Algae batteries

Researchers at the University of Cambridge have been experimenting using algae to produce electricity directly: Algae-powered computing: scientists create reliable and renewable biological photovoltaic cell | University of Cambridge
I have had a go. Very preliminary results give 0.4V open circuit voltage, and 0.03 mA short circuit current. With electrode area around 10 cm*2
Using aluminium foil electrodes. One electrode is wrapped in two layers of toilet tissue paper. To separate the algae. I added salt, 20 grams per litre, which the algae should be able to tolerate. The salt is to improve the electrical conductivity of the electrolyte.
I have been growing algae for the last couple of weeks: spirulina and chlorella. Initially these were a blue-green colour in water but now is just green. I think the chlorella has out-competed the spirulina.
The tissue paper probably has large pore sizes, large enough for the algae to pass through. I have ordered some 2.5 micron filter papers. Hopefully it will keep most of the algae away from that electrode.
If anyone would like to have a go, I will bring some algae capsules to our next meeting.
Some more details:


Glad to hear you got it working!

I’ve always been a bit confused by batteries, as to how exactly they work, despite looking into it from time to time. Especially confusing if both electrodes are the same material - presumably in this case the asymmetry comes from the algae being in physical contact with one electrode but not the other.