Reliable and renewable biological photovoltaic cell

This system, containing blue-green algae, continuously powered the microprocessor for a year, using nothing but ambient light and water. Credit: Paola Bambeli

Calculations based on algae

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

The system, comparable in size to an AA battery, contains a type of non-toxic algae called Synechocyst which extracts energy naturally from the sun through photosynthesis. The tiny electric current that it generates interacts with the aluminum electrode and is used to power the microprocessor.

“Our photosynthetic device does not discharge like a battery because it constantly uses light as an energy source.” – Chris Howe

The system is made of ordinary, inexpensive and mostly recyclable materials. This means that it could easily be repeated hundreds of thousands of times to power a large number of small devices within the Internet of Things. Researchers say it will probably be most useful in off-line situations or remote locations where a small amount of electricity can be very useful.

“The growing Internet of Things is demanding more and more energy, and we believe it should come from systems that can generate energy, not just store it as batteries,” said Professor Christopher Howe of Cambridge University’s Department of Biochemistry. joint senior author of the work.

He added: “Our photosynthetic device does not discharge like a battery because it constantly uses light as a source of energy.”

In the experiment, the device was used to power the Arm Cortex M0 +, which is a microprocessor widely used in IoT devices. He worked in a domestic and fully outdoor environment under natural light and related temperature fluctuations, and after six months of continuous power generation the results were presented for publication.

The study was published May 12, 2022 in the Journal Energy and Environmental Science.

“We were impressed with how consistently the system worked over a long period of time – we thought it might stop in a few weeks, but it just kept working,” said Dr. Paola Bombeli of the Department of Biochemistry at Cambridge University, the first author of the paper.

Algae do not need feeding because in the process of photosynthesis it creates food for itself. And although photosynthesis requires light, the device can even continue to generate energy during periods of darkness. Researchers believe this is because algae processes part of their food when there is no light and it continues to generate electric current.

The Internet of Things is a vast and growing network of electronic devices, each of which uses only a small amount of energy to 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 in power plants. This figure is expected to grow to one trillion devices by 2035, which requires a large number of portable power sources.

Researchers say providing trillions of Internet of Things devices with lithium-ion batteries would be impractical: it would require three times more lithium than is produced annually worldwide. And traditional photovoltaic devices are made using hazardous materials that have an adverse effect on the environment.

The work was created as a result of a collaboration between the University of Cambridge and Arm, a company that develops microprocessors. Arm Research has developed a high-performance Arm Cortex M0 + test chip, built a board, and set up a cloud-based interface to collect the data presented in the experiments.

Reference: “Bombing of the microprocessor by photosynthesis” by P. Bombelli, A. Savant, A. Scarampi, S. L. Rowden, D. G. Green, A. Erbe, E. Artel, I. Eremovich, M. F. Homann- Marriott, S. P. Thrasati, E. Ozer and C. J. Howe, May 12, 2022, Energy and Environmental Science.
DOI: 10.1039 / D2EE00233G

The study was funded by the National Biofilm Innovation Center.

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