Are solid-state windmills feasible? Imagine a structure exposed to wind.  It is designed chemically so that a molecule striking the surface can transfer kinetic energy to electrons that are promoted to a higher energy state.  These move through a conduction band and are collected as in a solar cell.  Maybe a layered structure akin to graphite cut diagonally would be helpful to orient the interaction and transmit current.
Has anyone studied such a "wind panel"?  The energy density from wind friction is likely to be lower than that of solar energy, but could the energy threshold be used to slow wind to a desired velocity?
 A: The question @trula asked wasn't about the energy of a windmill in general. The question was about a single molecule. The distinction is very important.
It's kind of like ionizing vs non-ionizing radiation. You can blast a piece of semiconductor with as much radio wave radiation as you like, but the radio waves won't free a single electron (short of simply heating the semiconductor). However, if you apply even a small amount of x-rays radiation, you'll start to free electrons.
Why? Because electromagnetic radiation is quantized. A radio wave photon does not have the energy to free an electron, so it doesn't matter how many you apply. In contrast, an x-ray photon has the energy to free an electron, so even a single x-ray photon can free an electron.
Air is likewise quantized. It's made out of discrete particles, so the question here isn't: How much energy is there in the air? The question is: How much energy is there in a single particle?
BTW, that's not to say that air moving past a structure can't free any charges, but I don't think it's by the mechanism you propose.
