Yeah we know that. My point, that I tried to succinctly explain, was the Magenn MARS device could be modified for use in kite-reeling, starting with removal of the Savonius flaps, and reversing the current flow from down to up, so as to spin the sausage. Thanks for the links - I knew I had seen this somewhere. So is this concept still being pursued? Or is it on the scrapheap of wannabe wind energy breakthroughs, or what? If it didn’t work, what does that say about the 1 MW+ output in the paper Pierre cited?
On the tested balloon, the spin ratio was very low (a bit more than 1 with a low wind speed of 5 m/s), leading to a lift coefficient of about 2, while on the paper an ideal spin ratio of about 4 or 5 is considered with a consequent wind speed of 10 m/s. I don’t think such a spin ratio is easy or even possible to obtain with an inflatable cylinder, and the power consumption would be likely higher than for a rigid (and heavy) cylinder, because the shape is difficult to maintain, and would probably be hollowed out by the wind force unless the pressure is very high.
Well, that explains the low output. From what I read, there is a “magic” rotational tangential speed of equal to the wind speed where all lift disappears.
Still wondering about the 1 MW+ cited in the paper Pierre cited. If true, why is it not being pursued?
I just mentioned some difficulties to really achieve a suitable spin ratio. And also, page 22:
Magnus rotor mass 50000 kg
Too much.
Wow, thanks for clarifying, Pierre.
Crazy - 50 tons for one spinning sausage?
Wait, how big was it supposed to be? 80 meters long? ~250 feet?
Seems like it could weigh less than 50 tons.
And it’s supposed to fly???
Are you sure that was not the pull?
Geez you know, I get tired of working my feeble brain so hard trying to make sense of one “Professor Crackpot” paper after another.
All I needed to do was see the names of the authors to start out skeptical.
Most of this stuff turns out to be a waste of time.
I’m thinking all these flettner sail developers are suffering from The Professor Crackpot Syndrome. “Interesting…” “Unexpected…”
How about “Worthless…”?
I have a doubt. There may be an inaccuracy in the document.
Page 17, Table 1.2 Parameters of the medium scale Magnus rotor:
MM Mass of airborne subsystem 91.22 kg
MD Ground station rotor mass 2000 kg
Page 24, Table 1.3 Parameters of the MW scale Magnus rotor:
MM Mass of airborne subsystem 1.133×10000 kg
MD Magnus rotor mass 50000 kg
50000 kg applies to the ground station rotor mass, and 11300 kg to the airborne 80 m length balloon?
But even with “only” 11300 kg (6 times Makani M600) about 12000 m³ helium are required.
This is not a problem, anyway we are at the epicenter with the flying wind turbines.
Yeah, God forbid they could just put together an easy-to-read summary with some easy-to-understand graphics, and no typos.
I would not believe the 8% energy savings figure. Such projects are greatly motivated to “make their numbers work”. Slight adjustments in speed etc. could easily make this happen. Sorry to seem so skeptical, but after decades of these “press-release breakthroughs”, I’m seeing a pattern. The last thing they are about to say is “this thing barely made a difference”, or “it actually slowed us down and used more fuel due to its weight and energy needs for rotation” - no, they are almost obligated to try and frame it in the most positive light possible. 
https://www.norsepower.com/technology
An excerpt:
The Norsepower Rotor Sail technology is around ten times more efficient than a conventional sail, because more lift is produced with a much smaller sail area. Due to its simplicity, it requires no reefing or crew attention when in operation. It is “push-button wind propulsion” from the bridge.
An image:
We see that the rotor is well maintained, leading to a smooth and fast rotation. For an AWES, such a holding is more difficult if even possible, excepted with a heavier building. So a lower efficiency or/and a higher power consumption can be expected.
If there is one term that could win an award for “most abused word” in clean energy, it might be “efficiency”. These guys are obviously considering only frontal area, not even “swept” area or even “intercepted area” (since the spinning “intercepts” more than the silhouette (projected) area).
What they mention, but do not truly consider, is “sail area”. Their total sail surface area is 3.14 times the projected area, so that would reduce their “ten times as efficient” to “three times as efficient”. See how easy it is to lie with statistics? It takes almost nothing. Even engineers won’t catch it. But then you figure in the power required to provide the spin - OK now we’re lowering efficiency further, because a regular “passive” sail, does not USE power except for a small amount for trim and adjustments. With the energy losses from spinning the sail, the efficiency is… ??? I’m not sure how to compare it with a sail that uses zero power at that point. One thing that occurs to me is how modern passive (non-spinning) sails could be very automated, not requiring large crews climbing around 100 feet in the air after a few shots of rum, physically furling, unfurling, and generally man-handling them. Because you might note, when the steam engine emerged, sails required a lot of manpower to operate. So everyone gave up on sails, at least partly due to due to the labor cost. Maybe some modern version of a sailing ship, or auxiliary sails on a ship, could make sense if they were light, cheap, and easy to operate without people having to climb all over the place doing everything by hand. Maybe they don’t need the rotors.
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Indeed, in usual calculations, the (“projected”) surface area of a Magnus cylinder is the length x diameter. So the whole surface area is multiplied by 3.14. That said their argument in favor of simple, space-saving device looks correct, since the cylinders do not move from side to side like a sail.
Hi Pierre: If a magnus/flettner powered cylinder were “10 times as efficient” as an airfoil, with regard to projected area, then STOL airplanes, and model airplane attempts using powered magnus flettner wings, would only need a very thin (narrow, “skinny”) rotor, with a diameter of one tenth the chord of the competing wings. If such a super-thin, high-aspect ratio, powered, magnus/flettner rotor could match a wing with ten times the chord, then it seems everyone would be using them.
Now, bypassing your comment, and pretending I am someone else responding to my own post, I would say “Thanks Doug, you just made a great argument for kite sails”. I acknowledge that, and as I’ve stated, I’m not sure why kite sails are not working out, having assumed it was my own invention back in the 1980’s. (That is NOT to say I believed nobody else had thought of it - I assumed other people had probably also thought of it, really. Most ideas were thought of by multiple people before anyone actually pursued the ideas.)
But what I’ve recently learned, that kite-ships must travel SLOWER than a regular ship in order to actually utilize the kite, or benefit from its pull, THAT is the exact type of deal-breaker/show-stopper problem I’ve been saying must exist, given the poor results shown so far for kites pulling ships.
Do I have that right? Did I read somewhere that the ship must travel 30% slower in order to benefit from a kite pulling it? Kind of reminds me of hydrogen as energy storage - SO inefficient when you consider the whole picture, that it will never catch on as energy storage.
Actually, without citing a specific configuration, I’m thinking of sails made of perhaps some durable, industrial “cloth”, or perhaps a more rigid sheet material, possibly using masts, booms, and guy wires, similar to known sailing configurations, but powered and automated to operate without large crews doing everything by hand. Yes, I know, there are a few examples of such, but not sure how effective they have been so far. Still, I guess I’m saying something closer to known sail technology might end up working out better than either kites or rotating cylinders.
Here would be what I would call “the acid test” for a boat powered by flettner/magnus rotors:
Have the spin powered by, for example, a propeller in the water driving a generator - so often talked about as “the answer” to seabound hydrogen production, etc.
I’m pretty sure a ship with non-spinning sails of a more conventional type could successfully power itself. After all, they did for thousands of years… Whether a boat propelled by a flettner/magnus cylinder sail, with its spin powered by, say, a propeller dipped in the water, could actually work, or work well enough to bother with, I’m not convinced. MAYBE SOMEONE SHOULD TRY THAT as a proof-of-concept, as just a start.
Show us any boat, powered by a flettner/magnus spinning sail, that DOES NOT NEED an engine to spin its rotor(s), but is self-sufficient, capable of just sailing, using no fuel.
Hi Pierre: Sounds good at first. And I’m a big fan of the Sharp rotor concept. However, the idea of the flettner/magnus concept is to increase “circulation” around the “wing”, meaning to increase the speed of airflow over the top of the wing, compared to the bottom of the wing.
The Sharp rotor USES the force of the wind hitting the top of the rotor, to spin the top of the rotor backwards. It seems to me that this would DECREASE the velocity of the wind over the top of the rotor, rather than increasing it. To push the top of the Sharp rotor back, requires force, which would slow the wind speed over the top, not increase it.
What I’m thinking now is that our previous discussions of the Sharp rotor did not include the fact that pushing the top of the rotor downwind would reduce the wind speed over the top. To believe otherwise might be similar to thinking one could fly by pulling up on one’s own shoelaces - a “perpetual motion” scenario.
Am I missing something here? Quite possible. I’d love to know your opinion!
Back in the 1800’s, in New York State, they wanted to connect the Great Lakes to the Hudson River, so they built a canal across the state. It’s called “The Erie Canal”. I grew up using the dirt mule roads on the side of it for riding dirt bikes. Today it’s a tourist attraction. But it looks like they need to build a canal across Eurasia.
Hi Guys
I just ran across three (3) videos of magnus/flettner sails and experiments that I think you might find interesting:
-
Adding fans instead of discs as endplates - patented: (would require more power to spin)
A new way to enhance the Magnus effect, faster and more efficient - YouTube -
Here’s a guy going pretty fast in a little catamaran powered by a spinning cylinder in the wind:
Rotorsail 2 0 - YouTube -
Same guy, same boat, different cylinder, earlier version which seemed a bit slower;
Catamaran with Magnus Effect Rotor Sail - YouTube
First of all, Thanks Pierre for reminding me of the Kramer effect lift, that would seem to overcome my objection regarding circulation over a horizontal Sharp rotor.
Beyond that, I saw in the comments of one of those flettner-boat videos I think, someone mentioned hanging a water turbine “propeller” (similar to a ram air turbine hanging from an airplane) off the back of the boat to power the rotor. I guess it could power either a generator to power a motor to spin the cylinder, OR it might spin the cylinder directly, by mechanical means, but that would require either a reverse gear or two turbines made to spin in opposite directions. Not so sure about the total efficiency of such a setup, but technically, it might work, so I thought it worth mentioning. I guess maybe a regular horizontal-axis turbine could be added to power the spin. At that point, however, it might get to the point where just a H-A turbine itself could be used to power a drive propeller in the water, or more likely, from what we’ve seen, it could HELP to power the existing propeller and we’d be treated to the “save 5%-20% of fuel” meme. Whether that is for real, I’m not so sure, considering these spinning “sails” for ships were given up on 100 years ago, but hey, who knows?