The U.S. Naval Research Labatory (NRL) has received a U.S. patent for solar microbial fuel cells (SMFC). These self-assembling, self-repairing, and self-contained microbial photoelectrochemical solar cells employ microorganisms to generate electric power by photosynthetic, explained the Center for Biomolecular Science and Engineering of NRL last week.
The SMFC reactants (glucose and oxygen) are internally regenerated by a group of photosynthetic microbes whose reactants, carbon dioxide (CO2) and water (H2O), are the products of the microbial fuel cell. The research institute claims that this interdependency results in long-term power generation from sunlight without replenishment of the microbial fuel cell reactants.
“Natural photosynthetic systems, such as trees and algae blooms, self-repair, a property that makes them highly durable,” said Dr. Lenny Tender, research chemist, Center for Bio/Molecular Science and Engineering. “Here, we incorporate photosynthetic organisms with the self-assembling and self-maintaining benthic microbial fuel cell (BMFC) to enable durable land-based photoelectrochemical solar cells.”
According to the NRL, a BMFC produces power by oxidizing organic matter (fuel) residing in sediment pore water with oxygen (oxidant) in overlying water, and is composed of an anode embedded in the marine sediment linked by an external electrical circuit to a cathode located in overlying water. The SMFC apparatus, however, does not require a constant flow of reactants to continually produce power, but instead recycles the organic matter sealed within the unit to regenerate the reactants.
“Microorganisms harvested from sea water in shallow coastal environments, in relatively low abundance, become enriched when the cell is sealed due to the accumulation of carbon dioxide and depletion of oxygen in the overlying water,” Tender said. “These organisms use sunlight to convert the electrode products to glucose and oxygen, which can be re-utilized in the electrode reactions eliminating the need for a constant flux of new glucose and oxygen.”
He also added that the SMFC combines energy storage with power supply. When the sun shines, photosynthesis will result in generation of fuel and oxidant, that can be used to produce power immediately or accumulated to be used later when there is no sun. This is ideally done without the need for capacitor or battery storage devices, Tender claims.