RE: [Vo]:Re: Ocean glider uses ocean heat differentials
Good points. How is a small but powerful motion of something on a stationary platform best converted into usable energy? Lawrence -Original Message- From: Michel Jullian [mailto:[EMAIL PROTECTED] Sent: Wednesday, February 13, 2008 4:13 AM To: vortex-l@eskimo.com Subject: [Vo]:Re: Ocean glider uses ocean heat differentials Indeed, it doesn't seem obvious how to extract a lot of energy from the scheme, but it might work with stationary devices (see my Ambient temperature variations powered engine post). Apart from mechanical energy (stressing a spring or lifting a weight), the diurnal expansion/shrinking cycle scheme might also produce electrical energy by pushing/pulling a piezoelectric membrane... I doubt this could compete with Nanosolar type cheap photovoltaics, or even with classical Seebeck type thermoelectric devices, but it might be worth investigating... can thermal expansion or shrinking produce a significant force BTW? How would one go about calculating this? Michel - Original Message - From: Lawrence de Bivort [EMAIL PROTECTED] To: vortex-l@eskimo.com Sent: Tuesday, February 12, 2008 9:13 PM Subject: RE: [Vo]:Re: Ocean glider uses ocean heat differentials But what use might this device be? Random 'walks' through the ocean, which seems to be what it is used for, but beyond that? With only one knot of speed, no matter how it was guided, the thing if caught in the Gulf Stream in Florida it would end up off the coast of Portugal before its batteries required attention. That is, if it didn't go aground before then, which with a routine depth profile of 4,000 feet it surely would, to stay forever there on the ocean bed. Lawry -Original Message- From: Michel Jullian [mailto:[EMAIL PROTECTED] Sent: Tuesday, February 12, 2008 1:18 PM To: vortex-l@eskimo.com Subject: [Vo]:Re: Ocean glider uses ocean heat differentials Good point. Having air inside must be indispensable anyway to offset the weight of the metal hull and batteries. Michel - Original Message - From: Robin van Spaandonk [EMAIL PROTECTED] To: vortex-l@eskimo.com Sent: Tuesday, February 12, 2008 3:07 AM Subject: Re: [Vo]:Ambient temperature variations powered engine? (was Re: Ocean glider uses ocean heat differentials) In reply to Michel Jullian's message of Tue, 12 Feb 2008 01:26:20 +0100: Hi, [snip] Thanks Lawrence this makes more sense, the initial BBC article and the WHOI press release stated, wrongly it now seems, that [the surface] heat is used to push oil _from a bladder inside the hull to one outside_. If it's the other way round as the WP article below suggests (oil from outside to inside at the surface), then the outside oil bladder needs not contain anything but oil as I am sure Robin will agree. [snip] While I do agree strictly, consider that the oil is incompressible, and hence always takes up the same volume (almost) whether inside or outside. If the oil can be pumped into the device, then that means that there must be something compressible inside the device, i.e. an air bladder. In short, it makes no difference where that bladder is, as long as it is part of the device. The reference I provided to the manufacturers web site, makes clear that there is at least one air bladder. Regards, Robin van Spaandonk The shrub is a plant.
RE: [Vo]:Re: Ocean glider uses ocean heat differentials
But what use might this device be? Random 'walks' through the ocean, which seems to be what it is used for, but beyond that? With only one knot of speed, no matter how it was guided, the thing if caught in the Gulf Stream in Florida it would end up off the coast of Portugal before its batteries required attention. That is, if it didn't go aground before then, which with a routine depth profile of 4,000 feet it surely would, to stay forever there on the ocean bed. Lawry -Original Message- From: Michel Jullian [mailto:[EMAIL PROTECTED] Sent: Tuesday, February 12, 2008 1:18 PM To: vortex-l@eskimo.com Subject: [Vo]:Re: Ocean glider uses ocean heat differentials Good point. Having air inside must be indispensable anyway to offset the weight of the metal hull and batteries. Michel - Original Message - From: Robin van Spaandonk [EMAIL PROTECTED] To: vortex-l@eskimo.com Sent: Tuesday, February 12, 2008 3:07 AM Subject: Re: [Vo]:Ambient temperature variations powered engine? (was Re: Ocean glider uses ocean heat differentials) In reply to Michel Jullian's message of Tue, 12 Feb 2008 01:26:20 +0100: Hi, [snip] Thanks Lawrence this makes more sense, the initial BBC article and the WHOI press release stated, wrongly it now seems, that [the surface] heat is used to push oil _from a bladder inside the hull to one outside_. If it's the other way round as the WP article below suggests (oil from outside to inside at the surface), then the outside oil bladder needs not contain anything but oil as I am sure Robin will agree. [snip] While I do agree strictly, consider that the oil is incompressible, and hence always takes up the same volume (almost) whether inside or outside. If the oil can be pumped into the device, then that means that there must be something compressible inside the device, i.e. an air bladder. In short, it makes no difference where that bladder is, as long as it is part of the device. The reference I provided to the manufacturers web site, makes clear that there is at least one air bladder. Regards, Robin van Spaandonk The shrub is a plant.
Re: [Vo]:Re: Ocean glider uses ocean heat differentials
In reply to Lawrence de Bivort's message of Mon, 11 Feb 2008 14:28:56 -0500: Hi, [snip] Here is a better explanation of how the glider works, from the Science Notebook of today's the Washington Post: Monday, February 11, 2008; Page A05 Motorless Sub Keeps Going Scientists seeking to gather temperature, salinity and other data from the oceans have long had two choices: steam out to sea on expensive research ships or launch unmanned submersibles whose batteries typically die in a few days. [snip] See also http://www.webbresearch.com/thermal_glider.htm . Regards, Robin van Spaandonk The shrub is a plant.
RE: [Vo]:Re: Ocean glider uses ocean heat differentials
Here is a better explanation of how the glider works, from the Science Notebook of today's the Washington Post: Monday, February 11, 2008; Page A05 Motorless Sub Keeps Going Scientists seeking to gather temperature, salinity and other data from the oceans have long had two choices: steam out to sea on expensive research ships or launch unmanned submersibles whose batteries typically die in a few days. Now engineers and oceanographers have successfully tested a novel unmanned mini-sub that grabs energy from temperature differences in the ocean. In an ongoing test, the thermal glider has been traveling, without a propeller, for nearly two months. We now believe the technology is stable enough to be used for science. It is no longer just a prototype, said Dave Fratantoni of the Woods Hole Oceanographic Institution on Cape Cod. Made by Webb Research Corp. of Falmouth, Mass., the glider changes its buoyancy by pumping fluid back and forth between bladders inside and outside its hull. Near the surface, where waters are relatively warm, wax within a chamber melts and expands, producing a pumplike force that can push water between bladders. To ascend from frigid depths, fluid is pumped from an inner bladder to one outside. The vessel's mass does not change, but its volume increases, increasing buoyancy. Back at the surface, pumps are recharged as wax melts and expands anew, even as fluid is drawn again to the inner bladder, reducing volume and slowly sinking the vessel again. Fixed fins convert the rising and falling into forward momentum, just as a paper airplane's wings make it glide forward when dropped. The six-foot craft travels about 1 mph, repeatedly bobbing up and then sinking to 4,000 feet as it goes, fueled by a temperature differential of about 43 degrees Fahrenheit. Instruments that can run on batteries for months gather data from the ocean and transmit to satellites with each surfacing. One goal is to study climate change. And because the glider has no motor, Fratantoni said, it is ideal for underwater acoustic studies. -- Rick Weiss
Re: [Vo]:Re: Ocean glider uses ocean heat differentials
In reply to Michel Jullian's message of Mon, 11 Feb 2008 19:47:30 +0100: Hi, [snip] This would indeed work Robin, but their system seems more complicated, the wax expansion energy is stored somehow according to the WHOI News Release here: http://www.whoi.edu/page.do?pid=7545tid=282cid=37008ct=162 I think you may be reading a little too much into the word stored. Literally, energy is stored in the form of heat in the warm wax. That may be all that the reporter meant. Regards, Robin van Spaandonk The shrub is a plant.
Re: [Vo]:Re: Ocean glider uses ocean heat differentials
In reply to Michel Jullian's message of Sun, 10 Feb 2008 17:26:12 +0100: Hi, [snip] Quote from the link below: Wax-filled tubes inside the craft expand when it is gliding through warmer water. This heat is used to push oil from a bladder inside the hull to one outside, changing its buoyancy. Anyone knows how this works in more detail? From the above description one would expect the glider's buoyancy to increase when reaching the warmer surface (same mass, increased volume), instead of decreasing as required for diving. Michel The outside bladder must contain compressed air. When the oil compresses the air further, more volume is filled with oil, and less with air, so the average density is higher and the craft sinks. Regards, Robin van Spaandonk The shrub is a plant.
