Author Topic: Thermoelectric conversion news  (Read 7029 times)

Offline docmordrid

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Thermoelectric conversion news
« on: 01/18/2011 08:10 PM »
PhysOrg article, Northwestern research....

Claiming a heat to electricity conversion efficiency of 10-14 percent.
DM

Offline js117

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Re: Thermoelectric conversion news
« Reply #1 on: 01/19/2011 02:30 AM »
PhysOrg article, Northwestern research....

Claiming a heat to electricity conversion efficiency of 10-14 percent.

 I wander if this could be used in radioisotope thermoelectric generators (RTG) to  make them work better ( more power). 

Offline GraphGuy

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Re: Thermoelectric conversion news
« Reply #2 on: 01/20/2011 05:11 PM »
They get ~15% at temperatures of 700c.  This is a good step forward for ground based power plants but probably only slightly better for RTGs than what we already have.

Offline Joris

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Re: Thermoelectric conversion news
« Reply #3 on: 01/20/2011 08:36 PM »
Does anybody knows how this compares to the heat to electricity efficiency of a Sterling engine  ???
« Last Edit: 01/20/2011 08:36 PM by Joris »
JIMO would have been the first proper spaceship.

Offline 93143

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Re: Thermoelectric conversion news
« Reply #4 on: 01/20/2011 09:48 PM »
Not as good.  Stirling engines can get to 20-30%.

Offline GuessWho

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Re: Thermoelectric conversion news
« Reply #5 on: 01/21/2011 07:01 PM »
Not as good.  Stirling engines can get to 20-30%.

Depending on what the hot-side and cold-side temperatures are.

Offline Robotbeat

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Re: Thermoelectric conversion news
« Reply #6 on: 01/21/2011 07:04 PM »
Not as good.  Stirling engines can get to 20-30%.

Depending on what the hot-side and cold-side temperatures are.
Also, no moving parts and you could make a really tiny one if you wanted to (I often think about attaching a thermocouple to a RHU for a really tiny probe, perhaps like a small, persistent probe on Titan or something).
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Offline 93143

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Re: Thermoelectric conversion news
« Reply #7 on: 01/21/2011 08:24 PM »
Not as good.  Stirling engines can get to 20-30%.

Depending on what the hot-side and cold-side temperatures are.

Obviously.  I'm talking about practical radioisotope generator configurations.

Offline A_M_Swallow

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Re: Thermoelectric conversion news
« Reply #8 on: 01/21/2011 11:24 PM »
Not as good.  Stirling engines can get to 20-30%.

Depending on what the hot-side and cold-side temperatures are.
Also, no moving parts and you could make a really tiny one if you wanted to (I often think about attaching a thermocouple to a RHU for a really tiny probe, perhaps like a small, persistent probe on Titan or something).

Heat from an astronaut's body may be able to power some sensors.

On a spacecraft small heat power may remove the need for a power cable, permitting say glueing a vibration sensor to the side of a pipe.

Offline Joris

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Re: Thermoelectric conversion news
« Reply #9 on: 01/23/2011 08:00 PM »
Not as good.  Stirling engines can get to 20-30%.

Depending on what the hot-side and cold-side temperatures are.

Obviously.  I'm talking about practical radioisotope generator configurations.

What if you get you're heat beamed from elsewere, what would be the maximum heat it could sustain to get as much power as possibel with as little weight for the use in Electric propulsion.
JIMO would have been the first proper spaceship.

Offline Robotbeat

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Re: Thermoelectric conversion news
« Reply #10 on: 01/24/2011 04:52 PM »
Not as good.  Stirling engines can get to 20-30%.

Depending on what the hot-side and cold-side temperatures are.

Obviously.  I'm talking about practical radioisotope generator configurations.

What if you get you're heat beamed from elsewere, what would be the maximum heat it could sustain to get as much power as possibel with as little weight for the use in Electric propulsion.
You mean like from the Sun? In that case, photoelectric cells is much lighter and still much more efficient.
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Offline sanman

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Re: Thermoelectric conversion news
« Reply #11 on: 01/25/2011 01:24 PM »
What about VASIMR benefiting from this higher thermoelectric conversion efficiency?

Also, if this allows electricity to be produced more efficiently from heat, then shouldn't there be some reciprocal improvement in thermoelectric cooling - ie. producing heat transfer from electric current?

Offline Gene DiGennaro

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Re: Thermoelectric conversion news
« Reply #12 on: 01/25/2011 01:34 PM »
A 3-7 percent increase in efficiency is quite a leap. When I worked on RTG's back in the 90's, it was my understanding that with the tellurium/antimony/germanium/selenium alloy ( then the best available) efficiency was about 7 percent. Mind you, I wasn't an engineer, just a technician who processed the allloy. I wasn't involved in the efficiency studies.

Offline Proponent

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Re: Thermoelectric conversion news
« Reply #13 on: 01/26/2011 03:39 AM »
I would think that for RTG applications, a key question would be how the new proposed materials cope with particle radiation.  IIRC, the principal reason that the power output of current RTGs decreases over time is not that the source decays but that the thermocouple degrades because of the radiation.

Offline Proponent

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Re: Thermoelectric conversion news
« Reply #14 on: 01/26/2011 03:40 AM »
What about VASIMR benefiting from this higher thermoelectric conversion efficiency?

Also, if this allows electricity to be produced more efficiently from heat, then shouldn't there be some reciprocal improvement in thermoelectric cooling - ie. producing heat transfer from electric current?

Considering how low the efficiency of conversion of heat to electricity is, thermoelectric cooling is not going to be very effective.

Offline aero

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Re: Thermoelectric conversion news
« Reply #15 on: 01/26/2011 04:20 AM »
What about VASIMR benefiting from this higher thermoelectric conversion efficiency?

Also, if this allows electricity to be produced more efficiently from heat, then shouldn't there be some reciprocal improvement in thermoelectric cooling - ie. producing heat transfer from electric current?

Considering how low the efficiency of conversion of heat to electricity is, thermoelectric cooling is not going to be very effective.
Except where local cooling and space constraints are much more critical than energy efficiency. Computer CPUs for example, particularly overclocked CPUs.
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Offline sanman

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Re: Thermoelectric conversion news
« Reply #16 on: 01/26/2011 05:01 AM »
And don't forget the fact that thermoelectric cooling is solid-state, with no moving parts to wear out. They're even considering ion-wind tech to cool CPUs in place of CPU fans, for the same reason.

Offline Proponent

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Re: Thermoelectric conversion news
« Reply #17 on: 01/26/2011 05:08 AM »
Considering how low the efficiency of conversion of heat to electricity is, thermoelectric cooling is not going to be very effective.
Except where local cooling and space constraints are much more critical than energy efficiency. Computer CPUs for example, particularly overclocked CPUs.

So if I put a really good thermocouple in place, I can soak up maybe 15% of the heat produced by my over-clocked CPU.  I just don't see how that buys me much.

Offline randomly

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Re: Thermoelectric conversion news
« Reply #18 on: 01/26/2011 01:07 PM »
He's referring to the fact that thermoelectric devices can work both ways. Turning a heat differential into electricity or turning electricity into a heat differential.

By putting an appropriately sized thermoelectric device between the CPU and the heatsink and running a large current through it you can drop the temperature of the cold side of the device well below what it would be normally and decrease the temperature of the CPU and achieve better performance. However it's not particularly efficient and it takes a good deal of extra energy put into the thermoelectric cooler to drop the temperature significantly. Efficiency falls off as the temperature differential between the hot and cold side increases so temperature drops are limited. The heat sink side also has to now dissipate not only the cpu heat but all the energy you are dumping into the thermoelectric device as well so it needs a considerably larger capacity. You also want to keep the hot side of the device as cool as possible to reduce the temperature differential and keep the thermoelectric efficiency up so that requires even more heatsink. For typical CPUs it's a lot of effort and energy for fairly little temperature improvement.

Offline kevin-rf

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Re: Thermoelectric conversion news
« Reply #19 on: 01/26/2011 02:42 PM »
Does not make sense for a CPU, where you can just add better active cooling (be it liquid or air). But in the case where the you want to cool a semi-conductor based device well below ambient Peltier Coolers are often used. It is a very common way to cool low light CCD's (Think Astronomy, Spectroscopy, Fluorescent Microscopes, IR  cameras). You'll usually place the package with cooler attached inside a chamber that is either under vacuum or uses an inert non-condensing gas (Argon, Nitrogen) and then pumps the heat through the chamber wall. It is possible to get the chip down to -100 C with a stack of Peltiers and conventional cooling fan, though you usually don't get below -20 C with a single cooler. You just have a huge heat load on the other end. But for some cases it does work. They are small and light, just not very efficient. Sounds like RTG's...
« Last Edit: 01/26/2011 02:45 PM by kevin-rf »
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Offline docmordrid

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Re: Thermoelectric conversion news
« Reply #20 on: 01/26/2011 03:19 PM »
Peltier's are also used in small food/beverage coolers like those that plug into a cars cigarette lighter. I've used them for CPU/GPU cooling as well, but not so much since liquid coolers & heat pipes became affordable. Now all I use 'em for is beer, sandwiches and the CCD imager on my telescope.

DM

Offline Robotbeat

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Re: Thermoelectric conversion news
« Reply #21 on: 01/26/2011 06:01 PM »
Right, Peltier coolers are already used on CPUs sometimes and often on CCDs (i.e. thermal infrared), beverage coolers, etc. An increase in thermoelectric efficiency would help. It may also help keep medicine cool for treating diseases in remote parts of third-world countries.
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Offline Nomadd

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Re: Thermoelectric conversion news
« Reply #22 on: 01/26/2011 06:30 PM »
 I buy coolers and scavenge the Peltiers out of them for outdoor electronics in the oil fields. It's the cheapest way I've found to buy the ones with the capacity I need.
 The hot side just goes to the shaded box mount.
 I'd wondered about using them to radiate heat on spacecraft using a smaller radiator, but the low efficiency killed the idea quick. It's a ways from being better than the ammonia based , or any other compressed gas based A/C in large scale apps.
 Maybe David Brin will chime in with some details on his laser based cooling system in Sundiver.
« Last Edit: 01/26/2011 06:31 PM by Nomadd »

Offline clongton

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Re: Thermoelectric conversion news
« Reply #23 on: 01/26/2011 08:13 PM »
I'm actually thinking a little more down-to-earth. Homes that heat with geothermal energy may also be able to suppliment some of their power needs by including appropriate thermcouple devices in the hole drilled for the geothermal devices. And if one were to drill *really* deep, well there may be some major power generation possibilities using this material in thermocouples. It can get pretty hot. It all depends on how deep one is willing to drill.
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