Correct procedure for calculating Efficiency Coefficient of Wind Turbine

One can calculate how much Kinetic energy is passing trough vertical cross section or Diameter of turbine in case of VAWT turbine each second, but one can only calculate efficiency of turbine by measuring Wind speed in front (V1) and in the back of turbine (V2), find the difference (VL = Velocity lost) VL= V1-V2 and put this in relation to original Wind speed V1 as

TAEC (Turbine Apparent Efficiency Coefficient) = VL / V1 assuming turbine is ordinary one, pushed by Wind, which slow Wind down..

But calculated efficiency. is apparent one, while real efficiency is twice as big.

So TC = TAEC * 2

That is because Formula for Maximum of Extractable Kinetic Energy of Wind read as

TC (Turbine efficiency Coefficient) * 1/2 * m * v^2

or TC/2 * KEW (Kinetic Energy of Wind,  which is m * v^2  or   d * v^3 )

For ideal, 100% effective Turbine with TC = 1.0 read 0.5 * KWE

saying that absolute maximum (for push-me turbines with same size inlet and outlet of Turbine and unchanged Wind movement Vector) is

1/2 of actual Kinetic Energy.  and TC = 0.5 Or 50% in percentages.

That is also Proof that Betz Coefficient cannot exist, since if only 50% of Kinetic energy can be extracted, even on 100% effective Turbine, out of necesity at least 50% of Kinetic Energy must remain behind turbine, so V2 cannot be smaller than 2/3 of V1, therefore so called Betz RATIO

of 1/3 cannot exist, and anyhow it would be 0.3334  because it can in no way be 0.593 even on 100% effective turbine "With Countless number of blades" that Engineer Betz postulated.

Regards from Croatia, the Homeland of Engineer Nikola Tesla!