No sun, no problem: Bacteria-powered solar cells produce energy on cloudy days

Alex Crees
By Alex Crees July 11th, 2018
For business

Good news for people who live under cloudy skies: as it turns out, solar energy may not necessarily require sunny days after all.

Researchers from the University of British Columbia say they have found a cheap, sustainable way to build a solar cell using bacteria that converts light to energy, even on overcast days.

A solar panel, like you might see on a neighbor’s roof or along a highway, is made up of an array of solar cells – essentially the “building blocks” of the panel.  Solar cells convert the sun’s beams into electrical current.

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There are multiple types of solar cells, but most solar panels today use synthetic solar cells made of crystalline silicon, also known as “solar grade silicon.”  Producing these cells requires complex manufacturing and expensive materials.

Building a solar cell out of living organisms

The UBC researchers set aside synthetic solar cells in favor of biogenic cells, or cells made up of living organisms.  Biogenic solar cells essentially attempt to mimic photosynthesis, the natural way to harvest energy from sunlight.

Previous efforts to build biogenic cells have centered around extracting the natural dye bacteria use for photosynthesis.  However, this is a costly process involving toxic solvents, which can damage the photosynthetic chemicals.

In this study, the researchers instead chose to leave the dye in the bacteria.  They genetically engineered E. coli to produce large amounts of lycopene, a natural dye that gives tomatoes their red color and an important molecule in photosynthesis.  They then coated the bacteria with a mineral that could act as a semiconductor to produce electricity and applied the mixture to a glass surface.

With this mixture, the researchers generated a current density of 0.686 milliamps per square centimeter, nearly double that of the 0.362 previously achieved by other biogenic cell efforts.

“We recorded the highest current density for a biogenic solar cell,” said Vikramaditya Yadav, a professor in UBC’s department of chemical and biological engineering and lead researcher of the project. “These hybrid materials that we are developing can be manufactured economically and sustainably, and, with sufficient optimization, could perform at comparable efficiencies as conventional solar cells.”

Generating electricity from the sun on cloudy days

Notably, while the biogenic cells are not as efficient as synthetic cells, they perform just as well in low light as they do in direct sunlight – meaning they can produce electricity on cloudy days.

The process to build these cells may seem complex, but according to the researchers, it is both cleaner and cheaper than what it takes to produce synthetic cells.

The researchers say their discovery could lead to wider adoption of solar power in regions that are traditionally overcast, like British Columbia and northern Europe.

“Our solution…is a significant step toward making solar energy more economical,” said Yadav.

The researchers say a crucial next step would be to find a way to protect the bacteria, which dies during the semi-conductor process.  That way, the bacteria could continuously produce the dye, thus increasing the longevity of the cell.

The study was published in the journal Small.

Alex Crees is a writer covering issues related to energy, the environment and politics.  Her work has appeared in Fox News and Prevention. Alex earned a bachelor’s degree in journalism from New York University.