Well… the question should be: where does all this electric charge come from? I you harvest it from humidity in the Air, the charge would removed. Thus, you have to replace the humidity in the air with fresh, „charged“ humidity.
Is there any natural effect, that this works automatically? Or do you need a fan? How much energy would that need?
Too much questions, too less details for a too simple solution.
Oh… damn. I thought they were still on the same basis. Sorry, my fault. :(