Microbial Battery Eyed as Viable Storage for Renewables

Researchers for some time have been developing bio-batteries -- or batteries based on organic materials, such as bacteria -- as possible replacements for less environmentally friendly lithium-ion and other types of storage devices. They also have been working on better and more efficient ways to store renewable energy in a variety of battery systems, including liquid and solid-state options that range from small-scale to grid-capable.

These two areas of research have now come together in work by scientists at Wageningen University and Westus in The Netherlands to develop a microbial-based battery they said could one day help store energy from local renewable sources like solar power safely and at a lower cost than current options.

A team that includes PhD student Sam Molenaar -- lead author on a paper published in the American Chemical Society’s journal Environmental Science & Technology Letters -- has developed, for what researchers claim is the first time, two separate microbial energy systems. One uses bacteria to form acetate from electricity, and one converts what’s produced back into electricity.

Researchers in The Netherlands have developed a two-part microbial-based bioelectrochemical system that could provide reliable, safe storage for renewable energy.
(Source: Thinkstock)

“Bioelectrochemical systems hold potential for both conversion of electricity into chemicals through microbial electrosynthesis (MES) and the provision of electrical power by oxidation of organics using microbial fuel cells (MFCs),” Molenaar and his colleagues wrote in an abstract of the paper. Their work provides a proof of concept for a microbial rechargeable battery that allows for storage of electricity by combining MES and a MFC in one system, showing a new potential application area for bioelectrochemical systems as a future local energy storage device, they said.

The team used hexacyanoferrate as counter redox couple, with acetate being the main energy carrier, they said. An energy density of about 0.1 kilowatt hour per cubic meter -- normalized to anode electrolyte volume -- was achieved at a full cycle energy efficiency of 30% to 40%, with a nominal power output during discharge of 190 watts per cubic meter, normalized to anode volume.

Researchers successfully charged the battery over a 16-hour period and discharged it over the next eight hours to mimic the day-night pattern that’s typical in solar-energy production. They then repeated this cycle 15 times in as many days, which demonstrated that the process was able to be repeated.

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As they continue to optimize the battery, researchers said that the battery’s energy density could be competitive with conventional technologies to store and reuse renewable energy sources.

Indeed, storage for renewable energy is a growing need and opportunity, with various battery chemistries likely to come into play as the market evolves and matures. Research firm Lux Research is predicting the market for energy storage for solar-energy systems alone will grow to $8 billion by 2026.

Elizabeth Montalbano is a freelance writer who has written about technology and culture for more than 15 years. She has lived and worked as a professional journalist in Phoenix, San Francisco, and New York City. In her free time she enjoys surfing, traveling, music, yoga, and cooking. She currently resides in a village on the southwest coast of Portugal.