I may be wrong, but this is how I understand it. The propellers push against the wind. Effectively you’re creating a faster wind by pushing back at it. The ener

I may be wrong, but this is how I understand it. The propellers push against the wind. Effectively you’re creating a faster wind by pushing back at it. The energy that drives the propellers still comes indirectly entirely from the wind, but wind across a larger volume behind the propeller so therefore carrying more energy.