I just started researching into autonomous distributed power systems for a PhD. I'm just playing around with the idea of having small wind power stations that can be plugged into the grid and automatically adjust themseleves to match the phase and frequency of the local grid. I see two ways of doing this 1) by using power electronics to convert a DC signal into an AC one, or 2) by generating the AC signal directly.
My question has to do with the overall output efficiencies of each strategy. Which is overall better for today's technology, and which has more promise for the future? Money is not as much a consideration as feasability is.
Of course, it's impossible to use a windmill to generate AC directly at a steady 50/60Hz without some sort of transmission, so these losses must be taken into account. However, correct me if I'm mistaken, but I seem to recall that during my freshman mechanical engineering classes we learned that squirel cage induction motors had a torque in function to the field current. So, I could create a AC induction alternator that would torque up or down depending on the conditions in order to ensure a constant rotational speed. This sort of technology would seem to be very cheap and easy and could generate electricity efficiently over a wide range of wind values, no?
On the flip side, a power electronics windmill that generates an AC current that's then transformed into DC for battery storage and regulation before finally being transformed back into AC at 110/220V must be quite far from 100% effecient, I'd think. Still, if cheap power electronics can do this sort of conversion, for very little losses, than I suppose that they're the superior technology because they will require little to no maintenance.
I'm having trouble finding an apples to apples comparison of power electronics conversion vs direct mechanical generation. I'm new to this field, so I'm really looking more for interesting reading links than I am for a detailed explanation and answer to my question. Feel free to give an indepth response, too, don't get me wrong, I just don't want to give the impression that I'm running to ask for an easy answer before googling a bit.
Thanks,
Kenn Sebesta
