The_Betz_limit_applied_to_Airborne_Wind_Energy.pdf (1.3 MB)
The paper. I haven’t read it.
Some weird claims made by Pierre are that a kite is dragged kilometers in case of tether break (I haven’t seen examples of that happening, and if it does, don’t use kites that do that), that AWES need to be spaced double their tether length apart (you program them so that they avoid each other), and that land below the tethers can’t be used for other purposes (you tell them to avoid the area or land when human or animal life is detected, while reliability is still low).
Since AWES fly crosswind, only having the fast moving blade, equivalent to the outer 20% of a wind turbine blade, it stands to reason you would have much less of a wake and the systems can be placed closer together because of that.