power of the wind

[rotornuts]

Ok, thinking of another rotor design so I want to calculate how much power is in 7.85sqft of air at 15mph. All my files are still packed in a box somewhere in the basement so I searched the computer and came up empty so I fiqure I must have it bookmarked somewhere. Hmm, only a hundred or so bookmarks so I'll try this one. Nope but hey that's kinda interesting, oh wait I'm looking for something, ok I'll try this one. Nope, next, nope, next, arrg. Ok maybe I should just ask before I drive myself crazy looking. Can't remember everything.

So, how about the power available in 7.85 sqft at 15 mph no corrections for betz or rotor efficiency.

[zap]

Something like this?

[monte350c]

Hi again Rotornuts,

The formula behind that spreadsheet is fairly simple:

 .00502 x area in square feet x windspeed in mph^3

so...

 .00502 x 7.85 x 15^3

 = 132.99 watts

That takes Betz into account, but not blade, or alternator efficiency.

If you want the number for the 2.5 foot diameter machine, it's PIr^2 for the area of a circle:

 3.14 x 1.25^2 = 4.9 square feet

 .00502 x 4.9 x 15^3

 = 83 watts (same as above not counting blade or alt efficiency)

ps. if you have a high speed connection you can get a reader that will open Excel files:

http://tinyurl.com/5az9k  that's from ms and it's 10mb

or... practically any spreadsheet program should open it, like Star Office, or various Linux spreadsheets etc.

Good Luck!

Ted.

[rotornuts]

thanks guys I had a feeling It was in the 50 -75 watt range so with blade and alt corrections it'll be down to 40ish.