A small thermocouple would produce tiny amounts of electricity as temperature unevenly fluctuates. But if I tried to store that energy using a diode and capacitor, I would guess that the tiny reverse current flow through the diode would be enough to not allow for such a self charging system to work. Is there a "perfect" diode? Not necessarily a diode, but just something that would act like a perfect diode? Or is there another practical way to charge a low energy system that does not involve a chemical battery, using just natural fluctuations in air temperature, sound, electromagnetic noise, etc? I'm looking for something very small that could fit in a microchip.