Algae Poised to Power Future Fuel Cells

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Image credit: World Energy Foundation

Researchers at the University of Cambridge have developed a new algae-powered fuel cell that is five times more efficient than existing plant and algal models. Both cost-effective and practical to use, scientists expect the fuel cell to bring algal-based systems one step closer to practical implementation.

In recent years, biophotovoltaics (BPVs) have emerged as a sustainable and low-cost approach to harvesting solar energy. They harness the photosynthetic properties of microorganisms such as algae to convert light into electric current that can be used to produce electricity. Traditional BPVs have been single-chamber systems in which light is harvested, electrons produced and energy transferred to the electrical circuit.

In the journal Nature Energy, researchers from the University of Cambridge’s departments of biochemistry, chemistry and physics describe a new two-chamber BPV system where the two core processes involved in the operation of a solar cell — charging and power delivery — are separated.

According to researcher Kadi Liis Saar, the two processes have conflicting requirements. With a two-chamber system, researchers were able to design two unique units that optimize the performance of the processes.

“Separating out charging and power delivery meant we were able to enhance the performance of the power delivery unit through miniaturization,” said Tuomas Knowles, professor of chemistry and a researcher in the Cavendish Laboratory. “At miniature scales, fluids behave very differently, enabling us to design cells that are more efficient, with lower internal resistance and decreased electrical losses.”

Researchers tested the new system with algae genetically modified to carry mutations that enable the cells to minimize the amount of electric charge squandered during photosynthesis. The combination resulted in the creation of a biophotovoltaic cell with a power density five times that of previous designs (0.5 W/m2). Though they possess only a 10th of the power density of conventional solar fuel cells, BPVs boast several attractive features. For example, because of algae’s ability to grow and divide naturally, algae-based BPVs may require less energy investment and could be produced in a decentralized manner. The two-chamber system also has the benefit of allowing the charge to be stored rather than having to be used immediately.

Scientists envision algae BPVs being of particular use in areas such as rural Africa, where there is an abundance of sunlight, but no formal electric grid system. What’s more, BPVs do not necessarily require dedicated facilities for their production — they can be built directly in local communities, the researchers said.

“This is a big step forward in the research for alternative, greener fuels,” said Dr. Paolo Bombelli of the University of Cambridge Department of Chemistry. “We believe these developments will bring algal-based systems closer to practical implementation.”

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