Voltage Multiplier Question

My Usenet reader is playing up so if this is a double post I apologize:

I am experimenting with a wind turbine home built with a brushless, permanent magnet, three phase Fisher and Paykel washing machine motor.

To do some tests, I have used a variable resistive load and, by manually varying the load on the wind turbine, I have found that a 6km/h wind can generate 10W, a 12km/h wind can generate 80W, a 23km/h wind can generate

The problem is when I use batteries instead of a variable load. At lower wind speeds, the produced voltage of the motor is not higher than the batteries, so the turbine just spins and spins but does not make any useable power. The turbine only starts charging the batteries at 20km/h winds, which is a shame as a lot of power just flies by without being collected. This is a battery impedance mis-match problem.

So I think it would be very worth while designing a circuit that doubles triples or quadruples the voltage at lower wind speeds, so that I can get every last bit out of the wind.

I have looked at voltage multipliers, and since the F&P motor is three phase, I wonder what your opinion is of this circuit right at the bottom of the page:

I was thinking of using a microprocessor to control mosfets to select the optimum output voltage for the RPM of the wind turbine. Each mosfet would be connected to each subsequent voltage doubler point.

I am not too familiar with voltage multipliers, hence if anyone has any opinions on their use in this purpose, I would be very interested to know. Voltage ripple is not much of an issue, I am more interested in what the efficiency of such a circuit would be or any drawbacks that I have not forseen.