Submersible Robot Runs on Sea's Heat
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Submersible Robot Runs on Sea's Heat Clara Moskowitz
LiveScience Staff Writer
SPACE.com
Mon Feb 11, 11:50 AM ET
Scientists have invented the Prius of ocean-going submersibles - a new
"green" robotic glider that runs on energy absorbed from the heat of
the sea, rather than batteries.
The new underwater glider can stay at sea at least twice as long as
previous submersibles that used battery power. It is the first
autonomous underwater vehicle to travel great distances for extended
periods running on green energy, according to the Woods Hole
Oceanographic Institution (WHOI).
Submersibles gained fame in 1985 when WHOI's remotely-operated
underwater vehicle, "Argo," discovered the wreck of the RMS Titanic
near Newfoundland.
Built by the Webb Research Corporation in Falmouth, Mass., the new
submersible has successfully traveled back and forth between two of
the U.S. Virgin Islands, St. Thomas and St. Croix, more than 20 times.
WHOI researchers plan to use the data gathered by the craft to study
ocean currents in the area.
To power its propulsion, the submersible gathers thermal energy from
the ocean. When it moves from cooler water to warmer areas, internal
tubes of wax are heated up and expand, pushing out the gas in
surrounding tanks and increasing its pressure. The compressed gas
stores potential energy, like a squeezed spring, that can be used to
power the vehicle.
"This glider allows longer missions than previous [battery-run]
versions," said Ben Hodges, a physical oceanographer at WHOI. "It
could be out there for a year or two years. None of the old ones could
go beyond six months. And producing fewer batteries is good for the
environment."
The torpedo-shaped glider moves through the ocean by changing its
buoyancy to dive and surface, unlike motorized, propeller-driven
undersea vehicles. To rise, oil is pushed from inside the vehicle to
external bladders, thus increasing the glider's volume without
changing its mass, making it less dense. The oil can be shifted inside
to increase the density and sink the vehicle. A vertical tail rudder
allows the glider to be steered horizontally.
Technically, the new vehicle is a hybrid, like Toyota's Prius, because
it uses a small amount of battery power to run the onboard instruments
and to move the rudder.
Gliders of this type are perfect for long-term, long-distance journeys
that humans can't make, Hodges said.
"They can be very helpful in getting measurements that would be too
expensive to get otherwise - any kind of study that requires long-term
measurements from multiple locations," Hodges told LiveScience. "If
you had to be there in a ship, it would cost millions of dollars."