Ok I have this car powered by the wind. In order to caclucalte the efficiency I would like to compare the maximum energy possible to be taken out of the wind(air) compared to the actual energy output 1/2mv^2. Is this viable? And could someone give a formula for wind energy? Also to create the gust I am using a fan with a certain power (45W) can this be utilized? The turbine is vertical axis as in: Code (Text): O--O--O | ------- O O The formula for kinetic energy of the wind I have is: K.E. = 1/2*m*v^2 where M=p*A*v*t A=the area of the turbine that is affected by the wind p=density of air M=mass v=velocity Now the problem I have is to determine A. I have six cups with 60degrees between them. What is A? Ok I understand A now but what is t. What I have without t is some kind of power output. Can this be compared with the power output of the car and in that case what is the power output of the car or can the wind power be made energy?