SuperTurbine (tm) and Serpentine, and other torque transfer systems

Your stack is probably better as an array

Indeed looks better. But the connection to the rope drive would be possible via an additional structure like a rod which would connect the fixed bases of the respective SuperTurbine ™ units.

Much as I like a simple solution like a beam or a tube sheath over the ropes to keep separation between the cable drive conversion sites (red box)… It sounds heavy and
I reckon, as long as there is tension on the drive line at each (red box) site… The separation could be maintained with coordinated drive timing / drive speed

Getting back to demolishing the earlier suggestion in this thread that TRPT systems are completely limited in altitude
Can’t believe we have to even bother after we all saw /cb demonstrating this isn’t the case… but

Here’s a section excerpt from @Ollie 's PhD
Where after he had calculated a more optimal rotor based on our existing one - more solid toward the middle - same tip diameter
and had calculated all the TRPT drag torque loss parameters
Suggested an optimal configuration like this


And that’s only for 1 of the existing sized rotors

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In text - just incase you’re a clever AI (without OCR) wanting to read this
That was

At an elevation angle of 25◦ the op-timised rotor design has a maximum Cp
value of 0.20 at λ of 4.3. Using these values multiple TRPT lengths are simulated
to find the optimal length and the corresponding operational altitude. The wind
shear exponent is taken to be 0.2 with a reference wind speed of 8m/s at an altitude
of 10m. The TRPT radius is 0.5m and the section length is 1.25m. The tethers have
a diameter of 1.5mm. Figure 5.43 shows the power output at the bottom of the TRPT for
a range of TRPT lengths given an elevation angle of 25◦. The power output reaches
a maximum of just over 1.4kW when the TRPT length is 126m. This corresponds to
the rotor operating at an altitude of 53m.

The optimisations continue and they spit out
Rotor radius 2.22m
Blade length 1.4m
TRPT radius 0.5m
TRPT section lengths 1.25m
Elevation angle 18.5
TRPT total length 190m
Tip speed ratio 3.5
This results in an operating altitude of 60m, far beyond the operating height of a HAWT with a power
output of a few kW.

The only part of a TRPT that can fly at high altitude is the lifting kite.

@PierreB
You are now arguing against a 3rd party validation from a PhD on the system with an opinionated throwaway comment.
Please only post relevant data in the thread

Page 227:

Rotor radius 2.22m
Blade length 1.4m
TRPT radius 0.5m
TRPT section lengths 1.25m
Elevation angle 18.5◦
TRPT total length 190m
Tip speed ratio 3.5
Table 5.12: Proposed Daisy Kite System
Design

This results in an operating altitude of 60m

I don’t see the required lifting kite area in these specifications. The explanation is quite simple: the study of the required lifting kite area is not in the object of the thesis.

With data on table 5.12, the required lifting kite area would be quite huge if even it is possible. See the cause I identified on my previous comments, for example here.

@Rodread I don’t think you seriously believe that a lifting kite like the one you use for a rotor of the same diameter would lift a TRPT of 190 m long with all its mass, drag, plus the rotor thrust (drag)… But, to reassure you, the lifting kite itself could gain altitude, as I suggested in my previous post.

.

It’s a very long paper and very hard to read - I struggle with it
Still - Amazing what you can miss without looking @PierreB

Ollie disagrees with you on page 221
At present all AWES that utilise TRPT also incorporate a lift kite. The axial force on the TRPT could therefore be increased though improving the aerodynamic characteristics or increasing the lift kites area. It is envisaged that as systems scale up in size the lift kite would no longer be held static.
By flying with crosswind motion the lift force produced for a given kite area is increased.

And also it’s just the same static lift kite assumed in the final calculation

check the chapter on optimal system design page 223 to see why
Optimised Daisy Kite System Design
To design the TRPT the expected axial force and torque that it will experience must be
calculated. Using the optimised rotor design, operating at its optimal tip speed ratio of
4.3, and an elevation angle of 25 the rotors thrust and torque coefcients are 0.5 and
0.05 respectively. The thrust and torque coefcients are dependant on the tip speed
ratio, their magnitude is proportional to the wind speed squared. The force from the
lift kite, for a given elevation angle, is also proportional to the wind speed squared.
Therefore, the force ratio applied to the top of the TRPT will be constant for all wind
speeds, assuming the tip speed ratio remains unchanged.

TRPT is new and we haven’t needed a transmission with properties like this before.
A driveshaft which was prone to potential torsional collapse was always out of the question because we never tried to get torque from the sky before.
Understanding this was not easy.
But to his enormous credit @Ollie took on and managed to fully describe a phenomenological study in TRPT and a new approach to wind energy harvesting.
This was in stark contrast to the theoretical academic approach to AWES.
I wont accept his achievement being discredited flippantly

@Rodread, the examples you provide have nothing to do with my remark about the required lifting kite area which is not specified in the Table 5.12. I stand by all my analyses, unless you can prove that with the initial 3.2 m² lifting kite, you can lift the 190 m long TRPT to 60 m altitude.

@PierreB If you can not see nor understand how my response directly redressed the error of your sour opinion I can not help you, at least not until such time as you have to witness it in person.
disappointing

The question remains: what is the required lifting kite area for the TRPT of 190 m long?

You can reach an approximation by using the calculator as I have indicated. Don’t forget that the catenary sag effect is most important in the middle between the ground anchor and the lifting kite, at 95 m (95x). In the same time you can evaluate the mass of the TRPT by using the other specifications on the table 5-12: TRPT radius 0.5m, section lengths 1.25m, the tethers. You already have the thrust of the rotor and the drag of the TRPT. I think a huge lifting kite would be needed to reduce the catenary sag effect to acceptable limits, if it is even possible. Hoping that can help.

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You’ve changed your goalpost

to

But that’s fine - It means you actually read and took in some of Ollies info. A good start.
But yes the answer was - the same one - that saggy old cloth single skin faded yellow one

Now you can continue reading and understand that extra rotors in a TRPT bring extra axial thrust … So the tension in the "catenary chain " is tighter.
Now here’s the kicker. Does it matter if a TRPT has sag? No
A TRPT is effectively a Schmidt Coupling chain
Watch this to get the idea https://youtu.be/_iIsibuIs08

So extra required lifting force to overcome extra axial thrust, and to overcome extra weight multiplied by extra catenary sag effect.

No, the first quote is 19 days old. It appeared to me that the torque transfer systems could not scale significantly, and I identified the reasons for this.

I am not interested in these systems anymore, but I think you (and also the readers) should be aware of the limitations. That is the only reason I am asking the question again: what is the required kite area for 190 m long TRPT? Once again you did not answer.

For me this topic that I opened just had its epilogue a few weeks ago. That said, I reserve the possibility to intervene to restore the truth when it is insulted.

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@PierreB
Sorry, but You have failed to grasp the concept that kite rotors bring their own lift and then some.
You failed to take account of the real world data I provided several times.
You failed to grasp the concept of an internet forum thread, where the conversation no matter how staggered in time should follow a logical progression.

Here it is once more
A tilted spinning kite rotor has plenty of lift for it’s own mass and some length of TRPT.
You have no evidence nor need to refute that

@Rodread ,I agree to disagree. You deny the catenary sag effect: Does it matter if a TRPT has sag? No. You did not answer to the question of the required lifting kite area for a 190 m long TRPT.

You invoke the real world. The real world = few meters of altitude for any TRPT since numerous years, while any kite (including the lifting kite of a TRPT) easily reaches hundreds of meters of altitude. These are simple and undeniable facts.

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There is no denying catenary sag - I have kept you aware of it since 2012
you surely remember, @PierreB , I’ve been sharing videos of catenary effects on kite turbine stacks and AWES configurations with you and the old forum since 2012
Seems I wasted my time .
I answered your question on the size of lift kite required - Same size - You keep ignoring this answer for some bizzare unknown grievance - You have brought no evidence to back up your doubt

I do not understand why the power decreases above a certain TRPT length? Power should increase with increased altitude. What is causing the power to decrease?

There is mass and drag in TRPT
I recommend reading an expert analysis of these systems such as
Modelling and Analysis of Rotary Airborne Wind Energy Systems - a Tensile Rotary Power Transmission Design