industrial...

toolslive 10y ago

"why... very often the turbines aren’t turning at all?" Someone told me that demand varies and it's easier to shut down a windmill than a nuclear reactor.

tlb 10y ago

More blades and closer spacing between windmills optimizes power / land area. But what matters is power / capital cost.

mark-r 10y ago
He tried to touch on that - making the blades shorter but in greater quantity will drive efficiencies of scale in manufacturing and shipping. And smaller turbines lead to cheaper towers. Hard to know if he's right without crunching actual numbers though.
CydeWeys 10y ago
With land area being one factor that goes into capital cost.

Cerium 10y ago

Three blades is the smallest number that reduces the vibrations due to the blades crossing the support structure. When a blade crosses the support its applied force is reduced because the wind is slower around the support. This reduction in forces creates a yawing torque that can lead to unwanted vibrations. Much of the structural stiffness and bearing requirements are related to these effects. Three blades minimizes the effect because when one blade crosses the support the other two blades are out in a Y shape, shortening the force differential when compared to two blades.

mark-r 10y ago
There's a question then, why are support towers solid? Maybe they should be made more like the Eiffel Tower?
- elcapitan 10y ago
  Probably to be more durable, because of the closed surface - the Eiffel tower has very high maintenance costs as it has to be steadily re-painted. It would probably not be necessary that much for modern steels, but unlike wind turbines the Eiffel tower also does not stand close to the coast or directly in the sea, where highly corrosive winds blow.
  - Cerium 10y ago
    Additionally the enclosed space is useful. Inside the wind tower is a lot of equipment. There is the electronics for converting the power and monitoring the wind tower. There is a lift for ease of access to the nacelle. Current wind towers are 80m tall, next generation wind towers are more than 100m to access more reliable higher strength winds.
    - brandmeyer 10y ago
      I don't think this is a strong driver. GE 1.5 MW turbines only have a relatively small space near the base of the tower that is consumed by power electronics and control systems. Siemens has largely gone to a system where everything is in the nacelle. This way it makes it easier to completely test and connect the power electronics and control, since more of the work is done at the factory instead of in the field. Labor and equipment is much more expensive in the field than in the factory.

at-fates-hands 10y ago

Here's a much better Wind Resource Map than the one in the article: http://www.tindallcorp.com/site/user/images/USA_Wind_Map_for_Tindall_Transp_2.jpg http://www.tindallcorp.com/site/user/images/USA_Wind_Map_for...

scblock 10y ago
http://apps2.eere.energy.gov/wind/windexchange/wind_maps.asp http://apps2.eere.energy.gov/wind/windexchange/wind_maps.asp has this map plus state by state maps available for download as relatively high resolution PDFs.

manmal 10y ago

It seems Steve Jobs was inspired by Socrates: https://en.m.wikipedia.org/wiki/Socratic_method https://en.m.wikipedia.org/wiki/Socratic_method

elcapitan 10y ago

I would have guessed that it's a trade-off between efficiency and mimizing public outrage in densely populated areas (yes, outside the US that can be an issue). Three blades, when the turbine is not working, block less from the view than a large number of blades (which converge towards giant white surfaces).

lorenzfx 10y ago

I'm not saying he is wrong, but he makes some bold claims without giving any proof. Some examples: > Twelve blades is a nice number. Why twelve? Why not 50, it's a nice number as well. > Lipps turbines can operate in faster winds [...] turbines could be allowed to run 24/7 in any wind with no computer So even in the strongest winds turbines with 40 feet blades do not need to be stopped? > using permanent magnet generators instead of alternators, but those are more expensive > Use permanent magnet generators leading to [...] even lower cost. Which is it now? > what matters isn’t power efficiency per turbine so much as power production per acre of wind farm. Isn't it rather electricity production efficiency in terms of invested capital?

amelius 10y ago
I get the feeling that the best answer to the question is that empirical testing (perhaps by simulation) points out that three is the optimal number of blades. This leads me to the question: is it possible to determine a good rotor design by using optimization techniques such as simulated annealing or genetic programming? Or are the simulations too costly?
- Bartweiss 10y ago
  I can help with this a bit. The simulations are quite difficult - flow simulation is well-established, but it's a big step from that wind farms. You need to simulate many turbines interacting at a specific site, under a variety of conditions. That's not the problem with modeling single turbines, though. Rotor design is hard to simulate productively for the same reason that Cringely's analysis is flawed: many of the biggest factors are unrelated to everyday running. - Even blade counts create resonance patterns that stress your tower. - High solidity designs suffer more stress in storms (even while stopped), so they break more - Noise interferes with putting rotors near houses or over pastures - Storage is difficult and consistency is valuable, so expanding the operating range up to high winds is less useful than expanding it down to low winds And so on. If you model pure efficiency, the sims are pretty easy. If you model real value, you either can't do it, or you get a search space so jagged that finding maxima is hopeless.

scblock 10y ago

There is a lot of bad information here, and it appears there are others in these who are also better informed than the author. Let me just hit up a couple of points that are fundamentally wrong, though. - "Conventional wisdom says wind farms should have their turbines placed in such a way that they don’t interfere with each other, the fear being that placing one turbine too closely in the shadow of another will reduce the efficiency of the showed turbine." True, and this is why we have wake models based to predict the losses from other turbines and optimize placement. - "The rule of thumb, then, is that turbines be placed no closer than seven diameters apart. Keep that number in mind." Not true. You may find that a 7x7 array is relatively common in offshore applications, but a typical onshore application is more likely to be between 2-4 diameters apart in a row, with rows 7-13 diameters apart front to back. - "Oh, and turbines are placed seven diameters apart. That’s it, no CFD." Wrong. But CFD is generally computationally complex, so we usually use models with reduced fluid dynamics equations to make it possible to iterate quickly. See previous comment about wake models. - "In some cases wind farm automation can cost as much as the turbines, themselves." I'd like to see these magical cases. A typical 2 MW turbine costs $2 million to purchase, and about $3-3.5 million total as part of an overall project of 50 turbines. SCADA is a minor fraction of this, as is operations. - "Shorter blades are stronger than longer blades, so the Lipps turbines can operate in faster winds." This is a non-issue. There are very few sites in the world that require even the highest wind speed turbine designs; most of the world is less windy, and the majority of sites benefit from using turbines designed for lower winds. - "Use permanent magnet generators and the turbines could be allowed to run 24/7 in any wind with no computer control required at all, leading to more production at even lower cost." Computer control of turbines is a non-issue, and the cost is minimal relative to the raw materials cost of the machines. - "This is because they use alternators that consumer electrical power to energize their windings so there is no point in turning-on the alternator (energizing those windings) until there’s enough wind to generate a net positive amount of electricity." This is only a little bit correct, and mostly not. Wind turbines by design generally need to be connected to the grid to run, but winding energization is not why they don't start generating until there is enough wind. Turbines are generally on all the time, and typically consume anywhere from 10 to 50 kW at idle. And I don't know why he's using the term "alternators" to describe the turbine generators. The most common generator type is a doubly-fed induction generator, but squirrel cage induction generators, permanent magnet generators, and synchronous generators are often used. Usually turbines are connected to the grid through power converters which allow them to run at various speeds while remaining electrically synchronized with the grid. - "Remember the diameters are smaller so instead of hundreds of turbines we’re talking about thousands of turbines for the same wind farm. Imagine a field of mature dandelions." This is actually a problem. When you can get 100 MW with a 50% capacity factor by building 50 machines in one township in Nebraska, why would you want to build 1,000 machines instead? How is that less complex? - "Try breaking into the industrial wind power business without at least $1 billion in capital. It can’t be done. The incumbent companies like it that way, too." Manufacturing is capital intensive. News at 11. - "Lipps wind farms could be closer to cities and therefore have lower transmission losses, further increasing power output." Wind farm placement is about where the wind resource is. It's an economic decision. - "The result of all this not starting and then stopping is that throughout the year an average workload of 23 percent is reached by inland wind farms, 28 percent for coastal farms and 43 for off-shore." I have to assume his "average workload" here (a term I've never heard in the industry) is equivalent to capacity factor, which is the ratio of actual energy produced to the maximum possible. Most new projects in the windy areas of the US have predicted capacity factors of greater than 40 percent. High wind losses are typically very low, and online time is typically very high. - "China will build the heck out of those smaller blades." China is also building the heck out of the larger blades. China has more wind capacity installed than any other nation. - "And no insane cows, either. Cattle can’t be pastured under wind farms because the motion of the turbine blades and especially their sound drives cows crazy." Tell that to these cows https://www.flickr.com/photos/ashcreekphoto/7793429362 https://www.flickr.com/photos/ashcreekphoto/7793429362 (did he even do an image search before posting that? I've built wind projects on cattle ranches.) Why does this post use such an old, crappy US wind map? Why not the newer DOE wind maps available at http://apps2.eere.energy.gov/wind/windexchange/wind_maps.asp http://apps2.eere.energy.gov/wind/windexchange/wind_maps.asp I'm sure I could go on, but this is just a fundamentally misinformed article. It's trying to make an aerodynamic argument (which I am not qualified to judge) using a mess of bad or incorrect information.

coldcode 10y ago

The more worrying part of this is that you need 1H capital to even try to get into this business if all you do is build the monsters. So that means few competitors (or even one) which makes monopolist behavior and unimaginative thinking likely.

scblock 10y ago

This is only partially related to my other long post here, but it should be mentioned. This article appears to be largely about potential to disrupt the wind industry with outside the box thinking. But in the more than a decade I have been working in this industry the single most disruptive change in project performance was targeting low wind speeds rather than high, and accepting that turbines will have to shut down in higher winds. The main way this is achieved is to take a huge rotor and put it on a small generator. More energy is lost at high winds, but the ramp up from no generation to maximum is much faster. Since most projects spend the majority of their time along that ramp rather than at rated power this results in large gains in annual energy. This means that some sites once considered to be marginal to end up being good to very good. One area I've been working in saw a more than 25% increase in predicted energy for the same capital cost with the new turbine types.

beat 10y ago
Wind power is still largely a greenfield industry. There's no point in putting expensive (and risky) effort into suboptimal sites when so many optimal sites are still unexploited. Cringely's assumption that new designs aren't being tried because the industry is stupid is almost certainly wrong. More likely, they're still going after the low hanging fruit, and will start optimizing design for suboptimal locations once they've fully exploited the optimal ones. But there's a lot less profit in using more expensive turbines to harvest less wind.
- scblock 10y ago
  There are a number of companies and people working on potentially innovative ideas, but it's not an easy thing. Serrated trailing edges and vortex generators are easy enough to test (reduced noise from one, increase energy from the other). Others such as shrouded turbines, or multi-segment blades are difficult. Another thing vendors are doing now is purposefully running generators beyond their design at higher wind speeds (getting 2.2 MW from a 2.0 MW generator, for example), provided that other operating parameters are measured to be within range. This is usually driven by cooling requirements.

neilk 10y ago

Erm, I don't know if I trust Cringely when it comes to this sort of thing. He sold a reality show to PBS, "Plane Crazy (1998)"[1] with the promise he could design and build a small plane in 30 days that was unlike any other that had ever been built.[2] His engineer just flat out refused to produce any plans for this design. He tried to make something like his plane happen anyway, going without sleep for weeks, and had a meltdown on camera. The show eventually had to be about him giving up on his cherished design and building a throwback to biplanes, with a family of artisans who are experienced in building them. I had the feeling that Cringely was trying to channel Steve Jobs and it didn't work out. (Note: Jobs drives other people to do impossible missions without sleep, not himself, and doesn't display his work until it's ready, giving the appearance of effortless superiority). Anyway as for this wind farm idea, the evidence of his friend's alternative propeller design is interesting. But let's also note that that this friend chose not to pursue wind farms, maybe for a reason. [1] http://www.pbs.org/cringely/pulpit/1998/pulpit_19980724_000578.html http://www.pbs.org/cringely/pulpit/1998/pulpit_19980724_0005... [2] EDIT: I am not an aviation person, and my memory of this is poor, but from Googling I see apparently he wanted to make it out of unusual materials, have foldable wings, and put the engine behind the pilot. I have a memory of his design requiring the pilot to straddle the drive train to a front-mounted propeller. I don't know how problematic that is, but I remember it as being presented as a major problem. EDIT 2: To be honest I feel a bit bad now about this being a top-voted comment, as Cringely learned a lesson on camera that many startup people learn behind closed doors – confidence is great, but trying to innovate in too many directions at once will kill you. Maybe that means that he is more cautious now, so perhaps he's really sure this thing will work. On the other hand, it was the first thing I thought of, that maybe he doesn't have a great track record with aviation iconoclasm.

rhaps0dy 10y ago
> His engineer just flat out refused to produce any plans for this design Do you know why? I'm thinking maybe it's because it was dangerous for the pilot?
- neilk 10y ago
  Sorry, I'm relying on my memory of a show I saw like 20 years ago. I know nothing special about aviation. But I just found a contemporary thread about it here from other homebuilt aviation enthusiasts. https://groups.google.com/forum/#!topic/rec.aviation.homebuilt/0uMOHlci8DQ https://groups.google.com/forum/#!topic/rec.aviation.homebui...

trhway 10y ago

The less number of blades - the higher efficiency, should be an odd number to avoid standing wave and symmetric too. Thus 3.

mrfusion 10y ago

Why can't the blades be staggered so they don't follow in each other's wake?

stcredzero 10y ago

This comment on the post is pure gold! Fascinating! It’s not about asking questions, it’s about asking the right questions! The first framing question is efficiency from blade to outlet, but it’s really about effciency from capital markets to factory floor to farm to outlet. That should become a mantra. It's about efficiency from capital markets to revenue per customer.

yason 10y ago

I don't know much about wind turbines and the behaviour of moving volumes of air with regard to airfoils but there's one point I picked off of the article. If I were to put my money either in the most advanced big-farm wind high-tech or in something that is decentralized, mass-produced, and well-abused by all kinds of groups of people, it would be the latter. The article mentions that one billion is not enough to enter the game. That surely excludes a lot of the smartest and brightest people who might come up with new innovations and the billion-scale investments also seek conservative returns, further culling new ideas.

Animats 10y ago

In the 1970s and 1980s there was much more variety in wind turbine design. There were two bladed machines, multi-blade ducted turbines, Darrieus rotors, and other exotic technologies. Outputs were in the 50KW range. Pacheco Pass in Northern California had examples of most of those. Some didn't work too well. Loss of blade accidents were common in the early days, with blades thrown considerable distances. The three-bladed machines won out commercially. Machine size went up because output vs cost decreases with size, at least up to 1-2 MW. Lots of little machines were a pain to install and maintain. Wind generators used to be AC generators synchronous to the grid. But with higher power semiconductors available, putting a big AC-DC-AC converter on the output to sync it to the grid is becoming popular.[1][2] This allows generating some power during low-wind conditions, and provides much more adaptability to wind gusts. When the wind speed changes, the blade pitch is adjusted to compensate, but on big turbines, this takes tens of seconds. Being able to adjust electrically in milliseconds avoids power grid transients. The push for permanent magnet motors in wind turbines is more about converting to direct drive and getting rid of the gearbox. Wind turbine gearboxes are a huge pain, wearing badly for reasons that were only understood in the last few years. [1] http://www.theswitch.com/wind-power/ http://www.theswitch.com/wind-power/ [2] http://new.abb.com/motors-generators/generators/generators-for-wind-turbines/doubly-fed-generators http://new.abb.com/motors-generators/generators/generators-f...

Ericson2314 10y ago
Pacheco Pass or Altamont Pass?
- Animats 10y ago
  Right, Altamont Pass. The Veg-E-Matic for birds - a long, narrow valley filled with row after row of medium-sized wind turbines.
  - Ericson2314 10y ago
    Indeed it is.

eonw 10y ago

this is one of the best articles i have read recently. I too am a big fan of always asking why and trying to buck the trend of "thats just the way it is".

xutopia 10y ago

In some parts of the world they use 2 blades so they can lay down the system when the wind is too high (think tornado/hurricane season)