The two curves on the page below show the large difference between the generation phase and the full cycle, as usual for yo-yo systems.
http://www.kitenergy.net/technology/experimental-results/
But I believed (before @Rodread’s correction) the video below showed [another conversion system, allowing avoiding reel-in phase, a little like Paynes’ patent US 3987987 figure 5, but with the large advantage of a single station, allowing a simpler installation and facing all wind directions without significant additional devices.]
[This type of conversion is based on the variation in the length of each of the two lines during each figure-eight. Perhaps specially designed trajectories will optimize this type of conversion.]
I put the last parts in brackets due to later @Rodread’s correction as it is not a type of conversion but a mean to adjust the tension of the 2 lines. That said perhaps it could become a low (or even negatively) efficient conversion system even if the distance between the two lines is large enough (implying high kite span) leading to more line motion through the pulleys, using figure-eight with two circle close each other in order to always put the lines in motion. The reason of the expected low or negative efficiency is that the kite is not fully involved: only its turns would be used, and energy is even used to act them.
As corrected by Rod, Kitenergy uses a yo-yo system.
https://www.youtube.com/watch?v=9NR49k0xSCw