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Nano-engineered thermoelectrics enable scalable, compressor-free cooling

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Re: Nano-engineered thermoelectrics enable scalable, compressor-free cooling

#31

Post by nandomrumber »

scotty79 wrote: post #26
adrian_b wrote: post #17

Earlier quoted context omitted.

Heat pipes only reduce the thermal resistance between 2 points. They cannot cool something below ambient temperature. Thermoelectric coolers do not compete with heat pipes. They are useful only when you want to obtain a temperature lower than the ambient temperature. Otherwise, heat pipes or liquid flow cooling are the right solutions.

You could have heat pipe filled with liquid that evaporates at 5 degrees. This way it would draw heat from ambient level temperature and lead it to peltier device that would cool it below 5 deg and liquefy it back again. This way you could have peltier in the middle of your thick insulation layer with heat pipes drawing the heat into it from the cooled space and drawing the heat from the other side of it outside (usi…

I think you may have just reinvented absorption refrigeration, previously invented by Ferdinand Carré in 1858.

https://en.wikipedia.org/wiki/Absorption_refrigerator

Re: Nano-engineered thermoelectrics enable scalable, compressor-free cooling

#33

Post by audunw »

vlovich123 wrote: post #20
fnordpiglet wrote: post #7

Thermoelectric cooling needs as much research as possible. Mechanical cooling is extraordinarily space consuming. CHESS has the potential over the next 10 years to largely replace vapor compression in most systems other than the most extreme gradients or scales. They are small enough to incorporate into most devices and would allow smaller devices more thermal load. In some ways I think efficient TEC like CHESS could…

Nah. Heat pumps are ~10-100x more efficient than thermoelectric. Thermoelectric is just inefficient mechanism and is inherently difficult to scale up as the more electricity gets generated so does more heat which inhibits the temperature gradient you’re trying to utilize. There’s a reason water cooling is preferred instead of peltier to ferry heat away from electronic. Magnetocaloric is super interesting though as an…

It’s really, really weird to comment on the efficiency of these devices on an article like this, without actually checking the paper being referenced. Like, we know traditional thermoelectric are inefficient. But that’s the whole point of this research. To improve it.

It seems like they achieve a CoP of 1.3-6.8 (depending on heat transfer load) versus e.g. - CoP of 2-4 which is common for a household refrigerator. So we are already in similar territory.

The article also references a Samsung refrigerator already in the market using a hybrid system with thermoelectric to achieve higher efficiency. So clearly commercial thermoelectics are already efficient enough to have a role in efficient cooling.

https://news.samsung.com/global/samsung-unveils-new-refriger...

The article has the CoP numbers for the thermoelectric element used in that Samsung refrigerator as well, if you’re interested.

Re: Nano-engineered thermoelectrics enable scalable, compressor-free cooling

#34

Post by audunw »

vlovich123 wrote: post #20
fnordpiglet wrote: post #7

Thermoelectric cooling needs as much research as possible. Mechanical cooling is extraordinarily space consuming. CHESS has the potential over the next 10 years to largely replace vapor compression in most systems other than the most extreme gradients or scales. They are small enough to incorporate into most devices and would allow smaller devices more thermal load. In some ways I think efficient TEC like CHESS could…

Nah. Heat pumps are ~10-100x more efficient than thermoelectric. Thermoelectric is just inefficient mechanism and is inherently difficult to scale up as the more electricity gets generated so does more heat which inhibits the temperature gradient you’re trying to utilize. There’s a reason water cooling is preferred instead of peltier to ferry heat away from electronic. Magnetocaloric is super interesting though as an…

It’s really, really weird to comment on the efficiency of these devices on an article like this, without actually checking the paper being referenced. Like, we know traditional thermoelectric are inefficient. But that’s the whole point of this research. To improve it.

It seems like they achieve a CoP of 1.3-6.8 (depending on heat transfer load) versus e.g. - CoP of 2-4 which is common for a household refrigerator. So we are already in similar territory.

The article also references a Samsung refrigerator already in the market using a hybrid system with thermoelectric to achieve higher efficiency. So clearly commercial thermoelectics are already efficient enough to have a role in efficient cooling.

https://news.samsung.com/global/samsung-unveils-new-refriger...

I think the role of the peltier is to allow them to design the compressor to be more efficient in a temperature maintenance mode.. so their peltier is probably not more efficient than the compressor in low heat transfer mode. That’s exactly the mode where the CHESS device is making massive improvements, so clearly it unlocks the potential for a thermoelectric-only refrigerator that’s more efficient than one using a compressor

The article has the CoP numbers for the thermoelectric element used in that Samsung refrigerator as well, if you’re interested.

Re: Nano-engineered thermoelectrics enable scalable, compressor-free cooling

#35

Post by leptons »

vlovich123 wrote: post #24
leptons wrote: post #22

Earlier quoted context omitted.

>Heat pumps are ~10-100x more efficient than thermoelectric. Peltier junctions are a type of heat pump.

Mechanical heat pumps are 10x-100x more effective than peltier heat pumps.

That doesn't change the fact that Peltier junctions are a type of heat pump.

Re: Nano-engineered thermoelectrics enable scalable, compressor-free cooling

#36

Post by audunw »

petermcneeley wrote: post #3

> the APL team achieved nearly 100% improvement in efficiency over traditional thermoelectric materials at room temperature Peltier effect refrigeration has very low efficiencies (5%) so while this is an amazing accomplishment it will not replace other more mechanical cooling methods.

I’m not sure what they mean by “traditional materials” here, but from their paper the COP is in the range of 1.3 - 6.8 depending on heat load which is similar to a modern household refrigerator. So yeah, it really does seem to be good enough to replace mechanical cooling.

The paper also references a Samsung hybrid refrigerator that already uses a thermoelectric device to improve efficiency (probably by letting the compressor operate in a more efficient mode most of the time).

According to the paper Samsung uses a bulk TEC device with a COP of 1.2 - 3 depending on heat load. That’s already fairly close to mechanical cooling. If it wasn’t it wouldn’t have made sense for Samsung to use it in a refrigerator whose whole selling point is efficiency.

I mean, clearly the 100% improvement is for the high heat load COP relative to that Samsung device, right? From 3 to 6.. and I think 6 is better than most commercially viable mechanical cooling solutions, no?

Re: Nano-engineered thermoelectrics enable scalable, compressor-free cooling

#37

Post by dvh »

ajb wrote: post #25
s_tec wrote: post #21

Thermoelectric cooling is pretty inefficient, because the materials need to balance competing requirements: - Good thermal insulator - Good electrical conductor - Good semiconductor This is because the hot & cold sides are sandwiched closely together as a PN junction, so once you move heat from one side to the other, it just leaks right back. Mechanical cooling doesn't have this problem, because the hot & cold sides…

Twenty years ago there was a company trying to commercialise thermoelectric cooling based on a vacuum gap: https://web.archive.org/web/20031213235132/http://www.coolch... They claimed 55% Carnot efficiency based on a 30-100 angstrom gap maintained by piezoelectric controllers, and a method to construct large electrodes with matched surfaces so that the gap could be maintained over a large area. It all sounded plausib…

But isn't condensation based cooling like 500% efficient?

Re: Nano-engineered thermoelectrics enable scalable, compressor-free cooling

#38

Post by cjbillington »

dvh wrote: post #37
ajb wrote: post #25

Earlier quoted context omitted.

Twenty years ago there was a company trying to commercialise thermoelectric cooling based on a vacuum gap: https://web.archive.org/web/20031213235132/http://www.coolch... They claimed 55% Carnot efficiency based on a 30-100 angstrom gap maintained by piezoelectric controllers, and a method to construct large electrodes with matched surfaces so that the gap could be maintained over a large area. It all sounded plausib…

But isn't condensation based cooling like 500% efficient?

The Carnot limit is the theoretical upper limit of the efficiency of a heat pump, so the stated number is presumably with respect to that, not heat moved per unit energy input like you're quoting.

Re: Nano-engineered thermoelectrics enable scalable, compressor-free cooling

#39

Post by metalman »

there are other alternatives for refrigeration

https://en.wikipedia.org/wiki/Thermoacoustic_heat_engine

it should be pointed out that thermoelectric cooling that was able to outperform mechanical pumps, would still be mostly useless for on device cooling as it cant move heat any distance, with it's own heat stuck in the same box or package, making design pivot around that limitation.

Re: Nano-engineered thermoelectrics enable scalable, compressor-free cooling

#40

Post by [deleted] »

dvh wrote: post #37
ajb wrote: post #25

Earlier quoted context omitted.

Twenty years ago there was a company trying to commercialise thermoelectric cooling based on a vacuum gap: https://web.archive.org/web/20031213235132/http://www.coolch... They claimed 55% Carnot efficiency based on a 30-100 angstrom gap maintained by piezoelectric controllers, and a method to construct large electrodes with matched surfaces so that the gap could be maintained over a large area. It all sounded plausib…

But isn't condensation based cooling like 500% efficient?

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