Auto-Accretion Using Renewable Energy: Structural
Applications in Ocean Environments
INTRODUCTION
Solid matter is deposited upon submerged wires subjected to small electrical currents. An increased electrical current expedites the electrodeposition of matter. However, economical application of this accretion process depends upon the power source. Biological fuel cells, using ocean sediments as substrate, are a source of inexpensive, renewable power. A process using biological cells to produce current resulting in matter accretion could be applied in any ocean system, including ports, lagoons, and coastlines. Submerged structures, walls, seawater barriers, and coastal properties could be strengthened and repaired in situ using this auto-accretion technology.
Research combined these two independent technologies. Naturally occurring aqueous microbes were used to produce electricity that promoted matter accretion in a seawater medium. Figure 1 illustrates the system where electrons move from a carbon fiber anode suspended in a microorganism and nutrient rich sediment to a cathode suspended in a mixture of salt and fresh water by means of a wire.
Figure 1. Schematic of the Coupled Process.
The electrons move from the individual microbial cells to the carbon fiber electrode. The electrons from the cathode move through the wire mesh, resulting in a potential difference, in turn the free ions (including calcium, magnesium, carbonate, and hydroxide) combine to form solids and adhere to the electrically charged wire mesh. The electrons then recycle themselves to the anode and microorganism rich environment.
Laboratory experiments showed promising results using sea water sediment
from
The next step involved optimizing biological fuel cell operation, understanding the deposited solid materials properties, and manipulating the wire mesh geometry to conform to different specifications such as walls, pylons, and other oceanic structures. Experiments conducted at the Boston Museum of Science waterfront property showed an occurrence of minimal accretion. By the manipulation of the key variables, mainly surface area of carbon fiber electrode, sediment depth, and water level, electrical current promoted the accretion of matter. Figure 2 shows the current production and resulting matter accretion over a 30-day period.
Figure 2. Rate of Accretion and Current Production over Time from Field Test.
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Boston Museum of Science (Field Test Site)
Department of Chemical Engineering
Department of Biology and Biotechnology
Department of Chemical Engineering
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