[HN Gopher] Vertical turbines are more efficient in large-scale ...
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Vertical turbines are more efficient in large-scale wind farms:
study
Author : kieranmaine
Score : 228 points
Date : 2021-04-28 12:07 UTC (10 hours ago)
(HTM) web link (eandt.theiet.org)
(TXT) w3m dump (eandt.theiet.org)
| kuprel wrote:
| The vertical axis turbine seems like it would scale in size
| better since the blades are spinning perpendicular to gravity
| jhayward wrote:
| They are subject to much higher dynamic forces, rapidly cycling
| between windward and lee side. Vertical turbines have worse
| wear characteristics, and it only gets worse as they get bigger
| and need more massive airfoils.
| exhilaration wrote:
| Wikipedia has pictures if like myself you have no idea what a
| vertical wind turbine looks like:
| https://en.m.wikipedia.org/wiki/Vertical_axis_wind_turbine
| mod wrote:
| So does the article.
| exhilaration wrote:
| You mean that header image? It's super small on my phone.
| sfblah wrote:
| Serious question. I live in a hilly area where there's a lot of
| wind much of the time. Is there some kind of residential analog
| to rooftop solar I could install? Or is the infrastructure just
| too expensive and complicated for a hobbyist?
| duffyjp wrote:
| You can buy something in the 1-3 KW range at Home Depot. I've
| seen one in person at an off-grid house and the owner couldn't
| understand why people even used solar. This was 15+ years ago
| though, so solar was MUCH more expensive than today while a
| turbine I'd imagine was about the same?
| sfblah wrote:
| I assume it'd be super expensive to grid tie it though,
| right? Sorry. I'm a total noob at this stuff.
| cr1895 wrote:
| Residential wind power? Wind energy is something that greatly
| benefits from scale: it's why the current and next generation
| of turbines have rotor diameters exceeding hundreds of meters.
| You'd probably be much better served by using solar panels.
| sfblah wrote:
| Sure. I just meant for fun or for a project. The biggest cost
| is probably grid tying, right?
| jillesvangurp wrote:
| The "Just have think" youtube channel did an episode on VAWTs
| just last week: https://www.youtube.com/watch?v=gcSnwW5v3f8
|
| Vawts are mechnically quite simple and compact. You can put them
| just about anywhere. And they can operate even at low wind
| speeds, regardless of where the wind comes from.
|
| There's a company experimenting with these along highways to get
| energy from vehicles driving by. The idea here is to simply wrap
| them around existing street lights. Not a lot of energy per
| turbine obviously but it adds up if you do it along a few miles
| of highway. And they are cheap, small, lightweight, and easy to
| install.
| A_No_Name_Mouse wrote:
| Nice video.
|
| > There's a company experimenting with these along highways to
| get energy from vehicles driving by.
|
| Those turbines will be slowing down the windflow, causing extra
| resistance for the traffic. The video doesn't mention that.
| Does anyone know if that effect is significant enough to reduce
| or even reverse the overall benefits (especially given the
| large % of ICE vehicles)?
| jeffreyrogers wrote:
| Has any research been done on the effects of wind farms on local
| wind/weather patterns? It seems like taking energy out of the
| wind in a relatively concentrated area would have downstream
| effects.
|
| (I'm not anti-wind energy, I'm just curious).
| achow wrote:
| Wind encounters far more resistance and obstacles when sweeping
| over land, ex. cities with buildings (tall and small) and other
| man made structures and then there are various natural ones -
| trees, hills, etc.
|
| Windmill probably is much less of a drag (pun!) as compared to
| above.
| lofi_lory wrote:
| I think offshore wind farms have been proposed to protect the
| US from hurricanes. So apparently they substantially decrease
| wind energy.
| cr1895 wrote:
| > offshore wind farms have been proposed to protect the US
| from hurricanes
|
| No, certainly not seriously.
| [deleted]
| Emma_Goldman wrote:
| There's some research that wind farms at scale have a small but
| non-negligible warming effect:
|
| https://www.sciencedirect.com/science/article/pii/S254243511...
| !
| baq wrote:
| i'm not aware of any comparisons but imagine a sparse forest.
| snowzach wrote:
| An interesting thought I've wondered about as well. I imagine
| the risks outweigh the benefits. I would think the same thing
| would happen when planting a forest (granted it taking much
| longer to produce an effect)
| mensetmanusman wrote:
| Yes,
|
| This is my favorite infrastructure project concept:
| https://www.scientificamerican.com/article/offshore-wind-far...
|
| help with hurricanes, direct DC to the entire country, tons of
| jobs for maintenance, etc
| Someone wrote:
| Yes, research has been done, if only because knowing about that
| is essential for figuring out at what distance from each other
| you should place your turbines.
|
| See for example https://energyfollower.com/wind-turbine-
| spacing, https://ep.liu.se/ecp/057/vol15/014/ecp57vol15_014.pdf
| mumblemumble wrote:
| Initial hot take: I'm not sure they're measuring efficiency in a
| way that's really meaningful to me?
|
| There are so many ways you could measure it. You could measure it
| as the % of wind energy passing through the turbine's plane that
| is taken out of the air, or the the efficiency of using that
| energy to get the rotor turning, or the efficiency of converting
| the rotor's kinetic energy to electrical energy.
|
| (edit: Or I could, y'know, do the sensible thing and check the
| article. They're measuring power output for a given wind speed
| and direction. Which I think means, in effect, all of that end-
| to-end.)
|
| But I'm not sure any of those are, in and of themselves, what
| really matters at scale. The more interesting questions, I'm
| guessing, are things like, "How much energy can we get out of a
| plot of land of a given size?", or, "How much energy can we
| generate for a given cost to install and maintain?" Both of
| which, I would assume, are more difficult to directly extrapolate
| from thermodynamic efficiency in wind turbines than they are for
| something like photovoltaics, because of the "moving parts"
| factor.
| 7952 wrote:
| I think this is efficiency in terms of much energy you can
| extract for a given area of sea or land. Wake effects mean that
| wind turbines cannot be placed in a particular zone downwind of
| another turbine. If wake effects are lower then you could
| potentially get a higher density of turbines in a given area.
| This is something that is already considered in terms of
| turbine height and placement. Sometimes they are placed at
| closer intervals along the perimeter of the zone and then lower
| densities within.
|
| Of course lots of factors are considered with the final
| "efficiency" being about getting the highest return for an
| investment.
| brianwawok wrote:
| If land is your dominating cost factor, its how many kw per
| acre can you generate. So dense circular turbines seem good.
|
| If the cost to produce the turbines is the dominating cost
| factor, and traditional turbines are "cheaper" to build, it
| could be a win in some cases to use more land with normal
| wind turbines. The more you spread them, the less problem you
| have with wake on downstream turbines.
|
| Or it could vary based on land value of where you are
| installing a given plant.
| 7952 wrote:
| But land value depends on what you can do with the land. It
| will always going to be more profitable to build a
| distribution center or yuppie condo but most sites cannot
| accommodate that. Wind turbines make sense when a land
| owner is trying to make more money out of an existing
| asset. Maybe it is moorland with sheep on it. The wind
| turbines supplement existing land use and give an extra
| source of revenue. The developer is competing with other
| developers. Once they have a land owner on board they will
| have a certain target they want to hit and will try and get
| away with as much as possible.
| kempbellt wrote:
| > "How much energy can we get out of a plot of land of a given
| size?"
|
| I don't believe this is an answerable question in this format.
| The size of a plot says nothing of land topography, nor the
| average wind currents for any given timeframe.
|
| Wind farms are great tech, but adequate calculation of
| efficiency and cost/benefit is always subjective to individual
| installations. Solar farm efficiency calculations are easier
| because the variables at play are much more consistent.
| Essentially: panel efficiency * sun exposure * array size. I
| don't believe this formula translates to wind farms.
|
| Finding a more efficient design for wind-to-energy conversion
| is a lot like making an improvement in the "panel efficiency"
| part of solar arrays. Or maybe wind has an "array design"
| variable to consider since one turbine's design can affect the
| wind energy capacity of another. This isn't the same for solar,
| unless panels overlap during certain times of the day.
| mumblemumble wrote:
| Yeah, that's more or less what I was getting at, albeit in
| less detail. Put topography and how it interacts with the
| wind and all of that under the category of "mechanics", I
| guess? But, in the simulation that this study is based on, it
| looked to me like they assumed flat terrain and laminar
| airflow coming into the field of turbines. Which I'm assuming
| happens in nature approximately never.
|
| So it's like, sure, maybe this turbine arrangement can get
| 15% greater power output under ideal conditions, but I don't
| think you can get from there to, "this is a clear win over
| the incumbent technology" anywhere near as easily as you
| could in the case of an photovoltaic efficiency improvement.
| k1rcher wrote:
| So this reflects economy of scale (more turbines per area) rather
| than higher output/turbine, right?
| lacker wrote:
| I hope these researchers don't stop with just writing papers, and
| actually see if they can convert their theory into practice. If
| it's true that there's a far more efficient way to run wind
| farms, it seems like it could be a huge profit opportunity.
| sn_master wrote:
| Do they have one shape or multiple? I tried searching for a photo
| of one but getting a mix of results.
| antattack wrote:
| If you look at the actual study[1] it's not just vertical
| turbines but also their formation [2]that (could) increase
| efficacy of large-scale wind farms.
|
| [1]
| https://www.sciencedirect.com/science/article/pii/S096014812...
| [2] https://ars.els-
| cdn.com/content/image/1-s2.0-S09601481210034...
| scythe wrote:
| >For the configurations analysed, pairs of VAWTs exhibited a
| 15% increase in power output compared to operating in
| isolation, when the second rotor was spaced three turbine
| diameters downstream and at an angle of 60deg to the wind
| direction.
|
| This seems like a major limitation of the finding. The wind
| direction is variable. If your clever idea only works when the
| wind is blowing exactly west, it's not so clever.
| mhandley wrote:
| From figure 6 in the paper, it looks like you get the win for
| anything from 30 degrees angle upwards. But with 0 degrees
| angle, the turbines seem to interfere, and you get something
| like 50% loss. So with a westerly prevailing wind (from 270
| degrees), you'd likely put the turbines in rows at 210 or 330
| degrees. If you used 210 degrees, and the wind comes from 210
| degrees, you lose. Almost all the rest of the time you win.
| With some simple analysis of historic wind directions, you
| ought to be able to choose the angle to maximize net output
| by putting the inefficient angle in a direction that is
| relatively uncommon.
| dylan604 wrote:
| But in areas where the wind farms are built, isn't one of the
| deciding factors that the wind primarialy blows in one
| direction? Similar to airports and how they decide which way
| to build their runways. LAX doesn't even have North/South
| runways because of this.
| bluGill wrote:
| Wind is rarely exactly in one direction. A constant west
| wind isn't always directly 270 degrees, there is a large
| plus/minus factor in that.
| olau wrote:
| The vertical turbines are not more efficient in themselves. In
| fact, they are less efficient. The paper does not claim that
| they are more efficient overall in a farm configuration either,
| just that they somehow seem to get a positive effect when
| placed in a (very small) farm.
| mikro2nd wrote:
| VAWTs suffer from 2 serious drawbacks: 1) they're crap at
| starting up - i.e. going from stationary to moving - and usually
| need some supplementary help to do so, and 2) they're _noisy_ -
| as in noisy as hell! I wouldn 't want one within 500m of my
| house.
|
| I recall seeing report of a similar result many years ago (at
| least 10, perhaps much more) where VAWTs deployed in
| complementary pairs were shown to be more efficient, so this
| looks like a repeat /rediscovery of the same result.
| rswskg wrote:
| All large wind turbines are loud. Like, unbearably loud.
| harg wrote:
| I don't believe this is true. There's an installation of 9
| 1MW turbines (perhaps quite small in comparison to the
| largest ones around today) near where I live that I
| frequently cycle past (within ~50m). Even in strong winds
| they are barely audible.
| baud147258 wrote:
| how audible wind turbine also depends on which direction
| the wind is blowing
| [deleted]
| blakesterz wrote:
| That's interesting. Hydro is crap at startup too (they need
| black start units, at least the big ones do) [What I wrote here
| about black start was pretty much wrong, not sure what I was
| thinking] so maybe that's not too big of a problem, but that
| sound thing seems bad, even if the units are out on the water.
| Those things are loud, I had no idea!
|
| "The noise emission from the wind turbine was measured, at wind
| speed 8 m/s, 10 m above ground, to 96.2 dBA"
|
| https://www.mdpi.com/1996-1073/9/1/19/htm
|
| [Edited to add: What I wrote about hydro black start units was
| really wrong, I wasn't thinking when I wrote that, it needs far
| more detailed explanation like the comment below.]
| antiterra wrote:
| The paper you linked suggests that horizontal turbines are
| even louder:
|
| "The noise emission at 6 m/s 10 m above ground was measured
| to 94.1 dBA, this while while operating at optimum tip speed.
| Available noise surveys performed on similar sized operating
| at optimum tip speed. Available noise surveys performed on
| similar sized HAWTs [27-30] HAWTs [27-30] has established
| noise emissions of 95.1-100.2 dBA and 97.3-102.4 dBA for 6
| m/s and has established noise emissions of 95.1-100.2 dBA and
| 97.3-102.4 dBA for 6 m/s and 8 m/s respectively"
| JohnJamesRambo wrote:
| Are you sure about that, because I was just reading the Black
| Start Wikipedia yesterday and it listed Hydro as one of the
| best at requiring little start up power. Hydro is often the
| Black Start source for other power plants.
| blakesterz wrote:
| I am sure I was wrong :-)
| probablypower wrote:
| > * Hydro is crap at startup too (they need black start
| units, at least the big ones do) *
|
| This is a misunderstanding. All generators require an
| excitation current to start up. Most generators get this
| excitation from the grid. For large, important generators
| they also have black start, so that they can provide
| excitation on-site. This means they don't need to bootstrap
| themselves from a grid.
|
| Hydro tends to have black start not because 'they need it'
| but because it is critically important from a grid security
| perspective. During a blackout, you want your high inertia,
| flexible machines online first - these are hydros for systems
| that have them. If you don't have blackstart on these
| machines, you need them on some other machine online first to
| energize the grid.
|
| You wouldn't put blackstart units on wind turbines, simply
| because they are worthless if there isn't already an
| energised grid to support into (they aren't grid forming). So
| you can always assume grid-based excitation current for wind
| generators.
|
| I think OP was talking about the cut-in speed (at what wind
| speed can the turbine start producing power). For HAWTs this
| is at wind speeds of around 5 m/s. For VAWTs, I don't know,
| but I assume it is a little higher based on the OP's comment,
| and that they may even need some mechanical assistance to get
| them spinning in the first place.
| blakesterz wrote:
| Nuts, you're totally right. I really know better, not sure
| how I got that so wrong.
| Valgrim wrote:
| What's the source of the noise? The turbine itself? the air
| flow around the blades?
| mikro2nd wrote:
| My guess (and that's all it is) is that it's the airflow
| around the blades -- it's a _loud_ humming noise, present
| even on an unloaded (no turbine) VAWT. Much the same way that
| ships ' propellers create noise: it is primarily generated by
| the blade causing a partial vacuum behind the trailing edge
| of the blade, and the collapse of that vacuum creates the
| noise.
| ethagknight wrote:
| My guess is the return stroke of the blade sounds like a
| helicopter
| jcims wrote:
| Hadn't thought of that, but the blades are going to be
| slapping the wake of the upstream blade 3-4 times per
| revolution. The helical blade style probably help with that
| quite a bit though.
|
| It'd be easier to sort out with all of the videos uploaded
| to YouTube if humans were capable of _not_ adding cheesy
| soundtracks to everything.
| JulianMorrison wrote:
| At a guess: the wobble/precession/oscillation of a turning
| column only anchored at one side, but sticking up into the
| wind.
| FriedrichN wrote:
| And would it still be an issue if they're in the sea?
| giantg2 wrote:
| I would guess that would increase the infrastructure/cost
| for transmission if you have to put them further out to
| sea.
| FriedrichN wrote:
| Where I live the turbines are already quite far out, I
| don't think I'd be able to hear them if they were of the
| vertical kind.
| giantg2 wrote:
| 95db over water could be heard from a couple miles away,
| especially if the atmospheric conditions are right. I
| don't know how far out the current ones are since we
| don't have any around here.
|
| This brings up another interesting point. If there are
| concerns around ship engines and submarine sonar or ELF
| for marine life, I wonder if any testing has been done
| concerning that with the turbines.
| JulianMorrison wrote:
| In the UK wind farms are usually put in the sea.
| jelder wrote:
| Noise pollution is pretty harmful to sea life, especially
| cetaceans.
|
| https://oceanservice.noaa.gov/facts/ocean-noise.html
| froh wrote:
| how much air noise transfers into the water though?
| jillesvangurp wrote:
| I think there may have been turbines with those two problems
| but that does not mean that all turbines are like that. Merely
| that there were some issues to sort out back in the day when
| you read about someone allegedly having these issues.
|
| Basically, noise would indicate either some problem with loose
| parts, a lot of friction, turbulence or something else that is
| clearly being inefficient. Obviously to compete with state of
| the art horizontal turbines, you'd use highly durable materials
| with awesomely low friction and generally be shooting for very
| high levels of efficiency.
|
| Some other things I've seen suggests that small vertical
| turbines are suitable for deployment in urban environments
| where they work with low/variable wind speeds at completely
| acceptable noise levels. You could put these on your roof even.
| I left a link elsewhere in this thread if you are interested.
|
| Basically the article is about a group of scientists that ran
| the numbers and came up with different conclusions than you.
| 15% more efficient is quite a lot.
| nabla9 wrote:
| Unfortunately they don't have video of the fluid flow simulation.
|
| The effect must come from vortex interaction or syncronization
| and it would be interesting to see. If there is some form of
| strong coupling it may increase efficiency but induce vibrations.
| buovjaga wrote:
| John Dabiri (referenced and thanked in the study) and his team
| have been researching this topic for a long time:
| https://dabirilab.com/
| fnord77 wrote:
| since the article doesn't say or show what a verticle axis
| turbine is:
|
| https://www.researchgate.net/publication/333316757/figure/fi...
| _Microft wrote:
| Wikipedia is also helpful:
|
| https://en.wikipedia.org/wiki/Vertical-axis_wind_turbine
|
| https://en.wikipedia.org/wiki/Wind_turbine#Horizontal_axis
| [deleted]
| Gravityloss wrote:
| You could have horizontal axis turbines with half of them
| rotating clockwise and half anticlockwise, though it seems the
| effect is minor, less than 2%:
|
| "counter-rotating configurations were more efficient in power
| generation than the control case in which all turbines have one
| clockwise rotor; the alternate-row case was found to produce 1.4%
| more power "
|
| https://www.sciencedirect.com/science/article/abs/pii/S22131...
|
| Overall there's probably a lot of ways left to optimize on wind
| farm level. For example the yaw angles
| https://www.sciencedirect.com/science/article/abs/pii/S03062...
| selimthegrim wrote:
| And just when I was imagining twiddling my thumbs in opposite
| directions...
| Kaibeezy wrote:
| I keep wanting to read that title as: _Vertical turbines far more
| efficient_ than _large-scale wind farms_
|
| But then you read up and it's really: _Vertical turbines far more
| efficient_ when in _large-scale wind farms_ than they are
| individually
|
| Whether they can ever be made to be efficient enough to make
| sense seems to be the question.
| blok wrote:
| > Vertical turbines far more efficient when in large-scale wind
| farms than they are individually
|
| The article is saying that in large-scale wind farms, vertical
| turbines are more efficient than _horizontal axis_ wind
| turbines (the "traditional form factor").
|
| With horizontal axis turbines in large wind farms, there is
| always a loss of efficiency through the "wake effect" where
| some of the turbines are downwind from the others.
|
| But the study seems to have found that this can actually
| _increase_ the efficiency of vertical turbines. Which is very
| unexpected.
| Kaibeezy wrote:
| > The article is saying that in large-scale wind farms,
| vertical turbines are more efficient than horizontal axis
| wind turbines
|
| Is it? So much for my reading comprehension score today.
|
| ETA: I read the underlying paper this time (https://www.scien
| cedirect.com/science/article/pii/S096014812...) and I'm
| fairly certain what it's actually saying is:
|
| _Vertical turbines far more efficient_ when in _large-scale
| wind farms_ than they are individually, and furthermore their
| increase in efficiency can be greater than the increase in
| efficiency readily attainable by HAWTs because VAWTs can be
| placed close together _and_ gain downstream efficiency,
| whereas HAWTs can 't be placed so close together and even
| when relatively far apart lose downstream efficiency due to
| turbulence, but YMMV depending on local conditions and other
| factors, for example: the steadiness of the wind, because
| VAWTs often need a boost to start from a stop.
|
| Which is probably not the title they wanted to use, eh? Imma
| hop in my boxy but safe Volvo and go watch "Crazy People"
| again now.
| ndonnellan wrote:
| Yes, I think your reading is correct. The article makes
| claims the paper does not about comparing Vertical vs.
| Horizontal wind turbines.
| [deleted]
| SavantIdiot wrote:
| That is surprising. They have an inferior efficiency already due
| to the Betz limit (it is proportional to surface area facing the
| wind) and will always be about 60% max for a HAWT and worse for
| VAWT. However, the dynamics of turbulance have been one of the
| hardest things to model in large wind farms. The article is a bit
| light on details, but the last time I went to the Sandia Labs
| wind turbine conference in Albuquerque, VAWTS were nowhere to be
| seen (2015) and the biggest modeling challenge was large farm
| interferrence. Very interesting.
|
| Betz Limit: https://en.wikipedia.org/wiki/Betz%27s_law
| nullifidian wrote:
| https://youtu.be/EM-gCvhQhPU?t=508
|
| This lady says Betz limit doesn't apply to VAWT.
| SavantIdiot wrote:
| Huh, did not know. Thanks for the link. Kind of
| disappointing, I was hoping for an explanation, not a claim.
| palae wrote:
| This paper has some insight:
|
| https://iopscience.iop.org/article/10.1088/1742-6596/753/2/
| 0...
| SavantIdiot wrote:
| I suppose I could have Googled instead of complaining, so
| thanks for doing the work for me! :) [I like how the
| first citation is from a 1920's paper (by Betz).]
| mabbo wrote:
| Land use efficiency is not the same as economical efficiency.
| Arguing that we should build vertical turbines because they are
| more land-use-efficient is silly, because land is cheap where we
| build wind farms.
|
| The only efficiency that matters is power generated per dollar
| invested. And if these vertical turbines were more efficient that
| way, then we would already be using them widely.
| worldsayshi wrote:
| Maybe the reason they are cheaper is simply because they have a
| head start on building the supply chain and manufacturing
| process?
| Flashtoo wrote:
| Not every part of the world has large amounts of cheap land
| available for wind farms. Land use efficiency is important
| there.
| hajile wrote:
| It's my understanding that vertical turbines need far less
| height to be effective. If you can get away with moderate
| towers on various existing structures, then the amount of
| available land increases dramatically.
| probablypower wrote:
| > _"Modern wind farms are one of the most efficient ways to
| generate green energy. However, they have one major flaw: as the
| wind approaches the front row of turbines, turbulence will be
| generated downstream. The turbulence is detrimental to the
| performance of the subsequent rows."_
|
| Yes, this is called a 'wind shadow' and it relates to the slower,
| turbulent, dirty air coming out of the back of a wind turbine
| being less energy rich for the turbines behind it. Wind farms are
| designed to minimize wind shadow impacts based on prevailing wind
| directions.
|
| > _"[VAWTs] can be designed to be much closer together,
| increasing their efficiency and ultimately lowering the prices of
| electricity. In the long run, VAWTs can help accelerate the green
| transition of our energy systems, so that more clean and
| sustainable energy comes from renewable sources."_
|
| This sounds like it will make the wind shadow effects worse.
|
| > _The research found that VAWTs increase each other's
| performance when arranged in grid formations_
|
| This seems like straight bullshit, and is really unclear. The
| argument seems to be that VAWTs are somehow positively impacted
| by wind shadows?
|
| The air coming out the backside of a turbine (VAWT or HAWT) is
| less energy dense and more turbulent, so the results seem
| fundamentally flawed. The best design is one that minimizes the
| amount of 'wind shadow' being swept by turbines.
|
| I am entirely unconvinced.
| throwaway316943 wrote:
| VAWTs have a better tolerance for turbulence since they don't
| need to face into the wind. They also continue to operate in
| gusty conditions. They do have downsides but make up for it
| with a smaller footprint, reduction in moving parts and the
| advantages listed above.
| _Microft wrote:
| If you want to have a look at the study, it is linked from the
| article.
| metalliqaz wrote:
| I'm not an expert, but I thought one of the main advantages of
| vertical turbines was better usage of rapidly changing wind
| mumblemumble wrote:
| The paper's here, if you want to see how they came to the
| result. The PDF is paywalled, but you can view it in their
| online reader for free.
|
| https://www.sciencedirect.com/science/article/pii/S096014812...
|
| Properly understanding it is well beyond me, but it looks like
| it's about carefully arranging the turbines with respect to
| each other's wakes. While this is based on modeling and not
| empirical experimentation, it doesn't look like they just
| pulled the idea out of a hat. Getting the 15% improvement seems
| to require that the pattern is optimally oriented with respect
| to the wind direction, so I'm guessing real world benefit
| wouldn't be anywhere near that great.
| _Microft wrote:
| You can download the paper using the download button in the
| top right corner of the online reader's menu bar.
| wizzwizz4 wrote:
| Direct link: https://www.sciencedirect.com/science/article/
| pii/S096014812...
| ivanhoe wrote:
| > The argument seems to be that VAWTs are somehow positively
| impacted by wind shadows?
|
| I'm totally wild-guessing here, but from the header image it
| looks that they place them in rows with a light offset, with
| free air-flow channels in-between. Considering the look of the
| wings, this actually might use the shadow effect to improve the
| performance, as they role like Tibetan prayer wheels, in
| succession, where one side is pulled by air going through the
| channel, while the other half (the one going against the wind
| direction) is in the shadow which is reducing the negative
| push.
| amelius wrote:
| Perhaps the new design somehow reduces the shadow effect by
| extracting wind energy from higher layers of air?
| efnx wrote:
| I've been wondering why we don't have these on top of our street
| lights. I imagine a street light with a Darrieus vawt on the pole
| under the light and a small solar panel on top.
| tachyonbeam wrote:
| Noise, maintenance, added cost and complexity. Then you also
| have the issue that you need an inverter and some kind of
| scheme to communicate with the mini wind turbines so they don't
| drive the voltage too high or some other kind of scheme for
| regulating that.
| foolfoolz wrote:
| because a whole city with turbines on each street light might
| produce the same amount of power as 1 large scale wind farm at
| a fraction of the maintenance cost
| patrickk wrote:
| https://www.youtube.com/watch?v=gcSnwW5v3f8
|
| There is a roadside vertical turbine concept which seems
| promising. It uses lampposts as a mounting point, reducing
| materials needed, reusing existing cables in the lamp, and
| scavenges energy from trucks thundering by. And since it's in
| a developed area, you don't affect existing views.
| lofi_lory wrote:
| The new Siemens offshore turbines put out up to 16MW. This
| has blown me away. Tho, they are scary machines and I get
| uncomfortable looking at them (like single balcony on a huge
| wall kind of uncomfortable). Aesthetically the vertical ones
| are much, much better IMO. Especially if they can be placed
| in an symmetrical pattern, not this super optimized complex
| mess traditional ones show.
| darig wrote:
| A pilot or bird can see the blades on a horizontal turbine, as
| they are perpendicular to the flight path.
| wingineer wrote:
| Wind turbine design engineer here:
|
| There are several significant barriers to adoption that VAWTs
| face.
|
| 1. The wind resource is more powerful and more consistent higher
| off the ground. The hub heights of industry standard horizontal-
| axis wind turbines are reaching 135+ meters for the new
| generation of large offshore machines. These vertical axis
| machines are much lower to the ground.
|
| 2. Contrary to the claims of the authors in the Renewable Energy
| Paper (they say "The potential applications for VAWTs are
| endless, because the turbines are cheaper and easier to
| manufacture and maintain. "), vertical axis turbines have
| consistently had fatigue issues. There is an interesting history
| of the test-campaigns of vertical-axis machines at Sandia
| National Laboratories [1] that discusses this. In the 70s and 80s
| vertical machines were much more common than they are today.
|
| 3. It is a huge risk for an industry that is shipping proven
| technology to switch to a new paradigm that will require much
| more research and testing to work at scale. It's certainly
| possible and I find the possibility fascinating as a curious
| engineer. I would love to have a secure position developing VAWT
| tech or working on airborne wind machines (check out ground-based
| generator concepts to get an idea of where I think that will
| progress, not ill-conceived onboard generator kites like Makani).
|
| The problem of wake blockage in large wind farms (and from
| adjacent farms to each other) is definitely significant though.
| The current "top" strategy is wake steering, where turbines at
| the front use their yaw drive to capture less power and allow for
| more power to reach the turbines in the rows following. [1]. The
| bleeding edge of this may be vertical wake steering, which can
| entrain high-energy wind from above the farm into the plant to
| capture more power [3].
|
| [1] https://energy.sandia.gov/wp-
| content/gallery/uploads/SAND201... [2]
| https://www.nrel.gov/docs/fy17osti/68396.pdf [3]
| https://ieeexplore.ieee.org/document/7963037
| ncmncm wrote:
| I am interested in what has been done to study no-moving-parts
| wind power extraction.
|
| Alvin Marks (who beat out Edwin Land for the polarized-
| sunglasses patent) filed a patent on this back in the '80s.
|
| The idea is simple: you ionize air moving through your system,
| and the wind carries the ions away, accumulating a grid voltage
| vs. ground. The restoring current can do work. If your screen
| is on a kite, it can be very high up, to catch very high wind
| speed. It is very cheap to construct, with no mechanical parts
| at all; restoring current runs up (strictly speaking, down) the
| kitestring. Or, a screen could be stretched between upper parts
| of pairs of existing skyscrapers, or towers of a bridge, almost
| invisibly.
|
| The trick is how to ionize air cheaply. Certain materials give
| up electrons to moving air spontaneously; you could have
| streamers of such materials, modified to be slightly
| conductive. Otherwise, you need some sort of charge pump to
| favor losing surface charge. Maybe a mist of water carries away
| the ions.
|
| Measures of efficiency can be confusing. Ultimately, the
| measure that matters is W/$. If the installation is cheap
| enough to build and operate, percentage of available wind power
| extracted may be almost irrelevant. Stretched between existing
| structures, you might not want to extract much of the available
| energy anyway, because of the load it would place on the
| structure. But the next screen downwind could extract as much
| power, again.
| breischl wrote:
| Tangentially, I ran into the bladeless vortex concept recently
| (https://vortexbladeless.com/), do you have a take on that?
|
| It seems like all your concerns/critiques from above would
| apply equally, but then I don't have any real expertise in the
| area.
| wingineer wrote:
| I think the bladeless vortex concept makes no sense. Here's
| why:
|
| 1. The surface area of the machine is small. Think of this as
| the area that can capture power from the wind. Due to the
| cylindrical shape this is way smaller than the rotor area of
| a HAWT or even a VAWT.
|
| 2. Vortex induced vibration [1] is a real phenomenon that can
| extract energy from a flow. However, to extract this energy,
| the natural frequency of the structure must synchronize with
| the vortex shedding frequency of the flow around the
| structure. This is called "lock-in". Since the wind is a
| highly variable resource, it will not consistently be in this
| "lock-in" range in real-world conditions. To give perspective
| on the norm for HAWTs, pitch control for the blades is used
| along with generator torque control to achieve power
| production from 3 m/s all the way to the maximum (cut-out)
| wind speed of ~25 m/s.
|
| [1]https://en.wikipedia.org/wiki/Vortex-induced_vibration
| fho wrote:
| I guess you can "tune" the tower by adjusting a weight in
| the tower ... but I agree on the area issue.
| petre wrote:
| What about Gorlov helical turbine designs?
| olau wrote:
| Regarding the risk - I don't think this characterization is
| doing the issue justice. It's really about decades of building
| up a manufacturing capacity with suppliers, etc. to get to a
| position where wind turbines are now competitive because of
| this manufacturing capacity.
|
| For an alternative to develop, it is not enough that it is
| slightly better. And both turbines driven by kites and vertical
| turbines are known tech, with known problems. They are likely
| not slightly better. Early wind pioneers knew about vertical
| turbines. They have some nice properties. But also some not so
| nice ones.
|
| And this paper does not study vertical vs. horizontal as far as
| I can tell from a cursory look. It studies what happens with
| vertical turbines in a small farm.
| wingineer wrote:
| Fair. I once was told by a senior NREL engineer that
| industrialization of a different concept than HAWTs would
| take over $1B in investment. Which is a lot in a low-margin,
| capital -intensive business like wind energy. And that number
| is probably on the low end.
|
| Kites have the potential of much lower material costs to
| produce energy. If you have a pumping cycle kite, the
| "support structure" is the tether, compared to the tower and
| foundation required for a HAWT. The problems are indeed well
| known: 1. Tether material difficulties. 2. Need for self-
| launching 3. Airspace sharing problems at heights of kites 4.
| Controller design. This last one is what intrigues me
| personally.
|
| The paper looks at vertical turbine arrangements, but the
| linked article about the paper starts with "The research
| suggests that the now-familiar sight of traditional propeller
| wind turbines may be eventually replaced by the sight of wind
| farms containing more compact and efficient vertical
| turbines." I had to respond to this rather wishful statement.
| pwnna wrote:
| Not a wind turbine design engineer, but have done some fluid
| dynamics work. Thus, I'm not super familiar with what "wake
| blockage" is. A tentative look suggests that it might be
| similar to this work that I encountered[1], which suggests that
| by carefully positioning the wind turbines, one can extract
| more energy basically via the Bernoulli effect. Not sure if
| this is something of interest (or relevant) to you or not, but
| when I talked to some of the people working on that subject, it
| was implied to me that the manufacturers of wind turbine
| weren't interested in this, as it may decrease the number of
| wind turbines they can sell...
|
| [1]: https://onlinelibrary.wiley.com/doi/epdf/10.1002/we.1806
| wingineer wrote:
| Interesting paper. When I refer to "wake blockage", think of
| the turbines in the middle of a huge grid of machines. The
| energy in incoming wind on any side of the farm is mostly
| extracted by the outer turbines. The inner turbines typically
| produce ~15-20% less energy due to this effect. Also, the
| wind hitting them is more turbulent/"dirty" as it recovers
| back to free-stream velocity behind the front row of
| machines, which can cause abnormal fatigue patterns.
|
| That's definitely of interest to me, although I think that
| manufacturers are interested in it. Many manufacturers are
| very conservative with installed/environmental conditions of
| their production machines and want to minimize risks, instead
| of potentially alienating a developer by suggesting a scheme
| that could fatigue turbines or have other unintended
| consequences. If anything, the paper suggests to me that if
| adopted, manufacturers could sell even more turbines!
| pwnna wrote:
| It's very possible that I misinterpreted the situation as
| effectively I got to this information through an overheard
| in discussions with other fluid dynamicists in school. I
| thought the information presented is kind of interesting,
| so I was surprised that no one continued to pursue this
| avenue of research. I'm glad that you find this
| interesting, perhaps this knowledge could be put to good
| use. Although, there may be there are other factors that
| I'm not aware of impacting the real world performance of
| this, as my specialty is not in wind turbines (not yet
| anyway).
| olau wrote:
| FWIW, I know that Vestas has a department with a super
| computer dedicated to helping their customers choose optimal
| positions. And I also know of some recently commissioned
| large wind farms where the company behind explicitly
| mentioned wake optimizations. All the big turbine
| manufacturers are in an optimization race.
| pwnna wrote:
| That's interesting to know. I didn't know that turbine
| manufactures are that state of the art. I mostly thought
| they are just building some sort of standard turbines and
| deploying it to different places like building houses.
| Evidently I'm mistaken. Perhaps I should investigate this
| area a bit further...
| jacquesm wrote:
| The big problem is resonances. A VAWT has various modes of
| resonance that are very hard to engineer against due to some of
| their basic properties. The largest of these, the one at Cap
| Chat in Quebec ended up being scrapped after an embarrassingly
| short period of operation.
|
| There are some VAWTs in the rockies that lived for more than a
| decade but they made really little power compared to the amount
| of money that went into them.
|
| But they look nice and are deceptively simple on paper (one
| less parameter to deal with due to the fact that you don't need
| to steer them, and the generator stays at ground level). So
| likely people will keep trying but it almost certainly isn't
| going to move the needle in the longer term.
| patall wrote:
| That reminds me of that recent finding that wind turbines would
| be a few percent more efficient if they turned anti clock-wise
| (at least on the northern hemisphere), but practically turbines
| in use today turn clock-wise. Sure, it should not be to much
| engineering to change that but still you need to adopt the
| entire manifacturing process to it.
| dividedbyzero wrote:
| Would you have a source for this? Really curious what might
| cause that.
| Spare_account wrote:
| I can't vouch for the sources, but here is some reading
| material:
|
| https://wes.copernicus.org/articles/5/1623/2020/wes-5-1623-
| 2...
|
| [PDF] https://wes.copernicus.org/preprints/wes-2019-105/wes
| -2019-1...
|
| https://www.economist.com/science-and-
| technology/2020/05/14/...
| Wohlf wrote:
| Interesting, so it's not the rotation direction of any
| individual turbine that matters but how the wake of
| turbines affect others around it.
| dzhiurgis wrote:
| Can you use huge regular turbine to vertically steer wake in to
| array of smaller vertical turbines?
| singularity2001 wrote:
| wind sails (kites) are the future
| Faaak wrote:
| absolutely not. I'm sorry makani went under (there's an
| excellent documentary about them on YT), but when you compare
| their extreme complexity for a "simple" 600kW unit to newer
| wind turbines that are now reaching 10MW, you'll see why
| usrusr wrote:
| Skysails Power is shipping.
| Faaak wrote:
| Per their datasheet, the SKS PN-14 produces 80-200 kW. Now
| compare this to a modern Vestas V164 8000kW turbine. The
| latter seems way simpler engineering-wise to me
| usrusr wrote:
| You are comparing a 20 tonnes system to a 1300 tonnes
| system
| cr1895 wrote:
| But then having a nominal capacity of 8000kW from the
| 20mt system, you'd need maybe 1200 tonnes of the 20mt
| systems.
|
| I'm not sure how that's better or simpler. Sounds vastly
| more complex and expensive.
| gmokki wrote:
| This company has been slowly developing vertical wind trubines:
| https://windside.com/
|
| They are not (yet) for mega installations, but since they are
| almost silent and maintenance free they can be used both in urban
| areas and in sahara/antarctis where things just have to work.
| vanviegen wrote:
| The article seems to be talking about the efficient use space
| (sea area). However, speaking as a layman, these vertical
| turbines appear to be structurally more complex and to consist of
| more material, so I would expect them to be more expensive per
| MWh.
|
| Would they be more efficient than traditional horizontal wind
| parks when looking at total cost of ownership?
| Pxtl wrote:
| On the other other hand they seem mechanically simpler because
| the entire turbine doesn't have to be mounted to pivot
| depending on the direction of the wind, and the column that
| holds up the turbine and blades is much shorter.
| JulianMorrison wrote:
| Also the generator can be at ground level, rather than having
| to perch at the top.
| tobtoh wrote:
| Don't quote me on this, but I recall reading that there is
| a layer of air at ground level that is very
| turbulent/choppy due to it's interaction with the ground
| which makes it terrible for wind power generation.
| lippel82 wrote:
| Only the generator is at the bottom, the power still
| comes from the upper part of the structure and is
| transferred mechanically, I would assume.
| Pxtl wrote:
| What the parent-post means is that the machinery of the
| generator is positioned at the bottom _below_ the blades
| instead at the top of a tall column _behind_ the blades.
| Presumably this creates some savings in terms of
| construction and maintenance.
| bigfudge wrote:
| perhaps also aerodynamics relative to a big generator
| blob right at the top?
| throwaway316943 wrote:
| VAWTs do ok in turbulent conditions. HAWTs don't like it
| because they need a consistent stream of air flowing in
| one direction.
| mc32 wrote:
| However the variability of physical forces on the blades as
| they rotate means the materials have to have properties that
| make them less brittle or prone to fatigue due to these
| conditions. Those materials I think are mor expensive than
| those on traditional blades.
| brudgers wrote:
| Generally, turbine farms are built where the wind mostly
| comes from one direction. When the wind is not in a favorable
| direction the turbines are idle.
| ahartmetz wrote:
| Why would they be idle? They can pivot for a reason and I
| haven't seen turbines very close together in any direction.
| Sometimes they are indeed arranged in a long row, but even
| then, why not use all the wind energy they can get? I could
| imagine problems with turbulence and mechanical wear close
| to maximum design wind speed and yeah, they might shut down
| then.
| dylan604 wrote:
| >Why would they be idle?
|
| Sometimes they are idle not because of the lack of wind,
| but because of the lack of need for the electricity. When
| power demand is low, the wind turbines are the first
| things to be stopped. In fact, they use an electrical
| braking system to keep them from turning. The power
| companies say that it is much easier to stop/start wind
| turbines than lower/raise the output of gas/nuclear/coal
| power plants.
| avianlyric wrote:
| GP is asking why the turbines would be idle if the wind
| isn't coming from a particular directions. They're not
| asking for a list of unrelated reasons for why a turbine
| might be idle.
|
| > When the wind is not in a favorable direction the
| turbines are idle.
| dylan604 wrote:
| Actually:
|
| >Why would they be idle? They can pivot for a reason
|
| It seems to me you are reading into the post something
| not there. The person I replied to, quoted above, did not
| ask what you asked, and actually stipulated that HAWTs do
| pivot to turn into the more favorable direction.
| brudgers wrote:
| In the Texas panhandle along Interstate 40 west of
| Amarillo there is a continuous east-west line of wind
| turbines running about forty miles. The turbines face
| north because the wind is almost always from the north
| and the turbines are there because the wind is almost
| always from the north. Each turbine is placed to avoid
| casting its wind shadow on the other turbines...there are
| typically three or four banks of turbines from north to
| south.
|
| Suppose the wind shifts to the east, enfilading all those
| miles of turbines. It's a turbulence nightmare. But
| fortunately a rare event. An edge case where idling makes
| sense and staying online doesn't.
|
| At the extremes of nacelle yaw, the upwind turbines may
| cast a wind shadow on a downwind bank. Again an edge case
| where idling some turbines is a reasonable tradeoff.
|
| These are networked smart devices. And humans in the loop
| monitoring and tweaking.
| chrismorgan wrote:
| Can you comment on
| https://weatherspark.com/y/4750/Average-Weather-in-
| Amarillo-...? It suggests that although during winter
| north and west are the strongest wind directions, in the
| summer you get south winds up to three quarters of the
| time, and precious little north wind at all.
|
| This is pretty consistent with my loose understanding of
| how these winds work and my experience in south east
| Australia: the predominant wind directions vary very
| significantly by season, and even within seasons
| substantial deviation is much more common than people
| often think.
| brudgers wrote:
| Amarillo is near the eastern edge of the Llano Estacado.
| The large wind farms are to the west on top of the mesa.
|
| The Llano is the southern end of the High Plains that
| extend all the way into Montana. As it passes the Rockies
| the Jet Stream tends to bend south. Further east the
| weather is more varied.
|
| Or to put it another way, its a fair bet people settled
| in Amarillo for its less horrible weather. There's not a
| major city between it and the Rio Grande at Albuquerque
| 450km to the west just some small towns here and there
| mostly where the railroad did something interesting.
|
| The Llano and the high plains weather patterns are
| dominated by macro scale climate patterns. This is why
| the large wind farms are there.
| blake1 wrote:
| The short height is a serious problem.
|
| I think we can make some conclusions about the power output
| for a given material input. Based on the the images, my
| assumptions are: 100m mast and 80m blades; for the vertical
| turbines, a radius of 50m. The blades look to be lighter
| weight, but the mast looks heaver weight, so say the two
| styles use similar amounts of materials. Also, windspeed is
| logarithmic with height.
|
| Wind power goes as the cube of wind velocity over the swept
| area. With my assumptions, the vertical turbine outputs about
| 2.7MW, while the horizontal turbine outputs about 8.4MW. The
| reason is height: it helps to have the blades sweep more
| higher altitudes wind, where it's faster.
|
| These might be easier to pack tightly into a windfarm, where
| the metric that matters is W/m^2. But most of us care about
| W/kg because that is proportional to W/$: the winner looks to
| be horizontal turbines because they reach higher.
|
| A hybrid of horizontal behind vertical might be interesting.
| There are diminishing returns to how "deep" you can make your
| windfarm: the trailing edge suffers from turbulence from
| leading edge, and these could work better in turbulence.
| eloff wrote:
| Indeed, we have lots of space. The more important efficiency is
| turning capital into electricity. I believe horizontal turbines
| still have the edge here. This could possibly change if
| produced in enough volume to get the manufacturing costs down -
| it depends if they have an advantage in materials use, install
| and shipping costs, and maintenance costs.
| Mauricebranagh wrote:
| I think its also reducing the losses of turbines in the lee of
| other turbines.
| seanalltogether wrote:
| Additionally the larger ones appear to need guy-wires to
| presumably prevent the whole structure from wobbling as rpms
| increase.
| teachingassist wrote:
| > vertical turbines boost each other's performance
|
| Meanwhile, horizontal turbines impair each other's performance
| when they sit in each other's wake.
|
| I remember reading that the loss of power generation was more
| than previously expected, as you increase the area of the wind
| farm?
|
| So, it could be financially worth it to optimise vertical
| turbines, if they work in a more synergistic way.
| probablypower wrote:
| I would take that claim with a pinch of salt unless they're
| able to explain the physics of how one turbine suffers in
| less energy dense, muddy air whilst another thrives.
| fatboy wrote:
| I can imagine there's a difference in wake from a classic
| turbine blade that slices through the wind coming at it,
| and these vertical ones that are sort of pushed out of the
| way.
| pbhjpbhj wrote:
| "Classic" 3-blade HAWTs (the same style as modern off-
| show wind turbines) are aerofoils, they're working on
| lift - like a sailing boat or glider - and are
| surprisingly narrowly angled to wind direction.
|
| Darrieus VAWTs are operating by the same mechanism for a
| deal of each blades rotation.
|
| Unless you're thinking of "American" style wind turbines
| that used to drive water pumps, which are like like water
| wheels and closer to Savonius VAWTs in operation.
|
| I think people often mistakenly think of 3-blade HAWTs as
| working principally in the same way as a anemometer.
| olau wrote:
| Here's a machine-translated post on vertical turbines by one of
| the pioneers in the modern wind turbine market:
|
| https://translate.google.com/translate?sl=auto&tl=en&u=https...
|
| TLDR; they have been tried out and found impractical.
|
| I'll add to that that many, many years have gone into the
| manufacturing of current big wind turbines. Making something
| that can withstand the weather, have a high uptime, relatively
| cheap to manufacture and put up - these are not easy problems.
| supportlocal4h wrote:
| I'd caution generally against the argument that "it has been
| tried before and didn't work." There are undoubtedly value
| lessons to learn from earlier attempts. But "don't even think
| about it" is almost never one of those lessons.
| olau wrote:
| I would kindly ask you to read the article I linked to
| before passing judgement on my extremely short summary.
|
| I skimmed the paper, and its contribution is a study on how
| vertical turbines seem to behave in a very small turbine
| farm. It does not study whether vertical turbines make more
| sense than horizontal. But the only reason we see it here,
| is because this article makes some pretty big and unfounded
| statements about the current horizontal wind turbine
| approach.
|
| So we're here because of misinformation.
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