I was looking at the box fan in my living room, and noting that the blades are much fatter and wider than wind turbine blades. Common sense would seem to indicate that you'd want propellar blades to take as much lateral surface area as possible to transfer as much kinetic energy from that linear area as possible. So, why are wind turbine blades skinny? Airplane props are the same way, although in that case their high angular velocity in relation to the wind speed moving through them likely makes up for it. Wind turbine blades though don't move nearly as fast....so why are they long and skinny as opposed to fatter and wider like a house fan?