How do I determine total efficiency

[imsmooth]

I have my 10.5' MPPT grid-tie turbine running.  I can program in a power curve based on the input voltage.  Using some formulas I compute what load is needed on the open voltage to yield a power output at that RPM.  I figure out what the voltage drop across the load is and program that number into the inverter.  

I first computed 15% power from the available wind energy.  Next, I tried drawing 20% of the theoretical wind power.  How high can I go (I know I can't get above the Betz limit plus other power losses) and how do I tell if I'm trying to draw off too much power?  Will the blades just not speed up in high winds?  Will there RPM just platue?

[Flux]

Typical decent home made blades should reach about 35% or possibly a little more when tracked with a mppt inverter. With the voltage rising with speed you may obtain 60% or a little better over most of the range with an alternator  so I think you can go over 20%.

I would guess that you may get close to 30% in the lower winds, perhaps dropping to near 20% at furling point.

These are the sort of figures I seem to get with a mppt battery charger, I don't think your grid tie inverter would be much different.

When you get the load right your blade rpm will track wind speed. Too much load and the speed holds down. Too little and the blades run too fast. You aim for blade design tsr over the working range.

Flux