Warm and Cold Patches Power Underwater Probe

THE GIST:

• New underwater vehicles draw power from temperature differences in the oceans.
• The technology has potential to revolutionize monitoring of the world's oceans.
• A prototype probe worked flawlessly for three months.

Engineers have come up with a unique solution to the problem of powering underwater robotic vehicles -- tapping the unlimited energy difference between the ocean's cold spots and its more temperate regions.

A prototype submersible southwest of Hawaii has been chugging away for more than three months collecting data about ocean temperature, pressure and salinity, producing more power than it consumes.

"Having a long-duration underwater vehicle has been a dream for a long long," oceanographer Li Chao, with NASA's Jet Propulsion Laboratory in Pasadena, Calif., told Discovery News.

Chao is the lead scientist on a project called SOLO-TREC, an acronym for Sounding Oceanographic Lagrangrian Observer Thermal Recharging, which makes use of naturally occurring temperature variations in the ocean to generate electrical power.

Here's how it works: Ten tubes outside the underwater vehicle contain a wax which melts and expands when exposed to warmer ocean water. When it encounters deeper water, it contracts.

WATCH VIDEO: With 3,000 monitors floating through the world's oceans at once, scientists are getting a flood of information about our seas.

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This expansion and compression pressurizes oil, which drives a hydraulic motor. The motor generates a high torque and rotation that is passed on to a generator. The energy is then stored in rechargeable batteries.

It's a horribly inefficient way to generate electricity -- the thermodynamic efficiency is about 2 percent or less -- but that hardly matters when there is literally an ocean of potential power.

"The fact that we have so much energy in the ocean allows us to do this," Jack Jones, the lead SOLO-TREC engineer, told Discovery News.

"Finding a mechanical means to do this really was the biggest stumbling block. The trick was making this simple."

"The beauty of this technology is that it's scaleable," added Chao. "You can almost start with the science you want to do and pretty much design to scale. We can generate more power than what you need to power the entire vehicle."

SOLO-TREC has the potential to revolutionize ocean monitoring, providing a long-term solution to the problem of powering the armada of 3,200 underwater robotic vehicles currently keeping tabs on the oceans' health.

About 70 percent of the world's oceans have enough of a temperature variation for a system like SOLO-TREC to operate. It would not work in the ubiquitously cold waters around the Antarctic and Arctic.

SOLO-TREC, which has been under development for five years, is sponsored by NASA, the Office of Naval Research Institute, Scripps Institution of Oceanography and the University of California, San Diego.

A successful, three-month pilot project, which included three dives per day, wrapped up in March. The vehicle remains in the ocean, collecting data and generating power, while project leaders develop plans for a next-generation vehicle that would include wings for increased mobility.