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The idea involves a physics concept called gyroscopic precession. This is a phenomenon occurring in rotating bodies in which an applied force is manifested 90 degrees later in the direction of rotation from where the force was applied. We use the right hand rule to determine the torque direction or spin vector.
Applying the right hand rule to the double windmill, based on direction of blade rotation, means that the spin vector is a force acting outward towards the wind. Each blade set is doing that so both forces are balanced. But, what if you design one of the blades so it spun in the opposite direction? And, then, you make the tail smaller?
The result would be that higher winds will cause the windmill to yaw out of the wind slightly. This will slow the blades down, then gyroscopic procession will decrease as the blades start to spin back into the wind and the process repeats...until a sweet spot is found. This should work nicely for small fast spinning wind turbines. This should protect them in higher winds. Just imagine 40 mph winds while the wind turbine is furled sideways at a 45 degree angle and still producing safe power.