Hi Joe,

I would like to know your advice as AWE expert about the technical points mentioned by Mario Marchitti I quote from the previous message you transmitted:

" The projects which carry the generators on board are doomed to industrial failure, even though they are backed by a giant of the financial world, even though functioning prototypes up to 600kW of target power have been built and flown. Here the weaknesses are easily detectable: they lie on three major drawbacks: it is necessary that the wing carries heavy generators, therefore the wing efficiency is thus reduced, moreover it is necessary to transfer the energy produced to the ground, via a cable. Those projects, suggested by Miles Loyd, are just a sort of reversed aircraft, like the turbine which is a reversed compressor. I don’t think they could be more efficient than the traditional wind turbines – on the contrary.

Also the projects which have the generators on ground are easily distinguished on their effectiveness and efficiency. It should be excluded those which have a rigid wing, like that of a traditional airplane, with ribs and spars. Because the manufacturing of such a device with , for example, one MW of power, with the cables from the wing which unroll at 10 m/s, should withstand 10 tons of pull, which originates on the wing structure. I wonder how that load can be sustained from such a wing, that should be light and efficient. Also the C-shaped kites which carry the actuators in flight, as  pods just below them, are dramatically affected in their aerodynamic efficiency, technical design and control; they also require significant power from the ground to drive the actuators, which cannot produce a swift response, moreover the retraction phase would be difficult and slow.

The dancing or roto kites solutions are not a sensible answer to the cable drag issue, which seems a false problem. The two kites which are rotating at the opposite of a circle, pulling the cable, is a naive concept design, which mimic the blades rotation of the traditional wind turbine, but paradoxically requires a complex technology for the flight control of their reciprocal movements, and also for the retraction phase; moreover the dancing kites also fail to intercept a large wind area, therefore they will be subjected to the Betz law power reduction, like the traditional wind turbine.

There is a confidence that the cable drag issue, that was raised by Ivan Argatov, was a consequence of a wrong assumption: of a cable that oscillates like the windscreen wiper - even taking into account the catenary effect. The geometry of the movement, and consequently its dynamic, is very different: you have to think at the whip tip or the launch of the fishing line, and reverse their tip movement." Thanks.

PierreB

Flygen energy kite systems?

PierreB just asked in another topic about my thoughts concerning Mario Marchitti's comments on the same topic.  Mario Marchitti commented on Tuesday, January 22, 2019 6:53 PM: 

Some other source provodes a quite different or opposite analysis. Please what do you think about the following?

https://reader.elsevier.com/reader/sd/pii/S1364032115007005?token=04B69BAA0C5B40D2480356271BD78C8D61389B12E94C9AF3F6969AF8077DADFBF31B489EC14580D94490623A5FE59C4D 

"Airborne Wind Energy Systems: A review of the technologies" (A. Cherubini), see page 1473, 7.1:

For discussion:

"The dancing or roto kites solutions are not a sensible answer to the cable drag issue, which seems a false problem. The two kites which are rotating at the opposite of a circle, pulling the cable, is a naive concept design, which mimic the blades rotation of the traditional wind turbine, but paradoxically requires a complex technology for the flight control of their reciprocal movements, and also for the retraction phase; moreover the dancing kites also fail to intercept a large wind area, therefore they will be subjected to the Betz law power reduction, like the traditional wind turbine." (Mario Marchitti)