This topic is about high drag coefficient. Yo-yo mode is described in numerous topics, so it can be easy to know why a high Cd could be interesting, and why I mentioned it, although such an application is not the main object of this topic.
However, the many substantive errors in the previous message lead me to clarify some points already made. First of all it is obvious that what is dealt with here takes place in tether-aligned category as for Guangdong parachute HAWP, not in crosswind category: see the AWES classification which clearly distinguishes these two categories. See also Tethered-aligned vs crosswind kites in yo-yo mode
There is no TSR (tip speed ratio) for tether-aligned AWES, and in this case no “this 0.7”.
In addition, the reel-out speed of the tether depends on the wind speed, not the (crosswind) kite speed, and is conventionally set at 1/3, although it can vary significantly. As a result, the characteristics of the generator will not change fundamentally between using a fast crosswind kite and a tether-aligned device.
Guangdong HAWP describes how their tether-aligned parachute device works: their description is available on Zhonglu High Altitude Wind Power Technology - 中路高空风力发电技术 - #2 by PierreB.
See the section “Parachute Aerodynamics” page 10 and following pages whose the first equation page 14.
The main point to consider is what is called the “tangential force T (along the axe)” (page 10) which is the vector sum of the drag and lift. The coefficient provided on page 11 varies between 0.6 and 1.2.
When I started this topic, I was surprised to see 2.2 Cd, having noticed later that much larger Cd exist: tested Cd of 3.224, perhaps Cd of 5 for some rescue parachutes.
Assuming our Cd of 5 parachute is about 100 m², at 12 m/s wind speed and an air density of 1.2, we would have a power of 76.8 kW (force x reel-out speed of 1/3 wind speed, taking into account the loss caused by the decrease in apparent wind) during reel-out phase.This is not far from half of the average 92 kW tested with a soft wing of equivalent or even larger size and flying crosswind, and by maximizing Power to space use ratio while simplifying steering, not to mention rigid wings which, assuming a positive average power in reeling mode, deviate still more from this important ratio.
Of course, the parachute kite could not fly strictly horizontally (hence the illustrations in my previous post) and would have to have a minimum angle of elevation: at this stage, I don’t know what its Cd would be and also its Cl, hence its tangential force.
But the existence of very high Cd gives food for thought for AWES in yo-yo mode and capable of scaling up to any dimensions, stacking them if necessary.