Professor Pengchen (Patrick) Fu is using cyanobacteria to produce ethanol from sunlight, carbon dioxide, and water. I got to see this first-hand at Wired NextFest. This is exceedingly cool since ethanol, a useful fuel, burns cleanly to produce energy, carbon dioxide, and water. See the pattern? It’s a sustainable cycle, essentially storing solar energy in a fuel that we already know and love. There is very little waste in this process, and it’s quite harmless, in the form of oxygen and some dead bacteria at the end of their natural life cycles. This is already cool enough that I think I need to sit down for a while and take it all in, but there is more! In case the photo didn’t make things amply evident, let me state clearly: Pengchen (Patrick) Fu has come up with a possible solution for renewable energy using large, glowing cylinders full of bubbling green liquid. These things look like they came straight off the set of a science fiction movie. You know, the good kind, with lots of explosions.
Some more details: The tubes shown in the pic each yield about 5 grams of ethanol per day. Fu expects improvements to this yield after more research into the process. He also talked about setting up kiloliter-sized tanks of this stuff for larger output.
5 grams of ethanol contains about 134 kilojoules of energy. If we had solar panels instead, assuming about 8 kWh/m^2/day, and 40% efficient solar panels, we would need about 116 square centimeters of solar panel to get the same yield (an 11 cm x 11 cm patch would do). I would estimate that Fu’s process is therefore less than one order of magnitude less efficient than the best solar cells at the moment. That’s not shabby, considering that the energy is stored in a fuel instead of a (costly) battery. Deeper vats of the stuff would mean more sunlight gets absorbed by the cyanobacteria, so the kiloliter tanks would probably have much better efficiency.