Yup. DC won't flow through capacitors. The ones across each bridge are OK, but the two at the ends of that rectangle above the buck converter need to go. You could put them across the buck converter inputs if you want more filtering/storage. I agree with Nando that the scheme is a little crazy though. Both mechanically and trying to get the voltage up so you can use a buck converter to bring it back down.
> I have a small vertical axis sailwing wind turbine
Is this the one at http://www.fieldlines.com/story/2007/2/23/124116/813 or a similar one? There you mention 40 RPM.
> The starting speed of the turbine will definitely go down with this system. But I
> thought ant other turbine with a generator connected to it would start with a
> starting load unless we have a centrifugal clutch or an induced magnetic field
> proportional to the rpm on the generator. Correct me if I am wrong please.
More complex than needed. A generator won't charge a battery until it's producing more voltage than what the battery already has. The voltage produced by a generator varies linearly with the speed of the generator. So at startup the generator isn't putting out enough voltage for the battery to draw any current from it. You'll see cut-in mentioned often here, that's when the generator's turning fast enough to start charging the battery. You don't have to do anything extra. When things are turning fast enough the battery will start charging. As they turn faster the voltage (and eventually current) will increase, which in turn causes more mechanical load on the windmill. In some small sense it's almost self-regulating for a narrow range of windspeed because the faster the mill turns the more voltage it produces, so the battery draws more current, which causes more mechanical load, which slows it back down. Until you get a lot of wind at once, or this has been going on long enough that the battery's gotten charged.
You can let a lead-acid battery get up to 14.2 volts or more on peaks without hurting it, but for sustained high wind conditions you should use a dump load controller or shunt regulator to keep the voltage down. That just applies a load by dumping off electricity into resistors when the voltage gets too high, which also works to prevent gradual overcharging.
The part about the generator not putting a load on the windmill until the voltage causes cut-in is only true if the generator doesn't cog. Bicycle dynamos do cog. Cogging is almost like friction in that it doesn't gain you anything, it's just waste. It's caused by attraction of the magnets to steel parts inside the generator. Peter Dinges just did a couple of good posts on decogging motor conversions at http://www.fieldlines.com/story/2007/5/31/212633/814 and http://www.fieldlines.com/story/2007/6/12/152738/467 DC motors, bicycle dynamos, motor conversions and iron-cored generators in general cog. Axial flux and air-cored generators don't. See http://www.otherpower.com/woodax.html and http://www.otherpower.com/pmg2.html for a couple of air-cored ones.
I think you should build an axial flux or air core alternator. Make it as big in diameter as you practically can. Running at low RPMs just means building a fairly expensive generator and then not utilizing most of its capability because of the low RPM. It's like buying a bigger engine so you never have to run it above an idle. Use as much magnet (Neo) as you can afford. Get it all built except the coils, then you can wind a test coil and spin it up and see what happens. Use a drill or something to turn it at something close to the right speed. See how much voltage you get out of one coil with a small number of turns (it'll be AC voltage) and then multiply by the number of coils you'll have. You can adjust the number of turns up and down once you've done a simple test coil. Voltage will be linearly proportional to the number of turns on all the coils, the RPM, and the strength of the magnetic field. Until you run out of space that is. You'll need to keep an eye on the total resistance of the wire you're using because it will limit how much power you can get out. More/stronger magnets will give you more power with the same wire, but probably with more expense. 3 phase designs work better than single phase. Motor conversions aren't out of the question if you can decog them, and the F&P motors look great for low speeds (but still cog).
I would put the buck converter someplace safe and not use it. Wind is wild, and it's not unusual to get a 10:1 or more variation in voltage. It fries things, even without lightning to help.
Alan
