Comparison of the traction force of a static parachute kite and a crosswind kite, both with the same projected surface

[PierreB]

@PierreB

These last losses are due to the kinetic energy increase when the kite goes faster within the trajectory, and having to be dissipated when the kite slows down, at the cost of enormous energy consumption.

Kinetic energy is dependent on mass and velocity squared. We saw that kinetic energy worsened the mass issue, both preventing to maintain speed in the climbing path.

@PierreB

The wind speed aloft (first circle in the left) was about 8-10 m/s. The kite speed was between about 38 and 56 m/s. The power generation was negative about half of the time (kite slowdowning), and between 0 and -500 kW, the positive power generation (kite accelerating) having the same values. So there was roughly no generation in average.

A mean to partially solve both cosine and kinetic energy issues would be using a tower. In the process, you replace the crosswind kite with conventional wind turbine blades.

Or, if one wants to stay within AWE, to capture high-altitude winds, tether-aligned of type parasail AWES, although still underestimated, could be a possibility. This is what the trials mentioned on this topic could lead to, showing that the superiority of the crosswind kite over a parachute kite of the same area is far from overwhelming: one should not confuse peaks of force or power with the average force or power (see below).

@PierreB

it seems that in this case (and maybe in general?) the average traction force of the crosswind kite is only 3 times that of the static parachute kite.

This rough estimate made on a small scale could be corroborated by (in French) SkySails — Wikipédia:

La voile peut opérer à une altitude comprise entre 100 et 300 mètres où l’on trouve des vents plus forts et plus stables et délivre 2 à 3 fois plus de puissance au mètre carré qu’une voile conventionnelle.

Translation:

Sailing can operate at an altitude between 100 and 300 meters where stronger and more stable winds can be found, delivering 2 to 3 times more power per square meter than a conventional sail.