Flight control of tethered kites in autonomous pumping cycles for airborne wind energy.pdf (1.1 MB)
See the figure 21 with the huge variations of force (so power) during large crosswind figure-eight, apart reel-in phase. Numerous papers show similar curves. The variations of force imply a big loss (about 1/2) of power.
It would be possible to obtain the same or a little more power by using a low radius loop. After some problems can occur as a swivel requirement or other.