I juste made some simples calcultation to find out if it's possible to power the robot with potatoes energy.
The energy is harvested from a single potato in two super capacitor (2.7V / 350F).
If i place the two capacitor in series, it gives me a single capacitor of 5.4V / 175F.
The energy inside capacitor is :
I don't want overcharge it, so i will charge at maximum 5V :