3 ms·

don't be silly, you just claimed that it doesn't matter whether you have 3 meter blades or 30 meter ones. Of course the swept area matters. P = 1/2 x ρ x A x v

• danmaz74 13y ago
  Don't be silly yourself. What happens if you add or remove a blade, or change their shape or pitch? The swept area stays the same, but the energy captured changes. The "swept area" is a useful abstraction that gives us the total energy that you can extract from - with your formula - but it's the blades being there with their length that extract that energy. These wind towers on the other hand capture and manipulate the whole air flow from the area of their intake, not just the part directly interacting with the blades of a traditional turbine. That's why it is physically possible to extract much more power than with a traditional turbine with an equivalent "swept area".
  • whage 13y ago
    That's right, the above formula is just the power of the wind, the amount of energy you are able to harvest from it does depend on the characteristics on the blade. The swept area is still a key factor. (see Betz limit for another interesting fact) You are right about the second part, those 'tunnels' do catch all the wind of their area.
    • danmaz74 13y ago
      Ok, I think you got my point. To sustain it: "Theoretically, an infinite number of blades of zero width is the most efficient, operating at a high value of the tip speed ratio. But other considerations lead to a compromise of only a few blades.[22]" http://en.wikipedia.org/wiki/Wind_turbine_design#Blade_count http://en.wikipedia.org/wiki/Wind_turbine_design#Blade_count