Hi @rschmehl , thank you for the change about AWE classification in the introduction of the discussed paper. The last explains make sense until some point.
But on https://www.researchgate.net/publication/324135034_Airborne_Wind_Energy_Conversion_Using_a_Rotating_Reel_System , page 540, 22.1 Introduction:
The present study proposes a new airborne wind energy system, the RotatingReel Parotor (RRP), which combines a rotary ring kite with a ground-based rotating reel conversion system [8].
On the now defunct rotating reel system the flying and ground rotors are connected only by tethers, with an option of additional lines. So there is, in flight, no “more or less rigid elements (that can support compressive forces), other than tether or bridle lines (that can support only tensile forces).”
So was RRP a rotary or a crosswind kite?
More generally, the line between purely rotary and crosswind kites seems rather blurry.
The current paper seems to aim some different means (airplane structure connected to computerized control) in order to improve flight stability.
In rotary kites flight stability is partially assured by structurally constrained means. Conversely, rotating kites like Daisy aim to move the blades away from each other in order to increase the swept area for minimal additional mass. The flight diameter (about 4 times blade-span) tends to approach the flight diameter of a crosswind kite performing circular figures like Makani wing, which even tends to decrease if we believe the latest projections (about 6 times wing-span, table 2 page 26, NREL Airborne Wind Energy, and even less on preprint, page 19 (" For the targeted wingspan of 60m"), page 23 (“The drag-mode AWE system operates at a constant tether length l ≈ 650 m and follows an near-circular flight path of diameter D ≈ 200 m at a mean elevation of about 17 degrees”) ).
The concerns of rotary and crosswind AWES seem to meet: more sweeping with less material, stability.
The decision remains in the percentage of the material construction and that of the control algorithms.
Therefore, a joint and comparative study of rotary and crosswind AWES, with MEASURED TESTS, might be desirable.