Which way a wind turbine turns might not seem to matter, but it does | Hacker News Reader

Which way a wind turbine turns might not seem to matter, but it does

economist.com

158 pointsedward101 comments

Fun-fact pot-shot time!

The first paragraph states the thesis that there's something about wind patterns in the northern hemisphere that make windmill directionality important.

The first paragraph also says:

> It is convenient to have all clock hands turn in the same direction, but it is an accident of history which direction that is.

Clockwise is not a random coin-flip of history. Ironically, clockwise is clockwise also because something about the northern hemisphere: the shadows on a sundial move clockwise in the northern hemisphere, so when europeans first started making clocks, they continued the sundial convention!

That’s both true and not.

Yes, it’s true that once clock makers started adding dials they used clockwise because they mostly lived in the northern hemisphere, and decided to mimic the design of sundials.

What’s less obvious is the inclusion of dials at all. While in popular imagination the road from sundial to clock is clear, in reality some of the first modern clocks had no faces at all. The initial responsibility of medieval clocks was actually chiming, first in “liturgical hours” and then eventually regular hours. Their weight, cost, and inaccuracy meant that they were more commonly used to call monks to pray (hence liturgical hours) than for economic activity.

Jumping from chiming to circular clocks was actually a pretty significant leap for clock makers, and one that only seems obvious in retrospect. Especially since sundials typically trace semi-circular paths and not the full circle that a clock uses, and the installation of clocks into tall, prominent locations took a few centuries.

You could argue that the fact that we use clock face designs derived from sundials built in the northern hemisphere, rather than the southern, is itself an accident of history.

I mean, sure, if you assume settlement and development patterns in both hemispheres had equal probability to develop a need for standardized mechanized time keeping.

But I would direct that armchair discussion more to the comments section of Guns Germs and Steel and all the TED talks that talk about how geographical differences are suspected to influence societal developments, all while keeping your racism and eugenics radar on maximum-alert.

Really, though, I think it was just some overworked Economist journalist trying to crank out another science summary piece, completely unaware that the top-commented criticism was going to be a bunch of nerds bikeshedding the omission of a mildly-interesting historical anecdote rather than anything substantial about the science being reported on. :)

There's a very simple explanation for why most of human history happens in the northern hemisphere.

Take a look at a map.

Notice which hemisphere has 70% of the land.

More land _and_ due to current orbital geometry, north hemisphere summers are not as hot and winters not as cold as in the southern hemisphere.

Just because you can guess at a simple reason doesn't make it true. Nobody in most of that land ever invented a sundial. Something special happened around the middle east/Europe that spawned all this civilization stuff. How do you know it was simply a matter of more land leading to more chance of civilization appearing there? It might have taken a special type of land combined with a special history of human migration or other factors.

In general the hemisphere with more land likely has more land fulfilling any particular properties that are not inherent to the distinction, and we do know that humans are terrestrial. So ceteris paribus, "might have taken a special type of land combined with a special history of human migration or other factors" is more or less a matter of more land leading to more chance.

It is not a comprehensive explanation. It is quite obvious that there are other variables involved!

But as a simple explanation it has the advantage of being conceivably predictable without hindsight.

It's too simple to be interesting. You could obviously divide up the world into some other halves where the half with less land ended up with the sundials and say "even though it predicts the wrong outcome, this explanation is obviously right."

Other arbitrary divisions don't have the sundial property that north and south have.

That's the point. It is an explanation reduced enough to suggest that the phenomenon is not particularly interesting.

> How do you know it was simply a matter of more land leading to more chance of civilization appearing there?

Human brains are energy intensive. More land means higher likelihood of arable land, more livestock and so better nutrition. It also makes your land more valuable to invaders, which leads to people organising to protect their land, and innovating weaponry, tactics, etc.

Certainly it might have taken some special circumstances like you said, but when there are perfectly plausible reasons suggesting the contrary, there seems little reason to give speculative possibilities much attention until there's evidence.

> Guns Germs and Steel and all the TED talks that talk about how geographical differences are suspected to influence societal developments, all while keeping your racism and eugenics radar on maximum-alert.

I really have no idea about those theories but they could perfectly be NOT racist at all just like saying a girl from a poor neighborhood has less chances to be rich as an adult than a kid from a mid-class neighborhood is NOT racist, just stating the (sad) reality.

And as a complete ignorant I guess that in a primordial society, climate had a huge impact on access to food, and the less you have to think about surviving the more you can think about improving your life.

I have read the book: it explicitly and thoroughly debunks the idea that race was a factor in the development of modern societies. It provides a myriad of geographical and climate-based explanations why the course of history would result societies in the northern hemisphere set the direction of clocks for the globe.

It's honestly pretty refreshing to have a scientific explanation for why Aboriginals or Africans didn't set the direction of 'clockwise'. Without that explanation, I can faithfully assert "all humans are equal" but be confused by the apparent dominance on the world stage of Western societies. Armed with an explanation that has nothing to do with the innate abilities or intelligence or suitability in the modern global economy of the victims of circumstance, I can genuinely believe in equality.

> I have read the book: it explicitly and thoroughly debunks the idea that race was a factor in the development of modern societies. It provides a myriad of geographical and climate-based explanations why the course of history would result societies in the northern hemisphere set the direction of clocks for the globe.

Given that ethnic differences develop alongside migrations into new territories, you'd expect them to be formed by those geographical and climate-based explanations. It's a chicken and egg problem, but it doesn't really help if you're dealing with people who believe in racial superiority, they'll just say "yeah, so we became a super great race because we settled in Whatever Region and they didn't because they didn't".

I believe race is blown way out of proportion by believers, but I found Guns, Germs and Steel to be very hand-wavy and starting from the end, working backwards to tell a story that leads where the author wants it to lead.

As Wikipedia puts it, the academic reaction to the book was "mixed".

How does it show that race differences weren't a factor? Not how does it show that other factors existed, but how does it exclude race?

It shows that other explanations are sufficient and make much more sense. But it's a historical explanation, not a double blind experiment.

Nothing will ever disprove "scientific racism" to people who are racist unfortunately.

That's not a rigorous answer which is possibly why you felt the need to play the racism card at the end.

There's no way to make a rigorous (to the "prove" level) argument from history on racism (or most social issues) because it relies on counter-factuals. Counter-factuals are inherently untestable.

Thanks for getting back to me. I don't know that the assertions of cause and effect made in that book can be asserted any more confidently than racist ones. Nature doesn't care about our feelings.

Have you actually read the book? There's nothing about feelings in it, and some of the arguments can be stated as irrefutable facts:

There are more species of animals that can be domesticated in the Eurasian landmass than in Africa, the Americas or Australia. 14 out of the 14 large domesticated species are from Eurasia (including North Africa), with the only exception being the Illama/Alpaca. There isn't a single species of large animal in Sub-Saharan Africa or North America that has been domesticated, even in modern times.

There are more plants suitable for cultivation in Eurasia, and the ones that are turned out to be more useful. Rice, barley, wheat and flax are all Eurasian crops. The only major non-Eurasian crops are Maize and Bananas. The East-West orientation of Eurasia proved a major advantage here, because crops domesticated at one latitude could thrive right across the continent, while in Africa and the Americas crops could be successfully locally but were unable to move North/South because of different climates. In Australia there were zero indigenous candidate crops except the macadamia nut, which is slow growing and hard to grow reliably.

Finally, germs: The larger populations and large trade volume in Eurasia meant Europeans were immune to diseases that killed large numbers of native Americans when they arrived. It seems likely the only disease to go the other way was syphilis - which is a lot less contagious and kills a lot slower than smallpox and measles.

Nothing in there even suggests that race wasn't a factor. The very fact that you listed multiple factors admits that multiple factors may have combined to cause it. It could just as well have included race too.

I'll just refer you to my previous comment: There's no way to make a rigorous (to the "prove" level) argument from history on racism.

However, these factors do appear to provide sufficient non-race based evidence to explain the outcome. That's a reasonable way to read the claim that the book "debunks the idea that race was a factor in the development of modern societies".

> The very fact that you listed multiple factors admits that multiple factors may have combined to cause it. It could just as well have included race too.

Since the factors are based around geography, and race is also based around geography you sure would expect to see a correlation!

The explanations in the book give a causal link between geography and outcomes. There will be a large number of other factors correlated with that. A good example is "was beer drunk in country" - countries where beer was drunk were much more successful than countries where it wasn't. Race appears to be the same - dependant on geography, but not part of the causal chain of factors mentioned in the book.

Then Leifcarrotson's claim that it "it explicitly and thoroughly debunks the idea that race was a factor" is false. Just because something agrees with your prejudice doesn't make it a good argument. It just means it feels satisfying to believe it.

https://en.m.wikipedia.org/wiki/Guns,_Germs,_and_Steel

I haven’t read the book, but my understanding is that racism did play a preferential factor in that an ethic group that achieved geopolitical dominance tended to impose sanctions on more economically primitive people both intentionally and unintentionally. An unintentional example was the case with 1000 years of exposure to many pandemics for Eurasian people that isolated people never experienced, but once exposed suddenly dwindled.

The book suggests Europe had the biggest head start followed by Asia due to geography and plant and animal species, with races being completely irrelevant.

I am not claiming race is a developmental or preferential factor but instead was an imposed factor in the consequences of one group achieving dominance comparative to another. National groups were still most strictly ethnically homogenous at that point and frequently used that as a point of identity. I also don’t think comparing European groups to East Asian groups is productive in this context because both were well connected and technologically similar at the point of colonialism. Better comparisons would be European groups to Pacific Islanders of the same colonial period who were often highly isolated aside from immediate neighbors.

A more interesting comparison is European conquerors to civilizations of the Americas during the colonial era. The Aztecs were only conquered as a result of Spanish exploiting social unrest. They didn’t have the numbers themselves for their technological military advantage to matter, though that wasn’t the case with the Incas further south. Had the Incas developed metal working as advanced as their agricultural refinements they probably could have repelled the Spanish invasion. Conversely, the Spanish were never able to conquer or subdue the Maya communities around Mexico’s current southern border due to the environment, geography, and decentralization.

From memory (and it's probably 15 years since I read it) I seem to remember that the argument for European domination as opposed to Asian was because the European landmass favoured smaller city states. That in turn allowed them to avoid the critical mistake of the isolationist Chinese policy of the Ming dynasty right at the moment the European states were beginning to colonise.

Chinese and European technology was roughly equivalent at the time, but the huge increase in economic activity by European states associated with colonisation gave them a lead that was impossible to reverse.

And yes, the book make it extremely clear how little race had with anything.

I think you're slightly confused about the kind of racism being discussed.

You rightly point out that there has been tremendous exploitation of (for instance) Africa by Europe, and that a lot of this exploitation has been justified by racism.

But separately from that, consider the question: why were Europeans able to do this to Africans in the first place?

If you asked question back in the Nazi regime, you'd probably get answers like, "Europeans are somehow inherently racially superior to Africans, and this superiority allowed them to become dominant."

Guns, Germs, and Steel lays out a different and detailed explanation. The author is quite aware of this history of racist explanations. He provides a competing theory, backed by considerable research and evidence. I found it quite good, but also very dry. :)

> the less you have to think about surviving the more you can think about improving your life.

This is still very much true in our current non primordial "advanced" world.

I wonder at what threshold from between being born into poverty / riches that this reverses due to a lack of the same pressing motivation. Or if that's even the case.

I would say that my comment applies at the aggregate level, not the individual level. Its about how the environment people operate in increases or decreases their odds of advancement.

I mean, it doesn't take more than a model where the same area of landmass anywhere on the globe has the same chance of birhting a civilization with a need for clocks, for the northern hemisphere to become the most likely candidate to do so simply by virtue of having much more landmass than the southern hemisphere.

>an accident of history.

another accident of history

https://en.wikipedia.org/wiki/Homochirality#Symmetry_breakin...

"One supposition is that the discovery of an enantiomeric imbalance in molecules in the Murchison meteorite supports an extraterrestrial origin of homochirality: there is evidence for the existence of circularly polarized light originating from Mie scattering on aligned interstellar dust particles which may trigger the formation of an enantiomeric excess within chiral material in space.[11]:123–124 Interstellar and near-stellar magnetic fields can align dust particles in this fashion."

Isn't everything an accident of history, given enough history?

I sometimes reflect on the fact that, were it possible to be an intelligent fly on the wall at the moment of the big bang, molecules were not a foregone conclusion. Certainly I'd accept they'd be a good prediction, but molecules evolved just like everything else. We think that molecules, and even more fundamental properties, are just that, intrinsic, but they have something of the serendipity of clockwise moving right from 12 noon.

I’m not quite sure what you mean, can you clarify?

Take Conway’s game of Life as a cut-down example. It might not be obvious right at the start that many (most?) initial setups will produce gliders. But gliders aren’t a lucky accident, they’re fundamental. Anyone who applies the same rules will quickly discover gliders.

Are you thinking that there could be initial conditions that don’t produce gliders/molecules? Or that the underlying rules/laws might have been different, and not conducive to gliders/molecules? Both of those seem extremely speculative to me. The rules are as they are, and gliders and molecules are inevitable.

Ah yes, good point. And Conway's Game Of Life is a better example because yes, indeed, gliders are fundamental (as are molecules). And Conway didn't make GoL for the gliders specifically, they may have surprised him just as much as us (although I'm sure he was searching for emergent phenomena).

So yes I think there are certain initial conditions and rules that don't produce gliders/molecules, but that is only obvious either through simulation or hindsight. In the beginning, as a pundit, or a fly on the wall, it feels like there's everything to play for. So a weird thought experiment is if we could somehow contain a randomly-seeded, massively slowed down Big Bang and have modern day scientists (without recourse to modern knowledge) observe it. I imagine there'd be all kinds of theories, conversations, schools of thought, etc on which direction the universe would take.

So I think the point is that, in fact, we are observing a Big Bang! Just at a later stage. We're trying to understand what's happened and what will happen. A very prescient example of that is Fermi's Great Filter[1], ie does intelligent life necessarily destroy itself?

So perhaps I can summarise my original comment with the thought experiment of those scientists observing the impossibly contained early universe asking themselves in the same way we ask ourselves about the Great Filter, "are protons, neutrons and electrons, capable of stabilising into complex but harmonious structures?"

1. https://en.wikipedia.org/wiki/Great_Filter

Thank you! Yes, that’s definitely interesting to think about. The long-term fate of the universe is another open question -- does it accelerate forever, could it collapse somehow, or cycle somehow? Physics seems to suggest that space will eventually just atomize completely, with individual galaxies or perhaps even molecules expanding beyond each others’ observable horizons. Or could some interesting new unanticipated structures arise, maybe at massive distances or ultra-slow timescales? The general question, I guess, is are we witnessing the long decline of a mature universe, or is it still in its youth?

I love these questions too! I feel like the universe is still very much in its youth, but who knows. There's so many profoundly different evolutionary stages the universe could go through. Such a shame that I won't be around to see them :'(

Technically, the earth having life is an accident if you look at the rest of the cosmos. If life was brought to this rock by comets and asteroids crashing into the planet, then that's definitely an accident.

It's accidents of history all the way down.

As much as having significantly more landmass and arable land in the northern hemisphere is an artifact of history.

You could argue that the bulk of the world's landmass and hence people being in the northern hemisphere is itself an accident of history.

But that we call it the "north" hemisphere is itself an accident of history. We could've easily called it the south hemisphere instead.

That's just English. In my language directions are named from where the sun is at given time, so it wouldn't change.

East is "sunrise", south is "midday", west is "sunset" and north is "midnight". Context and grammatical case differentiate between midnight as time vs midnight as direction.

That's really interesting, what language is that if you don't mind me asking?

Polish, but I think all Slavic languages are similar.

BTW this is why "decadent west" work so well in Russian propaganda. "Zapad" is west but also "sunset" or literally "falling [sun]".

Thanks! That's a really cool fact to start my Friday.

East means dawn and west means evening.

https://en.wikipedia.org/wiki/%C4%92ostre

The word Sun is related to South. North to night.

That could be inconvenient in Australia no?

No doubt. But we cope with September, October and December not being the 7th, 8th, and 10th months respectively. If it was your regular language, you would probably hardly notice.

If you didn't knew that north-south is inverted vs the sun in southern hemisphere and tried to navigate based on the intuitive rules - yes.

Otherwise not really.

You just made me spend 5 minutes wondering if sundials would work on the equator, and if so, do they go counter-clockwise or clockwise during which parts of the year.

Also, a fun fact: even if you have a wall-mounted sun dial (which was common in the ancient era) it still moves clockwise in the northern hemisphere, even though noon would be near the bottom of the clock.

A sundial on the equator has a horizontal gnomon (oriented north-south), and the shadows move underneath it from west to east. (There is of course a slight curve in one direction or the other based on the seasons.) See e.g. https://en.wikipedia.org/wiki/Sundial#/media/File:Sundial,_S...

I spent some time in Australia a few years ago. My sense of time and direction got totally confused, because the sun went the "wrong" direction in the sky. It was surprisingly disconcerting to me, I did not realize how much I oriented myself by the sun.

It was only made worse by the Australians driving on the "wrong" side of the road :-) I was one disoriented man.

Of course they do. On the equinox it would follow a straight line through the middle of the pointer with times marked on it. At other times of the year, they behave Northerly in the northern summer and Southerly in the southern summer. Always west-to-east, though, obviously.

And around noon near the equinox, there's no shadows at all:

https://en.wikipedia.org/wiki/Lahaina_Noon

https://boingboing.net/2017/04/13/lahaina-noon-when-the-sun-...

Even an approximation of that is quite convincing. In the right time of year, palm trees in Los Angeles have their shadows pretty darn perfectly centered, and if the top of the tree is narrow the shadow is nearly invisible.

That's a really good point, and comes up in first result to a google query:

https://www.google.com/search?q=why+is+clockwise+to+the+righ...

...

Beat me to this.

Water also drains clockwise and foucault pendulums process clockwise in northern hemisphere. These are somewhat less likely to have a bearing on the matter than a sundial.

The coriolis effect is too weak to have any appreciable effect on the way that water drains in any sink or bath.

I've been to the equator in Ecuador. It was clever how the "museum" made everyone think that simply by walking 20 yards north or south equator that the water would drain differently. They had a rectangular basin with a drain in the center. When we were in the northern hemisphere, they poured the bucket so it would induce a clockwise swirl, and counterclockwise in the southern hemisphere. When were were on the equator, they just poured it right in the center so no swirl was induced.

Definitely has an effect - https://www.youtube.com/watch?v=mXaad0rsV38

Whether or not it meets the standard of 'appreciable' is subjective i suppose.

This is poor science, and very weak support for 'definitely'.

I didn't watch this all the way through this time, but I do recall watching it back in 2017 when it was posted -- IIRC he did this experiment <sic>, asserting all variables were controlled for, but in a garage with leaky walls, on a poorly insulated floor, with no control test and only once, in one location.

Consider that hurricanes don't form within 5 degrees (~ 550km) of the equator - which gives a good indicator of just how strong (or not) the Coriolis effect is.

There has been experiments, published in Nature in the 60s that did confirm an effect. I personally know one of the authors.

The tub they used was something like 60cm deep and 3 or 4m in diameter.

I can pull up the reference if you like.

It wasn't perfectly reproducible though; in classic fashion when they demonstrated for a local newspaper (Sydney Morning Herald) the water went the "wrong" way.

I have given the url / details here in HN a few years back.

That it's not perfectly reproducible should be setting off alarm bells, even for people who would really like this effect to work at the scale of a few metres.

I'm not sure that any experiment is perfectly reproducible. Though I would be very surprised to see a hurricane going the wrong way at mid-latitudes!

Anyway, we're in agreement that it is a thing, and we just need a big enough tub to demonstrate it, correct?

The force is perfectly calculable, and we can compare that to the effect of, say, a breeze across the top.

ps. the reference https://www.nature.com/articles/2071084a0

"Published: 01 September 1965 The Bath-Tub Vortex in the Southern Hemisphere LLOYD M. TREFETHEN, R. W. BILGER, P. T. FINK, R. E. LUXTON & R. I. TANNER

pps. my earlier mention https://news.ycombinator.com/item?id=15122988 Nature volume 207, pages1084–1085(1965)"

Yeah, I can't access that Nature link from 1965.

AIUI the math is that the delta in acceleration across a 1m bathtub north-to-south would be 1x10-8 m/s/s due to Coriolis ... so your starting conditions would have to be at a level of perfection that I don't think anyone's achieved, certainly not some bloke in a drafty garage with a kiddy's wading pool one time.

I accept that in theory that delta definitely exists, but I don't accept that it can be, has ever been, observed at the tiny scales of a few metres, let alone the 100mm (toilet flushes) that's typically asserted by the faithful.

I accept that across dozens of kilometres we definitely do see this phenomenon as it generates consistent, hemisphere-dependent, large wind events (eg hurricanes) once you get a good way from the equator.

It's probably reproducible in the sense that if you do it a 100 times you get a strong statistically significant effect. They were probably unlucky that day.

Hurricanes don't form near the equator due to the equatorial subduction zone.

Hmm, I hadn't heard this claim before.

And searching for neutral questions like 'Why don't hurricanes form near the equator' reveals consistently Coriolis Effect explanations.

Wikipedia's article on subduction makes no mention of weather events at all.

Do you have any citations for your claim?

My mistake, I was misremembering some things related to the the Inter Tropical Convergence Zone from geography class 10 years ago.

As an aside, the ITCZ is a trigger for hurricanes when it moves too far from the equator.

https://www.eoas.ubc.ca/courses/atsc113/sailing/met_concepts...

Perhaps something relating to this was meant? https://en.wikipedia.org/wiki/Thermohaline_circulation

This must be one of the most misunderstood pieces of popular science.

The Coriolis effect is WAY too weak to affect the direction the water is flowing. Typically the way the water moves initially and the shape of the container will have an outsized impact in the final direction.

I think the issue is between people who interpret the statement as "water is predisposed to drain in a particular direction depending on hemisphere" or as "water will drain in a particular direction depending on hemisphere".

Does it have an effect and can it sometimes be seen? Yes. Is it often swamped by other factors and rendered irrelevant? Also yes. That doesn't mean it's false, but it does mean that some statements that rely on it as a factual basis are at best mistaken.

When you have a large reservoir with a drain, keep it still, and the water reaches the level where it starts to rotate, the Coriolis effect is the dominant influence.

It is something large enough to be plainly visible, but not something that appear on every drain.

typo: process -> precess

Preprint of the full paper here:

https://www.researchgate.net/publication/338882074_Should_wi...

It's cool work. Some things I've picked out from a quick skim:

- Only the downstream turbines gets a boost, cutting gains of a pair in half*

- The boost only occurs at night, cutting gains approximately in half again.

- Veering winds only occur 75% of the time

This already cuts the gains from an ideal 23% to roughly 4.5% real world.

I don't see any treatment of incoming wind direction - it appears to only consider pure West to East wind with turbines precisely aligned with the wind. I suspect the effect would disappear as the wind shifted from other directions. While wind is generally westerly in the US, it varies a lot hour-to-hour.

Combine this with the above and I'd suspect real-world benefit is in the 1-2% range, at which point the added complexity of maintenance and production probably cancels out the benefit.

Not a knock on the research, because it is great work, but it is incomplete.

*This may be unfair, as it's unclear what affect multiple in a row would have. But the power production of multiple turbines in a row when the wind is blowing precisely parallel to the row drops off pretty quickly. Commercial turbines are something like 45% efficient these days, so turbine 3 only has ~30% of the original power available.

A 5% gain is worth it when you have some severe constraints. If you can just plop down another wind turbine, that 5% almost certainly won't pay off. If you can imagine some scenario where you absolutely have to get the most energy out of the wind in a specified footprint, then it would make more sense (and cents).

As a counter-example, consider internal combustion engines (ICEs): they have had to get more efficient and cleaner, so you see more and more abstruse dingusses and doohickeys added to them. A 4.5% improvement in ICE efficiency is beyond amazing these days, and would justify well more than a 4.5% increase is cost for the engine.

Seems like the turbines rows should be positioned in alternating CW and CCW rows in order to benefit from a potentially substantial (up to 23%) increase in efficiency in the downwind turbine(s) during the night.

But I wonder is the tradeoff is worth it. There would definitely be increased costs with always building 2 mirror versions of the same turbine blades. The logistical effort would also likely increase.

This [0] is the cost breakdown for manufacturing blades. Unfortunately it's hard to tell how much "up to 23% at night" translates to in real life gains.

100 turbines' worth of tooling costs $250K-$1.5M. Two sets of these being recouped from the efficiency improvement alone is a tough sell. Building 10% more "regular" turbines might be cheaper and provide more output. Unless you really need to get the max efficiency out of the lowest number of turbines.

Perhaps as manufacturing gets cheaper, turbines get more popular, we run out of good places to put them and need to max out efficiency, and we get decent energy storage options for night-time generated power this will make more sense.

[0] https://windpower.sandia.gov/other/031428.pdf

There are some massive simulations to determine turbine siting, check it out: https://www-gs.llnl.gov/energy-homeland-security/windpower/t...

Terrain, weather, etc. all affect power capture.

I think that, at the scale we will be building wind turbines, and given the relative scarcity of areas with good wind, having separate production lines will be worth it, even if the difference is ‘only’ about 5%.

I agree, it will make more sense when we run out of improvements and upgrading turbines is the only way to squeeze more. It's a very high hanging fruit.

Any initial additional costs during construction/installation should be easily recouped in short period of usage allowing for net gains after that point for rest of the lifetime of the turbine

Should they really build mirror versions? Can’t they just rotate alternate turbines by 180 degree to achieve the same?

The rotor is upwind because the blades would be subjected to frequent jerks when they enter and leave the wake of the tower otherwise.

If I understand you correctly, you are asking if wind turbines can operate with the wind blowing from behind them?

Wind turbine's are designed and built with wind coming in front of them. I am unaware of any designs that would work from both directions (horizontal axis wind turbines of course).

Outline link: https://outline.com/GTwkCb

I’m kind of surprised that this research wasn’t already done decades ago.

I just assumed the placement and positioning of turbines within a cluster was already subject to rigorous modelling, seeing as these turbines are huge and likely very expensive

Wake effects are studied extensively and automated systems exist that will optimize the turbines' yaw direction to maximize power output (and / or keeping loads in check) of the entire plant instead of just a single turbine.

For example: https://www.siemensgamesa.com/en-int/newsroom/2019/11/191126...

What's novel here is the effect the counter-clockwise rotation has on the power output of the down stream turbines... I think it hasn't really been a point to research as the costs of blades, maintenance, etc... are assumed to far outweigh the potential gains.

Something else to keep in mind is that it's not as pleasant to look at a park full of turbines spinning in different directions.

Huh. Seen in retrospect, it's sort of obvious. Propeller efficiency can be increased by mounting them in pairs, one behind the other, where the two are rotating in different directions. This reduces the "twisting" movement of the airflow behind the propeller, which is a sign of energy that's lost and not used for propulsion.

Stands to reason that the same thing would be the case with wind turbines, and maybe a little surprising that it hasn't been on anyone's radar before now.

The way this effect works, however, is dependent on a Coriolis-force-induced veer in the atmospheric boundary layer, something that is not an issue in contra-rotating propellers. Unless one understands the mechanism, one will be unaware that, for any given location, it matters which way the first turbine rotates. At best, an arrangement based on an analogy to contra-rotating propellers would be a lucky guess, right for the wrong reasons.

It probably was, many times over.

I was once curious about if in a line of propellors, having the propellors rotating in the same direction (line wheels on a shared belt) or counter rotating (like interlocking gears) would produce any difference in thrust. I made a rig to test this https://www.youtube.com/watch?v=SJ7BVa8Ol1I. Unfortunately it seems I didn't upload the strain gauge measurements, but I remember the net difference was negligible.

Pretty much the same as the reason why stacking fans adds little benefit unless they rotate in different directions.

Stacking identical fans that run at similar speed is probably not effective. Jet engines seem to use many compressor stages though - none of them the same.

But every 2nd one is stationary, effectively meaning the air sees counter-rotating fans...

I am guessing vertical axis turbines do not have this bias but they only seem to be used in smaller designs?

I would guess that their awake is asymmetrical (though in a different way) and so there might be a favored way to arrange them, but as they are inefficient compared to conventional turbines, and because the blades undergo a large cyclic variations of wind load with each rotation, they are not cmpetitive for large-scale commercial use.

Reply on news.ycombinator.com