The U.S. Navy has enlisted some very tiny sailors to fuel their latest research vessel. Microorganisms are descending into the sea, enabling unmanned pods to gather data beneath the surface. Weeks later, (perhaps even years researchers say), the craft could emerge via power it had generated on board. No batteries required—just bacteria.
The Navy has dipped its toes into microbe power before, looking to power vehicles and instruments that monitor environmental conditions in the ocean. Within recent years, they’ve been testing microbial fuel cells that feed on decomposing marine detritus. The devices in those cases capture free electrons produced by the microbes’ metabolic activity. But what they dub the Zero Power Ballast Control (ZPBC) is different. It’s hydrogen powered.
Microbes supply the hydrogen to the vessel. The hydrogen provides the needed buoyancy for it to surface.
The probe has two chambers. The top compartment holds electronics, valves, wires and timers. Within the bottom chamber, a tube contains the microbes. As they produce hydrogen, the gas pressure within the tube rises. And eventually so does the probe. For zero-power operations, how fast the microbial community grows sets the data collection schedule. For more on-demand sinking and surfacing capability, researchers could set a 10-milliwatt timer to control the release of the hydrogen.
The Navy hopes the ZPBC might eventually outlast the Expendable Bathythermograph XBT, a common monitoring device invented in the 1960s. Once cast off, XBTs do not always return from their missions. If all goes well, the ZPBC will. So far during testing in waters off Thailand, the new vessel has lasted a week.
Tethered to a pier with mooring lines (right), the ZPBC rose and fell as it collected water temperature and pressure data. Ideally, the dive leashes won’t be necessary. The researchers say hooking up the ZPBC with geographic sensors would allow them to set the pod free in future tests.
Preliminary trials were successful in many ways. The device surfaced and submerged periodically as designed via hydrogen gas produced from the microbial inoculum and growth medium, proving the device generated gas in sufficient quantity to produce buoyancy.
Should the bacteria-powered probe prove seaworthy, the Navy hopes to assign ZPBC many more tasks, scientific and militaristic in scope. They include reading water temperatures and visibility, recording meteorological activity, surveillance, reconnaissance, and detecting submarines and undersea mines.
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Images: U.S. Navy Reserve/Tom Boyd