A little more info here: Slow Chat - #71 by Windy_Skies
Interesting video. Some other discussed points (comprising a link to their document chinese umbrella description.pdf ) are on The most basic airborne wind energy system - #15 by PierreB.
I presented also an option by replacing the parachute with a flexible rotary kite.
If this is verified, would this be the most significant electricity production made by any AWES?
In the video you can see they are generating no more than 22kW. They’d need to generate around 600kW to get to 30MWh in 50 hours, and they would have done that in 2015. Verification needed I think. But then all that money must also have gone somewhere.
This looks like a promo video shot in a single day and in little wind, perhaps to get nice drone shots. What happened after this? The bigger news I think is that they’ve now got some funding to do more research.
If this picture from their website is real and they flew it in stronger winds they might have generated some power. And then times four if they flew four of these at the same time. But it would have cost some power to reel it in too if only 2 of the parachutes could be collapsed. One wonders about the size of the lifters or balloons to maintain the tether angle in higher winds.
chinese umbrella description.pdf page 12:
Normal force coefficient VS Angle of attack ɑ
CN /CT＜ 0.01
Wind Tunnel Result
The required lifting force to keep an opened umbrella’s angle of attack constant is very small
compared with the polling force it generates
But already significant flying bodies such like a balloon and at least one static lifter parachute assure required lifting force to the working umbrella(s), and under an apparently low wind. For a small required lifting force, small lifters should be sufficient, or there is something I do not still understand. The angle of attack could be connected to the tether angle in some way.
I wonder why so much time is spend on crosswind flight if the same amount of power can be generated with a slightly bigger kite / parachute
Welcome to the forum @Ewout
Good question! The response is not obvious. I think almost all scientific circles reason in terms of power / wing area ratio, following the seminal Loyd’s publication: Crosswind Kite Power.
On this criterion, crosswind flying wings are much superior to parachutes, according to a lift to drag (L/D) squared ratio. This ratio still increases when the wing is rigid, leading to increasing of the L/D ratio.
Now if power / weight aloft ratio is applied, things are different.
And now if Power to space use ratio is taken into account things can be still different: the path of a crosswind (above all rigid) kite is far larger than the useful swept area (being able to be the parachute area) due to the flight requirement; and within a kite-farm very large spacing between unities (and also the inhabited areas) is required due to safety needs as they fly fast.
So in the end a kite-farm using parachutes flying slowly could be denser…
I see the relevance of crosswind flight for utility scale deployments.
But let’s consider a small scale deployment ,such as the 10kw Eaz turbine below. Turbines like these are popping up next to farms all over the country. Instead of expensive electronics it uses purely mechanical controls to become cost competitieve. A big fin to face the wind and tilting blades as a overspeed protection.
If you would apply the same design strategy to a let say 5 kw AWE system. What will it look like? I think you will end up with something in between the traditional paradropper kite and the Zhonglu concept. A lifter kiter, a parachute that flags out when it reaches a certain hight/obstance and a ground gen. No airborne controls needed.