You can start by throwing away variable pitch, sure it's cool, that system midwould has on fieldlines is sexy as hell but Chris has shown that with properly tuned MPPT it's totally unnecessary.
I had to do a complete reversal on that one. For a long time I was against the MPPT control because I figured it wasn't reliable. Well, frankly, the guys that build that controller didn't whap me over the head with a pipe to tell me different. And with me, that's usually what it takes.
Until I got one in my hands, tested it, built a turbine for it, and flew it, I found out a whole bunch of stuff that I
assumed about that controller that were dead wrong.
First thing is, you can't get it to explode and leave a smoldering crater in your utility room by running it over-voltage. The controller is smarter than that.
The second thing is, you can't run it over it's amp limit and get it to melt down into a glowing pile of goo. The controller is smarter than that.
After getting off my stump and preaching against it, I decided I'd better try it. What I found, is that thing can wake up even the poorest designed turbine and get better efficiency from it. If you build a book-design turbine, go to all the work to build a tower for it, get it wired up and get it running - assuming you live on even a halfway decent wind site, that controller is the cheapest $800 you will spend to actually get some decent power from your turbine project.
And what's more, instead of turning a homebrew turbine into a "MPPT buzz bomb" it actually enhances the safety of the turbine because it increases the chances of the turbine furling correctly, it reduces the chances of a generator burnout (and subsequent runaway) by keeping the power dissipation down in the stator, and it logs the power output of your turbine every single day so you don't have to guess at what it's actually making for power.
I spent the better part of two years designing turbines that were more efficient than the standard book designs. Well, when you're wrong, you're wrong. And I was wrong. You can't even come close to the full wind-speed-range efficiency with a direct battery charging turbine that you can get with that controller. The same principles that apply to solar panels wired series with MPPT apply to wind turbines.
And the nice thing is, it is designed and built by guys that have been in the RE business since Moby Dick was a minnow and have contributed a lot to the business from names like Trace Engineering and Outback Power Systems. It ain't no Asian-imported unit that only does half of what it says in the advertising material.
So that's my .02 cents on it.
--
Chris