Ocean Robots That 'Feed' on Whale Food

Scientists are figuring out how to use one of the tiniest creatures on the planet to generate a virtually endless supply of electricity that can power remote sensors scattered across the world's far-flung oceans

They call it "plankton power."

Most oceanographic sensors, used to detect everything from temperature changes to the sounds of remote earthquakes, are powered by batteries. But batteries exhaust their internal fuel and run down, and replacing them thousands of feet below the ocean surface, in very remote areas of the planet, is not only expensive. It's impractical, and in some cases, nearly impossible.

So thinking there has to be a better way, oceanographer Clare E. Reimers of Oregon State University began working several years ago with other scientists at the Naval Research Laboratory in Washington, D.C., to see if they could come up with a better idea.

If they could figure out how to provide a self-sustaining source of electricity for oceanographic vehicles, they could develop machines that could swim like a fish, prowling across the ocean for months, if not years. These mobile robots could collect data over wide areas that could add immeasurably to our understanding of such critical issues as changing global weather patterns.

But you can't do that with batteries. So to succeed, they would need to rely on a type of fuel that is abundant throughout the oceans. What might that be? Well, what do fish eat? Other fish. What do small organisms eat? Smaller organisms.

"Organic matter is the basic fuel of the ocean," says Reimers, who directs an interdisciplinary lab at OSU's Hatfield Marine Science Center in Newport, Ore.

A Digesting Fuel Cell

The researchers have already demonstrated that it is possible to use decaying organic matter to power fuel cells. Prototypes developed by several institutions that are participating in the project have been tested in Oregon's Yaquina Bay and in a deep-sea canyon off Monterey, Calif.

These fuel cells were pretty basic, consisting of anodes imbedded in marine sediments on the sea floor and connected to cathodes in the overlying seawater. The decaying microorganisms in the mud caused electrons to flow, thus demonstrating that fuel cells can indeed work on the ocean floor by using the relatively limitless supply of decaying organic life as fuel.

"So we've demonstrated that the idea is feasible," Reimers says. "The efficiency is good enough to make it worthwhile."

The researchers still need to work out problems associated with corrosion and all the other troublesome issues found in a marine environment, but at least they've shown they can produce enough electricity from the muck at the bottom of the sea to run a fairly basic electronic device.

But that's not good enough.

Reimers and her colleagues weren't content with harnessing power from organisms that have already died. They wanted energy-rich fuel that would be available just about anywhere in the oceans, and it had to be something that would lend itself to capture by a moving, autonomous robot.

The answer, she figured, lay in plankton, those tiny organisms that drift through the water, including small crustaceans, algae, and protozoans. If that's good enough to fuel the powerful bodies of some whales, it ought to work for small electronic devices.

Reimers did the calculations and came up with an estimate of how much plankton it would take to match the energy output of a small battery.

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