709
'Windmill': China tests world’s first megawatt-level airship to capture high winds
(interestingengineering.com)
This is a most excellent place for technology news and articles.
Edit: I'm wrong, see edit below!
Huh? Kinetic energy increase is square, not cubic.
KE=1/2 m v^2
So every doubling of speed should increase the available kinetic energy by 4 times, not 8. 3 times the speed is 9 times the energy. Granted there are probably some efficiency gains in excess of this at the low end, ~~but as a rule that's just wrong.~~
Edit: Cool, I learned something new! I neglected to consider it in terms of power, just thought about kinetic energy.
So something like: KE = 1/2 m v^2
= 1/2 ( rho V) v^2
= 1/2 ( rho A d) (d/t)^2
= 1/2 rho A d^3 1/t^2
Where P = KE/t
Thus:
P = 1/2 rho A (d/t)^3
= 1/2 rho A v^3
Lots of other aspects I'm sure I have wrong, but I see how the cubic came to be.
Its cubic actually
https://thundersaidenergy.com/downloads/wind-power-impacts-of-larger-turbines/
I don't understand the physics, but every model of power output from wind turbines uses V^3 for the formula
Thanks for the correction! I got way ahead of myself.