Maintaining a stable voltage on a wind turbine?
Every couple weeks a new instructable comes up on some green energy thing or another, but one I am really interested in is wind. The problem I see is that with wind ranges from 5 - 25 mph, the voltage change is extremely problematic. When I see people putting permanent magnets on alternators for use with wind, it seems ridiculous. Even if you are using an inefficient battery-storage off-grid system, you still need to maintain 12-15 volts to charge your battery, and an alternator is made to do that by varying the magnetic power. Now I understand the extremes of a alternator's voltage regulator are likely fairly narrow, but still quite useful in generating wind energy. What I am looking at is 3-5kw of grid-tied power. This is great and all, and possible in for me, but I don't see how I could maintain a stable enough input for it to work. Most inverters are for solar power and aren't grid tied. The next most common are grid tied solar which take 12v DC and scale it to 115 ac across three phases. Finding a grid-tie 5kw 3 phase in and out ac grid tie inverter is extremely hard, but not impossible. The only thing that is impossible is finding one that can handle highly unstable voltages. So the options I am left with are using a variable transformer to bring the wind power down to 12v and then rectifying it, then pumping it through an inverter which leaves me with 70 - 80 % of the original power. My other option is to, like a car alternator vary the rotor voltage to maintain the desired end voltage. The one problem I see with this is that there is a large amount of potential energy not tapped. For example lets use 1 as the relative output as well as the input to generate a magnetic field. If the speed is 1 then both in and out are 1. If the speed is 2 then the in will be .5 now the out should stay at 1. But if the in had remained at 1, then the out would be 2 so essentially you are losing half of your potential energy. This isn't a problem in cars because they aren't tapping the maximum power possible. All the time, they don't need it. This is a problem with wind turbines, so is there a way around this? What wold you recommend to do for grid-tied wind power.