The researchers used a widespread species of blue-green algae to power a microprocessor continuously for a year – and longer – using only ambient light and water. Their system has the potential to be a reliable and renewable way to power small appliances.
The system, comparable in size to an AA battery, contains a type of non-toxic algae called Synechocyst which naturally harvests energy from the sun through photosynthesis. The small electric current thus generated then interacts with an aluminum electrode and is used to power a microprocessor.
The system is made of common, inexpensive and widely recyclable materials. This means it could 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 likely to be most useful in off-grid situations or in remote locations, where small amounts of power can be very beneficial.
“The growth of the Internet of Things requires an increasing amount of energy, and we believe this will need to come from systems that can generate energy, rather than just store it like batteries,” said Professor Christopher Howe from the University of Cambridge’s Department of Biochemistry. main co-author of the article.
He added: “Our photosynthetic apparatus does not discharge like a battery, because it continuously uses light as its energy source.”
In the experiment, the device was used to power an Arm Cortex M0+, which is a microprocessor widely used in Internet of Things devices. It was operated in a domestic environment and in semi-outdoor conditions under natural light and associated temperature fluctuations, and after six months of continuous power generation, the results were submitted for publication.
The study is published today in the journal Energy and Environmental Sciences.
“We were impressed with how consistently the system worked over a long period – we thought it might stop after a few weeks, but it kept going,” said Dr Paolo Bombelli from the biochemistry department of the University. University of Cambridge, first author of the paper.
The algae does not need to be fed, as it creates its own food during photosynthesis. And despite the fact that photosynthesis requires light, the device can even continue to generate electricity during periods of darkness. The researchers believe this is because the algae processes some of its food when there is no light, which continues to generate an electric current.
The Internet of Things is a large and growing network of electronic devices, each using only a small amount of power, that collects and shares data in real time via the Internet. Using computer chips and low-cost 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 reach one trillion devices by 2035, requiring a large number of portable power sources.
The researchers say that powering trillions of Internet of Things devices using lithium-ion batteries would be impractical: it would require three times as much lithium as is produced globally each year. And traditional photovoltaic devices are made from hazardous materials that have adverse effects on the environment.
The work was a collaboration between the University of Cambridge and Arm, a leading company in microprocessor design. Arm Research developed the ultra-efficient Arm Cortex M0+ test chip, built the board, and implemented the data collection cloud interface shown in the experiments.
Portable generator powers small security devices
P. Bombelli et al, Powering a microprocessor by photosynthesis, Energy and Environmental Sciences (2022). DOI: 10.1039/D2EE00233G
Provided by the University of Cambridge
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