Top Tech: Zero-Power Bathythermograph Sensors

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The bacterial fuel source was attached to the two ZPBC devices, which were then deployed in situ off a military pier in Sattahip, Thailand, and held in place by mooring lines for seven days. (Photo: U.S. Navy Reserve/Tom Boyd)

The bacterial fuel source was attached to the two ZPBC devices, which were then deployed in situ off a military pier in Sattahip, Thailand, and held in place by mooring lines for seven days. (Photo: U.S. Navy Reserve/Tom Boyd)

Technology: Zero-Power Bathythermograph Sensors

Agency: Naval Research Laboratory

The Naval Research Laboratory created the Zero Power Ballast Control (ZPBC), a technology that relies on microbial energy for harvesting developments to enable unsupervised underwater sensing with subsequent surfacing and reporting capabilities.


It’s a self-sustaining ocean sensor, so to speak.  These zero-power bathythermograph sensors have the ultimate goal of producing simple, small, power- efficient data harvesting nodes with variable buoyancy.  The device will be able to monitor ocean temperatures with a stay time ranging from weeks to months and eventually years, providing a longer term than other mechanisms such as the Expendable Bathythermograph (XBT).


It’s ocean monitoring at its finest.  And convenient, too.  I mean really, it’s a pain to replace the batteries in a home smoke detector.  Could you imagine the inconvenience of replacing the batteries in a machine on the ocean floor?  At least you wouldn’t have to hear that constant, annoying beeping.

This is why the self-sustaining sensor is such a good idea.  It does the job it is designed to do without being needy, and who doesn’t want that in a unsupervised underwater sensor, right?

In the future, the ZPBC will provide input for robust modeling of ocean temperatures and other parameters. The ZPBC could also be used to provide in-water optical data.  This could enhance models for underwater visibilities, laser penetration depths, diver and target vulnerability assessments, electro-optical system performance predictions, and refining numerical models.


It allows us to monitor the oft-unpredictable oceans in an autonomous way.  This device can obtain data and recharge itself with little to no interference.

Here’s how it works:

Using a low power timer – or only the rate of microbial gas generation that requires zero power input – the device can be alternatively configured to surface “on-demand.” Sensors (for example acoustic, magnetic) are attached to the ZPBC.  These could be used to detect and classify, monitor the rise to the surface, report using RF or other communication, then re-submerge and continue monitoring operations.  It looks like it is effective, too.

“Preliminary trials were successful in many ways,” said Dr. Justin Biffinger, a leading scientist at the Naval Research Lab. “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.”


Well, I think we covered the fact that “self sustaining” is ideal for many circumstances, and this is no exception.  Some military utility and scientific applications include use in intelligence, surveillance and reconnaissance, anti-submarine warfare, mine warfare, naval special warfare, and meteorology and oceanography.

Continued prototyping could include geo-referencing capabilities so that the device could be untethered in future tests.

(Photo provided by the Naval Research Lab/Released)

(Photo provided by the Naval Research Lab/Released)

And that’s just the military aspect of it.  There are applications for civilian ships as well.  Knowing the best course to steer the ship is no small task, nor one to be taken lightly.  This could provide an ear to the ocean floor on the movements of our biggest bodies of water (and small ones, too!).


I know how this sounds, but this really is a great job for a machine.  Specifically this machine.  Humans need to monitor the ocean, whether that’s for military purposes, or weather-related, or threat surveillance and control.  This device is a scout for the seas, and it can take care of itself.  How is this not a good thing?  And let’s face it; it’s not like the ocean is going anywhere.  Our seas are still alive and teeming, and therefore naval welfare is still a necessary part of military – and even civilian – life around the globe.  In an environment not meant for us to live, knowing what you’re up against can save a life.

We might not have Poseidon’s trident, but we have NRL’s sensor.  And if you ask me, that’s worth wielding.

Want to learn more?  Click here for more information on this technology!

Are you interested more federal inventions? The Naval Research Laboratory has a broad portfolio of technologies that are available for commercialization. Visit their official website to learn more!


Jessica L. Tozer is a blogger for DoDLive and Armed With Science.  She is an Army veteran and an avid science fiction fan, both of which contribute to her enthusiasm for technology in the military.

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