Wind power

Anonymous-0 · Jul 23, 2008

This may sound stupid but interesting,

When the wind is blowing 70 mph how much force in psi does it put on a sq foot of flat surface, like a stop sign..course a stop sign is bigger that 1 foot sq. We had some 80 mph winds here and it was said that the wind blew round bales uphill and they rolled on to the interstate. That is a lot of force. Dont know what the weight of the bales were, but there was power there. Thanks

RAB · Jul 24, 2008

Work it out. Find the density of air and away you go. Work done is force multiplied by distance moved, in Newtons, metres kilograms in my case. Your units might be a bit more difficult - foots, pounds, BTU's etc.

Keep in mind Albert Betz, of course, who said you can't extract more than about 59% of the dynamic energy of the air, as you have to stop it to do that, as then there would be nowhere for the air to go without giving it back some kinetic energy!(probably not make any difference here but needs to be kept in mind by any potential wind turbine builders)

You will not find it much as you may, or probably may not, be aware that the typical brick house design is about 4 1/2 psi in your units.

Bales are a different problem. The force needed to roll a bale can be far less than picking it up against the force of gravity. That is why wheels were invented.

Regards, RAB

cj in wisconsin · Jul 24, 2008

We had a tornado here in 01 that picked a bunch of big rounds up, moved them into a grove of trees about 200 yards away, spun them around so much that they looked like they had afroes. It didnt roll them, but set them down there. I dont know how much force that takes in psi etc. But it sure was interesting to see.

Tramway Guy · Jul 24, 2008

I found a formula which says that wind pressure (in Pounds per square foot)= 0.00256 x [wind speed squared]; so at 70 MPH, the pressure would be 0.00256 x (70 x 70) = 0.00256 x 4900 or
12.54 psf.
That would be at sea level, of course at higher altitudes the pressure would be less due to less dense air.

Anonymous-0 · Jul 24, 2008

You probably had a micro burst or down burst storm there with isolated spots of unknown wind speeds to the experts or other areas. We get those kind of storms all the time and the damage with hail and down burst winds can do as much damage as a tornado but just doesn't flatten everything or move the debris as far.
NWS

Wind power

Anonymous-0

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RAB

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cj in wisconsin

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Tramway Guy

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Anonymous-0

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