Comment on 'Windmill': China tests world’s first megawatt-level airship to capture high winds
tate@lemmy.sdf.org 3 weeks agoWe don’t directly harvest the kinetic energy. That increase probably has to do with how the wind provides lift to the blades. Of course, you couldn’t keep increasing like that until the harvested energy is greater than the kinetic energy. But I’m sure at any wind speed we only get a tiny fraction.
inktvip@lemmy.dbzer0.com 3 weeks ago
Kinetic energy is exactly what’s harvested, which is why modern wind turbines are not far off the theoretical limit of the amount of energy that can be extracted. (Betz’s law)
By taking energy from wind, you slow it down. Slow it down too much, and it can’t get out of the way in time for new air.
tate@lemmy.sdf.org 2 weeks ago
I could have stated it better. What I meant was that the fraction of kinetic energy that is taken from the wind is so small that the total kinetic energy in the wind is probably not the important factor that changes with wind speed. The dynamics of how the lift depends on wind speed is probably much more important.
Redjard@lemmy.dbzer0.com 2 weeks ago
It is actually a notable fraction (~60%) and more importantly constant.
Meaning if your wind has 27x more energy, you can also capture 27x more energy.
This is the energy taken from the wind passing through the disk the turbine spins in, so turbines are placed in spaced out rows to let the wind mix with all the air that didn’t pass through a turbine and pick up speed again.