Blue-green algae that sat on a windowsill in a kind of mini aquarium have supplied a computer with energy for six months. They did this through photosynthesis.
A computer ran for six months on the energy of blue-green algae that lived in a closed container on a windowsill. This surprising source of energy could in the future be able to power small appliances cheaply, without using the rare and unsustainable materials found in batteries.
Biochemist Christopher Howe of the British University of Cambridge and his colleagues built a small aluminum and clear plastic housing, the size of an AA battery. They placed a colony of cyanobacteria in it. This one ‘Synechocystis sp. PCC 6803′, better known as blue-green algae, produce oxygen when exposed to sunlight. They do this through photosynthesis.
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During the corona lockdown, team member Paolo Bombelli took the device home, where he placed it on the windowsill. It was there from February to August. At the time, it provided a continuous voltage across the anode and cathode, which powered a microprocessor.
computing power
To ensure that the computer actually consumed computing power, the researchers had it make sums with successive integers for 45 minutes at a time. That task required 0.3 microwatts of energy. After the sums, the computer was on standby for 15 minutes, which required 0.24 microwatts. Then he started counting again.
The computer itself registered the power output of the algae device. He saved this data in the cloudso that the researchers could see them.
In the six months that the experiment lasted, there were no power outages. Even after the experiment, the cyanobacteria continued to produce electricity for at least another six months.
Make your own electricity
Howe sees two possible explanations for how this energy source works. Firstly, the blue-green algae themselves can produce the electrons that form a current. They can also create conditions in which the aluminum anode in the tank is attacked by a chemical reaction that releases electrons. Because the anode still seemed intact after the experiment, the researchers suspect that the blue-green algae themselves produce most of the current.
The algae source could be scaled up for larger applications, Howe says, but further research is needed to determine how feasible that is. “It’s not quite straight forward,” he says. ‘If you put one on your roof, it won’t supply enough power for your house at this stage. A lot still needs to be done. But it could make sense in rural areas of low- and middle-income countries, for example in applications where a small amount of power can be very useful, such as when charging a mobile phone.’
Food surplus
The blue-green algae make their own food during photosynthesis. As a result, the device can even supply power during dark periods: according to the researchers, they make enough excess food to survive in the darkness for a while.
The researchers experimented with making a similar housing from empty plastic bottles. They think that these devices can be produced very cheaply. They have also found algae species that provide a higher current. They hope to bring their work to market within five years.