A no-moving-parts windmill is much easier to construct than I had at first thought. Build a chain-link fence insulated from the ground. Mount, on the fence, a mist sprayer (like an ultrasonic humidifier) operated at a voltage differential from the fence, so it extracts electrons from the fence and puts them on the water droplets. In the absence of wind, the droplets are drawn back to the fence, neutralizing the charge. Wind blows the droplets away from the fence, which becomes, thereby, increasingly positively charged. A current from the ground to the fence can do work, such as charging a battery. The more wind you have, the more charged mist it can carry away, and the more current the fence will draw through your battery.
Nothing in this description depends on the size. The fence may be as big as the underside of the Golden Gate bridge, or the space between a pair of skyscrapers. The power available is limited only by the amount of wind that goes through. (The mist is optional, it just adds friction; you could ionize air particles instead.)