Researchers have taken a major step forward in the design of cleaner energy for electricity-dearth regions with the development of an algae-powered fuel cell that is less expensive to produce and five times more efficient than existing similar technology.
Key to the design of the biophotovoltaic (BPV) device—also known as a biological solar cell—developed by researchers at the University of Cambridge is that it separates charging and power delivery. This is something that’s different from the design of other such devices--which use the photosynthetic properties of microorganisms like algae to convert light an electric current for energy generation.
“Charging and power delivery often have conflicting requirements,” explained Kadi Liis Saar, a researcher on the project in the university’s Department of Chemistry. Researchers from the departments of Biochemistry and Physics also collaborated on the work. “For example, the charging unit needs to be exposed to sunlight to allow efficient charging, whereas the power-delivery part does not require exposure to light but should be effective at converting the electrons to current with minimal losses.”
BPVs generally work like this: during photosynthesis, algae produce electrons, some of which are exported outside the cell where they can provide electric current to power devices. In BPVs with a single compartment for both charging and power delivery, electrons generate current as soon as they have been secreted.
The design from the Cambridge researchers has a number of features that allow for unprecedented efficiency in a BPV system, researchers said.
First, as mentioned before, is the inclusion of two chambers, allowing for the two core processes involved in the operation of a solar cell—generation of electrons and their conversion to power—to be separated. Using this type of design, researchers could optimize the performance of both processes simultaneously, they said.
For the power-delivery unit, the team used another feature—miniaturization—to optimize the performance, researchers said. “At miniature scales, fluids behave very differently, enabling us to design cells that are more efficient, with lower internal resistance and decreased electrical losses,” explained researcher and Professor Tuomas Knowles from the Department of Chemistry and Cambridge’s Cavendish Laboratory.
A new design of algae-powered fuel cells that is five times more efficient than existing plant and algal models, as well as being potentially more cost-effective to produce and practical to use, has been developed by researchers at the University of Cambridge. (Source: University of Cambridge)
Another advantage to the two-chamber system is that it can store a charge rather than have to use it immediately, allowing for energy collected during daylight hours to be used at night, he added.
Finally, the system includes another unique element to boost performance—genetically modified algae, which minimizes the amount of electric charge dissipated during photosynthesis, researchers said.
Taken as a whole, the design resulted in a BPV with a power density of 0.5 Watts per square meters—five times that a previous design, researchers said.
This is still only about a tenth of the power density that exists in conventional solar fuel cells, but shows promise for the future of using BPVs for more cost-effective, cleaner energy production, said Christopher Howe, a professor with the Department of Biochemistry and researcher on the project.
"While conventional silicon-based solar cells are more efficient than algae-powered cells in the fraction of the sun’s energy they turn to electrical energy, there are attractive possibilities with other types of materials," he said. “In particular, because algae grow and divide naturally, systems based on them may require less energy investment and can be produced in a decentralized fashion."
The Cambridge team published a paper on its design in the journal Nature Energy.
Researchers aren’t eyeing their BPVs to be as widely used or efficient as typical solar cells are today, they said. However, areas where there is a lot of sunlight but a dearth of electricity—such as rural Africa or India—could benefit from their installation.
Moreover, because of the use of organic materials, local communities could benefit from producing the fuel cells rather than having them manufactured in large, dedicated facilities far away, researchers said.
Elizabeth Montalbano is a freelance writer who has written about technology and culture for more than 15 years.