
Which way a wind turbine turns might not seem to matter, but it does - edward
https://www.economist.com/science-and-technology/2020/05/16/which-way-a-wind-turbine-turns-might-not-seem-to-matter
======
floatrock
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!

~~~
teraflop
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.

~~~
floatrock
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. :)

~~~
darkwater
> 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.

~~~
LeifCarrotson
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.

~~~
lopmotr
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?

~~~
nl
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.

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

~~~
nl
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.

~~~
stormdennis
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.

~~~
nl
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.

~~~
lopmotr
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.

~~~
nl
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.

------
scrooched_moose
Preprint of the full paper here:

[https://www.researchgate.net/publication/338882074_Should_wi...](https://www.researchgate.net/publication/338882074_Should_wind_turbines_rotate_in_the_opposite_direction)

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.

~~~
csours
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.

------
close04
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](https://windpower.sandia.gov/other/031428.pdf)

~~~
sp1107
Should they really build mirror versions? Can’t they just rotate alternate
turbines by 180 degree to achieve the same?

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

------
nrki
Outline link: [https://outline.com/GTwkCb](https://outline.com/GTwkCb)

------
statictype
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

~~~
qsolo
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...](https://www.siemensgamesa.com/en-
int/newsroom/2019/11/191126-siemens-gamesa-wake-adapt-en)

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.

~~~
marvin
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.

~~~
mannykannot
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.

------
0xfaded
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](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.

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

~~~
phkahler
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.

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

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

~~~
mannykannot
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.

