Image: A container holding blue-green algae that powered a computer
A computer has been powered for six months by blue-green algae contained in a tiny container. In the near future, similar photosynthetic energy producers might be utilized to power a variety of tiny gadgets without the usage of scarce and unsustainable materials like those used in batteries.
Christopher Howe and his colleagues at the University of Cambridge made a tiny enclosure out of aluminum and translucent acrylic approximately the size of an AA battery. They put a colony of Synechocystis sp. PCC 6803 cyanobacteria – sometimes known as “blue-green algae” – inside, which create oxygen through photosynthesis when exposed to sunlight.
During the shutdowns during Covid-19 pandemic in 2021, the device was put on a windowsill at the residence of team member Paolo Bombelli and stayed there from February to August. It ran an Arm microprocessor with a constant current between its anode and cathode.
The computer cycled through 45 minutes of calculating sums of consecutive numbers to mimic a computational burden, using 0.3 microwatts of electricity, and 15 minutes of standby, using 0.24 microwatts of power. The computer monitored the device’s current output and stored the data in the cloud for researchers to analyze.
Researchers aren’t sure how it works though.
According to Howe, there are two possibilities for the power source. The cyanobacteria either make electrons directly, resulting in a current, or they create circumstances in which the aluminum anode in the container corrodes, resulting in an electron-producing chemical process.
“It’s not entirely straightforward,” says Howe. “So putting one on your roof isn’t going to provide the power supply for your house at this stage. There’s quite a bit more to do on that front. But [it could work] in rural areas of low and middle-income countries, for example, in applications where a small amount of power might be very useful, such as environmental sensors or charging a mobile phone.”
During photosynthesis, the cyanobacteria produce their own food, and the device can even produce electricity during periods of darkness, which the researchers believe is feasible because the cyanobacteria continue to digest extra food.
The researchers have experimented with making a comparable enclosure out of empty plastic bottles and believe that successful devices might be mass-produced at a low cost within five years. They’ve also discovered algae species that produce stronger currents.
