A team of researchers from the University of Oxford, UK, managed to power a microprocessor for a whole year using nothing but algae, light, and water, according to a study published in the journal Energy & Environmental Science. The system is still, and the authors believe it has the potential to be a source of energy to power small devices.
The system uses a non-toxic algae called Synechocystis that can harvest energy from the sun through photosynthesis. The electrical current generated can interact with an aluminium electrode, which is then used to power a microprocessor.
As the system only uses common and cheap materials, it could be replicated thousands of times to power small devices as part of the Internet of Things. The Internet of Things — IoT— is a growing network of electronic devices with sensors, processing ability, software, and other technologies to connect with other devices over the Internet — this includes, for example, mobile phones, smartwatches, and even temperature sensors in power stations. There are already millions of these devices, and the number is expected to grow to one trillion by 2035, and many of them will need a portable energy source. The authors suggest this approach could be instrumental in off-grid or remote locations, where even small amounts of power could be very beneficial.
“The growing Internet of Things needs an increasing amount of 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 in the University of Cambridge’s Department of Biochemistry, joint senior author of the paper. “Our photosynthetic device doesn’t run down the way a battery does because it’s continually using light as the energy source.”
In the study, the device powered an Arm Cortex M0+, a microprocessor very common in the Internet of Things. It worked in a domestic environment and semi-outdoor conditions using natural light and was subjected to temperature variations. It’s about the size of an AA battery and was built using common, cheap, and largely recyclable materials.
“We were impressed by how consistently the system worked over a long period of time – we thought it might stop after a few weeks, but it just kept going,” said Dr. Paolo Bombelli in the University of Cambridge’s Department of Biochemistry, and first author of the paper.
Crucially, the algae don’t need feeding because they can photosynthesise their own food. The device can even continue to operate in the dark, even though algae will stop photosynthesis. The researchers believe that’s because the algae can continue to process its food when there’s no light and continues to generate an electrical current.
The authors believe this could be a serious alternative to lithium batteries. Powering trillions of devices with lithium batteries will be virtually impossible: manufacturers would need three times more lithium than what is currently produced worldwide. In addition, photovoltaic devices use hazardous materials with adverse environmental effects, which means they’re not an option either.
Bombelli P, Savanth A, Scarampi A, Rowden S, Green D, Erbe A, Årstøl E, Jevremovic I, Hohmann-Marriott M, Trasatti S, Ozer E and Howe C (2022) Powering a microprocessor by photosynthesis. Energy and Environmental Science, https://doi.org/10.1039/D2EE00233G