So it provides 27.777 less force per unit area which means the parachute has to be that many times bigger in order to get the same thrust at same speed (= same power).
Considering paraglider wing area weight 3-4 times heavier than a domed parachute I think it is the winner.
Same calculation - wing area load vs sink speed - can be applied for other types of kite “wings” - like framed kites (rogallos/hang gliders) or very high AR rigid gliders.
These data appear correct, but do not allow us to directly conclude on the respective measured effectiveness of power kites (paragliders) compared to parachutes, in yo-yo mode for power generation where tethered kites are implemented instead of free parachutes and gliders, leading to a different behavior.
Indeed other factors come: crosswind power kites face the “stop and go” (due to power variations within the flight window) drastically reducing the power produced, for an efficiency ratio that I have roughly estimated at 3 (power kite) to 1 (parachute) per surface area unit, comparing a power kite to a parachute kite of the same surface area.
This small difference could perhaps be corroborated by figure 15 which indicates 12 m/s wind speed at mast height while the text suggests much higher wind speeds at kite height, and also (in a lesser extent) to the Chinese parachute-based AWES compared to flexible crosswind kites like SkySails (figure 15 linked above) or Mutiny.
I do not think the difference is significant enough to justify the land and space use required by the crosswind power kite, as well as a complex control system, and greater fabric wear due to higher stresses.
Well, to be convinced I would have to see more than a single experiment with a specific two line kite (without ability to test influence of AoA).
Control complexity issues - let’s talk about unassisted unfolding, launching or landing and folding of a huge parachute before a storm.
Space depends on use case, one motivation for flying wind power is it is less constrained to specific wind sites than tower windmills which need both high winds and heavy transport road access for e.g. the cranes needed to lift the turbine.
I disagree with the fabric wear argument because a ram-air flexible (paraglider style) kite:
maintains shape all the time, while a parachute will fold/unfold every cycle.
is not the only type of glider kite. Any flying thing using ripstop sail fabric needs replacement of the wing every 6 months. Longer lasting materials seem to require some degree of rigidity of the wing
Anyway, some device for inflight line tension measurement and recording would be of great help.
I experimented a 2 line power kite Vibe of 0.5 m² (on the photo), and also a 2 line power kite Ozone 0.8 m², compared to a parachute kite of about 0.5 m² (on the photo). Both power kites led to a similar result: 3x the power of the parachute kite equal surface area, no more. This is due, as I indicated previously, to the “stop and go” in crosswind flying where a lot of wind energy is spent accelerating and slowing down the kite in a flight window where the power is not the same everywhere.
The power kite can be set to different AoA depending on the wind speed. The higher the AoA, the more lift it will produce in static flight with a lower elevation angle, but it will also be slower.
A paraglider generally flies with a lower AoA than a power kite, and with a higher lift-to-drag ratio (no tether drag, no flight window).
See also the curves on Figure 15 and Mutiny I mentioned on my previous comment: not so good in regard to the wind speed at the height of the kite.
It can give a maximum value, but I preferred to follow the variation (huge, 4x or 5x in maximum value, almost nothing in minimum value, and probably less than 3x on average: we are far from 15x or 27.777x) of force during the crosswind flight, whereas there was no force variation (as expected) with the flight with the parachute kite.
I was wondering why we see so many AWES and not conventional wind turbines…
More seriously, AWES use significantly more space and land than conventional wind turbines. For conventional turbines, land use is limited to the area occupied by the tower. Concerning AWES, the huge space should be maximized to make them effective, allowing easy secondary uses (agriculture, or offshore fishing) just like conventional wind turbines.
For AWES, a dome-shaped or cylindrical area with a radius at least equal to the tether length must be considered, taking into account all wind directions.
For a crosswind AWES, the airspace occupied by the figure-eight pattern is much larger than the area of wind actually captured, resulting in areas that are either unusable or difficult to use by other crosswind AWES within the same wind farm. In contrast, a parachute-based AWES utilizes the entire captured area, making it possible to have other parachute-based AWES operating in close proximity within the same wind farm.
typically, a paraglider can last anywhere between 200 to 300 hours of airtime
So, two weeks in continuous use.
our professional series fabric weighs in at 1.3 oz and can endure approximately 5000 flights or more
That’s already at least 10x better (although not sufficient for a daily use). And between each flight, the parasail is folded up.