I don't konw where to post this. Does anyone know why the windmills of Spain are short and fat with 4 rotor blades that look as though they are fixed on one side of the building while those in the USA for pumping water are tall and slender with multi-bladed rotars like daisy petals that move to face into the wind? And the newer wind generating mills seem mostly to be tall with 2 long slender blades. Is there a difference in the kinds of wind, the depth of water, the amount of power produced? the purpose of the power? (if you get right down to it, does anyone but me even care!)

It's difference in usage. The traditional white spanish windmill was used to turn wheat into flour, which implies the transmision of the wind movement to a set of heavy stones levered on strong mechanisms (residing in the building) in an activity that happenend in certain seasons. Thus the "blades" and structures needed to be solidly supported.

In the contrary water pumping requieres less torque but more continuity, that is way the lighter strctures are easily provided with directional mechanisms that allow for orientation.

The modern cases, is for transmitting the rotation to the electric generator in the base of the fan, and the dual-or triple blade is just the more efficient wind gathering system due the winds charges and efforts requiered

Thank you. That makes sense.

Wow! I thought it was all just about "old" technology versus new technology. This is one of those bits of information that I may never use but like knowing!