A (train of) parasail(s) as AWES ?

Engineering System Design
1

Parachutes were tested as AWES and were discussed.

It appears that the aerostat provides all of the lift for both parachutes. And whatever the first parachute is open or shut does not significantly change the elevation angle of the two parachutes while that of the aerostat is very high.

Under these conditions, to increase the number of parachutes or their total area as well as stability, it would be necessary to increase the dimensions of the supporting element (aerostat or kite lifter), which would become difficult from a certain threshold.

I myself tried to experiment with an admittedly rudimentary parachute, and with a very good lifter kite (a sled) of 1.7 m², today, after the previous experiment with a 0.2 m² lifter kite for the same parachute:

Parachute of projected area of about 5 m², with a lifter kite of 1.7 m². In spite of the high area of the lifter kite compared to that of the parachute, this one flew at a low angle of elevation (about 10 to 20 degrees) compared to that of the lifter kite (50 degrees). Moreover oscillations occurred from top to bottom. The tether of the lifter kite was attached to the periphery of the central hole.

A photo:

Parachute 5 m² sled 1.7 m² a
Parachute 5 m² sled 1.7 m² a1920×1440 82.7 KB

In contrast, a parasail provides its own lift thanks to vents and vent slits, and a little ballast at the bottom plus the user’s weight.

With equal traction, parasails seem to be of a price comparable to that of power kites which have a significantly smaller surface area.

1 700,00 $US -2 000,00 $US

Min. Order: 2 Pièces

Compared to:

Used in yoyo mode, a simple power-depower module (which also plays the role of ballast) should be studied.

It would be interesting to know to what dimensions a parasail could scale. Already the basic products are of respectable dimensions (diameter 10 to 12 m) but insufficient for AWES use.

2

It will work, but I dont see it providing enough lift, It cant take advantage of apparent wind, crosswind might prove to be difficult. I may be mistaken.

3

Indeed, both Guangdong parachute device and the presented parasail device are tether-aligned AWES. They are not crosswind kites. So the power-to-area ratio is far lower than that of power kites as I mentioned. In the other hand the implementation can perhaps be easier (relatively simple control). Power to space use ratio can be comparable or higher since the whole wind area could be harnessed (while in crosswind mode some wind areas are not harnessed within the figure). And also:

And as the parasail absorbs less power per unit of area, wear could be less.

In my initial comment, I presented solutions with parachutes, showing the problems, then going to parasails as a possible solution.

The other alternative would be the implementation of power kites in Low radius loop mode. But I don’t have any ideas for yo-yo mode, other than the implementation of a control pod (close to the kite) which could be too heavy and hinder the rotations. And stacking in a train could be more difficult.

4

Yo Yo mode… Rotating and reeling out. Like a funnel shaped corkscrew. The shape is easy enough to understand, but to orchestrate in real life… It would actually be possible to do with a two line power kite and two people holding a reel each, I’d watch that dance.

5

Reel-in/-out was done with the Chinese device, as shown on the first video.

The implementation of the parasail would allow autonomous lift.

Rotating and reel-out simultaneously remains a problem if a control pod aloft is not used.

7

A parasail has a lot of vents, vent slits, plus the central hole, all separating the fabric elements, so perhaps it could be seen as a kite network, hence more scalability?

8

Interesting proposition @PierreB
Yes a parafoil has topological complexity and many interconnected parts so … sure we could call it a network and it’s a kite

In a similar way we could now call a wedding dress a Network Wedding dress or a shirt a network shirt

By the way, flying trousers :jeans: kites are common

For me though, the distinction of a network kite is having multiple kites tied and flown together.
The simplest form may be the 2 kite arch kite
-:kite::kite:-

AWES is complicated enough
Let’s call a sled a sled

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9

Hi Rod,

A parachute or parafoil is made in one piece.

Conversely, a parasail contains many separate pieces of fabric. This is why I am tempted to qualify it as a network kite (unlike the parachute or the parafoil), even though the said elements form the whole shape.

If one of the scaling possibilities is linked to the existence of separate elements, even if they are not identical kites flying together, we could reconsider the different forms of kite networks.

On the photo of a parasail below, we see the elements that are separated by vents and vent slits:

For example, imagine that for a multitude of Daisy, you use a sort of giant parasail connecting them all and forming the kite network…

Of course the scalability remains to be verified.

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10

My apologies @PierreB
I mistakenly was thinking parafoil not parasail
Yes
Sure why not
I reckon a parasail can be an off the shelf network kite

11

You ask good questions @Rodread.

Thus we assume that a kite network can scale far more than a unit which composes it, in the classic conception of a kite network made of identical and autonomous units. For what? Perhaps thanks to the air spaces between the units, and not exceeding the limits of the fabric according to the bridle per piece.

But in this case the air spaces between the not necessarily identical and non-autonomous elements of a whole forming a single kite could have the same utility. And here we have the parasail, which is indeed an existing example of a starting kite network, and which could be reworked for an AWES yo-yo, or as a more easily achievable (?) giant lifter kite.

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12

Sure a parasail has been proven to work as a kite.
Who doesn’t love an Air-Bear

Air bear isn’t as heavy as a full sized bear
In towed mode behind a boat the average minimum take off speed for a parasail with passenger is ~6.5m/s
Surely we can find panel configurations with higher lift performance (maybe less stable) than that

13

For a yo-yo use, I am interested in the indications below if they are true:

For tethered-aligned AWES a huge drag coefficient leads to a higher thrust. If the Guangdong AWES (video) was equipped with parasails instead of umbrellas (parachutes) the thrust and the power would be higher, and each unity would have autonomous lift.

And it seems that parasails fly at an angle of elevation of about 25-35 degrees when we look the photos. So this confirms that the lift coefficient (Cl) is likely high. That said parasails can be made in several versions. For a lifter kite, 35 degrees is not enough. But for power generation, this is a value we found for other AWES (yo-yo, flygen, rotary) in (quasi) crosswind flight. Power generation induces a strong horizontal component.

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14

Given the wind shear profile and history of parasail use - offshore may be the best place to fly this low elevation AWES design

16

Normally a boat tows a parasail. But this could very well be reversed: the parasail, then placed at the bow, would tow the boat.

For downwind winds, just let it go.

To go upwind a little, the parasail could be piloted by using a pod bringing together the suspension lines and placed at the bow, and by winding some lines.

17

On a boat, a parasail or another High drag coefficient kite could perhaps advantageously replace a spinnaker when going downwind, because of a higher Cd above 2.

A boat could include a set of kites depending on the gait (downwind, crosswind, upwind) just as a classic boat includes a set of sails.

18

Yes I can agree. A quiver of kites is preferred… maybe one day we will have a kite that can change shape, Either way, solid control strategy is essential

19

I noted a very High drag coefficient (Cd) of 2.727 for a parasail, and lift force (as for any parasails), tested and reported on:
Sea recovery system for small UAV | NTU Singapore

Title: Sea recovery system for small UAV
Authors: Muhammad Feroz, Muhammad Shaffarudin

I tried to summarize the information of the potential and advantages of (train of ) parasail(s), first due to their own respective lift, second due the high Cd, so a high thrust coefficient _ being combined drag and lift coefficients _ (Tc), in a preprint:

Parasail-based Airborne Wind Energy System
https://www.researchgate.net/publication/378970090_Parasail-based_Airborne_Wind_Energy_System

20

The concept is to use this with very high drag coefficient (Cd) parachutes like that, or parasails with high drag coefficient mentioned on
https://hdl.handle.net/10356/78460

The higher Cd the smaller parachute area for a same power.

21

So would a bounding parachute give 100% of betz power? if that is the case, drag coefficient is not relevant.

23

For this parasail-based AWES mainly based on the drag force, the thrust (tension) force increases above all with the Cd. The equation (4) is applicable to a simple (not crosswind) kite: for a same Cl, the higher the Cd, the higher the tension (thrust) while, for a crosswind kite, the higher the Cl and, above all, the higher the L/D ratio, the higher force.

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