Where did the extra 3600 units of energy come from to do this? Did it extract the energy from the airflow? Did the temperature of the airflow decrease to supply the energy? Did it move slower, having given up some of it's "oomph"? No, and no. It got hotter (from being whacked by the rotor blades) and it moved faster, because the blades ADDED energy to the airflow. However, if it did somehow extract energy from the airflow, how does it "give it back" when it turns back into wind?
It's a thoughtful point, but...
Whirl a 1 kg stone attached to a string around your head so it has a velocity of, say, 6 m/s. It has a KE of 18 J, constant around the circle. Now take it on to a bus travelling at 6 m/s, and continue to twirl it in the same way. It now goes from a KE of zero when it is moving backwards with respect to the twirler, to a KE of 72 J when it is moving in the same direction as the bus.
Does it behave differently? No it doesn't, and if you don't believe me, try it next time you're on a moving walkway in a deserted airport.
So how does it get and give back that extra energy?