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. > >
