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SkySails (wikipedia.org)
126 points by aoeaoeaoe on July 4, 2019 | hide | past | favorite | 42 comments



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?


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)


Since half of your comment is plainly wrong, all I'll bother with is asking you to inform yourself. Here's a good start: http://www.imo.org/en/mediacentre/hottopics/pages/sulphur-20...


Oh wow thanks! I thought this was still being proposed but I was reading Wikipedia. Cool that the sulfur reductions are in place, but that's still not going to affect co2 emissions, and because these rules apply - lets assume equally - to all ships it doesn't necessarily impact the economics. If the sail really reduces the cost by the stated amount minus the caveat at the bottom of the article that would be impressive.


If the technology actually works then the companies would burn less fuel, and save money in the process. That should be an effective incentive.


Read the caveats at the bottom of the article -- the ship owner who has to make the capital investment doesn't pay for the fuel, so there's a perverse disincentive to invest in this technology (assuming it works).


Maybe the SkySail could own the sail system and sell the "thrust" - basically charging a success fee for saved fuel. In a similar vein in how the airlines don't own the engines of their airplanes but rent them from manufacturer - https://aviation.stackexchange.com/questions/12528/jet-engin...

Of course this is an armchair thought experiment, but I am curious about your opinions.


Not really a disincentive, if the person paying the fuel could pay less it for it while using fleet X it would surely be a competitive advantage to the fleets owner. Perhaps the keyword in the quote is "untested", with a unwritten "why bother unless I have to / other owners do it".


Exactly. The key hurdle is getting the first ship fleet owner to invest in the technology. Once that's working, he'll have a competitive advantage offering renters lower fuel costs. He'll have some combination of higher booking rates or ability to charge higher prices, effectively splitting the gains


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.


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?


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.


> 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.


I guess the point is that these systems have to be retrofitted to existing ships. The ship owners don't see the benefit - it costs them to do the modification - and the ship renters don't see the benefit, because ultimately the owner passes on the modification costs to the renter, displacing the fuel cost savings.

Whats needed is for regulation to come in and say 'ships that have these systems pay less to dock in port' or whatever. But, the technology has to be proven to reduce costs and carbon footprint - so someone needs to make an investment to prove this works before governments will get behind it.


I think this was replaced with Rotor Sails (which have indeed been installed on Maersk ships): https://en.wikipedia.org/wiki/Rotor_ship


I guess a complication is that you need to know how to operate the kite. And there is the risk that kites get broken or go missing.


there is an initial cost of the sky sail that is amortized over many journeys


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.


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

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

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


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...

[1] http://www.cruisersforum.com/forums/f109/colonial-or-greenwi...


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.


This sort of argument gets used against all sorts of renewables. It doesn't have to be about replacing 100% of energy usage with renewables with zero compromises. If you can slap a kite on a cargo ship and save 10-20% of fuel costs, why wouldn't you? If the wind dies down you can still motor along just like you did before.

Best is the enemy of good, and perfect is the enemy of possible.


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


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.


"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/...


That's not how it works. Of course ultimately the customer pays for the fuel, but you order customers a lower price in order to gain business, making them choose you over your competitors.


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.


"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.


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.)


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


Figure out something we're happy to leave on a beach on a coast of africa and maybe nuclear has a potential.

That or always make it so valuable to always strip the power unit to use again.


Until the captains figure out that selling the fuel to the highest bidder is better than delivering the actual cargo.


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


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.


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.


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.


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.


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.


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.


>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.


There are designs for wind power generation based on kites that work like that.

You basically let the kite fall, then use its pull to generate energy and make it soar, then let it fall again..


Depends on the speed at which you reel it in but I can't see it being hugely significant. You would, however, recoup that energy when reeling the kite out again if the winch has regenerative braking (assuming the wind speed is constant).

If the wind speed isn't constant then you could save power by only reeling the kite in when the wind slacks off. If you felt especially proactive you could generate power by reeling it out during gusts then back in during lulls.




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