[HN Gopher] A cargo ship's 'WindWing' sails saved it up to 12 to...
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A cargo ship's 'WindWing' sails saved it up to 12 tons of fuel per
day
Author : hotdailys
Score : 65 points
Date : 2024-03-22 00:06 UTC (1 days ago)
(HTM) web link (www.ajot.com)
(TXT) w3m dump (www.ajot.com)
| mattmaroon wrote:
| And who says you can't reinvent the wheel?
| aoki wrote:
| Surprisingly, these appear to be rigid foils (hence WindWing)
| instead of Flettner rotors.
| M95D wrote:
| What I don't understand is why they didn't use normal sails
| instead. The sails could have a much larger area and a thinner
| mast would create less problems for docking, or it could even
| be a telescopic cilinder, able to be retracted below deck.
| hollerith wrote:
| My guess is that the WindWing requires much less labor. Even
| by the standards of the 1700s and earlier, working on a
| sailing ship had a reputation for being dangerous work that
| chews through sailors, and kidnapping people and not letting
| them leave the ship was a common way to "recruit" sailors.
| These days, when kidnapping is no longer in the Overton
| window, and even unskilled workers have more options than the
| workers of the 1700s had, it would be cost prohibitive to
| staff these sailing ships you propose, I am guessing.
| M95D wrote:
| No need to pull the ropes manually. We have motors now.
|
| https://www.yachtingmonthly.com/sailing-skills/mainsail-
| furl...
|
| https://solar.lowtechmagazine.com/2009/04/sailing-at-the-
| tou...
| hollerith wrote:
| I know. Still.
| UberFly wrote:
| Likely a mechanical system offers more predictability and
| longevity compared to fabric.
| jasonwatkinspdx wrote:
| Two reasons:
|
| First, solid wings are dramatically better in lift drag
| ratio.
|
| They start out around 3x better per square meter than
| conventional sails on a bermuda rig, and can get up to 7x
| better with careful design. This is why the America's Cup
| boats with wings are dramatically faster than conventional
| rigs (the other reason being foils).
|
| Second, the simplicity of the rig.
|
| These designs are self trimming, which means there's a
| control flap you set, and that causes the wing to have a
| consistent angle of attack vs the wind. As the wind vector
| shifts around the sail just tracks it without needing any
| active control or electronics. You only have to change the
| control flap when the bow or stern crosses the wind during a
| turn.
|
| If you get into severe weather you just put the control flap
| in neutral and the wing just acts like a weather vane.
| Surprisingly enough a feathered wing like this has _less_
| drag than a bare cylindrical mast with no sail lifted.
| Aerodynamics can be counterintuitive.
|
| That's what's so cool about this technology. It really is
| just a bolt on.
| wolverine876 wrote:
| > solid wings are dramatically better in lift drag ratio
|
| Why has anyone used fabric sails? If they could build a
| wooden boat, they could have made wooden sails. Too heavy,
| and thus modern strength/weight materials were needed?
| mrcartmeneses wrote:
| Weight and the fact that wings are a modern invention
| that requires an understanding of aerodynamics
| machine_coffee wrote:
| I wonder how well they hold up in strong storms, or if they can
| be folded away for safety.
| mayd wrote:
| From the article: "Pyxis Ocean reportedly saved an average of 3.3
| tons of fuel each day."
| kkoste wrote:
| But does the overall cost of these 'WindWings' recoup over the
| lifetime of cargo ship. Including the fact that they can now
| carry less cargo per trip. And the trip might take longer due to
| 'route optimizations'. Insurance is probably also going to be
| higher now that you have giant sails on top of the ships that
| makes it both more expensive but also i suspect less safe in
| rough seas(even when folded).
|
| I feel that is the only true measure otherwise cargo ship
| builders are not inclined to build more of these.
| mgiampapa wrote:
| 3.3 tons of fuel per day adds up to a lot of extra cargo that
| isn't fuel.
| Merad wrote:
| A lot of these ships carry upwards of 150000 tons of cargo.
| Not sure if an extra 60-70 tons (assuming a 20 day trip) of
| cargo would be very meaningful. A quick google suggests that
| would only be 2 or 3 additional shipping containers.
| thih9 wrote:
| I guess the question is how much space would the sails
| take.
| mgiampapa wrote:
| You don't need to compare to the size of the ship, you need
| to compare to the size / mass / cost of the sails.
| jtbayly wrote:
| There's also the cost of the fuel. Can't be cheap.
| rascul wrote:
| That's approximately two Honda Civics.
| akira2501 wrote:
| The fuel is around the bottom hull of the ship. It provides
| good stability to the ship. As you use fuel you'll often take
| on sea water as ballast to regain the lost stability and to
| maintain your draft.
|
| These are not simple machines.
| mgiampapa wrote:
| That is because of the difference in mass over the voyage,
| the less delta in your fuel math the less of a problem it
| is. Also, nothing prevents you from doing exactly this with
| a smaller amount of fuel. Last I checked dense liquids
| continue to be dense liquids and will flow to the lowest
| point.
| exe34 wrote:
| Do they use separate tanks or does the water go into empty
| fuel tanks?
| wafflemaker wrote:
| Seawater is initially filtered and goes into ballast
| tanks that have very special yearly inspection and
| cleaning procedures. If you just go into a chamber that
| has been empty/full of seawater for a couple months you
| can drop dead because of CO2 buildup (or some rusting
| processes that eat up oxygen). Credit to sailor(s) who
| post about things like that on hejto.pl.
|
| It's even more fun with clean water tanks (painting and
| cleaning, specific concentration of chlorine for a day
| plus taking samples and eventually more chlorine before
| flushing).
|
| Might be slightly inaccurate as I'm writing from memory.
| dctoedt wrote:
| > _If you just go into a chamber that has been empty
| /full of seawater for a couple months you can drop dead
| because of CO2 buildup (or some rusting processes that
| eat up oxygen)_
|
| And deadly hydrogen sulfide. "Hydrogen Sulphide can be
| found in tank sediment as a result of decomposing sea
| life which may enter the tank[.]"
|
| https://www.imca-int.com/safety-events/crew-member-
| fainted-a...
| exe34 wrote:
| Can confirm that sea water corrodes everything. I used to
| live on an island and we joked that it even corroded
| plastic. In practise it was the UV that killed all
| plastic, while the sea water ate all the metals,
| including stainless steel.
| mschuster91 wrote:
| > But does the overall cost of these 'WindWings' recoup over
| the lifetime of cargo ship.
|
| Well... 1 ton of bunker fuel costs about 650 dollars, so you're
| looking at 7.5k saved _each day_ , or 150k per trip (assuming
| an average of 20 days at sea). Cargo ships have ridiculous life
| expectancies measured in decades, so it's very likely to make a
| significant dent.
|
| [1] https://www.statista.com/statistics/1109263/monthly-vlsfo-
| bu...
| dtech wrote:
| Cargo ships cost $100 million or thereabout, and operate for
| at least 30 years. Estimating that about 1/3'rd of that is
| time where these would be useful, this would save about $27
| million and the savings grow with inflation, so that's no
| small change.
| Johnny555 wrote:
| _Cargo ships have ridiculous life expectancies measured in
| decades, so it 's very likely to make a significant dent._
|
| Note that 12 tons/day was the best case, the average was 3
| tons, so that's more like $2000/day or around $400K/year
| assuming the ship is at sea 200 days/year.
|
| Anything on a ship with moving parts has significant
| maintenance costs, so it'd be nice if they had a ballpark
| figure of the installation/maintenance costs as well as
| expected lifetime of the system.
|
| And what happens in a serious storm? It looks like these can
| be rotated but not folded down flat, so what happens in
| unpredictable winds during a storm?
| jcgrillo wrote:
| They do fold flat [1]. [1] https://youtu.be/AB7cLkSVmJA
| wolverine876 wrote:
| The calculation is perverted by the free externalities of
| dumping carbon in the atmosphere, a very expensive discount. I
| know it's not news, but it perverts economic decisions.
| desmond373 wrote:
| The problem is that while that has no dollar value attached,
| the companies dont care.
|
| It would be good if there was some global carbon tax that
| required equivilent carbon biomass be grown from scratch to
| offset emmisions. Said biomass could the be processed and
| stored.
|
| Its not really a tax, its taking responsibility for the waste
| you produce.
|
| Same goes for plastics. If a plastic is used in manufacturing
| in a way that means its going to get thrown oit eventually
| then that company should be responsible for collecting that
| amount of that said plastic from garbage and storing it long
| term.
|
| This would hopefully drive people to the most efficient
| solutions. Some fossil fues and plastics would still be used
| but their negitive effects would be offset by the collection
| and storage process.
| ajb wrote:
| So, they are saving 14% and expect to multiply that by 1.5 by
| having an additional wing. Is there any prospect of getting near
| 100%? Naively 15 wings would get there. From the image maybe 7
| would fit on this ship without a redesign. Once it's proven, will
| it gradually evolve to taking more and more of the energy
| requirements?
|
| Obviously I realize there has to be some fuel in case the vessel
| would be becalmed, but apart from that, what are the limits?
| jtbayly wrote:
| You can fit that many, maybe, but most of them won't be able to
| effectively harness the wind as the other sails will interfere.
| ilkke wrote:
| Why stop there? Add more than 15 sails and you could be
| generating fuel!
| wolrah wrote:
| > Why stop there? Add more than 15 sails and you could be
| generating fuel!
|
| AFAIK there are a few companies that have been adding
| electric drive systems to sailboats that actually do work
| this way, not only can it be used to maneuver around when the
| wind is uncooperative but it can generate power when the wind
| is good, basically acting as a "hybrid" of sorts where
| hypothetically given enough battery storage and maybe some
| solar it could be possible to never have to plug in or run a
| combustion generator.
| wolverine876 wrote:
| Why not put a windmill on the ship and generate electricity,
| turn the screw, and drive the ship? Not as efficient?
| akira2501 wrote:
| They're saving 12%, on the best days. The average is 3.8%.
|
| What's not covered in the article is the weight of the devices
| and the amount of cargo that must be removed from the load to
| support them. Without that you can't project forward at all.
|
| And even so, you're never going to get to 100%. Cargo ships
| need electricity to keep cargo refrigerated. They need to be
| anchored for long periods of time. They need to navigate
| harbors and other channels.
| ordu wrote:
| _> They 're saving 12%, on the best days. The average is
| 3.8%._
|
| According to the article it is 12 tons/day on the best days
| and 3.3 ton/day average. 14% average with 37% max for
| reduction of greenhouse gases emissions.
| nradov wrote:
| 100% of what? In principle with favorable winds a large
| merchant ship could cross an entire ocean using sail power, but
| it would be very slow. Due to capital expenses, crew wages, and
| customer demands that wouldn't be economically viable. Even
| with "slow steaming" to save on fuel, merchant ships on long
| crossings are generally cruising at least 13 knots. There's no
| way to consistently hit such a high speed on a large vessel
| with any practical sail rig.
| bilsbie wrote:
| Why don't sailboats use these?
| andrewflnr wrote:
| Some really high end racing sailboats do use rigid "sails". But
| there's a lot to be said for a wind surface that can stow away.
| I assume regular sails are lighter. Also, of course, momentum
| and habit.
| rightbyte wrote:
| There are those who do.
|
| https://en.wikipedia.org/wiki/Wingsail
|
| Apart from being complex and expensive, you can't reduce their
| size for hard winds.
|
| Rigid sails seems very inconvenient to fold too.
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