Quote:
Originally Posted by jamesqf
Just think about it in steps. Say you've got your wind-powered vehicle, as in the picture in that linked article. It's stationary, and the wind is blowing - say a 30 mph headwind, just to make things simple. So the wind turbine can capture energy from a 30 mph wind at whatever efficiency, and transfer it to the wheels. This means that the vehicle starts moving at say 1 mph. Drag increases, but so does the apparent wind, which means the speed can keep increasing until the energy captured is just sufficient to overcome the total drag. Seems pretty obvious, and as the article shows, it does work.
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The problem is that at 30mph head wind it's going to take 1,400 watts to keep the car from moving backwards with the wind! so 1,400 watts just to keep it standing still and more energy to move it forward, so at that point it needs a prop that is larger then the frontal area of the car to generate enough power to move it forward and that would work if the wind generator was stationary next to the car with a long cord but as soon as you put that turbine on the car it increases the frontal area by the swept area of the turbine.