A variant, using something similar to Flexor which implements flexible blade technology, but here the rotation is used as for other VAWT:
As previously, the Sharp rotor could be replaced with a Flettner rotor.
As @dougselsam would say, this only works on paper…
Pierre: At least it does work on paper. Doesn’t seem to violate the laws of physics.
Then again, I’m not sure how the Darrieus rotor might provide either more up force, or, maybe a down force though…
It’s an interesting idea!. 
Come to think of it, there would be a severe wind shadow (wake) downwind of the cylindrical, spinning sausage. which would probably cause power loss and oscillation issues on the downwind blades.
We need to better know how much of the area swept by the VAWT would be taken up by the Sharp rotor. It would be like for a Darrieus turbine with a Savonius rotor inside to help starting.
What interests me about Sharp or Flettner rotors is the possibility of coupling them to VAWT so that they form a rotating unit, with no moving parts relative to each other. If, in addition, the blades are light, for example by using shapewave® technology, this could be a possibility. But all this remains hypothetical.
Which is the old, traditional design of combining a split oil drum Savonius at the base of a vertical-axis Darrieus, to make it self-starting. Funny how you never see one of these. Actually, you seldom if ever see any vertical-axis turbine running - or even not running. You just don’t see them anymore. There are probably good reasons for that. Either they don’t work so well, or they break down, or both. It’s certainly not for lack of trying. One of the first windfarms in California was Darrieus V-A machines, but they were failing so fast they were torn down and replaced with regular wind turbines. This is the kind of turbine design that is always making the rounds again, often appearing in offbeat “back-to-nature”-type magazines, along with houses made of dirt, composting toilets, etc. In other words, it is a favorite of people who aren’t familiar with wind energy technology, and they are quite drawn to the idea, because it seemingly bypasses even the requirement of being elevated into a decent wind. I say “seemingly” because getting up into better wind is a real thing, not just some formality that can be ignored, but vertical-axis machines are usually located at or near ground level. Well, the symptoms come together with other symptoms - the main symptom is not following what is known and proven, and trying to go down a disproven or inadvisable path. Anyway, suffice it to point out, V-A type machines are a known “symptom” of “the syndrome”, which is something to keep in mind.
What I am looking is is some nice thinking but I don’t se a bridge over to a working prototype. That would need some more time, effort, money and who knows. But also maybe a drive to crystallize the idea into something that other people would believe in and want to build. I realize that is hard though, maybe you don’t have the desire also
Seems like one more hopefully simple, yet unexplored, AWE configuration family to me.
But I will say, those without experiencing what happens to rotors in a wind shadow of even a fat tower will be surprised at how severe it can be. Especially if it matches a natural resonant frequency of any part or group of parts. Think what it’s like trying to waterski in waves versus glassy water. When those blades hit any inconsistency in the air at 170 MPH, it can cause a severe reaction that affects the entire machine.
Magenn Power investigated a Magnus effect balloon surrounded by blades of Darrieus-like turbine.
See FIG. 4A. Adding rope drive transmission and Sharp rotor.
Amazing. I guess they had half a brain after all. Looks like someone shot down their balloon though…
It’s up to us to bring the other half of brain, as long as the two halves match.
As a Flettner rotor can have a high spin ratio thanks to the spin motor, it could be extended by blades forming a horizontal VAWT then again by a Flettner rotor and so on, the TSR of the VAWT (3-4) matching the spin ratio of the Flettner rotor which should be constantly adjusted according to the wind speed, using an rpm-check. Rope drive transmission as previously.
According to P. Sharp, a Sharp rotor could also be used, consuming slightly more energy than a Flettner rotor.
But as a Sharp rotor without a motor has a higher lift coefficient (Cl = 2.5-3) than a Flettner rotor (Cl = approximately 2 at spin ratio of 1) at its natural spin ratio of approximately 1, we can deduce that with a motor and at higher spin ratios, its lift would also be higher, but all that remains to be seen.
According to a simplified variant, the spin motor could be removed, the VAWT providing both lift of the Flettner or Sharp balloon, and power generation.
Some sketches of Sharp or Flettner rotors lifting regular or rope drive (@Kitewinder Kiwee style) wind turbines. Here the Sharp or Flettner rotors generate both aerodynamic and aerostatic lift, and facilitate spacing of wind turbines.
Some study about the power coefficient vs TSR of different two bladed troposkien shape VAWT on
https://www.researchgate.net/publication/336984857_Power_coefficient_measurements_of_a_novel_vertical_axis_wind_turbine
F I G U R E 3 Comparison between troposkien and straight/arc blade shapes
F I G U R E 9 Power coefficient (Cp) vs TSR after corrections at 600 rpm
My take: the power coefficient is not high and is optimal in a very narrow range of TSR. But mixing Sharp or Flettner rotors with VAWT maybe remains possible to achieve simplicity of building because the elements rotate at a same angular speed and form a single block.
For VAWT, straight blades can be more efficient.
In French language:
See Fig.8, with optimal power coefficients (Cp) about 0.45, for a TSR of 3-4. These values do not seem to be verified experimentally. The Cp looks very high: the reality is perhaps a lower Cp.
A sketch with a Sharp or Flettner rotor:
A rough calculation leads me to think that a Flettner rotor would consume relatively little energy, and would be more easily achievable.
A VAWT of 3 m² (1.732 m x 1.732 m) with a power coefficient Cp of 0.3, wind speed 10 m/s, power 540 W, TSR 3.
Power consumption of the inside Flettner rotor (first of the two sketches above) of 1 m², 1.732 m x 0.5773 m and TSR 1: only 13.2 W. Lift with 1.8 lift coefficient: 110 N. Drag with 0.82 drag coefficient: 50 N. These numbers are consistent with Omnidea experimental numbers.
Drag of the 2 m² of VAWT without the area of the Flettner rotor: about 110 N, perhaps less.
Drag of the whole: about 160 N.
The elevation angle would be about 35°.
The power would perhaps be 540/3 x 2 = 360 W – 13.2 = 346.8 W.
Between Sharp and Flettner rotor the difference by Flettner power consumption is small, and an inflatable Flettner rotor is easier to build.
That said I don’t know if the Sharp or Flettner rotor settled inside could really generate lift.
I tested today a Sharp rotor within a vertical axis wind turbine (VAWT) of type Darrieus, beside a similar Sharp rotor but alone. Wind speed 10-12 m/s.
The Sharp rotor generated lift, lifting its own weight from a wind speed of 5 m/s. But within a vertical axis wind turbine (VAWT) of type Darrieus, the lift looked to be cancelled.
After playing the video in slow motion (0.25), it appears, according to the orange adhesive indicator, that the rpm was 360, for a wind of at least 10 m/s. However, in front of the fan which sends air at 3 m/s onto the VAWT, it rotated at rpm 320 (incidentally the same rpm 320 with the Sharp rotor alone), which is barely less, the TSR becoming 3 times lower at 10 m/s wind speed compared to the 3 m/s fan air. My VAWT therefore plateaued from a certain wind speed, which drastically limited the TSR of the internal Sharp rotor and therefore its lift.
According to the figure 4 of Experiments on a Flettner rotor at critical and supercritical Reynolds numbers | TU Delft Repositories, a TSR 3 times lower implies a lift coefficient 3 times lower. And by the figure 7, a TSR 3 times lower implies a drag coefficient about 2.5 times lower. The thrust combines both lift and drag. On this video I measured a thrust of 10 N with 10 m/s wind speed, and 16 N with 12 m/s wind speed.
I deduce (without certainty because a Sharp rotor is not exactly a Flettner rotor) that with a TSR 3 times lesser the respective thrusts were 3.3 N and 5.3 N. I would have felt such a thrust, and for the last value of 5.3 N, the whole thing would have lifted slightly, which was never the case during the experiments, both when holding and when releasing: it fell immediately, which also confirmed the very low drag due to the low TSR which probable resulted from the condition of my old blades, too deformed to be efficient at high wind speed.
If the lift is cancelled in a too large proportion, it would be necessary to separate, to put side by side, the Flettner or Sharp rotor and the VAWT(s), as shown in the sketches above.
Here is what was tested (Sharp rotor 0.5 m x 0.11 m, VAWT 0.52 m x 0.3 m, whole weight 0.360 kg):
This video on Youtube was in private mode and is now in public mode:
If it is not available I can put the video directly on the forum.
it says the video is private…
I just published this video (my other videos being private now) whose only interest (for me) was to count the rpm while idling.
I retested by trying to separate the rotation of the Sharp rotor from that of the VAWT as much as possible. The wind speed was at least 10 m/s during the test. The Sharp rotor retained its diminished rpm (orange adhesive light) but, as can be seen by looking at idling at 0.25, it appears that the VAWT had a faster rpm (look at the brown adhesive light).
As in the previous test, and despite its relative independence of rotation speed from that of the VAWT which surrounded it, the rotation of the Sharp rotor was considerably slowed down, and its lift reduced in addition.
Then I tested the same VAWT but alone, with a wind that became weaker, perhaps 8 m/s maximum: the rpm was significantly higher, around 500, which gave a TSR of a little more than 1, which remains low but understandable given the condition of the blades.
This would confirm that it is better to put the VAWT side by side with the Sharp rotor. And it is possible that it is preferable for each of the rotors to have their freedom of rotation, even if it is tempting to tune the TSR of each of the rotors by fixing them side by side. All you need is an axis around which the rotors rotate freely.
However, the simplest solution is to attach an inflatable Flettner rotor (like Omnidea balloon) side by side to a VAWT which will “decide” the TSR of said rotor (and also its own TSR with the Flettner rotor) according to its diameter, of the order of 1/3 of the diameter of the rotor of the VAWT, for a TSR of approximately 1 for the Flettner rotor, and 3 for the VAWT. The energy consumption of the Flettner rotor remains minimal compared to the power of the VAWT.
I remember to have tested a foam cylinder of 0.54 m span and 0.27 m diameter glued side by side to a foam Savonius rotor of the same dimensions. The whole thing flew for a short time at a correct elevation angle of 40 degrees.
The Darrieus type VAWT that I experimented with does not generate a Magnus effect but is more powerful than a Savonius rotor and can sweep much more.
If we can use the shapewave® technique for the blades and their profiled uprights (which moreover can perhaps also be stabilizers of the whole), and as the Flettner balloons are easy to make, we would have a relatively lightweight, with a rope drive transmission around the Flettner cylinder(s).
Another experiment today: a vertical axis wind rotor (VAWT, not yet a turbine), between two Sharp rotors side by side. Wind speed about 5-7 m/s.
Getting the whole thing started was very difficult because of the bending. Once started, things improve and a rotation of 380 rpm (6 m/s at the tip of the blade) was able to stabilize until the wind weakened, which is better than during previous tests however at a higher wind speed. This was not enough to achieve a TSR allowing the Sharp rotors to produce lift and fly.
We probably don’t have the aerodynamic problems of interference between the two types of rotors, but we must take into account the size of the assembly and the mechanical difficulties. One can imagine that a large device will need to include several cable drive transmissions in order to mitigate bending.
In front of my fan, my current VAWT rotates at 6 m/s, i.e. a TSR of 2. While the Sharp rotor rotates at approximately 1.73 m/s, i.e. a TSR of 0.575. Things get worse for my VAWT when the wind gets stronger while they get better for Sharp rotors, as long as they are not associated with this VAWT in some way.
The rpm is counted at idle (0.25) with the help of adhesive tapes:
