Understanding an MFC
A microbial fuel cell exploits the electrons produced by the bacteria metabolism placed in the anodic chamber to make energy. When building a MFC several parameters ust be taken into consideration:
- The anodic chamber must be under anerobic conditions to favor the transfer of electrons to the electrode.
- The two chambers need to be separated by a proton exchange membrane (Nafion) for the equilibration of the total charges.
- The material of the electrodes needs to be highly conductive (carbon cloths connected with a tinned copper wire).
- In the cathode it needs to be placed an acceptor with a high redox potential (i.e. Ferricyanide, air cathode).
- In the anode it is important to place an electroactive bacteria (i.e. Schewanella oneidensis) or supplement the media with chemical mediators (i.e. methylene blue, neutral red) that can cross the bacterial membrane to steal the electrons and bring them outside.
- Additionally, our Solar pMFC needs to be built with a material that allows the light to go through.
Our goal was to build a functional prototype to:
- Enhance current production. This was achieved by connecting 6 small MFCs in parallel.
- Avoid dispersion of energy due to the different potential of the units MFC connected in parallel. This is possible if the potential values of the single units are identical, which is difficult when working with bacteria. To overcome this problem in our design, the 6 cathode chambers are individually connected with the same anode, so that they share the same homogenous bacterial culture.
- Maximize the surface of contact between the bacteria and the anode, and simultaneously increase light exposure of the bacteria. Exploit the redox potential of oxygen with a cathode partially in contact with air (i.e. the cathodic chambers are open to the air, although filled with water).
- Have a sealed anodic chamber to maintain anaerobic conditions.