It is an old report that is updated and corrected. All the paper is about the appropriate swept area rA by the turbines aloft in regard to the kite area kA as the turbines aloft should add 50% drag of the kite alone. 221.47466 m² (kite area) x 0.3 (drag coefficient) = 66.442398, so two times 33.2212 (turbines area x drag or thrust coefficient = 1).
All is in the table about parameters.
In the utility-scale model 33 m² rA (swept area by the turbines, r = rotor, estimated drag coefficient being 1) go with a 221 m² soft wing.
33 m² = 8 turbines of 2.3 m diameter that are used for the 600 kW Makani M600.
All this is precised in the paper. But, as the conclusion indicates, a deeper analysis is required.
Hypothesis for a calculation of M600: 2/27 x 1.2 x 1.2 x 50 [supposed area] x 1000 x (10.6)² = roughly 600 kW before cosine loss.
L/D ratio wing alone = 10.6; optimized L/D ratio with turbines = 7.0666666; wing area estimated at 50 m². With a lift coefficient CL of 1.2, wing area x CL = 60; so wing area x CD should be 5.66, leading to a drag coefficient of 0.1132. The thrust (drag) of the turbines should add 50% of 5.66, so 2.83. The thrust coefficient of the turbines is 2.83/33 = 0.0857575.
Verification: 33 x 1.2/2 x 70.666666 x70.666666 x 70.666666 x 0.0857575 = roughly 600 kW.
It looks that the turbines are large due to E-VTOL requirement, then the thrust coefficient is lower during operation.