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Maersk installed 100-foot-tall rotating sails on one of its tankers

wsj.com

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Re: Maersk installed 100-foot-tall rotating sails on one of its tankers

#31

Post by sjbase »

alex_duf wrote: post #24
IB885588 wrote: post #8

Another option is skysails (giant kites that drag the ship forward): https://en.wikipedia.org/wiki/SkySails Hopefully someday almost all ships have a mix of these things + maybe run on algae-based advanced biofuels or something like that.

Edit: I'm wrong, see responses bellow for correction Original message: I seem to remember (if I'm wrong please correct me) that the Magnus effect works regardless of the direction of the wind, whereas the sky sail needs the wind to be roughly in the same direction of travel. They could be combined but as far as I understand these spinning columns are more generic

It seems like Magnus sails work best when the wind is coming from the side (port or starboard), since the direction of force is perpendicular to the wind [0]. Doesn't matter which side, since you can just reverse the rotation of the cylinder.

With a headwind or tailwind, tacking could be used but the increased distance traveled may offset the gains from the Magnus sail.

0: https://en.wikipedia.org/wiki/Magnus_effect

Re: Maersk installed 100-foot-tall rotating sails on one of its tankers

#32

Post by LeifCarrotson »

alex_duf wrote: post #24
IB885588 wrote: post #8

Another option is skysails (giant kites that drag the ship forward): https://en.wikipedia.org/wiki/SkySails Hopefully someday almost all ships have a mix of these things + maybe run on algae-based advanced biofuels or something like that.

Edit: I'm wrong, see responses bellow for correction Original message: I seem to remember (if I'm wrong please correct me) that the Magnus effect works regardless of the direction of the wind, whereas the sky sail needs the wind to be roughly in the same direction of travel. They could be combined but as far as I understand these spinning columns are more generic

You are, unfortunately, incorrect. The Magnus effect doesn't gain you anything other than the helpful drag of a tall cylinder when going in the same direction as the wind. Rotating it only pulls you sideways, which doesn't help.

However, it can pull you forward when the wind is coming from the side. You change the direction of rotation based on which side the wind is coming from.

Without tacking, no (edit: solely) wind power systems will help when going straight upwind.

Re: Maersk installed 100-foot-tall rotating sails on one of its tankers

#33

Post by jherdman »

abtinf wrote: post #18

Some years ago I read The Box by Marc Levinson, a history of containerized shipping. Highly recommend it. If you live in SF and have wondered about the numerous barely used piers, this book explains their history as well - and why the major container terminal ended up in Oakland instead. One of the painful early lessons for the industry was the discovery that minimizing operational costs (particularly fuel and mainte…

You might enjoy "Containers", an eight episode podcast about the shipping industry too. https://medium.com/containers

Re: Maersk installed 100-foot-tall rotating sails on one of its tankers

#34

Post by factsaresacred »

Copying the first comment from WSJ 'cause it's interesting:

> These are known as Flettner rotors after the German engineer Anton Flettner who invented them and made the first rotor sailing ship in 1924, with one sailing one across the Atlantic in 1926 - and they are not turbo sails. They have generally been in disuse as it has been deemed that the energy expended in propulsion by Flettner rotors was higher than that for propellers - perhaps it seems with modern materials, wind monitoring and computer assisted controls this has been tilted to the favor of Flettner rotors. Flettner also invented trim tabs which any large power boat operator knows very well.

> An interesting note, Flettner was considered so valuable to the Germans in WW2 that Heinrich Himmler, the head of the Gestapo saw to it that Flettner's Jewish wife was escorted to Sweden for her safety for the duration of the war.

Re: Maersk installed 100-foot-tall rotating sails on one of its tankers

#35

Post by jacquesm »

LeifCarrotson wrote: post #32
alex_duf wrote: post #24

Earlier quoted context omitted.

Edit: I'm wrong, see responses bellow for correction Original message: I seem to remember (if I'm wrong please correct me) that the Magnus effect works regardless of the direction of the wind, whereas the sky sail needs the wind to be roughly in the same direction of travel. They could be combined but as far as I understand these spinning columns are more generic

You are, unfortunately, incorrect. The Magnus effect doesn't gain you anything other than the helpful drag of a tall cylinder when going in the same direction as the wind. Rotating it only pulls you sideways, which doesn't help. However, it can pull you forward when the wind is coming from the side. You change the direction of rotation based on which side the wind is coming from. Without tacking, no (edit: solely) wi…

> You are, unfortunately, incorrect.

No, you are, unfortunately, incorrect.

> Without tacking, no wind power systems will help when going straight upwind.

https://en.wikipedia.org/wiki/Windmill_ship

Re: Maersk installed 100-foot-tall rotating sails on one of its tankers

#36

Post by jacquesm »

joering2 wrote: post #19

What these ships are mostly surrounded by are waterfields that go as far as you can see. Can they come up with some sort of rolled flexible solar panels that once ship goes into full sail they release their “solar tail” behind that floats on the water surface and captures sun and turns it into electricity for ships’ engines? I mean 300 meters square of solar panel should be sufficient to push the ship at its nominal…

For free, when there are no waves, when the sun is shining, when there is no other vessel that crashes in to them and when you convince someone to make it all and then gift it to you.

Re: Maersk installed 100-foot-tall rotating sails on one of its tankers

#37

Post by LeifCarrotson »

joering2 wrote: post #19

What these ships are mostly surrounded by are waterfields that go as far as you can see. Can they come up with some sort of rolled flexible solar panels that once ship goes into full sail they release their “solar tail” behind that floats on the water surface and captures sun and turns it into electricity for ships’ engines? I mean 300 meters square of solar panel should be sufficient to push the ship at its nominal…

300m^2 only gets you a couple hundred kW on the brightest days at peak efficiency. These ships require powerplants providing on the order of 50,000 kW.

A 40-acre floating solar farm would add a LOT of drag. Better to make the solar farm stationary, use it to synthesize fuel, and run the ship with an internal combustion engine for power density. Maybe someday batteries could be used.

Re: Maersk installed 100-foot-tall rotating sails on one of its tankers

#38

Post by macmac »

DannyB2 wrote: post #27

From TFA... > Maersk Line spent around $3.4 billion on fuel last year for its fleet of around 800 vessels. Wouldn't savings from wind power be bad for the petroleum industry? And therefore by lobbyist extension bad for everyone?

That's Maersk Line, which is the container shipping division of Maersk. The rotor sails are being installed on a tanker vessel from Maersk Tankers. Deck space is a valuable commodity on a container vessel, so not as obvious where to place the rotors.

Re: Maersk installed 100-foot-tall rotating sails on one of its tankers

#39

Post by jacquesm »

cwmoore wrote: post #30
village-idiot wrote: post #21

Earlier quoted context omitted.

I think the issue would be salt water. Salt water destroys everything , I can’t imagine that a PV array floating in water would have a good life expectancy. On the plus side, if the insulation fails you could turn container ships into accidental fishing boats.

> Salt water destroys everything This is the statement I hear relating to all kinds of ocean-based renewable energy ideas. Sources are never provided. The problem must have to do with economic viability and the replacement/maintenance costs exceeding savings. Could you supply sources to elaborate on where the break even point of solar tail (or any two other ocean renewable energy) systems would be as relates to costs…

> Sources are never provided.

We also do not need to provide sources for statements such as 'water is wet'.

Anything on a boat, or even shoreside near to the ocean is subject to corrosion and corrosion protection is a serious maintenance issue. I've lived 2 km from the sea and even there the nails would rust right out of the building due to the salt that the wind would carry in.

Re: Maersk installed 100-foot-tall rotating sails on one of its tankers

#40

Post by tomtimtall »

ValleyOfTheMtns wrote: post #23

I've been wondering why shipping companies haven't been doing this for years now. Whenever I brought it up with friends they would say it's probably not worth the effort, but I can't see how it wouldn't be worth it. It's essentially free energy to help move the ship around. Got to say, I feel vindicated by this story.

Essentially free energy... except the cost to install, the cost to operate, maintainable and of cause the cost when one of them breaks and causes damage.

For a lot of these “why don’t they just” the answer is simply that they did the math and saw too small an upside for too big a risk.

They are trying this out to see if the overall concept works in practice or if it falls short.

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