[HN Gopher] Rotating Sails Help to Revive Wind-Powered Shipping
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Rotating Sails Help to Revive Wind-Powered Shipping
Author : ystad
Score : 183 points
Date : 2020-12-27 13:31 UTC (9 hours ago)
(HTM) web link (www.scientificamerican.com)
(TXT) w3m dump (www.scientificamerican.com)
| julosflb wrote:
| Related to this, a french startup is trying to build fleet of
| autonomous ships to harvest energy from ocean. They make use of
| flettner rotors also.
|
| https://farwind-energy.com/
| JamisonM wrote:
| Perhaps also of interest: E-Ship 1
| https://en.wikipedia.org/wiki/E-Ship_1
|
| In service since 2010!
| Tepix wrote:
| I've already bought some chocolate that was transported by cargo
| sailboat Avontuur, a 100-year-old 2-master schooner.
|
| Here's some information in English :
|
| https://www.zotter.at/en/about-zotter/projects/translate-to-...
|
| https://timbercoast.com/en/ship/
|
| and in German:
|
| https://www.zotter.at/das-ist-zotter/kakao-setzt-segel
|
| https://timbercoast.com/de/schiff/
|
| PS: The chocolate was delicious! It's also a fantastic gift for
| sailors
| usrusr wrote:
| Oh, there's more than one? I only know the one that ends up
| with https://chocolatemakers.eu/eu/de/19-schokofahrt getting
| distributed from the Netherlands across neighboring countries
| by cargo bike. Surely won't scale for anything other than
| awareness luxury gifts, but that cannot be seen as a reason to
| look the other way when you happen to buy luxury gifts.
| UI_at_80x24 wrote:
| This looks similar to something Jacques Cousteau implemented. On
| his ship the Alcyone.
|
| https://en.wikipedia.org/wiki/Turbosail
| satori99 wrote:
| While they look similar, Turbo sails are not Flettner rotors.
|
| Turbo sails use an internal fan to draw air into the tubes, and
| vents are used to control where the air pressure drops.
|
| They do not rotate at all.
| [deleted]
| kebman wrote:
| I'm just thinking out loud. Some things don't need fast shipping.
| Instead it needs a steady and even supply. And if a ship doesn't
| use any fuel, it could even serves as a kind of movable storage
| house. Thus I'm really looking forward for the developement of
| autonomous sailing ships. I really believe there's a market for
| them, or at least a niche within shipping.
| lopmotr wrote:
| Although reducing speed and fuel usage reduces fuel costs, it
| increases fixed costs (you need more ships for the same
| throughput) as well as operating costs like crew. It might turn
| out to still be more expensive in the end. Then there's the
| problem of less certainty about price changes if you have to
| wait longer for the product to be delivered which leads to
| inefficiency (over/under-supply if mispredicted). There's also
| the opportunity cost of money being tied up for longer in the
| delay between production and consumption.
| AtlasBarfed wrote:
| I just wonder if massive sails that double as solar panels, and
| additional fold-out solar arrays, would be superior overall and
| lighter.
|
| But any short-term "jury rig" is valuable.
|
| And if we get enough cheap excess green energy, carbon-neutral
| artificial fuels might be superior too.
| chooseaname wrote:
| This comes around every so often, with the same claim, then
| disappears.
| geocrasher wrote:
| Indeed. It's one of those recurring engineering memes that
| makes the rounds every decade or so. Id be surprised if it
| hasn't been on the cover, or in the pages of, Popular
| [Science|Mechanics] at least once a decade for the past 50
| years.
|
| What I personally don't understand is why these aren't
| themselves driven by a vertical air wind turbine. The
| rotational speeds aren't very high, and it seems like a no-
| brainer. A VAWT with variable vanes could easily be shut down
| in a storm.
| selimthegrim wrote:
| Savonius turbines just aren't very efficient.
| carapace wrote:
| The interesting thing about the Magnus effect is that the lift
| goes up with the second power of the radius of the rotor, so
| twice as large gets you four times as much lift. The largest
| Magnus effect vehicle I know of was a huge sphere with the crew
| cabin hanging below it from the axle. The whole sphere was the
| lifting body.
|
| The old OMNI magazine had an article wherein they calculated that
| you could put Magnus effect rotors on a bus and it would fly at
| (speeds as low as) 35mph.
|
| I've had plans for years now to build large flying buildings (if
| I can get my act together I might eventually do it) using
| geodesic cellular kites and the Magnus effect. (Look up Alexander
| Bell's kites, and Bucky Fuller's "Cloud Nine" aerial city
| concept.)
|
| - - - -
|
| http://www.rexresearch.com/flettner/flettner.htm
|
| http://www.rexresearch.com/skybow/mueller.htm
|
| http://www.rexresearch.com/aero/1aero.htm#thompson
|
| http://www.rexresearch.com/aero/1aero.htm#flettner
|
| And I found some images but not the name of the upside-down-hair-
| band-sphere design on this blog post:
| https://steemit.com/airship/@everittdmickey/magnus-effect-ai...
| vernon99 wrote:
| I'm pretty sure a lot of folks from HN will help you fund such
| research and prototyping if needed, me included :)
| joshspankit wrote:
| Based on the responses so far, consider "How much money would I
| need to actually commit enough time to this?", and then share
| that number.
|
| If it 'doesn't stick', you'll still be able to keep it as plan
| refi ing for now, but if it does, investors might surprise you.
| dragosmocrii wrote:
| Can you get your act together and build this? I'd like to see
| the end result, and the process.
| dghughes wrote:
| I remember seeing this on the cover of Popular Science in 80s
| (maybe early 90s). A ship with a large cylinder used for
| propulsion from wind energy.
|
| edit: I found the issue
| https://www.google.ca/search?sa=X&sxsrf=ALeKk01n7hvalLGEwW3e...
| sradman wrote:
| From Wikipedia [1]:
|
| > A rotor ship is a type of ship designed to use the Magnus
| effect for propulsion. The ship is propelled, at least in part,
| by large powered vertical rotors, sometimes known as rotor sails.
| German engineer Anton Flettner was the first to build a ship that
| attempted to tap this force for propulsion, and ships using his
| type of rotor are sometimes known as Flettner ships.
|
| Container ships reduce the superstructure to enable loading but
| these rotor sails could possibly be used on oil tankers and bulk
| carriers. We don't hear about autonomous water vessels very
| often, perhaps a Flettner water drone is possible.
|
| [1] https://en.m.wikipedia.org/wiki/Rotor_ship
| icegreentea2 wrote:
| As noted in the article, many of these ships may need the
| ability to stow away the rotor to be able to pass under bridges
| anyways. It could still be viable for container ships.
| jdeibele wrote:
| Looking at a picture of a large container ship there's more
| of a challenge siting rotors. Up high they would be in the
| way of cranes loading containers and might require really
| strong (and large) towers to hold the rotors. Built only as
| high as the containers, it doesn't seem like they would see
| any wind.
|
| How would you envision them working on a container ship?
|
| https://zeymarine.com/wp-
| content/uploads/2020/01/container-s...
| icegreentea2 wrote:
| I'll admit that I straight up don't know how the structural
| loading would be like - but I seems to be me that you might
| be able to get some sort of telescoping solution that works
| ok. Since you'd probably need to clear the containers
| anyways to get the most of the power out of the system, the
| lower portion of the sail doesn't need to be a rotor - just
| a mast for the rotor section to telescope over.
| cadence- wrote:
| From some photos I saw, they install them very close to
| the edges on the sides of the ship.
| musingsole wrote:
| I can't recall the researchers name, only that they had some
| association with NCSU, but they worked heavily with wind-
| propelled aquatic drones. I remember a talk they gave about
| waiting for wind conditions and the quirks of the control
| system.
| yread wrote:
| Slightly related: wind powered car that goes faster than the wind
|
| https://phys.org/news/2010-06-wind-powered-car-faster.html
| comboy wrote:
| This is so counter-intuitive. I couldn't wrap my head around
| this and wikipedia article was more helpful to me than the
| article: https://en.wikipedia.org/wiki/Blackbird_(land_yacht)
|
| Thanks for the link.
| nabla9 wrote:
| MS Viking Grace has rotor sail. Fuel savings are 300 tons per
| year from the sail. It also uses LNG fuel. In best conditions the
| sail can provide 20% fuel savings. In reality much less than
| that, but it's a small sail compared to the size of the ship.
| Viking Grace is a cruiseferry, so even in full capacity it's
| almost empty compared to a cargo ship.
|
| Maersk Pelican (tanker): 8.2% fuel saving during the first year
| of operation.
|
| M/V Estraden (ro-ro cargo): 6.1% fuel saving.
|
| https://www.norsepower.com/
| PopeDotNinja wrote:
| I don't see the article specifically mention slow steaming...
|
| https://en.wikipedia.org/wiki/Slow_steaming
|
| Using sails to increase fuel economy seems like a no brainer,
| but now I'm wondering if cargo ships were ever using sails to
| increase their maximum safe cruising speed. Does anyone know?
| ghaff wrote:
| Before steam they did :-)
|
| Sail died off pretty quickly once steam came in. [EDIT:
| Apparently in some applications much faster than others.] In
| the case of modern examples, I'm pretty sure it's been
| exclusively for fuel economy. And, until recently, the
| overhead associated with using sails was generally more
| trouble than they were worth.
| nabla9 wrote:
| Steam ships used to have sails for a long time. Gradually
| the amount of sails deceased. Last ocean liners with sail
| assist were build in 1884.
|
| The most famous clipper (fast sail ship) Cutty Sark (later
| Ferreira) operated between 1870 - 1922 (17.5 kn max speed).
| Retric wrote:
| Yea, the original limitation was the manpower cost of
| manning the sails which is why they where eventually
| dropped. With modern systems they are almost completely
| automated, which makes them far more viable.
| nabla9 wrote:
| It was not the manpower cost that was the limit. Steam
| ships had huge crews managing the engines. Titanic had 25
| engineers, 170 firemen, 73 coal trimmers and 33 greasers.
|
| It was the size. Sail ships had practical upper limit for
| their size and weight. Size of the mast and sails could
| not just grow.
|
| Square-cube law: (drag) surface area is proportional to
| the square while the volume is proportional to the cube.
| Bigger the ship, more efficient it becomes.
| Retric wrote:
| It's important to realize that 300 man engine crew was
| needed in large part do to the Titanic's fast 21 knots
| cruse. A slower vessel of the same size and weight needs
| dramatically less power. By comparison the last
| commercial bulk cargo sailing ship Palmer which sank in
| 1957 needed an 85+ man crew, only had an 8-9 knots cruse,
| and was vastly smaller. For the titanic to add an extra
| 200+ crew to possibly save less than 10% on fuel costs
| was simply not tenable.
|
| Where combined steam and sail ships really benefited
| wasn't fuel, it was consistent power. Early steam engines
| where unreliable as was sail, but they rarely failed at
| the same time. However with more reliable steam it was
| just a question of economics.
| [deleted]
| walrus01 wrote:
| the economics of fast sail clippers such as the cutty
| sark were limited to high value, low weight products such
| as specialty teas. the actual cargo volume in such a sail
| clipper was fairly low. an analogy for today would be air
| cargo freight in 747s of fresh flowers or something.
| ghaff wrote:
| Ocean liners (and certain types of cargo) makes sense. An
| increase in speed can work economically even though it's
| not efficient. From what I was reading, sail went out in
| most military ships fairly quickly but that's a different
| set of constraints and priorities.
| [deleted]
| oli5679 wrote:
| Naive question: is solar + battery feasible for shipping?
| Animats wrote:
| Oh, Flettner rotors again. Those keep coming around. Jacques
| Costeau used to have a rotor ship, the _Alcyone_.[1] It wasn 't
| really worth the trouble. "In fact, we were motoring most of the
| time" - Alcyone's captain.
|
| [1] https://sea-to-summit.net/the-flettner-rotor-makes-a-
| comebac...
| geoduck14 wrote:
| >Those keep coming around.
|
| BAA HAHAHAHA
| ipsum2 wrote:
| That piece is some high quality independent journalism.
| williesleg wrote:
| Not gonna happen as long as those china ships belch diesel fumes
| underwater so we don't see them. They're killing the oceans.
| wefarrell wrote:
| Would like to see more about what's going on below the waterline.
| The challenge with any form of wind power is that the propulsion
| doesn't typically point forward - it's at an angle with a forward
| component. So on a sailboat you need a long keel (or
| centerboard/daggerboard) to translate the lateral propulsion into
| forward movement. That constricts the vessel from operating in
| shallow waters and causes the vessel to lean due to the opposing
| force under the waterline.
| silicaroach wrote:
| Wow ... this comes up a couple of times a decade. It's like the
| Simpsons 'We'll build a monorail'. It's right up there with the
| Solar Sail scam.
| burlesona wrote:
| It doesn't seem quite like that. There appear to be a dozen or
| so of these ships already running, and more being converted.
| Perhaps this remains a small niche, but it certainly is an area
| of active investment and growth today.
| colinmegill wrote:
| RC Plane leveraging Magnus effect
|
| https://youtu.be/GAqLyyg2AHk
| mmaunder wrote:
| Very little discussion here or in the article on why use these in
| favor of traditional sails. Looking at America's Cup, the trend
| one would expect would be foils supplemented by motor and more
| traditional sails. I'm sure these are easier to deploy, but
| consider that an America's cup boat can do 40 knots in a 12 knot
| breeze. Sure that's without cargo and on a highly optimized
| design with hard working crew, but it does prove the remarkable
| efficiency of a traditional wing.
| dzhiurgis wrote:
| Indeed one is for racing another for cruise.
|
| Wonder if you can make inflatable tower for lesser weight and
| reefing. Maybe there's some stable design where you start
| foiling using motors then when you are stable - use excess
| power to turn rotors. AC75 boats are very unstable without
| foils and these things are heavy as.
| throwaway0a5e wrote:
| Racing has a very different labor cost situation than
| commercial freight.
|
| Commercial freight will likely make use of far less energy
| efficient but far more labor efficient designs.
| nabla9 wrote:
| You can just install these rotating wings on the deck and get
| 5-7% increase in fuel efficiency immediately and lasts 20-30
| years with minimal maintenance. The investment pays itself back
| in 3-8 years.
|
| Wing is obviously more efficient. The problem with the wing is
| the cost and size. You need to design the ship for the wing.
| https://en.wikipedia.org/wiki/Oceanbird
| bufferoverflow wrote:
| Aren't kite systems much more efficient and lighter and cheaper?
|
| https://www.researchgate.net/figure/A-ship-sailing-with-the-...
| bserge wrote:
| Surprisingly, no. Last time this was posted there were some
| efficiency figures, wingsails being the best, but Flettner
| rotors still beating old-fashion sails and kites. And rotors
| are very likely cheaper than a sail/kite long term (they need
| complete replacement quite often because of rips and tears).
| frederikvs wrote:
| From the article : "Ships can easily be retrofitted, literally
| overnight, with rotors activated by an on/off switch."
|
| I think kite systems require more work, e.g. for launching &
| landing. When it gets taken down, you probably need to dry it,
| fold it, stow it, etc. So even if they are more efficient,
| lighter & cheaper, doesn't mean they're necessarily the
| preferred solution.
| studius wrote:
| With the technology we have today, why couldn't self-drying,
| self-folding, self-stowing sails be used to make ships even
| more efficient?
|
| Edit: there actually is a ship called the Oceanbird[1] with
| telescopic metal sails.
|
| [1]- https://www.youtube.com/watch?v=pZVDs4n_a0M
| Tade0 wrote:
| Because that's a fairly hard problem comparing to just
| tacking two rotating columns.
| studius wrote:
| There's a patent for a memory metal sail[1], telescopic
| sail mast[2], automatic retractable sail[3], and many
| others[4].
|
| Also, there's the Oceanbird[5], a modern car-carrying
| ship with telescopically retractable metal sails.
|
| [1]- https://patents.google.com/patent/US9481432B2/en
|
| [2]-
| https://patents.google.com/patent/DE202011101489U1/en
|
| [3]- https://patents.google.com/patent/CN103086280B/en
|
| [4]-
| https://www.google.com/search?q=telescopic+sail+patents
|
| [5]- https://www.maritime-executive.com/article/swedish-
| collabora...
| curtainsforus wrote:
| All this complicated, fiddly tech, vs. two spinning bits
| of metal. I know which one I'd be more confident in...
| frederikvs wrote:
| Perhaps they could, assuming somebody is willing to make
| the necessary investment to develop what you describe.
|
| However, it will probably be a complex system, and like
| most complex systems, it will be fairly fragile. Compare
| that to these Flettner rotors, which are essentially "a
| tube and a motor".
| mhb wrote:
| _Ships can easily be retrofitted, literally overnight, with
| rotors activated by an on /off switch._
|
| Kite systems seem far less practical but this can't possibly
| be true unless they're talking about a Sunfish. And even
| then, I'm skeptical. Or maybe they're using _literally_ , as
| is the fashion, to mean _figuratively_.
| jcims wrote:
| Yeah that claim stinks to high heaven. You're just going to
| bolt these suckers down to the deck and plug in an
| extension cord? https://en.m.wikipedia.org/wiki/Rotor_ship#
| /media/File%3ACar...
| fulafel wrote:
| That picture is not of an auxiliary retrofited sail, but
| of E-Ship 1 which is all sails. The retrofitted ones are
| much smaller relative to ship size and are used together
| with main engines.
| perlgeek wrote:
| Are they? How is maintenance? How sensitive are they in changes
| to wind? How much training does the crew need to operate
| either?
|
| https://en.wikipedia.org/wiki/Wind-assisted_propulsion says
|
| > In comparison to kite sails, Flettner rotors often offer
| considerable efficiency gains when compared to the size of a
| sail or kite vs. size of the rotor and prevailing wind
| conditions.
|
| But I'm not sure if this size comparison makes all that much
| sense (maybe the performance per dollar invested would be more
| interesting?)
|
| I'm genuinely curious about a comparison from an operator's
| perspective, and I also hope both approaches are being
| developed further.
| harperlee wrote:
| If I understand the concept correctly the rotor does not only
| work as "sail" but also as "air propeller", as you need to
| input energy through its rotation (that gets multiplied by the
| "sail" effect of the Magnus effect). So that's an apples to
| oranges comparison, that does not bode well for the kite (as it
| is "passive", not effecting any compounding of energy).
| rossdavidh wrote:
| What I've read previously is that the kite systems took more
| training and skill to utilize, which was holding back adoption,
| whereas this sounds like it would be a much easier technology
| to use. Although, I do wonder if one could use both.
| neurostimulant wrote:
| Why not both? Flettner rotor works best when the wind is
| perpendicular and kite works best when the wind blows in the
| same direction to the ship's course.
| paulryanrogers wrote:
| Kite lines can kill others nearby. There is some animosity
| between windsurfers and kite surfers because of this risk.
| yardie wrote:
| Kite surfers are the assholes of the sea according to some
| sailors. I've seen them zip in and out of navigation channels
| and between boats. Also had a few get dangerously close and
| cross our bow as we were sailing on a reach.
|
| Also, I do enjoy the sport. It's similar to endurance
| swimming and nearly every muscle in the body is worked. I
| found kitesurfers in some really remote banks and wondered
| how the hell did you get all the way out here.
| JoBrad wrote:
| Surely this isn't an issue in the open sea, where tankers
| would mostly be using this.
| hanniabu wrote:
| I can see the ecological disaster of loose kites in the ocean
| already
| odonnellryan wrote:
| How to kite systems work any direction into the wind? Like
| anything from the beam or closer?
| JamisonM wrote:
| Pretty sure you need a tail-wind to use a kite system, this
| works in any wind.
| frederikvs wrote:
| Pretty sure you don't need a tail-wind. Regular old sails as
| well as kites can be used at various angles to the wind. See
| e.g. https://en.wikipedia.org/wiki/Point_of_sail
|
| [edit] P.S. from my understanding of the mechanism, I'm not
| so sure these Flettner rotors are useful in a headwind. They
| work by creating a pressure difference, but in a headwind,
| you could only create a pressure difference between the port
| and starbord sides, not the front and back. Unless there's
| some mechanism I'm missing?
| mannykannot wrote:
| If, by headwind, you mean sailing directly upwind, then no,
| they cannot do that, but they can beat to windward like a
| sailboat (the direction of the rotation must be reversed
| when tacking.) According to Wikipedia, the rotor ship
| Buckau could sail within 20-30 degrees of the wind, though
| I suspect that is a misreading of the supposed source of
| that data, and that 50-60 degrees is a more plausible
| figure. Similarly, I suspect the claim that they can sail
| closer to the wind than conventional sailing vessels is in
| comparison to square-rigged ships.
|
| https://en.wikipedia.org/wiki/Rotor_ship#Pioneers
|
| https://books.google.com/books?id=9lqwg3iZyH0C&pg=PA656#v=o
| n...
| odonnellryan wrote:
| I would be surprised if a kite system could get much closer
| than 90 degrees to the wind.
| Ericson2314 wrote:
| To second the others, "reaches" are the fastest. I forget
| why, but I suspect it's like gearing, less force, more
| distance, for the same amount of work.
| rightbyte wrote:
| Aslong is the wire points forward of left and right the net
| force is forward right?
|
| In practice you probably want the wire +-45 degrees from the
| bow or something. That is where you would use a gennaker or
| spinnaker.
| odonnellryan wrote:
| I feel like this would be a worse version of a symmetric
| spinnaker, which you generally sail in 100-180
| dzhiurgis wrote:
| So how well does these sails point into wind and how do control
| lift angle?
| _hl_ wrote:
| They don't. The lift is orthogonal to the wind direction, so it
| will be most efficient when the wind is directly from the side,
| with the forward force falling of with the cosine of the wind
| angle. There's really no way to change that with these types of
| sails.
|
| This is actually quite an important limitation for cargo ships,
| as wind directions on the large oceans are somewhat constant
| and mostly east-west. Hence these sails would be better for
| north-south routes.
| jeffreyrogers wrote:
| There were some planes that used this concept, but they were
| never commercially successful (partly because if they lose power
| they cannot glide to a landing like a normal plane can). I think
| it was used in some bomb designs as well.
| BurningFrog wrote:
| Some questions after spending 10 minutes studying this:
|
| 1. These ships all seem to have two towers. Why not more? Can't
| they be closer for some science reason?
|
| 2. This works by spinning the towers using a motor. How do the
| propulsion gains compare to using the same motor power on a
| propeller?
| frederikvs wrote:
| Regarding the two towers : if you look at the E-ship 1 [0]
| you'll see 4 towers - 2 in the front, 2 in the rear. There are
| no towers in the middle, probably because that area is intended
| for cargo.
|
| I presume there is also a minimum distance they need to be
| separated - if you look at some of the illustrations of the
| Magnus effect [1], you'll see a turbulent region downwind of
| the tower. Another tower in this turbulent region won't work as
| intended.
|
| This is pure speculation on my part, but perhaps most ships
| simply aren't wide enough to have two towers side by side (the
| E-ship 1 being an exception). That, and wanting to use most of
| the ship for cargo, explains why most ships only have 2 towers.
|
| [0]
| https://en.wikipedia.org/wiki/E-Ship_1#/media/File:Bateau_en...
|
| [1] https://en.wikipedia.org/wiki/Magnus_effect
| voldacar wrote:
| Super interesting - is a perfectly smooth cylinder most
| desirable? or should it be a little rough in order to better tug
| on the air as it spins?
| cadence- wrote:
| On photos it always looks smooth. I guess you also need to make
| sure it doesn't cause too much drag when not in use (for
| example, if you travel against the wind).
| blacksmith_tb wrote:
| I wondered that as well - I suppose the added
| weight/complexity of using vanes that could be folded in
| (sort of like a big turbocharger) must not be worth any
| gains. Hard to beat the simplicity of a big tube.
| russfink wrote:
| Off topic, but would a practical plan be to build a solar powered
| ship, with a large, miles-long towed solar panel array?
| jacquesm wrote:
| You'd have to overcome the drag of that array. At a rough
| estimate at 1 KW / square meter for half the day it wouldn't be
| worth it unless you added a way for it to be pulled in at night
| (which is going to be pretty hard to do with solar panels which
| are quite fragile).
|
| On top of that, the ocean is about as hostile an environment as
| you could wish for and it wouldn't work anywhere near busy
| shipping lanes.
|
| Creative idea though, I haven't seen it before.
| m463 wrote:
| https://upload.wikimedia.org/wikipedia/commons/e/ef/Solar_Sa.
| ..
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