Finally! Some energy generated by the microbial fuel cell has been harvested and put to use~ 

The aim of this demonstration is to showcase that the concept does work and generate electricity in a beautiful and simple way. Once I figured out a way to make the fuel cell part more reliable, we will make it an educational kit since the electronics, apart from the maybe energy harvesting module, is very straightforward and ludic. 

The new setup was populated with moss (gathered locally) and as learned from the previous tests, waited for a few days for the system to settle (and to keep the moss happy and hydrated!). Then I monitored the voltage output for a day, which seems to average at 200mV, although I think it has not fully settled yet since I get wildly different measurements day to day. I plugged the energy harvesting circuit to it, and managed to charge a 220uF capacitor over 2 days to 4.2V! 

Here is a video of the capacitor powering the LED for a few seconds:

The setup is so far very similar to the 2 previous test samples, but much more reliable: the aluminium foil anode and cathode were not very stable. The parts you cannot see in this picture are just the switch, a resistor, the 220uF capacitor and energy harvester. The PCB construction allows for very good contact, although I completely forgot to plan for integration of the energy harvesting module and wiring in the design, so it is effectively a PCB that contains 0 electronics. As an EE engineer the irony is not lost on me. :) 

This setup also includes some artwork on the walls of our moss container: each panel shows a different phase of a day cycle. Morning to noon, noon to afternoon, afternoon to dusk, dusk to the dead of night, and into dawn which then cycles back into morning. We thought it was fitting for the very organic, natural theme of our experiment. 

The moss is powering an LED in the middle of a wire flower which "grows" from the center of the tiny moss garden. It represents a small ecosystem with living microbals and lifecycle.

Next Time!

It is a very small amount of power, but as an early PoC with my limited knowledge of fuel cells I am thrilled to see what we will power with this next make! The design of the cell should make it easier to build more and tile them together to increase current or voltage output. With a few more cells, I hope to be able to regularly pulse a low power radio or change text on an e-ink display. A low hanging fruit that has yet to be picked is using a low leakage current capacitor, and not the first one that looked decent from my spare part bin :'3. Stay tuned~