Nope, Plummet is rightKamikuza wrote:Wrong equation. http://large.stanford.edu/courses/2010/ph240/sleiter2/plummet wrote:What is the actual increase/decrease in kinetic energy from changing temperatures?

First up we have to use the ideal gas law to calculate the mass of the air

http://www.engineeringtoolbox.com/humid ... d_677.html

Lets use a 0 and 30 Degrees C for calculations.

0 deg c = 1.29kg/m2

30 Deg c= 1.17kg/m2

Then we throw that into the kinetic energy formula

https://en.wikipedia.org/wiki/Kinetic_energy

1/2 mass x velocity squared.

Lets use 4 knots for wind speed.

The increase in kinetic energy dropping from to 30 degrees to 0 Degrees = 11%.

That doesn't sound like much. But it could be significant in ultralight winds.

What is the increase in kinetic energy going from 4 to 5 knots or wind speed all other aspects being equal?

55% increase.

Wind speed increase is far more significant that temperature variations.

Power in the wind = 1/2pv^3

Maybe air density doesn't matter so much after all . . . But for sure, there is a big difference summer and not summer. Definitely less consistent, recently.

It can be easy to confuse Work and Power and Energy and Force.

But the power is not relevant, only if you have a wind turbine.

It is the total lift (or linepull/force) from the kite, which is proportional to the kinetic energy in an amount of air, so it is in fact proportional thus the same (like Plummet writes) as the lift/pull from a kite, so it is

Lift = area * liftcoefficient * airdensity/2 * airspeed^2 = area * liftcoefficient * kineticenergyoftheair.

Where the kinetic energy of the air is the same as the dynamic pressure thus = airdensity/2 * airspeed^2.

So Plummets calculation is correct, and air temperature has a very minor effect, compared to the actual windspeed

Which you also state Kami, but it is only squared to the windspeed and not the power of 3 like power.

But it CAN be felt slightly, eventhough not much difference from 25 to 35 degree celcius....

Peter