Mary Fe, Maria Paula and I finally got our shake on! We learned that it is best to use thin copper wire wound very tightly and many many times to get the most voltage. The best coil we got can put out a max of 10 volts.
We soldered up a board with 6 LEDs, a bridge rectifier and 4 0.0047F capacitors in parallel to hold some of the charge.
Starting voltage: 0 V
Ending voltage: 8.5 V
Capacitance: 4 x 4700 microFarad
Starting energy: 0 joules
end: (0.5) * 4 * (0.0047 F) * (8.5V) * (8.5V)= 0.68 Joules
power = 0.68/ 20 secs = 0.034 watts