Ok. So I had a chance to read both papers and they are really good. I guess any discussion of the Betz limit (or as the paper states, B-J limit, only an academic could come up with that? ) may well have these papers as a starting point to clear a lot of noise. Furthermore, the inclusion of the induction factor a is important.

So I’d recommend these papers to anyone into AWE.

Now for the bad parts: There seems to be a bias towards drag mode vs lift mode AWE which is fine and well grounded. But the plots I believe use a value of glide number (G_e = \frac{C_L}{C_D}) that is quite high (G_e = 10). These numbers are probably only realistic for a multi kite AWE rig (eg. dancing kites). We are in 2019 now and we should not need to publish papers not taking a nominal tether drag into account. Hint: D_t \approx \frac{1}{8} \rho v^2 C_{d,t} l d. For a 15 mm tether of 1 km that you might use for a 10 m2 wing, the area of that tether facing the wind is a whopping 15 m2. It will affect the glide number in a big way. A conductive tether a lot thicker, and with further detrimental mass effects to boot.

Also, the large simulated kite has a wingspan of 54 m and looping radius of 120 m. Again this would probably only be viable for dancing kites due to extreme centripetal forces required and also the difference in airflow along the wingspan of the kite. At the same note I believe these numbers are infeasible for a Makani type of rig due to tether mass (and then indirectly drag).

The speed we arrive at in the paper is thus > 90 m/s, which would be nice, but I doubt it will happen in near future. I would expect the blades for a drag mode turbine might even exceed the limit for subsonic speeds 273 m/s in this scenario

The author thus arrives at some plots showing that the induction factor described is of more importance than would be in real life situations.

Still a good paper. Though I wish we as an industry could stop overselling the potential of AWE