Hi all Arduino folks
Im currently writing a project about optimizing vertical wind turbines (VAWT).
I want to make a circuit for the output from our VAWT's generator, which is a DC motor.
I don't have the specifications of the motor yet, but I am working on that. It should approximately generate 20Watts of power give or take.
The wind turbine itself is a 3 bladed darrieus, with a hight of 40cm and a diameter of 1m.
The circuit should be able to measure the wind velocity and the angular velocity of the turbine and thereby keep the tip speed ratio (TSR) at the optimal value, thus giving the maximum output from the circuit. Im thinking of using a power-resistor as a "test-load" instead of using a battery, just for simplicity.
I have heard, that you can use a buck converter for something like this, though it was for photo voltaics I think.
can somebody lead me in the right direction please 
I don't have the specifications of the motor yet,
You will need not only those specifications, but the results of some actual performance tests of the completed rotor/generator assembly, before any circuitry can seriously be contemplated.
With todays electronics varying the speed of the rotors to control the output is a bit redundant.
Why not look at a full BOOST/ BUCK citcuit so you can use more of the energy from the generator (they do exist).
If you are looking at getting the most from your wind turbine this would be the way to go.
The problem is you have to find the point where your generator can supply current at a working voltage.
I tried a boost/buck on a 40 watt solar panel and set it to a max of 1.5 amps at 13.8 volts (20watts). What happened was when the pannel dropped below 20watts the unit tried to draw more and shorted the panel out. So a way to reduce the current demand is needed. Hence MPPT.
The only reason to monitor tip speed should be to stop the turbine from flying apart.