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.
This ingenious scheme where the cold source and the hot source are used at different places and at different times makes me think, why not just keep the "different times" feature and use ambient temperature variations (typically the daytime heat versus the nighttime cold) to power a --possibly stationary this time-- thermal engine similarly based on thermal expansion/shrinking of some material? An example would be a very long high thermal expansion coefficient metal rod pushing and pulling two ratchet mechanisms on opposite sides of a gear, which would thus rotate in the same direction whether at warming time (expansion of the rod) or at cooling time (shrinking of the rod). The gear shaft could e.g. tension a spiral spring acting as energy storage. No direct sunlight required, just temperature variations. Is this as totally absurd as it seems at first sight? ;-) Michel ----- Original Message ----- From: "Lawrence de Bivort" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Monday, February 11, 2008 8:28 PM Subject: 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 > ... > To ascend from frigid depths, fluid is pumped from an > inner bladder to one outside.... Back at the surface, pumps are > recharged as wax melts and expands anew, even as fluid is drawn again to the > inner bladder...
