Magenn

The problem with crosswind flight for a Magnus rotor is the power consumption to spin the rotor. Indeed the tangential speed³ is the wind speed X the glide number (lift to drag ratio as simplification, generally between 2 and 3 for a high spin ratio) of the Magnus wing (that to obtain the apparent wind) X the spin ratio.

An example with 10 m/s wind speed, for a Magnus rotor of 1 m², spin ratio of 2, Lift coefficient of 3.8, drag coefficient of 1.5 (according to the figures 4 and 7 of the paper Experiments on a Flettner rotor at critical and supercritical Reynolds numbers).

Power consumption (equation (3)) : 0.007 X 1 X 3.14 X 1.2/2 X 50.6³ = 1708 W.
Power harnessed: 2/27 X 1.2 X 1 X 1000 X 3.8 X (2.53)² = 2162 W before losses by cosine and by mass @tallakt includes in his calculations.

So it appears that for a Magnus rotor the higher apparent wind due to crosswind flight is the killer in regard to the required power consumption.

https://www.researchgate.net/publication/333600036_Magnus_Based_Airborne_Wind_Energy_Systems/comments is a question I asked about the power consumption.

The equation (3) of Experiments on a Flettner rotor at critical and supercritical Reynolds numbers assumes that the tangential speed of the Magnus rotor is cubed, while the equation (5/18) on https://www.researchgate.net/publication/332799296_Airborne_wind_energy_system_Control_and_experimentation and the equation (12.21) page 293, chapter 12 of
Airborne Wind Energy - Advances in Technology Development and Research consider that only the wind speed is cubed, the spin ratio X being not cubed. This would lead to huge differences.

As an example wind speed = 10 m/s, and spin ratio X = 4, all other parameters being equal.

By the equation (5.18) the power consumption is …4000…

By the equation (3) the power consumption is …64000…

@tallakt and me used the equation (3) in this topic. I think equation (3) leads to results that are closer to the experienced reality (Omnidea on https://collegerama.tudelft.nl/Mediasite/Play/e51a679525fe491990de3a55a912f79d1d as an example, and also some historical literature).

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More Flettner news https://www.nrk.no/vestland/sea-cargo-med-heilt-ny-form-for-seglskip_-monterer-roterande-master-pa-lasteskip-1.15067391

The turbosail was also seen as an alternative to the Flettner rotor. This is (in theory) a very high lift sail. I remember a lift coefficient of 6 but some problems of implementation occurred. Perhaps the turbosail can be a start for R&D for AWE wings.

Just adding a relevant news article with nice pictures

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For what I experimeted and and took into account analyzes in scientific publications (see the links above), rigid Magnus effect based rotors could be more efficient than inflatable ones and require less power consumption for an equivalent spin ratio.

Magnus / Flettner vertical cylindrical spinning sails have been tried for many years. As far as I am aware, they use more power than they save, because it takes energy to spin the sails.

It depends on the peripheral speed (reasonable power consumption until about 10 m/s for an inflatable cylinder, about 20 m/s for a rigid cylinder, see Fig. 13) of the balloon during the rotation. See the curves at 9:50 on the video below:

Another company using Flettner rotors for ships:

Some specifications such like the rotor weight, diameter, height, rpm (but not the power consumption)… are on:

from (button download at the bottom of the page)

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I re-read this chapter 12, and just noticed that the authors were referring to friction in the pulleys, pages 286 then 287.
Page 286:

We have noticed that friction in the pulleys is significant. The increase of mechanical friction forces is a well known physical phenomenon when scaling down.

Page 287:

Fig. 12.8 The measured
tension in the tether as a
function of the tether length r
for different angular speeds ω
of the Magnus rotor and tether
speed ˙r, for a wind speed
vw = 6.2 m/s. The zone A is
the possible force difference
that can be used to produce
energy. This zone is reduced
to zone B due to the pulleys
friction. This gives an idea
of the feasibility of a positive
power production cycle and
what one could potentially get
if this friction is reduced