Fuel cells powered by energy from the sea floor could indefinitely supply electricity to instruments used to monitor ocean currents and water temperatures, according to a report in the December 28 issue of Environmental Science & Technology, a peer-reviewed journal of the American Chemical Society, the world's largest scientific society.
Fuel cells convert chemical energy to electrical energy. The small, lightweight devices have been likened to cleaner, safer batteries that never run down. Fuel cell technology has been used by NASA for onboard power during space flight and is currently being investigated for use in automobiles and home power.
The researchers found that the electrical potential of sediment on the sea floor differs from the electrical potential of the surrounding salt water, according to Leonard Tender, a co-author of the study from the U.S. Naval Research Laboratory in Washington, D.C. Collecting power from that difference could supply energy for fuel cells for self-sustaining oceanographic equipment, he said.
Organic matter in sediment on the ocean floor ordinarily releases energy as it decays. In shallow waters (less than 1,000 meters, or 3,280 feet), that energy is concentrated just below the ocean floor. Energy for the fuel cell - like the voltage between opposite poles of a battery - comes from a reaction involving chemicals released from the buried sediment and the oxygen, according to Clare Reimers, a co-author of the paper from Oregon State University in Corvallis.
The battery-powered equipment now used for ocean monitoring must be periodically raised or replaced to replenish power, Tender said. This is a costly, time-consuming process, he added. In contrast, the fuel cell described in the research could be continually recharged by decaying marine organisms like plankton.
"These devices could significantly reduce the cost of ocean monitoring, which is important for naval and commercial marine operations and early warning of changes in marine ecosystems and resources," Reimers said.
In laboratory testing, the researchers were able to harvest approximately one microWatt of power per centimeter of fuel cell - the amount needed to power a small light-emitting diode, Tender said. The researchers are field-testing the fuel cells in the ocean and trying to get more power from them, he said.
"We calculate that optimized power supplies could run oceanographic instruments based on this phenomenon for routine long-term operations in the coastal ocean," Tender said.
The research cited above was funded by research grants from the Defense Advanced Research Projects Agency and the Office of Naval Research, both part of the US Department of Defense.
The online version of the research paper cited above was initially published November 16 on the journal's Web site. Journalists can arrange access to this site by sending an email to newsroom@acs.org or calling the contact person for this release.
Clare Reimers, Ph.D., is director of the Cooperative Institute for Marine Resources Studies at Oregon State University in Newport, OR, and a professor in the college of oceanic and atmospheric sciences at Oregon State University in Corvallis, OR.
Leonard Tender, Ph.D., is a researcher at the Center for Bio/Molecular Science and Engineering at the Naval Research Laboratory in Washington, DC.
Journal
Environmental Science & Technology