
SkySails - aoeaoeaoe
https://en.wikipedia.org/wiki/SkySails
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thinkingkong
This is super cool, but until cargo vessels have any sort of restrictions on
their carbon emissions, I hardly see this being adopted. We're on track to
burn 500 million tonnes of Bunker oil by 2020 and the EU is just _proposing_
some sulfur and nitrogen reduction standards. Without any international
restrictions or some other factor to increase the cost of operating, what
incentive are companies going to have to adopt these new technologies?

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djokkataja
Because it would save money, presumably. For example, in a 10,000 ton boat:
"While the kite was in use, the ship saved an estimated 10-15% fuel, $1,000 to
$1,500 per day." (From the linked article)

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Gustomaximus
They said a limitation in addition is;

"There’s a structural problem slowing down the process: ship owners (who have
to make the investment) often don’t pay for the fuel – that’s the charterer’s
duty. The charterer on the other side doesn’t charter the ship for long enough
a period to make low-carbon technologies pay back"

I know bugger all about shipping but this doesn't seem logical. Wouldn't the
person hiring said boat look at the estimated fuel cost as part of their
cost/quote? If they know a ship has this or other effeciency features it
should become part of their pricing comparison to alternate ships.

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skribbj
Exactly. If the charterer has to pay less fuel for your ship because you put a
kite on it, surely they will choose your ship over others? Is there no
competition in this market or why does fundamental market principles seemingly
not apply?

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dmurray
It's one extra level of indirection. In the housing market, landlords do
sometimes pay for upgrades to their rental properties, but they are less
likely to do so than owner-occupiers.

Additionally if the ship owner was also the operator, they could benefit from
some vertical integration, training their crew on the new technology.

If the effect of the kites on prices becomes large enough or the technology
becomes standard, expect widespread adoption, but it's a reasonable claim that
the existing market structure slows rollout when it's only marginally
profitable.

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Gustomaximus
> In the housing market, landlords do sometimes pay for upgrades to their
> rental properties, but they are less likely to do so than owner-occupiers.

Is that a fair companrison? An owner occupier will often over capitalise
because they desire something or have a lifestyle benifit beyond money. A
rental owner wil look at dollars in/out. With the ships, its all coming down
to a spreadsheet of cost vs benifit for both owner and hirer.

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inflatableDodo
I think they hold the current record for the largest tonnage under sail. If
they want to survive they should probably diversify into making some systems
for yachts and promote them with a racing class. Kiteboats can shift and don't
heel much, so is nice for pleasure craft if you can sort out the control, the
current downside being that you can't just set them and sail to the wind.

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franole
Related discussion [1] about using Rotor ships [2] and the Magnus effect [3]
to reduce carbon emissions and shipping costs. IMHO a much more interesting
tech/physics phenomenon :)

[1]
[https://news.ycombinator.com/item?id=17885284](https://news.ycombinator.com/item?id=17885284)

[2]
[https://en.wikipedia.org/wiki/Rotor_ship](https://en.wikipedia.org/wiki/Rotor_ship)

[3]
[https://en.wikipedia.org/wiki/Magnus_effect](https://en.wikipedia.org/wiki/Magnus_effect)

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mycall
There is opportunity here. Various people have had success with SkySails, such
as 15%-20% fuel savings [0], but not yet available for pleasurecraft [1].

[0]
[http://www.cruisersforum.com/forums/archive/index.php/t-1328...](http://www.cruisersforum.com/forums/archive/index.php/t-132825.html)

[1] [http://www.cruisersforum.com/forums/f109/colonial-or-
greenwi...](http://www.cruisersforum.com/forums/f109/colonial-or-greenwich-
yachts-26676.html)

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keyle
It would be extremely ironic if this would be use by an oil tanker. Jokes
aside, this is great, but it will never be the primary mode of propulsion
since those tankers are on a timeline and you can't predict wind as much as a
combustion engine.

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mycall
If you can save up to 20% in fuel, you bet they would try it.

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komali2
They won't, because the cost of fuel is passed to the shipper, not whoever
owns the boat.

If shell owned and operated their own boats, maybe, but I haven't seen that.

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atdt
"Shell manages one of the largest fleets of oil/chemical tankers and liquefied
natural gas (LNG) carriers in the world" [https://www.shell.com/business-
customers/trading-and-supply/...](https://www.shell.com/business-
customers/trading-and-supply/shell-shipping-and-maritime/our-shipping-
fleet.html)

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therein
This looks like an excellent idea but does anyone have the numbers? What kind
of force could one expect from these? It got me thinking all kinds of
electronic control systems to deploy/undeploy these.

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bufferoverflow
_" Totally computer operated by an automatic pod to maximise wind benefits,
this kite is believed to generate a propulsion power of more than 2,000 kW
(approx. 2,700 HP)"_

2 megawatts. Tremendous amount of force.

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rrosen326
Wow - that’s amazing. Look how tiny that is compared to the load it is
pulling. It looks like it would hardly make a difference. (I’m a kiteboarder
and my kites are way bigger than I am.)

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sunkenvicar
Nuclear could really clean up the shipping industry and provide numerous other
benefits.

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sunkenvicar
Thorium (U-233) is one way to solve the proliferation risk.

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alecmg
You even put U-233 in there

How proliferation of fissionable U-233 is different from proliferation of
fissionable Pu-239? Both share ability to be separated from fuel without
enrichment factories, both can be used to build a bomb.

I like thorium cycle, but proliferation should not be used as argument for it.

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ian0
Kind of a dumb question but I'll ask anyway. If the wind is blowing in the
exact same direction as the ship is travelling and you begin to retract the
sail - do you recoup some of the energy you use during this retraction process
through increased pulling power of the sail? Is the ship being pulled a little
stronger during the retraction process or the exact same amount as if the line
wasn't being retracted?

Im imagining something similar to when you'r flying a kite and begin to reign
it in - it seems like it pulls you towards it.

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kirrent
Newton's 3rd law. If you're applying a force to reel in the kite, that force
is equally propelling you forward. Plus, the faster apparent air flow over the
kite will produce more power, which is why sailboarders pump their sails while
they race. In the real world, I've only ever pumped a kite like this to
momentarily get some more energy into it to help with ram air inflation.

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murgindrag
I don't think that's quite how the physics works out.

Speed of airflow is approximately constant. Extreme case is reeling it in at
1mph in a 200mph wind. Force is approximately fixed.

Consider that I have an object with a fixed force on it (a good approximation
in that case). If I reel it in, I do work equal to force times distance. That
work goes into heating up the air. The force on my boat is the same.

I'm not sure it's a problem we care about, but you know how we solve the
problem? Collapse (or partially collapse) the kite before reeling it in.

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kirrent
No the force is not the same. To actually reel the kite in you will need to
pull on the lines with more force than during normal constant distance flight.
It is this delta that I was implicitly referring to. The work done as you reel
the kite in will largely go into kinetic energy for the boat. You're literally
pulling on something in front of you.

Your wind figure is crazy large by a factor of 10. Nevertheless, my point
wasn't on the magnitude of extra energy produced through apparent wind, it was
referring to the fact that apparent will in general produce more apparent.

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murgindrag
My point was that Newton's 3rd law isn't the right way to think about it.
Newton's 3rd law means that if I throw a rock with 1 N-s of impulse, I will
also gain 1 N-s in the opposite direction. It's a conservation law: "Equal and
opposite reaction."

Yes, you do get pulled forward a little bit more, but you can reel in the kite
with arbitrarily little "pulled forward a little bit more" (by pulling in
slowly) or arbitrarily much (by jerking hard).

The force on me and on the kite is equal-and-opposite, but it was equal before
I started reeling it in too.

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kirrent
>The force on me and on the kite is equal-and-opposite, but it was equal
before I started reeling it in too.

Yeah, of course. The force is always equal when objects aren't accelerating,
so when you reel in the kite at a constant speed with an increased force, the
force on your ship is increased as well. When you reel in with more force you
reel in faster, which means that you can make your increase in force
arbitrarily small, but in doing so you'll make you're increase in speed
arbitrarily small and make your reeling time arbitrarily large. In doing so,
you'll end up accelerating the ship by the same amount.

The work done in reeling in the kite is obviously larger than the kinetic
energy imparted on the ship and is minimised by reeling in the kite
arbitrarily slowly. That energy doesn't just go into fluid interactions but
also the potential energy of having your foil back at the ship as well as the
ship's kinetic energy.

All of that is a bit of window dressing. To reel in your kite you need to
increase the pull or force on its lines. That increase will equivalently act
on the ship. The ship is being pulled a little bit stronger in the retraction
process just like the original commenter asked.

