Submersible Glider Powered By Thermal Changes

An anonymous reader writes about a new robot submersible that uses temperature differences in the sea to power operation for more than twice as long as previous, battery-dependent vehicles. "The torpedo-shaped glider moves through the ocean by changing its buoyancy to dive and surface, unlike motorized, propeller-driven undersea vehicles. 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. 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."

Comments

Sounds like the perfect drug-smuggling device.

[jcr]

Just sayin'...

-jcr

Re:Wait... what?

[MichaelSmith]

Last I checked submarines had air tanks for buoyancy control, and newer subs are not motorized, but nuclear-powered. Something change in the past few hours while I was sleeping?

Submarines don't use changes in depth to push them horizontally. This device is a bit like a sailplane.

thevapowaretagisincorrect

[z0idberg]

I know, I was shocked too, but the vaporware tag is wrong.

They have had one working that has traveled 1400 kms so far since launch in December. Better article here
http://www.cbc.ca/technology/story/2008/02/08/tech-glider-undersea.html

Re:thevapowaretagisincorrect

[auric_dude]

Also sighted by the BBC http://news.bbc.co.uk/1/hi/technology/7234544.stm

Re:Wait... what?

[hcdejong]

Last I checked submarines had air tanks for buoyancy control

The air tanks are used mainly used to switch between surface and submerged modes, for trimming (keeping the sub horizontal), and to compensate for changes in water density. Because the amount of lift generated by a body does not change much with its depth, the air tanks cannot provide fine control of your diving depth. Also, a naval sub prefers not to use the air tanks once submerged, because venting air leaves a trail on the surface.
For fine depth control, a sub uses its diveplanes: wing-like surfaces that provide lift (positive or negative) as long as the sub keeps its speed above a minimum.

In effect, this glider reverses the process: changes in buoyancy are used to generate an upwards/downwards force, which is converted by the wings into forward motion.

newer subs are not motorized, but nuclear-powered.

You mean some newer subs are nuclear-powered. Conventional-powered submarines are still being built today. Often, in addition to the traditional diesel engines, an air-independent propulsion system is installed, either a Stirling engine or a set of fuel cells.

Good for surface work

[Anonymous Coward]

Its an interesting invention that will be great for near-surface work, but I guess it will not be a whole lot of use for deep exploration since temperatures remain pretty constant in deep ocean and if anything tends to get slightly colder with depth. But given its a hybrid perhaps you can burn the battery on the way down and use temperature increase on the way up :-)
Still and interesting piece of equipment. Research veseel time is very, very expensive, so if the cost of creating an autonomous vehicle coudl be kept relatively down and be given enough range to propel itself to areas of interest, this could be very useful both for science and other maritime work (like pipe/cable inspection).

Re:New problem, same root cause

[jim.hansson]

I'm not saying that we shouldn't use wind power, or solar power, or thermal power, or even combustion engines. BUT, we need to every bit of energy we take from the world -- in WHATEVER form -- depletes it, and that the only real solution is to cut back on how much we take. NO, wrong, transform maybe, but depletes totally wrong

Re:This would have been brilliant in WWII

[esocid]

I can't see how modern day subs would have ANY interest in this. Seriously. You would have to modulate your path based on water temperature, and baby-jesus forbid, you are forced to transverse water the same temperature for a few months. This is useless technology unless WWIII starts tomorrow.

You seem to be missing the point, or didn't RTFA. This is a science vessel that uses a hybrid battery/thermal powered propulsion and electronic system. This allows the research vessel to remain submerged longer than normal by not needing to rely completely on battery power.
Nice try though.

Re:Ask Newton.

[zippthorne]

No, the energy in that plan doesn't come from the sea temp, it comes from the ballast. The thing you're depleting is the available buoyancy material, whether it be helium, air, or oil.

For a closed-circuit buoyancy engine, you have to physically pump the buoyancy material around to get your change in density. This pumping is against whatever the ambient pressure is, so the deeper you allow it to drop, the more force you have to pump against to get your buoyancy back and return to the surface.

Since you have to pump the same volume of material either way, against a force that depends on the depth , it takes more work to get your buoyancy back the deeper you go. This works whether do the pumping on the bottom with oil-bladders, or at the top with air bladders.