# How to calculate the power generation from the given kite size? Approximation.

I am currently working on kite based wind power generation and I do not know how to calculate the power generated from my 12m2 airrush lithium kite. Need your help.

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Welcome @Roystan,

I put again my previous message with light modifications here.

A basic paper about calculation is

Assuming wind speed is 5 m/s, cubed wind speed is 125, air density is 1.2, lift-to-drag ratio is 4, lift coefficient is 1, elevation angle is 30° leading to cosine = 0.866 then cosine cubed = 0.65. I use the equation (2) from the paper, adding cosine loss which is mentioned later in the paper.

(1.2) (2/27) (12) (125) (4²) (0.65) = 1386 W during reel-out generation phase. The time and the power consumption during reel-in phase lead to an average of about 600 W.

A similar result can be obtained by multiplying the force (equation 1 from the paper) with reel-out speed which is 1/3 of 5, so 1.66. The reel-out speed is the speed of the unwinding speed of the rope which is seen as optimal when it is 1/3 wind speed. The cosine squared is 0.75.

(1/2) (1.2) (12) (5²) (4²) (0.75) = 2160 N. Then (2160) (1.66666) (4/9) (0.866) = 1386 W.
I precise 4/9 is due to the squared loss of force due to the 1/3 loss of apparent wind speed during reel-out phase.

Other losses are not mentioned and comprise losses by transmission of irregular power as the power varies within the flight window, by cosine due to the gravity (see the paper)… So one can expect an average of 300 or 400 W.

The power can be measured by knowing the force (using a peson) X the reel-out speed.

I would like to just comment that kitesurf kites are specified with area of the skin flat, so when you add the «C-shape» of the kite, the projected area is probably a lot less than 12 square meters.

Hi @Roystan ! Welcome to the Forum! 