A Reliable and Renewable Biological Photovoltaic Cell

This system, which contains blue-green algae, continuously powered a microprocessor using only ambient light and water for a year. Credit: Paolo Bombelli

Algae powered computers

Scientists used a widespread strain of blue-green algae to continuously power a microprocessor — and counting — for a year with nothing but ambient light and water. Their system has the potential as a reliable and renewable way to power small electronic devices.

The system, similar in size to an AA battery, contains a type of non-toxic algae called Synechocystis that naturally harvests energy from the sun through photosynthesis. The small electrical current generated by this interacts with an aluminum electrode and is used to power a microprocessor.

“Our photosynthetic device doesn’t drain like a battery because it constantly uses light as a source of energy.” † Chris Howe

The system is made of ordinary, cheap and largely recyclable materials. This means it can easily be replicated hundreds of thousands of times to power large numbers of small devices as part of the Internet of Things. The researchers say it’s probably most useful in off-grid situations or remote locations, where small amounts of electrical power can be very beneficial.

“The growing Internet of Things needs more and more power, and we think this will have to come from systems that can generate energy, rather than simply store it like batteries,” said Professor Christopher Howe of the University’s Department of Biochemistry. of Cambridge, co-senior author of the article.

He added: “Our photosynthetic device doesn’t drain like a battery because it constantly uses light as a source of energy.”

In the experiment, the device was used to power an Arm Cortex M0+, a microprocessor commonly used in Internet of Things devices. It operated in domestic and semi-outdoor conditions under natural light and associated temperature variations, and after six months of continuous power production, the results were submitted for publication.

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

“We were impressed with how consistently the system worked over a long period of time — we thought it would stop after a few weeks, but it just kept going,” says Dr. Paolo Bombelli of the University of Cambridge’s Department of Biochemistry, lead author of the paper.

The algae do not require any nutrition as they create their own food as they photosynthesize. And despite the fact that photosynthesis requires light, the device can continue to produce power even in dark periods. The researchers think 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 consuming only a small amount of power — that collect and share real-time data across the Internet. Using cheap computer chips and wireless networks, many billions of devices are part of this network – from smartwatches to temperature sensors in power plants. This figure is expected to grow to a trillion devices by 2035, requiring a large number of portable energy sources.

The researchers say it would be impractical to power trillions of Internet of Things devices with lithium-ion batteries: it would require three times more lithium than is produced annually around the world. And traditional photovoltaic devices are made using hazardous materials that have adverse effects on the environment.

The work was a collaboration between the University of Cambridge and Arm, a company that leads the design of microprocessors. Arm Research developed the ultra-efficient Arm Cortex M0+ test chip, built the board, and set up the cloud data collection interface presented in the experiments.

Reference: “A microprocessor powered by photosynthesis” by P. Bombelli, A. Savanth, A. Scarampi, SJL Rowden, DH Green, A. Erbe, E. Årstøl, I. Jevremovic, MF Hohmann-Marriott, SP Trasatti, E. Ozer and CJ Howe, May 12, 2022, Energy and Environmental Sciences
DOI: 10.1039/D2EE00233G

The research was funded by the National Biofilms Innovation Center.

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