Renewable and reliable biological photocell

This system, which contains blue and green algae, runs a microprocessor continuously for a year using nothing but ambient light and water. Credit: Paolo Bombelli

Algae-powered computing

Scientists have used a pervasive form of blue-green algae to run a microprocessor continuously for a year — and counting — using nothing but ambient light and water. Their system has potential as a reliable and renewable way to power small electronic devices.

The system, which is comparable in size to an AA battery, contains a type of non-toxic algae called synchronous It naturally harvests energy from the sun through photosynthesis. Then the small electrical current it generates interacts with an aluminum electrode and is used to power a microprocessor.

“Our photosynthetic apparatus does not work the way a battery does because it is constantly using light as an energy source.” – Chris Howe

The system is made of ordinary, inexpensive and mostly recyclable materials. This means that it can easily be repeated hundreds of thousands of times to power a large number of small devices as part of the Internet of Things. The researchers say it is likely to be most useful in off-grid situations or in remote locations, where small amounts of electrical power can be most beneficial.

“The growing Internet of Things needs an increasing amount of energy, and we believe this should come from systems that can generate energy, rather than store it like batteries,” said Professor Christopher Howe from the University of Cambridge’s Department of Biochemistry. Co-lead author of the paper.

He added: “Our photosynthetic apparatus does not work the way a battery does because it is constantly using light as an energy source.”

In the experiment, the device was used to power the Arm Cortex M0+, a microprocessor widely used in IoT devices. Operating in a home environment and semi-outdoor conditions under natural light and associated temperature fluctuations, after six months of continuous power production, the results have been submitted for publication.

The study was published in the journal May 12, 2022 Energy and Environmental Sciences.

Dr Paolo Bombelli from the University of Cambridge’s Department of Biochemistry, first author of the paper.

Algae do not need to feed, because they create their own food as they carry out photosynthesis. And although the process of photosynthesis requires light, the device can continue to produce energy during periods of darkness. The researchers believe this is because the algae process some of their food when there is no light, and this continues to generate an electric current.

The Internet of Things is a vast and growing network of electronic devices – each using very little power – that collect and share real-time data over the Internet. Using low-cost computer chips and wireless networks, many billions of devices are part of this network – from smart watches to temperature sensors at power plants. This number is expected to rise to one trillion devices by 2035, requiring a large number of portable power sources.

The researchers say that powering trillions of IoT devices with lithium-ion batteries would be impractical: they would need three times more lithium than is produced worldwide annually. Conventional PV devices are manufactured using hazardous materials that have adverse environmental impacts.

The work was a collaboration between Cambridge University and Arm, a leading microprocessor design firm. Arm Research developed the ultra-efficient Arm Cortex M0+ test chip, manufactured the board, and prepared the data-collecting cloud interface shown in the experiments.

Reference: “Operation of a microprocessor by photosynthesis” by P. Bombelli, A. Savanth, A. Scarampi, S. J. L. Rowden, D. H. Green, A. Erbe, E. Årstøl, I. Jevremovic, M. F. Hohmann-Marriott, S. P. Trasatti, E. Ozer and CJ Howe, 12 May 2022, Available here. Energy and Environmental Sciences.
DOI: 10.1039 / D2EE00233G

The research was funded by the National Center for Innovation in Biofilms.

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