
Wind-powered ships are making a comeback - Osiris30
https://amp.economist.com/business/2018/10/06/wind-powered-ships-are-making-a-comeback
======
escherplex
This idea was already broached at HN in

 _Maersk installed 100-foot-tall rotating sails on one of its tankers_

[https://news.ycombinator.com/item?id=17885284](https://news.ycombinator.com/item?id=17885284)

But a question arises as to practicality of this configuration in extreme
weather at sea. That's a lot of wind swept area aloft abovedeck. In extreme
weather conditions with rolling seas, an elongated cargo vessel such as a
tanker will be subject to _sagging_ (central portion suspended in space
between two wave crests). Given strong head or tail wind force imposed on tall
rotor shafts it would seem that extra torque would be imparted on the central
section increasing the liklihood of hull failure under full cargo load.

~~~
qbrass
You quit spinning the rotors and they stop acting like a sail.

~~~
infogulch
I wonder if they have enough rotational inertia to cause gyroscopic effects
while they're spinning. I wonder if it could be used to stabilize the ship. Or
it causes more issues than it solves you can just stop spinning it, just like
you can stop it to stop it acting like a sail.

~~~
ansible
Without running the numbers, just looking at the mass of the sail vs. the mass
of the ship, is say the effect is neglible.

~~~
marmadukester39
I know of a company that makes these as retractable spinning cylinders

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mattlondon
Some more info on the actual tech:
[https://www.norsepower.com/technology](https://www.norsepower.com/technology)
and [https://www.norsepower.com/rotor-sail-
solution](https://www.norsepower.com/rotor-sail-solution)

Obligatory wikipedia entry:
[https://en.wikipedia.org/wiki/Rotor_ship](https://en.wikipedia.org/wiki/Rotor_ship)

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slycke
A different but interesting concept: [https://www.skysails.info/skysails-
marine/skysails-antrieb-f...](https://www.skysails.info/skysails-
marine/skysails-antrieb-fuer-frachtschiffe/vorteile/)

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tzs
Good demonstration of the Magnus effect:
[https://www.youtube.com/watch?v=QtP_bh2lMXc](https://www.youtube.com/watch?v=QtP_bh2lMXc)

~~~
cgag
This is the video they reference at the end that elaborates and shows off the
use in ships, as well as some planes that have spinning cylinders instead of
wings:
[https://www.youtube.com/watch?v=2OSrvzNW9FE](https://www.youtube.com/watch?v=2OSrvzNW9FE)

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cies
If petrol for ships was taxed like petrol for cars, this would have already
been common place.

Hell if petrol for planes was taxed like car-petrol they bring back zeppelins!

~~~
dwighttk
oh the humanity

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danielvf
For some actual numbers from a real freighter with four Magnus effect columns
on it, check out this pdf [https://www.ship-
efficiency.org/onTEAM/pdf/06-STG_Ship_Effic...](https://www.ship-
efficiency.org/onTEAM/pdf/06-STG_Ship_Efficiency_2013_100913_Paper.pdf)

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yskchu
This article is a bit lacking in the visual imagery department (that picture
in the article is super old) - here's a youtube link from Norsepower (the
article says they're the manufacturer):

[https://www.youtube.com/watch?v=FUCShEXkpL8](https://www.youtube.com/watch?v=FUCShEXkpL8)

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bcl
Current location and some before and after pictures -
[https://www.marinetraffic.com/en/ais/details/ships/shipid:73...](https://www.marinetraffic.com/en/ais/details/ships/shipid:730851/mmsi:565686000/vessel:MAERSK%20PELICAN)

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WalterBright
I recall back in the 80's someone made a freighter with a computer controlled
sail on it. It was written up in Popular Science (?) as the future of
freighters and tankers. Never heard about it again.

~~~
jandrese
IIRC it turned out to be impractical and was shelved after the test runs.

------
walrus01
I question whether the cost of doing this in new novel naval architecture
isn't excessive. You can have a green ship without installing Magnus effect
rotor sails:

A) install a massive ground mount photovoltaic system

Or massive wind farm on land.

B) use the kWh from it to crack water into pressurized tanks of hydrogen

C) transport the hydrogen to the ship, store it onboard, and run it through
fuel cells to drive electric azipods.

This require the engineering resources for on board hydrogen tank system,
fueling system and fuel cells. Less mechanically complex than massive rotor
sails, and something that all of the subcomponents exist for "off the shelf".

This lets you use otherwise useless, non arable land for the energy
generation. Even if the electricity to hydrogen process is extremely
inefficient. At a certain point if you plot the ongoing price drops for
massive grid scale PV, when PV panels hit $0.20/watt, it will be economical.

~~~
gumby
Hydrogen plumbing is not really a solved problem so I challenge the "less
mechanically complex". Those hydrogen atoms are really small!

The margin on shipping is low enough that I suspect they looked at everything
they could get off the shelf before settling on this one, which I agree is
complex. It will be interesting to see the long time life of these sails.

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lokedhs
The Magnus effect is pretty cool. I firs came across it when watching this
video which shows how effective it is by dropping a ball from a height while
spinning it. [https://youtu.be/QtP_bh2lMXc](https://youtu.be/QtP_bh2lMXc)

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mrfusion
Would wind turbines make more sense? It seems like they’d be catching a larger
cross section of wind.

~~~
strainer
I believe its possible, with stability being the big problem. Self stabilized,
floating, tethered and large scale wind turbines are already being built[1] -
so its something to look out for in the future.

[1][https://www.equinor.com/en/news/hywindscotland.html](https://www.equinor.com/en/news/hywindscotland.html)

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mrfusion
On the flip side could these replace conventional wind turbines to generate
electricity?

~~~
gpm
Hard to imagine how. They use wind to generate a linear force. We like to have
rotational forces to feed generators.

~~~
mrfusion
We have lots of ways to turn linear force into rotational. My car engine would
like to have a word with you.

Off the top of my head. Hook it up to a crankshaft. On the push stroke turn
the motor on and capture the wind. On the pull stroke turn off the spinning
and let it return to vertical.

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Pietertje
Interestingly the problem tends to be economical rather than technological. A
5 years ROI would normally be sufficient to get traction. Apparently the
current system of charterers is holding it back.

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agumonkey
What about populating building tops with these ?

~~~
ansible
Are your buildings moving around and eating each other like that recent
dystopian SF work, a la _Mortal Engines_?

~~~
agumonkey
It would require quite long devices to move.

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Apocryphon
It seems prudent to invest in some low-tech solutions, just in case resource-
intensive high-tech solutions fail us in the long run.

~~~
masklinn
Rotor sails aren't really low-tech though, the original pre-WWII attempts
failed because the sails were too heavy and the engines (to rotate the
"sails") not efficient enough, so the rotor sails were a net energy loss (aka
using the engines to power regular screws was more efficient even in best-case
scenarios).

The new attempts (since the mid-augths) use advanced modern material science
to build the sails, no way you can replicate that in a low-tech non-industrial
context. It's way more complex than an ICE (and in fact requires one to power
the rotors themselves).

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your-nanny
why use the amp link? Firefox on Android won't open

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tibu
And again, they try to be cheaper by manufacturing in China. When do we
realize that this is a trap we created for ourselves...?

~~~
kvartz
Why wouldnt we want to manufacture everything for less?

~~~
dredmorbius
Supply-chain control. Technical knowledge. Innovation capacity.

------
qume
I really want this to be a thing, but my rough calculations given the total
cross section area of the sail and the average wind conditions on shipping
routes come out to as close to nil as makes any difference for ships these
size.

I posted a very rough calculation on the last HN post about this and got
downvoted for some reason. I guess everyone else wants this to be a thing so
much they are happy to set aside physics through sheer force of will. HN
people and the investors / instigators of this project.

This is one time I'm desperately wanting to find out I'm completely wrong.

My last post in a nutshell - these things are order of magnitude the same size
as the sail on my own sail boat. Forget about the type of sail. Even if 100%
of that wind energy was converted to forward motion it's going to do
essentially nothing in the context of a big ship.

~~~
hexane360
You were downvoted because your calculations were for regular sails, and
sailboats, instead of for Magnus effect.

Wikipedia says:

    
    
        F = L*rho*v*2*pi*r^2*omega
    

where L is the length of the cylinder, rho is the fluid density, v is the
fluid velocity, r is the cylinder radius, and omega is the cylinder angular
velocity.

What angular velocity are you assuming in your calculations?

~~~
qume
My back of the napkin assumed all energy from the wind over the entire cross
sectional area.

Magnus effect or not, i'm just dealing in orders of magnitude and for the
average wind speeds on shipping routes, I just don't understand how this works
even if 100% of the wind energy is extracted from the cross sectional area of
the sail.

~~~
nikdaheratik
[Snipped after looking at how it works again]

~~~
danielvf
No, I don’t think that’s what it’s doing. It’s actually powered - using
electricity to make it spin. As a result of the spin, it creates vortexes that
push 90 degrees to the wind.

~~~
nikdaheratik
Yeah I think I was still confused about how it works, but I've just decided to
snip out my comment instead.

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newnewpdro
These green-washed headlines are getting absurd.

Wind-powered suggests there's no fossil fuel based propulsion, when these
rotors are _driven_ by the same propulsion system as the ship's propellors:
diesel.

~~~
masklinn
Wind-powered suggests that motile power is provided by the wind, which is the
case here.

Surely a sailboat with electrically controlled surfaces is still wind-powered?

~~~
dwighttk
There is still a diesel engine in the loop, which if turned off makes the ship
not move.

These are like electric hybrid cars which are sometimes thought* of more
valuable than increased efficiency of burning gas (which is all they boil down
to)

*at least I used to think that. Maybe I'm the only one.

~~~
masklinn
> There is still a diesel engine in the loop, which if turned off makes the
> ship not move.

So it is with my sailboat example?

> These are like electric hybrid cars which are sometimes thought* of more
> valuable than increased efficiency of burning gas (which is all they boil
> down to)

Most hybrid cars are plug-in, you can charge the battery directly and use
mixed-electric mode or even exclusively electric mode for short distances.

~~~
dwighttk
Most sailboats operate fine if the engine is off.

It may be that plugin hybrids are more numerous now, but for a very long time
most hybrids did not have the plug in option.

