Yoyo AWE based on VAWT

Impressed by this: http://www.cyberquebec.ca/_layout/?uri=http://www.cyberquebec.ca/normandajc/

I know this is far fetched, but could it be possible to buld a similar rig based on YoYo kite rigs? Ie: The kite flies upwind of the winch and then a deep power stroke? We also have mass and altitude to play with in AWE. One could play with the geometry of the path to make it even more optimal than the circle drawn above.

To be honest, I dont quite see the point in doing so right now, other than that it would be cool.

It could be a new class of AWE, a mix between rotary rigs and Yoyo…

I’m sorry I probably stole the thread from the Yahoo forum. Anyways, I will repost my reply for completeness:

To me this design is interesting for AWE, not because of an extra few % Betz limit, but because I see tether drag and then indirectly tether strength as a limiting factor for AWE. This design reels out when the energy harvesting is at its highest and so the practical loss of power compared to eg. Yoyo may not be very big.

The same reason (tether drag) will probably favor vertically looping AWE (yoyo) to horizontal looping AWE based on this design. Because if you have a slightly long tether (100 meter for a medium sized rig) the power loss when flying upwind a 200 m diameter circle i expect to be significant, and you are probably only at 30 m altitude in doing so.

I will add that geometry constraints make this approach more difficult. Without a tower the kite flying with 100 m tether, 30 deg elevation angle would be limited to a wingspan of 50 meter in order to not touch the ground. In practise you’d want more ground clearance both for safety and wind gradient…

If you decide on a tower, the sideforces will be huge and oscillating.

Peter Sharp’s thread on Yahoo here

Pierre Lecanu’s Active Lift Turbine is detailed in a paper on https://hal.inria.fr/hal-01300531v1/document .
A patent is on https://worldwide.espacenet.com/publicationDetails/originalDocument?CC=WO&NR=2015107304A1&KC=A1&FT=D&ND=3&date=20150723&DB=EPODOC&locale=fr_EP# . The search report suggests the existence of a significant prior art. A deeper analysis would allow to detail the documents.

I experimented different VAWT. The only two being able to fly as a kite was a Savonius-like using Magnus effect and the Sharp rotor using Magnus/Kramer effect.

VAWT based on Darrieus design don’t fly as such. Some other VAWT could perhaps fly using Sharp’s “cycloturbine using computer-controlled blade-pitching” configuration. Perhaps derived design from the Active Lift Turbine as explained in the present topic could also fly. Deeper analyses and tests could show it, or not.

Some precision as rotors based on Savonius design and also the Sharp rotor are very different from VAWT of type Darrieus that use lift in a comparable way as HAWT.

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Another remark: on the sketch on http://www.cyberquebec.ca/_layout/?uri=http://www.cyberquebec.ca/normandajc/ (active lift turbine, version V1) there is a linear generator for each blade. But unless significant modifications are realized there is no “global” lift to do the turbine flying.
The yoyo cycle seems to be something more or less close to the “alternative compression and expansion”.

This design is a tremendous increase in VAWT mechanical complexity, a WECS class already known not to be best in power-to-weight performance. I don’t see the enhanced power harvesting potential claimed; in any case fundamentally limited by conservation-of-energy principle.

Not surprising that there is no prototype offered, or that committed VAWT fans uncritically embrace this latest remote challenge to overwhelming HAWT dominance. Lets hope someone builds and tests this design to confirm or disprove predictions.

I would not say uncritically embrace. I am no VAWT fan, but still the potential of a more efficient windmill is very interesting to me.

Yes, its a more complex build, but if the C_p numbers are correct, that may well be justified. I assume that there are also better designs out there waiting to be discovered based on the same ideas.

Let the inventors prove that this is actually feasible.

Could it be that there are feasible options for short tether AWE on a tower?

The flight window for a stunt kite is lower than 180°.

If we add a boat’s drift, the wind window reachs about 270°, like this:

If we implement rigid arms, we obtain a VAWT with its 360°, leading to the rotating move.

It looks perhaps possible with some arrangements. The challenge is keeping the tension of the tether during the whole rotation.

You need much more mass compared to a stunt kite in order to fly 360 degrees, and the path cannot be long. The glide number of the wing and tether must be very high. So if this is feasible, it probably looks like a high efficiency plane with rigid wings on a short tether. I would assume tether in the area 2x wingspan would be a starting point for searching for a design.

A great benefit of an AWE based cycloturbine (?) compared to a thing rotating on arms is the total freedom of wing speed along the loop.

There are even some in-between design options with a triangular tether helping each wing maintain its speed.

To get 360 reach a portion of the cycle will be negative energy. The energy should be kinetic or potential throug altitude changes.

A static solution to this requires rigid arms

I agree with KiteFreak, but don’t get used to it.
This kind of crapola has been making the rounds forever.
Produce a few stick-figure diagrams, add a few professor crackpot equations to confuse everyone, and suddenly you have a wind turbine beating Betz and everyone else. But you can’t show anyone a working model.
Blah bla blah bla blah… nothing new under the sun. “Buh-bye.”

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Compounded disadvantages of capital cost of tower and not reaching upper wind with a short tether.

Get used to Doug agreeing with what cannot be indefinitely denied.

Get used to daveS indefinitely denying anything Doug can agree with (otherwise known as “facts”…

Anyway, nobody can usually know an improvement until they see it.
Endlessly trying to describe an elephant that doesn’t exist is hard for the blind - nothing to feel.

Reaching high altitude winds is a useful goal, but I would not also rule out useful low altitude windmills for AWE

No one rules out low altitude AWES, after all kitesurfing works low. Its just that AWES engineering reaching higher than towers, to at least the ~500m high altitude offered by FAA directive, is the prime resource targeted by current AWE R&D.

An aerospace scoring matrix analysis, with the FAA defined airspace target, is suggested best-practice.

After a more careful analysis of the patents and the different versions on the website it appears that Active Lift Turbine principle likely doesn’t lead to an efficient device, as it goes beyond Betz’s law, claiming a Cp exceeding Betz limit.

This may be true, for me the interesting thing would be new ideas for wind energy. Any talk about beating the Betz limit seems nonsense to me anyway, as any new design must be established before it may be optimised to its limits. There may be other benefits than maximum air utilization discovered along the way.

Still, claiming to beat Betz limit is surely a bad sign for a new idea. In this case Betz’ limit could have been exceeded in theory because the windmill exists in 3D. But for me it is of lesser interest

ALT principle aims to take energy where it is not possible. Yoyo does it during reel-out phase downwind.

If the studied VAWT is not workable, I don’t see it as a basis for yoyo AWES.
A new design should lead to a viable AWES.