RE: An energy discovery that will change the world

e14 Contributor — Fri, 08 Apr 2011 08:05:48 GMT

Thermocouples are very inefficient at converting temperature differentials to electricity. They're somewhat more efficient at using electricity to create a temperature differential, but more heat is produced on the hot side than is absorbed on the cold side. Peltier modules can be stacked to achieve a higher temperature differential - up to a point. Stack too many and the hot end of the stack will have bad things happen to it from getting too hot.

These junctions are used in stacks in RTG's or Radioisotope Thermal Generators. (Originally called SNAP for System for Nuclear Auxiliary Power.) They've been used on satellites and space probes. Each of the Viking Mars landers had a pair of them, which is why they lasted quite a bit longer than their design lifetimes.

In more recent years, photovoltaics have improved to the point where they're better than an RTG for most uses in Mars orbit or closer to the sun. Further out, an RTG can produce more power, but of course will eventually cool to the point where there's not enough heat for the thermocouples to produce a useful amount of electricity - but that's over 30 years. The Voyager probes are over 33.5 years old and expected to maintain some communication capability until 2025. The three RTGs on each Voyager produced a total of 470 watts at launch. I dunno how much that's gone down.

RTGs have been used on Earth, mostly in Soviet lighthouses and other remote navigation aids. A few idiots have been severely injured or killed when they removed shielding from them and used the toasty RTGs for heat instead of campfires. 'Course those were *Soviet* versions. American RTGs have survived at least one incident of a launch going bad, the rocket being blown up, fished out of the Atlantic then refurbished and built into a new satellite. [View:/resized-image/__size/16x16/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-4304ce29-c277-42fc-9e6c-eeae6b63fcd5/contentimage_5F00_3.png:16:16]

RE: An energy discovery that will change the world

DAB — Sat, 02 Apr 2011 20:51:24 GMT

I wonder how this approach differs in efficiency from using thermocouples to generate the power needed to separate the H2 and O from the water? Thermocouples would have the advantage of working with just heat and would be less constrained by non sunny days or cloud cover in warm climates.

Just a thought.

DAB

RE: An energy discovery that will change the world

e14 Contributor — Thu, 31 Mar 2011 12:18:18 GMT

This sounds like a more efficient water electrolysis process. A great thing, but hardly revolutionary.