[BillM]

The first Law of Thermodynamics states that energy can neither be created nor destroyed. If energy is transferred to the windmill from the air, the air WILL cool. The effects that you describe in the orchard or vineyard just move the air around exchanging warmer air aloft for the cooler surface layer. In the case where the fans are driven by power to move the air, the heat transfer is from the fan blade TO the air! The power generating windmill moves the energy from the air to the blade.

[Parmy]

What you say is undoubtedly true, but there is a warm inversion above the cold air at the surface, even in the winter. And what the fans do is cause the minicus(sp) layer to be penetrated so the warmer air can be mixed with the colder air to raise the surface temperature above the critical point that would damage the fruit buds.

We have done this for years, and it works. There are other factors in play here as well. For instance, the effectiveness of the fans ability to raise the temperature depends upon the dew point. The higher the dew point, the more the temperature can be raised, conversely, the lower the dew point, the less effective the fans are in raising the temperature.