A research team powered a microprocessor continuously for six months. The seaweed was even delivered in the dark. A research team from the University of Cambridge has managed to run a computer for six months using blue-green algae as the energy source. They used the non-toxic and widespread species of algae Synechocystis sp. PCC 6803, is known as the blue-green algae.
Through natural photosynthesis, it gains energy from solar radiation. The researchers enclosed the blue-green algae in a small container made of aluminum and transparent plastic - with a height of 61mm and a footprint of 31x23mm, hardly larger than an AA battery. 'Our photosynthetic device doesn't discharge like a battery because it uses light continuously as an energy source,' explains Christopher Howe of the University of Cambridge's Department of Biochemistry. He is one of the lead authors of the study.
The sun's rays and the resulting photosynthesis produce a small current. In order to use this, the team led by the first author of the study, Paolo Bombelli, allowed the algae to grow on a network of thin aluminum wires. The mesh was attached to the side of an acrylic glass housing and formed the anode. It was surrounded by a nutrient solution in which the algae thrived. This structure could operate the microcomputer continuously for six months.
The Cell Also Generates Electricity In The Dark
Surprisingly, the power supply was not interrupted when it was dark. According to the research team, it could be because the algae process some of their food without light; however, the intensity decreases. The researchers themselves had not expected this. Bombelli was sure it would "stop after a couple of weeks, but it just kept going."
The experiment was carried out in cooperation with the British microprocessor developer Arm. He delivered a Cortex-M0+ test chip and board and set up a cloud interface for data collection. The specially manufactured chip only requires 0.3V to operate, and the minimum required power is specified as 0.3μW (PDF). The setup did not produce significantly more than the required 0.3V - the measurements show voltages between 0.4 and 1V.
The photosynthesis of the algae does not provide much energy - when illuminated, a maximum of 0.36μW per square centimeter of the illuminated area was measured (PDF), in the dark period still 0.2μWcm -2. With an illuminated area of 10.2 cm 2, the structure generated just under 2 to 3.5 μW - the Cortex-M0+ requires 3 μW per MHz in the most economical implementation.
The first experiments with the structure were purely laboratory tests. In order to find out whether a usable current is actually generated, light-dark cycles were simulated with white LED lighting. Natural conditions were simulated for the final test setup shown above. The small experiment was conducted in an outdoor home environment under natural light. This exposed the experiment to temperature fluctuations. Only when the scientists made the algae too uncomfortable - in one experiment they cooled the reactor down to a few degrees - did they stop working.
Publication of The Study
The research team submitted the findings and data from the first experiments and six months of continuous power generation to the journal Energy & Environmental Science for publication. According to Howe, this technology could secure the energy supply of the future: "The growing Internet of Things requires more and more energy, and we believe that this must come from systems that can generate energy instead of simply storing it like batteries."
Whether smartwatches or temperature sensors in power plants: the research team assumes that the number of devices will reach the trillions by 2035. In their opinion, lithium-ion batteries are unsuitable for their energy supply - their production would require three times more lithium than is produced annually worldwide. The environmental impact would add to that.
The Cambridge experiment may offer a solution. At least the team found other species of algae that could produce more electricity. If they have their way, the technology could be ready for the commercial market in five years. Due to its independence and compact structure, the photosynthetic power plant is interesting for devices that are stationed in remote locations for a long time, such as sensor nodes.