Yaw Torque In Wind Turbine

Well it would be good to understand the moment of inertia for a rotating mass. For obvious reasons you should consider the moment of inertia around at least two axes. There will then be the effect from a changing wind direction. Fortunately for you the blades will not be spinning much when the wind is not blowing and by pointing into the wind you're just maximizing the energy transfer. Perfect alignment is not necessary to obtain power.

Now I will not do the math for you. You're getting paid for this, I'm not.

There are formulas for the forces of wind on the projected areas of surfaces. Torque is this force times the mean distance of the projected area from the yaw axis.

I figure the slew rate would have to be considered. The diameter too...

I assume that you want to turn the HAWT into the wind when the speed is above your minimum and turned away if it goes above a certain value?

Why not use a wind speed system that automatically measures the wind speed from any direction like an an Anemometer. Also a wind direction system is needed.

Use some sort of intelligence to ascertain as to whether the wind is within the correct speeds. Using the wind direction information to turn it on or off the wind.

Use a simple geared down servo system to move the blades in and out of the wind as needed.

A small PIC and some simple programming and interfacing will handle the whole deal....

Plan B: How about a variable pitch design, with the blades spring loaded to rotate on each of their radial axes? Almost instant response, versus motor driven schemes. And then a tail vane to keep everything pointed into the wind.

[???]

Along with Tornado, who has one GA coming up, I support spring-loaded rotors. Jacobs turbines have used this approach for decades -- simple, cheap, robust, and plenty accurate enough.