Turning a DC motor into a generator looks like very straightforward: mount and forget.
However, in the case of low-power projects (mine is a small desk-on vertical axis wind turbine) there are some question marks:
- friction of brushes may reduce power
- there is a need to spin the motor at faster rpm than when used as motor
At least that I could find.
On the other hand, brushless motors are smaller at the same power and I suspect they present lower friction.
If I get it right, brushless motors output three-phases - alternative current that can be converted to DC.
Some people on the net suggest a Shotkey diode rectifier to achieve this.
I found schematics but not sure they are effective at a small rpm (say 200- 500 rpm) considering that the Shotkeys do have a voltage drop, although very small.
Some info I found:
Still pending questions - no answer from browsing the internet:
a) how difficult may be to find, mount (or build?) a specific controller? Can be done via hobby resources/Arduino - if needed?
b) what is the minimal rpm to get some useful vortage out of this type of motors> By minimal - I expect some 1V - which is good for a Joule thief circuit to operate?
Thank you very much for your kind and patient help!
I am now working on the vertical axis turbine - very fun It is some 50 cm high and 20 cm radius. Two designs: a) classic 3 or 4 wings Savonius and b) Helical shape. If I will find a detailed Darrieus drawing, maybe I can go for that as well.